The water-powered car may soon become a reality and hydrogen fuel cells will be installed in many homes...

Hydrogen fuel cell technology is not new. It began in 1776 when Henry Cavendish first discovered hydrogen while dissolving metals in dilute acids. The first hydrogen fuel cell was invented as early as 1839 by William Grove. Since then, hydrogen fuel cells have been gradually improved and are now installed in space shuttles, supplying them with energy and serving as a source of water. Today, hydrogen fuel cell technology is on the verge of reaching the mass market, in cars, homes and portable devices.

In a hydrogen fuel cell, chemical energy (in the form of hydrogen and oxygen) is converted directly (without combustion) into electrical energy. The fuel cell consists of a cathode, electrodes and an anode. Hydrogen is fed to the anode, where it is split into protons and electrons. Protons and electrons have different routes to the cathode. The protons travel through the electrode to the cathode, and the electrons travel around the fuel cells to get to the cathode. This movement creates subsequently usable electrical energy. On the other side, hydrogen protons and electrons combine with oxygen to form water.

Electrolyzers are one way to extract hydrogen from water. The process is basically the opposite of what happens when a hydrogen fuel cell operates. The electrolyzer consists of an anode, an electrochemical cell and a cathode. Water and voltage are applied to the anode, which splits the water into hydrogen and oxygen. Hydrogen passes through the electrochemical cell to the cathode and oxygen is fed directly to the cathode. From there, hydrogen and oxygen can be extracted and stored. During times when electricity is not required to be produced, the accumulated gas can be drawn out of the storage and passed back through the fuel cell.

This system uses hydrogen as fuel, which is probably why there are many myths about its safety. After the explosion of the Hindenburg, many people far from science and even some scientists began to believe that the use of hydrogen is very dangerous. However, recent research has shown that the cause of this tragedy was due to the type of material that was used in the construction, and not to the hydrogen that was pumped inside. After testing the safety of hydrogen storage, it was found that hydrogen storage in fuel cells is safer than storing gasoline in a car's fuel tank.

How much do modern hydrogen fuel cells cost?? Companies are currently offering hydrogen fuel systems to produce power for about $3,000 per kilowatt. Market research has established that when the cost drops to $1,500 per kilowatt, consumers in the mass energy market will be ready to switch to this type of fuel.

Hydrogen fuel cell vehicles are still more expensive than internal combustion engine vehicles, but manufacturers are exploring ways to bring the price up to a comparable level. In some remote areas where there are no power lines, using hydrogen as a fuel or autonomous power supply at home may be more economical now than, for example, building infrastructure for traditional energy carriers.

Why are hydrogen fuel cells still not widely used? At the moment, their high cost is the main problem for the distribution of hydrogen fuel cells. Hydrogen fuel systems simply do not have mass demand at the moment. However, science does not stand still and in the near future a car running on water can become a real reality.

Fabrication, assembly, testing and testing of fuel (hydrogen) cells/cells
Manufactured in factories in the US and Canada

Fuel (hydrogen) cells/cells

The company Intech GmbH / LLC Intech GmbH has been on the market of engineering services since 1997, the official for many years of various industrial equipment, brings to your attention various fuel (hydrogen) cells / cells.

A fuel cell/cell is

Benefits of fuel cells/cells

A fuel cell/cell is a device that efficiently generates direct current and heat from a hydrogen-rich fuel through an electrochemical reaction.

A fuel cell is similar to a battery in that it generates direct current through a chemical reaction. The fuel cell includes an anode, a cathode and an electrolyte. However, unlike batteries, fuel cells/cells cannot store electrical energy, do not discharge, and do not require electricity to be recharged. Fuel cells/cells can continuously generate electricity as long as they have a supply of fuel and air.

Unlike other power generators such as internal combustion engines or turbines powered by gas, coal, oil, etc., fuel cells/cells do not burn fuel. This means no noisy high pressure rotors, no loud exhaust noise, no vibration. Fuel cells/cells generate electricity through a silent electrochemical reaction. Another feature of fuel cells/cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only products emitted during operation are water in the form of steam and a small amount of carbon dioxide, which is not emitted at all if pure hydrogen is used as fuel. Fuel cells/cells are assembled into assemblies and then into individual functional modules.

History of fuel cell/cell development

In the 1950s and 1960s, one of the biggest challenges for fuel cells was born out of the US National Aeronautics and Space Administration's (NASA) need for energy sources for long-duration space missions. NASA's Alkaline Fuel Cell/Cell uses hydrogen and oxygen as fuel, combining the two in an electrochemical reaction. The output is three by-products of the reaction useful in spaceflight - electricity to power the spacecraft, water for drinking and cooling systems, and heat to keep the astronauts warm.

The discovery of fuel cells dates back to the beginning of the 19th century. The first evidence of the effect of fuel cells was obtained in 1838.

In the late 1930s, work began on alkaline fuel cells, and by 1939 a cell using high pressure nickel-plated electrodes had been built. During the Second World War, fuel cells/cells for British Navy submarines were developed and in 1958 a fuel assembly consisting of alkaline fuel cells/cells just over 25 cm in diameter was introduced.

Interest increased in the 1950s and 1960s and also in the 1980s when the industrial world experienced a shortage of fuel oil. In the same period, world countries also became concerned about the problem of air pollution and considered ways to generate environmentally friendly electricity. At present, fuel cell/cell technology is undergoing rapid development.

How fuel cells/cells work

Fuel cells/cells generate electricity and heat through an ongoing electrochemical reaction using an electrolyte, a cathode and an anode.

The anode and cathode are separated by an electrolyte that conducts protons. After hydrogen enters the anode and oxygen enters the cathode, a chemical reaction begins, as a result of which electric current, heat and water are generated.

On the anode catalyst, molecular hydrogen dissociates and loses electrons. Hydrogen ions (protons) are conducted through the electrolyte to the cathode, while electrons are passed through the electrolyte and pass through an external electrical circuit, creating a direct current that can be used to power equipment. On the cathode catalyst, an oxygen molecule combines with an electron (which is supplied from external communications) and an incoming proton, and forms water, which is the only reaction product (in the form of vapor and / or liquid).

Below is the corresponding reaction:

Anode reaction: 2H 2 => 4H+ + 4e -
Reaction at the cathode: O 2 + 4H+ + 4e - => 2H 2 O
General element reaction: 2H 2 + O 2 => 2H 2 O

Types and variety of fuel cells/cells

Similar to the existence of different types of internal combustion engines, there are different types of fuel cells - the choice of the appropriate type of fuel cell depends on its application.

Fuel cells are divided into high temperature and low temperature. Low temperature fuel cells require relatively pure hydrogen as fuel. This often means that fuel processing is required to convert the primary fuel (such as natural gas) to pure hydrogen. This process consumes additional energy and requires special equipment. High temperature fuel cells do not need this additional procedure, as they can "internally convert" the fuel at elevated temperatures, which means there is no need to invest in hydrogen infrastructure.

Fuel cells/cells on molten carbonate (MCFC)

Molten carbonate electrolyte fuel cells are high temperature fuel cells. The high operating temperature allows direct use of natural gas without a fuel processor and low calorific value fuel gas from process fuels and other sources.

The operation of RCFC is different from other fuel cells. These cells use an electrolyte from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of mobility of ions in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). The efficiency varies between 60-80%.

When heated to a temperature of 650°C, salts become a conductor for carbonate ions (CO 3 2-). These ions pass from the cathode to the anode where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electrical current and heat as a by-product.

Anode reaction: CO 3 2- + H 2 => H 2 O + CO 2 + 2e -
Reaction at the cathode: CO 2 + 1/2O 2 + 2e - => CO 3 2-
General element reaction: H 2 (g) + 1/2O 2 (g) + CO 2 (cathode) => H 2 O (g) + CO 2 (anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. At high temperatures, the natural gas is internally reformed, eliminating the need for a fuel processor. In addition, the advantages include the ability to use standard materials of construction, such as stainless steel sheet and nickel catalyst on the electrodes. The waste heat can be used to generate high pressure steam for various industrial and commercial purposes.

High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures takes a long time to reach optimal operating conditions, and the system reacts more slowly to changes in energy consumption. These characteristics allow the use of fuel cell systems with molten carbonate electrolyte in constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide.

Molten carbonate fuel cells are suitable for use in large stationary installations. Thermal power plants with an output electric power of 3.0 MW are industrially produced. Plants with an output power of up to 110 MW are being developed.

Fuel cells/cells based on phosphoric acid (PFC)

Fuel cells based on phosphoric (orthophosphoric) acid were the first fuel cells for commercial use.

Fuel cells based on phosphoric (orthophosphoric) acid use an electrolyte based on orthophosphoric acid (H 3 PO 4) with a concentration of up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, for this reason these fuel cells are used at temperatures up to 150–220°C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells, in which hydrogen supplied to the anode is split into protons and electrons. The protons pass through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are directed along an external electrical circuit, and an electric current is generated. Below are the reactions that generate electricity and heat.

Reaction at the anode: 2H 2 => 4H + + 4e -
Reaction at the cathode: O 2 (g) + 4H + + 4e - \u003d\u003e 2 H 2 O
General element reaction: 2H 2 + O 2 => 2H 2 O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. In the combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate steam at atmospheric pressure.

The high performance of thermal power plants on fuel cells based on phosphoric (orthophosphoric) acid in the combined production of heat and electricity is one of the advantages of this type of fuel cells. The plants use carbon monoxide at a concentration of about 1.5%, which greatly expands the choice of fuel. In addition, CO 2 does not affect the electrolyte and the operation of the fuel cell, this type of cell works with reformed natural fuel. Simple construction, low electrolyte volatility and increased stability are also advantages of this type of fuel cell.

Thermal power plants with an output electric power of up to 500 kW are industrially produced. Installations for 11 MW have passed the relevant tests. Plants with an output power of up to 100 MW are being developed.

Solid oxide fuel cells/cells (SOFC)

Solid oxide fuel cells are the fuel cells with the highest operating temperature. The operating temperature can vary from 600°C to 1000°C, which allows the use of various types of fuel without special pre-treatment. To handle these high temperatures, the electrolyte used is a thin ceramic-based solid metal oxide, often an alloy of yttrium and zirconium, which is a conductor of oxygen (O 2-) ions.

A solid electrolyte provides a hermetic gas transition from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O 2-). At the cathode, oxygen molecules are separated from the air into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen to form four free electrons. Electrons are directed through an external electrical circuit, generating electrical current and waste heat.

Reaction at the anode: 2H 2 + 2O 2- => 2H 2 O + 4e -
Reaction at the cathode: O 2 + 4e - \u003d\u003e 2O 2-
General element reaction: 2H 2 + O 2 => 2H 2 O

The efficiency of the generated electrical energy is the highest of all fuel cells - about 60-70%. High operating temperatures allow for combined heat and power generation to generate high pressure steam. Combining a high temperature fuel cell with a turbine creates a hybrid fuel cell to increase the efficiency of power generation up to 75%.

Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in a long time to reach optimal operating conditions, and the system is slower to respond to changes in power consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels from coal gasification or waste gases, and the like. Also, this fuel cell is excellent for high power applications, including industrial and large central power plants. Industrially produced modules with an output electrical power of 100 kW.

Fuel cells/cells with direct methanol oxidation (DOMTE)

The technology of using fuel cells with direct oxidation of methanol is undergoing a period of active development. It has successfully established itself in the field of powering mobile phones, laptops, as well as for creating portable power sources. what the future application of these elements is aimed at.

The structure of fuel cells with direct oxidation of methanol is similar to fuel cells with a proton exchange membrane (MOFEC), i.e. a polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. However, liquid methanol (CH 3 OH) is oxidized in the presence of water at the anode, releasing CO 2 , hydrogen ions and electrons, which are guided through an external electrical circuit, and an electric current is generated. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Reaction at the anode: CH 3 OH + H 2 O => CO 2 + 6H + + 6e -
Reaction at the cathode: 3/2O 2 + 6 H + + 6e - => 3H 2 O
General element reaction: CH 3 OH + 3/2O 2 => CO 2 + 2H 2 O

The advantage of this type of fuel cells is their small size, due to the use of liquid fuel, and the absence of the need to use a converter.

Alkaline fuel cells/cells (AFC)

Alkaline fuel cells are one of the most efficient elements used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, i.e. an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The concentration of potassium hydroxide may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in an SFC is a hydroxide ion (OH-) moving from the cathode to the anode where it reacts with hydrogen to produce water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxide ions there. As a result of this series of reactions taking place in the fuel cell, electricity is produced and, as a by-product, heat:

Reaction at the anode: 2H 2 + 4OH - => 4H 2 O + 4e -
Reaction at the cathode: O 2 + 2H 2 O + 4e - => 4 OH -
General reaction of the system: 2H 2 + O 2 => 2H 2 O

The advantage of SFCs is that these fuel cells are the cheapest to produce, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. SCFCs operate at relatively low temperatures and are among the most efficient fuel cells - such characteristics can respectively contribute to faster power generation and high fuel efficiency.

One of the characteristic features of SHTE is its high sensitivity to CO 2 , which can be contained in fuel or air. CO 2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SFCs is limited to closed spaces such as space and underwater vehicles, they must operate on pure hydrogen and oxygen. Moreover, molecules such as CO, H 2 O and CH4, which are safe for other fuel cells and even fuel for some of them, are detrimental to SFCs.

Polymer electrolyte fuel cells/cells (PETE)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which there is a conduction of water ions (H 2 O + (proton, red) attached to the water molecule). Water molecules present a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and on the exhaust electrodes, which limits the operating temperature to 100°C.

Solid acid fuel cells/cells (SCFC)

In solid acid fuel cells, the electrolyte (CsHSO 4 ) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO 4 2- oxy anions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two tightly compressed electrodes to ensure good contact. When heated, the organic component evaporates, leaving through the pores in the electrodes, retaining the ability of numerous contacts between the fuel (or oxygen at the other end of the cell), electrolyte and electrodes.

Innovative energy-saving municipal heat and power plants are typically built on solid oxide fuel cells (SOFCs), polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PCFCs), proton exchange membrane fuel cells (MPFCs) and alkaline fuel cells (APFCs) . They usually have the following characteristics:

Solid oxide fuel cells (SOFC) should be recognized as the most suitable, which:

• operate at a higher temperature, which reduces the need for expensive precious metals (such as platinum)
• can operate on various types of hydrocarbon fuels, mainly on natural gas
• have a longer start-up time and therefore are better suited for long-term operation
• demonstrate high efficiency of power generation (up to 70%)
• due to high operating temperatures, the units can be combined with heat recovery systems, bringing the overall system efficiency up to 85%
• have near-zero emissions, operate silently and have low operating requirements compared to existing power generation technologies

Fuel cell type	Working temperature	Power Generation Efficiency	Fuel type	Application area
RKTE	550–700°C	50-70%		Medium and large installations
FKTE	100–220°C	35-40%	pure hydrogen	Large installations
MOPTE	30-100°C	35-50%	pure hydrogen	Small installations
SOFC	450–1000°C	45-70%	Most hydrocarbon fuels	Small, medium and large installations
POMTE	20-90°C	20-30%	methanol	portable
SHTE	50–200°C	40-70%	pure hydrogen	space research
PETE	30-100°C	35-50%	pure hydrogen	Small installations

Since small thermal power plants can be connected to a conventional gas supply network, fuel cells do not require a separate hydrogen supply system. When using small thermal power plants based on solid oxide fuel cells, the generated heat can be integrated into heat exchangers for heating water and ventilation air, increasing the overall efficiency of the system. This innovative technology is best suited for efficient power generation without the need for expensive infrastructure and complex instrument integration.

Fuel cell/cell applications

Application of fuel cells/cells in telecommunication systems

With the rapid spread of wireless communication systems around the world, as well as the growing social and economic benefits of mobile phone technology, the need for reliable and cost-effective backup power has become critical. Grid losses throughout the year due to bad weather, natural disasters or limited grid capacity are a constant challenge for grid operators.

Traditional telecom power backup solutions include batteries (valve-regulated lead-acid battery cell) for short-term backup power and diesel and propane generators for longer backup power. Batteries are a relatively cheap source of backup power for 1 to 2 hours. However, batteries are not suitable for longer backup periods because they are expensive to maintain, become unreliable after long use, are sensitive to temperatures, and are hazardous to the environment after disposal. Diesel and propane generators can provide continuous backup power. However, generators can be unreliable, require extensive maintenance, and release high levels of pollutants and greenhouse gases into the atmosphere.

In order to eliminate the limitations of traditional backup power solutions, an innovative green fuel cell technology has been developed. Fuel cells are reliable, quiet, contain fewer moving parts than a generator, have a wider operating temperature range than a battery from -40°C to +50°C and, as a result, provide extremely high levels of energy savings. In addition, the lifetime cost of such a plant is lower than that of a generator. Lower fuel cell costs are the result of only one maintenance visit per year and significantly higher plant productivity. After all, the fuel cell is an environmentally friendly technology solution with minimal environmental impact.

Fuel cell units provide backup power for critical communications network infrastructures for wireless, permanent and broadband communications in the telecommunications system, ranging from 250W to 15kW, they offer many unrivaled innovative features:

• RELIABILITY– Few moving parts and no standby discharge
• ENERGY SAVING
• SILENCE– low noise level
• STABILITY– operating range from -40°C to +50°C
• ADAPTABILITY– outdoor and indoor installation (container/protective container)
• HIGH POWER– up to 15 kW
• LOW MAINTENANCE NEED– minimum annual maintenance
• ECONOMY- attractive total cost of ownership
• CLEAN ENERGY– low emissions with minimal environmental impact

The system senses the DC bus voltage all the time and smoothly accepts critical loads if the DC bus voltage drops below a user-defined setpoint. The system runs on hydrogen, which enters the fuel cell stack in one of two ways - either from a commercial source of hydrogen, or from a liquid fuel of methanol and water, using an on-board reformer system.

Electricity is produced by the fuel cell stack in the form of direct current. The DC power is sent to a converter that converts the unregulated DC power from the fuel cell stack into high quality, regulated DC power for the required loads. A fuel cell installation can provide backup power for many days, as the duration is limited only by the amount of hydrogen or methanol/water fuel available in stock.

Fuel cells offer superior energy efficiency, increased system reliability, more predictable performance in a wide range of climates, and reliable service life compared to industry standard valve regulated lead acid battery packs. Lifecycle costs are also lower due to significantly less maintenance and replacement requirements. Fuel cells offer the end user environmental benefits as disposal costs and liability risks associated with lead acid cells are a growing concern.

The performance of electric batteries can be adversely affected by a wide range of factors such as charge level, temperature, cycles, life and other variables. The energy provided will vary depending on these factors and is not easy to predict. The performance of a proton exchange membrane fuel cell (PEMFC) is relatively unaffected by these factors and can provide critical power as long as fuel is available. Increased predictability is an important benefit when moving to fuel cells for mission-critical backup power applications.

Fuel cells generate energy only when fuel is supplied, like a gas turbine generator, but do not have moving parts in the generation zone. Therefore, unlike a generator, they are not subject to rapid wear and do not require constant maintenance and lubrication.

The fuel used to drive the Extended Duration Fuel Converter is a mixture of methanol and water. Methanol is a widely available, commercial fuel that currently has many uses, including windshield washer, plastic bottles, engine additives, and emulsion paints. Methanol is easy to transport, miscible with water, has good biodegradability and is sulfur free. It has a low freezing point (-71°C) and does not decompose during long storage.

Application of fuel cells/cells in communication networks

Security networks require reliable backup power solutions that can last for hours or days in an emergency if the power grid becomes unavailable.

With few moving parts and no standby power reduction, the innovative fuel cell technology offers an attractive solution compared to currently available backup power systems.

The most compelling reason for using fuel cell technology in communications networks is the increased overall reliability and security. During events such as power outages, earthquakes, storms, and hurricanes, it is important that systems continue to operate and have a reliable backup power supply for an extended period of time, regardless of the temperature or age of the backup power system.

The range of fuel cell power supplies is ideal for supporting secure communications networks. Thanks to their energy saving design principles, they provide an environmentally friendly, reliable backup power with extended duration (up to several days) for use in the power range from 250 W to 15 kW.

Application of fuel cells/cells in data networks

Reliable power supply for data networks, such as high-speed data networks and fiber optic backbones, is of key importance throughout the world. Information transmitted over such networks contains critical data for institutions such as banks, airlines or medical centers. A power outage in such networks not only poses a danger to the transmitted information, but also, as a rule, leads to significant financial losses. Reliable, innovative fuel cell installations that provide standby power provide the reliability you need to ensure uninterrupted power.

Fuel cell units operating on a liquid fuel mixture of methanol and water provide a reliable backup power supply with extended duration, up to several days. In addition, these units feature significantly reduced maintenance requirements compared to generators and batteries, requiring only one maintenance visit per year.

Typical application characteristics for the use of fuel cell installations in data networks:

• Applications with power inputs from 100 W to 15 kW
• Applications with battery life requirements > 4 hours
• Repeaters in fiber optic systems (hierarchy of synchronous digital systems, high speed internet, voice over IP…)
• Network nodes of high-speed data transmission
• WiMAX Transmission Nodes

Fuel cell standby installations offer numerous advantages for critical data network infrastructures over traditional battery or diesel generators, allowing for increased on-site utilization:

1. Liquid fuel technology solves the problem of hydrogen storage and provides virtually unlimited backup power.
2. Due to their quiet operation, low weight, resistance to temperature extremes and virtually vibration-free operation, fuel cells can be installed outdoors, in industrial premises/containers or on rooftops.
3. On-site preparations for using the system are quick and economical, and the cost of operation is low.
4. The fuel is biodegradable and represents an environmentally friendly solution for the urban environment.

Application of fuel cells/cells in security systems

The most carefully designed building security and communication systems are only as reliable as the power that powers them. While most systems include some type of back-up uninterruptible power system for short-term power losses, they do not provide for the longer power outages that can occur after natural disasters or terrorist attacks. This could be a critical issue for many corporate and government agencies.

Vital systems such as CCTV monitoring and access control systems (ID card readers, door closing devices, biometric identification technology, etc.), automatic fire alarm and fire extinguishing systems, elevator control systems and telecommunication networks, are at risk in the absence of a reliable alternative source of continuous power supply.

Diesel generators are noisy, hard to locate, and are well aware of their reliability and maintenance issues. In contrast, a fuel cell back-up installation is quiet, reliable, has zero or very low emissions, and is easy to install on a rooftop or outside a building. It does not discharge or lose power in standby mode. It ensures the continued operation of critical systems, even after the institution ceases operations and the building is abandoned by people.

Innovative fuel cell installations protect expensive investments in critical applications. They provide environmentally friendly, reliable backup power with extended duration (up to many days) for use in the power range from 250 W to 15 kW, combined with numerous unsurpassed features and, especially, a high level of energy saving.

Fuel cell power backup units offer numerous advantages for mission critical applications such as security and building management systems over traditional battery or diesel generators. Liquid fuel technology solves the problem of hydrogen storage and provides virtually unlimited backup power.

Application of fuel cells/cells in domestic heating and power generation

Solid oxide fuel cells (SOFCs) are used to build reliable, energy-efficient and emission-free thermal power plants to generate electricity and heat from widely available natural gas and renewable fuel sources. These innovative units are used in a wide variety of markets, from domestic power generation to power supply to remote areas, as well as auxiliary power sources.

These energy-saving units produce heat for space heating and hot water, as well as electricity that can be used in the home and fed back into the power grid. Distributed power generation sources can include photovoltaic (solar) cells and micro wind turbines. These technologies are visible and widely known, but their operation is dependent on weather conditions and they cannot consistently generate electricity all year round. In terms of power, thermal power plants can vary from less than 1 kW to 6 MW and more.

Application of fuel cells/cells in distribution networks

Small thermal power plants are designed to operate in a distributed power generation network consisting of a large number of small generator sets instead of one centralized power plant.

The figure below shows the loss in efficiency of electricity generation when it is generated by CHP and transmitted to homes through the traditional transmission networks currently in use. Efficiency losses in district generation include losses from the power plant, low and high voltage transmission, and distribution losses.

The figure shows the results of the integration of small thermal power plants: electricity is generated with a generation efficiency of up to 60% at the point of use. In addition, the household can use the heat generated by the fuel cells for water and space heating, which increases the overall efficiency of fuel energy processing and improves energy savings.

Using Fuel Cells to Protect the Environment - Utilization of Associated Petroleum Gas

One of the most important tasks in the oil industry is the utilization of associated petroleum gas. The existing methods of utilization of associated petroleum gas have a lot of disadvantages, the main one being that they are not economically viable. Associated petroleum gas is flared, which causes great harm to the environment and human health.

Innovative fuel cell heat and power plants using associated petroleum gas as a fuel open the way to a radical and cost-effective solution to the problems of associated petroleum gas utilization.

1. One of the main advantages of fuel cell installations is that they can operate reliably and sustainably on variable composition associated petroleum gas. Due to the flameless chemical reaction underlying the operation of a fuel cell, a reduction in the percentage of, for example, methane only causes a corresponding reduction in power output.
2. Flexibility in relation to the electrical load of consumers, differential, load surge.
3. For the installation and connection of thermal power plants on fuel cells, their implementation does not require capital expenditures, because The units are easily mounted on unprepared sites near fields, are easy to operate, reliable and efficient.
4. High automation and modern remote control do not require the constant presence of personnel at the plant.
5. Simplicity and technical perfection of the design: the absence of moving parts, friction, lubrication systems provides significant economic benefits from the operation of fuel cell installations.
6. Water consumption: none at ambient temperatures up to +30 °C and negligible at higher temperatures.
7. Water outlet: none.
8. In addition, fuel cell thermal power plants do not make noise, do not vibrate,

Fuel cells are a way to electrochemically convert hydrogen fuel energy into electricity, and the only by-product of this process is water.

The hydrogen fuel currently used in fuel cells is usually derived from steam reforming of methane (i.e., converting hydrocarbons with steam and heat to methane), although the approach could be greener, such as electrolysis of water using solar energy.

The main components of a fuel cell are:

• an anode in which hydrogen is oxidized;
• cathode, where oxygen is reduced;
• a polymer electrolyte membrane through which protons or hydroxide ions are transported (depending on the medium) - it does not allow hydrogen and oxygen to pass through;
• flow fields of oxygen and hydrogen, which are responsible for the delivery of these gases to the electrode.

In order to power, for example, a car, several fuel cells are assembled into a battery, and the amount of energy supplied by this battery depends on the total area of ​​the electrodes and the number of cells in it. Energy in a fuel cell is generated as follows: hydrogen is oxidized at the anode, and the electrons from it are sent to the cathode, where oxygen is reduced. The electrons obtained from the oxidation of hydrogen at the anode have a higher chemical potential than the electrons that reduce oxygen at the cathode. This difference between the chemical potentials of the electrons makes it possible to extract energy from fuel cells.

History of creation

The history of fuel cells goes back to the 1930s, when the first hydrogen fuel cell was designed by William R. Grove. This cell used sulfuric acid as the electrolyte. Grove tried to deposit copper from an aqueous solution of copper sulfate onto an iron surface. He noticed that under the action of an electron current, water decomposes into hydrogen and oxygen. After this discovery, Grove and Christian Schoenbein, a chemist at the University of Basel (Switzerland), who worked in parallel with him, simultaneously demonstrated in 1839 the possibility of generating energy in a hydrogen-oxygen fuel cell using an acidic electrolyte. These early attempts, although quite primitive in nature, attracted the attention of several of their contemporaries, including Michael Faraday.

Research into fuel cells continued, and in the 1930s F.T. Bacon introduced a new component to an alkaline fuel cell (one of the types of fuel cells) - an ion-exchange membrane to facilitate the transport of hydroxide ions.

One of the most famous historical examples of the use of alkaline fuel cells is their use as the main source of energy during space flights in the Apollo program.

They were chosen by NASA for their durability and technical stability. They used a hydroxide-conducting membrane that was superior in efficiency to its proton-exchange sister.

For almost two centuries since the creation of the first fuel cell prototype, a lot of work has been done to improve them. In general, the final energy obtained from a fuel cell depends on the kinetics of the redox reaction, the internal resistance of the cell, and the mass transfer of the reacting gases and ions to the catalytically active components. Over the years, many improvements have been made to the original idea, such as:

1) replacement of platinum wires with electrodes based on carbon with platinum nanoparticles; 2) the invention of membranes of high conductivity and selectivity, such as Nafion, to facilitate ion transport; 3) combining the catalytic layer, for example, platinum nanoparticles, distributed over a carbon base, with ion-exchange membranes, resulting in a membrane-electrode unit with a minimum internal resistance; 4) use and optimization of flow fields to deliver hydrogen and oxygen to the catalytic surface, instead of directly diluting them in solution.

These and other improvements eventually resulted in a technology that was efficient enough to be used in vehicles such as the Toyota Mirai.

Fuel cells with hydroxide exchange membranes

The University of Delaware is conducting research on the development of fuel cells with hydroxide exchange membranes - HEMFCs (hydroxide exchange membrane fuel cells). Fuel cells with hydroxide exchange membranes instead of proton exchange membranes - PEMFCs (proton exchange membrane fuel cells) - face less one of the big problems of PEMFCs - the problem of catalyst stability, since many more base metal catalysts are stable in an alkaline environment than in an acidic one. The stability of catalysts in alkaline solutions is higher due to the fact that the dissolution of metals releases more energy at low pH than at high pH. Most of the work in this laboratory is also devoted to the development of new anodic and cathodic catalysts for hydrogen oxidation and oxygen reduction reactions to accelerate them even more efficiently. In addition, the laboratory is developing new hydroxide exchange membranes, as the conductivity and durability of such membranes have yet to be improved in order to compete with proton exchange membranes.

Search for new catalysts

The reason for the overvoltage losses in the oxygen reduction reaction is explained by the linear scale relationships between the intermediate products of this reaction. In the traditional four-electron mechanism of this reaction, oxygen is reduced sequentially, creating intermediate products - OOH*, O* and OH*, to eventually form water (H2O) on the catalytic surface. Since the adsorption energies of intermediate products on an individual catalyst are highly correlated with each other, no catalyst has yet been found that, at least in theory, would not have overvoltage losses. Although the rate of this reaction is low, changing from an acidic medium to an alkaline medium, such as in HEMFC, does not affect it much. However, the rate of the hydrogen oxidation reaction is almost halved, and this fact motivates research aimed at finding the cause of this decrease and the discovery of new catalysts.

Advantages of fuel cells

In contrast to hydrocarbon fuels, fuel cells are more, if not perfectly, environmentally friendly and do not produce greenhouse gases as a result of their activities. Moreover, their fuel (hydrogen) is in principle renewable, since it can be obtained by hydrolysis of water. Thus, hydrogen fuel cells in the future promise to become a full part of the energy production process, in which solar and wind energy is used to produce hydrogen fuel, which is then used in a fuel cell to produce water. Thus, the cycle is closed and no carbon footprint is left.

Unlike rechargeable batteries, fuel cells have the advantage that they do not need to be recharged - they can immediately start supplying energy as soon as it is needed. That is, if they are applied, for example, in the field of vehicles, then there will be almost no changes on the part of the consumer. Unlike solar energy and wind energy, fuel cells can produce energy continuously and are much less dependent on external conditions. In turn, geothermal energy is only available in certain geographic areas, while fuel cells again do not have this problem.

Hydrogen fuel cells are one of the most promising energy sources due to their portability and flexibility in terms of scale.

Complexity of hydrogen storage

In addition to the problems with the shortcomings of the current membranes and catalysts, other technical difficulties for fuel cells are associated with the storage and transport of hydrogen fuel. Hydrogen has a very low specific energy per unit volume (the amount of energy per unit volume at a given temperature and pressure) and therefore must be stored at very high pressure to be used in vehicles. Otherwise, the size of the container for storing the required amount of fuel will be impossibly large. Because of these hydrogen storage limitations, attempts have been made to find ways to produce hydrogen from something other than its gaseous form, such as in metal hydride fuel cells. However, current consumer fuel cell applications, such as the Toyota Mirai, use supercritical hydrogen (hydrogen that is at temperatures above 33 K and pressures above 13.3 atmospheres, that is, above critical values), and this is now the most convenient option.

Perspectives of the region

Due to the existing technical difficulties and problems of obtaining hydrogen from water using solar energy, in the near future, research is likely to focus mainly on finding alternative sources of hydrogen. One popular idea is to use ammonia (hydrogen nitride) directly in the fuel cell instead of hydrogen, or to make hydrogen from ammonia. The reason for this is that ammonia is less demanding in terms of pressure, which makes it more convenient to store and move. In addition, ammonia is attractive as a source of hydrogen because it does not contain carbon. This solves the problem of catalyst poisoning due to some CO in the hydrogen produced from methane.

In the future, fuel cells may find wide applications in vehicle technology and distributed energy generation, such as in residential areas. Despite the fact that at the moment the use of fuel cells as the main source of energy requires a lot of money, if cheaper and more efficient catalysts, stable membranes with high conductivity and alternative sources of hydrogen are found, hydrogen fuel cells can become highly economically attractive.

A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into electricity through a chemical reaction. As a result of this process, water is formed and a large amount of heat is released. A fuel cell is very similar to a battery that can be charged and then used to store electrical energy.
The inventor of the fuel cell is William R. Grove, who invented it back in 1839. This fuel cell used a sulfuric acid solution as an electrolyte, and hydrogen as a fuel, which combined with oxygen in an oxidizer medium. It should be noted that, until recently, fuel cells were used only in laboratories and on spacecraft.
In the future, fuel cells will be able to compete with many other energy conversion systems (including gas turbines in power plants), internal combustion engines in cars and electric batteries in portable devices. Internal combustion engines burn fuel and use the pressure created by the expansion of combustion gases to perform mechanical work. Batteries store electrical energy and then convert it into chemical energy, which can be converted back into electrical energy if needed. Potentially, fuel cells are very efficient. Back in 1824, the French scientist Carnot proved that the compression-expansion cycles of an internal combustion engine cannot ensure the efficiency of converting thermal energy (which is the chemical energy of burning fuel) into mechanical energy above 50%. A fuel cell has no moving parts (at least not inside the cell itself), and therefore they do not obey Carnot's law. Naturally, they will have more than 50% efficiency and are especially effective at low loads. Thus, fuel cell vehicles are poised to be (and have already proven to be) more fuel efficient than conventional vehicles in real driving conditions.
The fuel cell generates DC electrical current that can be used to drive an electric motor, lighting fixtures, and other electrical systems in a vehicle. There are several types of fuel cells, differing in the chemical processes used. Fuel cells are usually classified by the type of electrolyte they use. Some types of fuel cells are promising for use in power plants, while others may be useful for small portable devices or for driving cars.
The alkaline fuel cell is one of the earliest developed elements. They have been used by the US space program since the 1960s. Such fuel cells are very susceptible to contamination and therefore require very pure hydrogen and oxygen. In addition, they are very expensive, and therefore this type of fuel cell is unlikely to find wide application in cars.
Fuel cells based on phosphoric acid can be used in stationary installations of low power. They operate at fairly high temperatures and therefore take a long time to warm up, which also makes them inefficient for use in automobiles.
Solid oxide fuel cells are better suited for large stationary power generators that could provide electricity to factories or communities. This type of fuel cell operates at very high temperatures (about 1000 °C). The high operating temperature creates certain problems, but on the other hand, there is an advantage - the steam produced by the fuel cell can be sent to turbines to generate more electricity. Overall, this improves the overall efficiency of the system.
One of the most promising systems is the proton exchange membrane fuel cell - POMFC (PEMFC - Protone Exchange Membrane Fuel Cell). At the moment, this type of fuel cell is the most promising because it can propel cars, buses and other vehicles.

Chemical processes in a fuel cell

Fuel cells use an electrochemical process to combine hydrogen with oxygen from the air. Like batteries, fuel cells use electrodes (solid electrical conductors) in an electrolyte (an electrically conductive medium). When hydrogen molecules come into contact with the negative electrode (anode), the latter are separated into protons and electrons. The protons pass through the proton exchange membrane (POM) to the positive electrode (cathode) of the fuel cell, producing electricity. There is a chemical combination of hydrogen and oxygen molecules with the formation of water, as a by-product of this reaction. The only type of emissions from a fuel cell is water vapour.
The electricity produced by fuel cells can be used in the vehicle's electrical powertrain (consisting of an electrical power converter and an AC induction motor) to provide mechanical energy to propel the vehicle. The job of the power converter is to convert the direct current produced by the fuel cells into alternating current, which is used by the vehicle's traction motor.

Schematic diagram of a fuel cell with a proton-exchange membrane:
1 - anode;
2 - proton-exchange membrane (REM);
3 - catalyst (red);
4 - cathode

The Proton Exchange Membrane Fuel Cell (PEMFC) uses one of the simplest reactions of any fuel cell.

Separate fuel cell

Consider how a fuel cell works. The anode, the negative pole of the fuel cell, conducts the electrons, which are freed from hydrogen molecules so that they can be used in an external electrical circuit (circuit). To do this, channels are engraved in it, distributing hydrogen evenly over the entire surface of the catalyst. The cathode (positive pole of the fuel cell) has engraved channels that distribute oxygen over the surface of the catalyst. It also conducts electrons back from the outer circuit (circuit) to the catalyst, where they can combine with hydrogen ions and oxygen to form water. The electrolyte is a proton-exchange membrane. This is a special material, similar to ordinary plastic, but with the ability to pass positively charged ions and block the passage of electrons.
A catalyst is a special material that facilitates the reaction between oxygen and hydrogen. The catalyst is usually made from platinum powder deposited in a very thin layer on carbon paper or cloth. The catalyst must be rough and porous so that its surface can come into contact with hydrogen and oxygen as much as possible. The platinum coated side of the catalyst is in front of the proton exchange membrane (POM).
Hydrogen gas (H 2 ) is supplied to the fuel cell under pressure from the anode side. When the H2 molecule comes into contact with the platinum on the catalyst, it splits into two parts, two ions (H+) and two electrons (e–). The electrons are conducted through the anode, where they pass through an external circuit (circuit), doing useful work (for example, driving an electric motor) and returning from the cathode side of the fuel cell.
Meanwhile, from the cathode side of the fuel cell, oxygen gas (O 2 ) is forced through the catalyst where it forms two oxygen atoms. Each of these atoms has a strong negative charge that attracts two H+ ions across the membrane, where they combine with an oxygen atom and two electrons from the outer loop (chain) to form a water molecule (H 2 O).
This reaction in a single fuel cell produces a power of approximately 0.7 watts. In order to raise the power to the required level, it is necessary to combine many individual fuel cells to form a fuel cell stack.
POM fuel cells operate at a relatively low temperature (about 80°C), which means that they can be quickly heated to operating temperature and do not require expensive cooling systems. Continuous improvement in the technologies and materials used in these cells has brought their power closer to a level where a battery of such fuel cells, occupying a small part of the trunk of a car, can provide the energy needed to drive a car.
Over the past years, most of the world's leading car manufacturers have invested heavily in the development of car designs using fuel cells. Many have already demonstrated fuel cell vehicles with satisfactory power and dynamic characteristics, although they were quite expensive.
Improving the design of such cars is very intensive.

Fuel cell vehicle, uses a power plant located under the floor of the vehicle

The NECAR V vehicle is based on the Mercedes-Benz A-class vehicle, with the entire power plant, together with the fuel cells, located under the floor of the vehicle. Such a constructive solution makes it possible to accommodate four passengers and luggage in the car. Here, not hydrogen, but methanol is used as fuel for the car. Methanol with the help of a reformer (a device that converts methanol into hydrogen) is converted into hydrogen, which is necessary to power the fuel cell. The use of a reformer on board a car makes it possible to use almost any hydrocarbon as a fuel, which makes it possible to refuel a fuel cell car using the existing filling station network. Theoretically, fuel cells produce nothing but electricity and water. Converting the fuel (gasoline or methanol) to the hydrogen required for the fuel cell somewhat reduces the environmental appeal of such a vehicle.
Honda, which has been in the fuel cell business since 1989, produced a small batch of Honda FCX-V4 vehicles in 2003 with Ballard's proton-exchange membrane-type fuel cells. These fuel cells generate 78 kW of electric power, and traction motors with a power of 60 kW and a torque of 272 N m are used to drive the drive wheels. it has excellent dynamics, and the supply of compressed hydrogen makes it possible to run up to 355 km.

The Honda FCX uses fuel cell power to propel itself.
The Honda FCX is the world's first fuel cell vehicle to receive government certification in the United States. The car is ZEV certified - Zero Emission Vehicle (zero pollution vehicle). Honda is not going to sell these cars yet, but leases about 30 cars per unit. California and Tokyo, where hydrogen fueling infrastructure already exists.

General Motors' Hy Wire concept car has a fuel cell power plant

Large research on the development and creation of fuel cell vehicles is being conducted by General Motors.

Hy Wire Vehicle Chassis

The GM Hy Wire concept car has received 26 patents. The basis of the car is a functional platform with a thickness of 150 mm. Inside the platform are hydrogen cylinders, a fuel cell power plant and vehicle control systems using the latest electronic control-by-wire technology. The chassis of the Hy Wire car is a thin platform that contains all the main structural elements of the car: hydrogen cylinders, fuel cells, batteries, electric motors and control systems. This approach to design makes it possible to change car bodies during operation. The company also tests experimental Opel fuel cell vehicles and designs a fuel cell production plant.

Design of a "safe" fuel tank for liquefied hydrogen:
1 - filling device;
2 - outer tank;
3 - supports;
4 - level sensor;
5 - internal tank;
6 - filling line;
7 - insulation and vacuum;
8 - heater;
9 - mounting box

The problem of using hydrogen as a fuel for cars is paid much attention to by BMW. Together with Magna Steyer, known for its work on the use of liquefied hydrogen in space research, BMW has developed a liquefied hydrogen fuel tank that can be used in cars.

Tests have confirmed the safety of using a fuel tank with liquid hydrogen

The company conducted a series of tests on the safety of the structure according to standard methods and confirmed its reliability.
In 2002, at the Frankfurt Motor Show (Germany), the Mini Cooper Hydrogen was shown, which uses liquefied hydrogen as fuel. The fuel tank of this car takes up the same space as a conventional gas tank. Hydrogen in this car is not used for fuel cells, but as fuel for internal combustion engines.

The world's first mass-produced car with a fuel cell instead of a battery

In 2003, BMW announced the launch of the first mass-produced fuel cell vehicle, the BMW 750 hL. A fuel cell battery is used instead of a traditional battery. This car has a 12-cylinder internal combustion engine running on hydrogen, and the fuel cell serves as an alternative to a conventional battery, allowing the air conditioner and other consumers to work when the car is parked for a long time with the engine off.

Hydrogen refueling is performed by a robot, the driver is not involved in this process

The same company BMW has also developed robotic fuel dispensers that provide fast and safe refueling of cars with liquefied hydrogen.
The emergence in recent years of a large number of developments aimed at creating cars using alternative fuels and alternative propulsion systems indicates that internal combustion engines, which dominated cars for the past century, will eventually give way to cleaner, more efficient and silent designs. Their widespread use is currently being held back not by technical, but rather by economic and social problems. For their widespread use, it is necessary to create a certain infrastructure for the development of the production of alternative fuels, the creation and distribution of new gas stations and to overcome a number of psychological barriers. The use of hydrogen as a vehicle fuel will require storage, delivery and distribution issues to be addressed, with serious safety measures in place.
Theoretically, hydrogen is available in unlimited quantities, but its production is very energy intensive. In addition, in order to convert cars to work on hydrogen fuel, two big changes in the power system must be made: first, transferring its operation from gasoline to methanol, and then, for some time, to hydrogen. It will be some time before this issue is resolved.

Description:

This article discusses in more detail their structure, classification, advantages and disadvantages, scope, efficiency, history of creation and modern prospects for use.

Using fuel cells to power buildings

Part 1

This article discusses in more detail the principle of operation of fuel cells, their design, classification, advantages and disadvantages, scope, efficiency, history of creation and modern prospects for use. In the second part of the article, which will be published in the next issue of the ABOK magazine, provides examples of facilities where various types of fuel cells were used as sources of heat and electricity (or only electricity).

Introduction

Fuel cells are a very efficient, reliable, durable and environmentally friendly way to generate energy.

Initially used only in the space industry, fuel cells are now increasingly being used in a variety of areas - such as stationary power plants, heat and power supply of buildings, vehicle engines, power supplies for laptops and mobile phones. Some of these devices are laboratory prototypes, some are undergoing pre-series testing or are used for demonstration purposes, but many models are mass-produced and used in commercial projects.

A fuel cell (electrochemical generator) is a device that converts the chemical energy of fuel (hydrogen) into electrical energy in the process of an electrochemical reaction directly, unlike traditional technologies that use the combustion of solid, liquid and gaseous fuels. Direct electrochemical conversion of fuel is very efficient and attractive from an environmental point of view, since the minimum amount of pollutants is released during operation, and there are no strong noises and vibrations.

From a practical point of view, a fuel cell resembles a conventional galvanic battery. The difference lies in the fact that initially the battery is charged, i.e. filled with “fuel”. During operation, "fuel" is consumed and the battery is discharged. Unlike a battery, a fuel cell uses fuel supplied from an external source to generate electrical energy (Fig. 1).

For the production of electrical energy, not only pure hydrogen can be used, but also other hydrogen-containing raw materials, such as natural gas, ammonia, methanol or gasoline. Ordinary air is used as a source of oxygen, which is also necessary for the reaction.

When pure hydrogen is used as a fuel, the reaction products, in addition to electrical energy, are heat and water (or water vapor), i.e. no gases are emitted into the atmosphere that cause air pollution or cause a greenhouse effect. If a hydrogen-containing feedstock, such as natural gas, is used as a fuel, other gases, such as oxides of carbon and nitrogen, will be a by-product of the reaction, but its amount is much lower than when burning the same amount of natural gas.

The process of chemical conversion of fuel in order to produce hydrogen is called reforming, and the corresponding device is called a reformer.

Advantages and disadvantages of fuel cells

Fuel cells are more energy efficient than internal combustion engines because there is no thermodynamic limitation on energy efficiency for fuel cells. The efficiency of fuel cells is 50%, while the efficiency of internal combustion engines is 12-15%, and the efficiency of steam turbine power plants does not exceed 40%. By using heat and water, the efficiency of fuel cells is further increased.

In contrast to, for example, internal combustion engines, the efficiency of fuel cells remains very high even when they are not operating at full power. In addition, the power of fuel cells can be increased by simply adding separate blocks, while the efficiency does not change, i.e. large installations are as efficient as small ones. These circumstances allow a very flexible selection of the composition of equipment in accordance with the wishes of the customer and ultimately lead to a reduction in equipment costs.

An important advantage of fuel cells is their environmental friendliness. Air emissions from fuel cells are so low that in some parts of the United States they do not require special permits from government air quality agencies.

Fuel cells can be placed directly in the building, thus reducing energy transmission losses, and the heat generated as a result of the reaction can be used to supply heat or hot water to the building. Autonomous sources of heat and power supply can be very beneficial in remote areas and in regions that are characterized by a shortage of electricity and its high cost, but at the same time there are reserves of hydrogen-containing raw materials (oil, natural gas).

The advantages of fuel cells are also the availability of fuel, reliability (there are no moving parts in the fuel cell), durability and ease of operation.

One of the main shortcomings of fuel cells today is their relatively high cost, but this shortcoming can be overcome soon - more and more companies produce commercial samples of fuel cells, they are constantly being improved, and their cost is decreasing.

The most efficient use of pure hydrogen as a fuel, however, this will require the creation of a special infrastructure for its generation and transportation. Currently, all commercial designs use natural gas and similar fuels. Motor vehicles can use ordinary gasoline, which will allow maintaining the existing developed network of gas stations. However, the use of such fuel leads to harmful emissions into the atmosphere (albeit very low) and complicates (and therefore increases the cost of) the fuel cell. In the future, the possibility of using environmentally friendly renewable energy sources (for example, solar energy or wind energy) is being considered to decompose water into hydrogen and oxygen by electrolysis, and then convert the resulting fuel in a fuel cell. Such combined plants operating in a closed cycle can be a completely environmentally friendly, reliable, durable and efficient source of energy.

Another feature of fuel cells is that they are most efficient when using both electrical and thermal energy at the same time. However, the possibility of using thermal energy is not available at every facility. In the case of using fuel cells only for generating electrical energy, their efficiency decreases, although it exceeds the efficiency of “traditional” installations.

History and modern uses of fuel cells

The principle of operation of fuel cells was discovered in 1839. The English scientist William Grove (1811-1896) discovered that the process of electrolysis - the decomposition of water into hydrogen and oxygen by means of an electric current - is reversible, i.e. hydrogen and oxygen can be combined into water molecules without combustion, but with the release of heat and electric current. Grove called the device in which such a reaction was carried out a "gas battery", which was the first fuel cell.

The active development of fuel cell technologies began after the Second World War, and it is associated with the aerospace industry. At that time, searches were conducted for an efficient and reliable, but at the same time quite compact source of energy. In the 1960s, NASA specialists (National Aeronautics and Space Administration, NASA) chose fuel cells as a power source for spacecraft of the Apollo (manned flights to the Moon), Apollo-Soyuz, Gemini and Skylab programs. . The Apollo used three 1.5 kW units (2.2 kW peak power) using cryogenic hydrogen and oxygen to produce electricity, heat and water. The mass of each installation was 113 kg. These three cells worked in parallel, but the energy generated by one unit was enough for a safe return. During 18 flights, the fuel cells have accumulated a total of 10,000 hours without any failures. Currently, fuel cells are used in the space shuttle "Space Shuttle", which uses three units with a power of 12 W, which generate all the electrical energy on board the spacecraft (Fig. 2). Water obtained as a result of an electrochemical reaction is used as drinking water, as well as for cooling equipment.

In our country, work was also underway to create fuel cells for use in astronautics. For example, fuel cells were used to power the Soviet Buran space shuttle.

Development of methods for the commercial use of fuel cells began in the mid-1960s. These developments were partially funded by government organizations.

Currently, the development of technologies for the use of fuel cells goes in several directions. This is the creation of stationary power plants on fuel cells (for both centralized and decentralized energy supply), power plants of vehicles (samples of cars and buses on fuel cells have been created, including in our country) (Fig. 3), and also power supplies for various mobile devices (laptops, mobile phones, etc.) (Fig. 4).

Examples of the use of fuel cells in various fields are given in Table. one.

One of the first commercial models of fuel cells designed for autonomous heat and power supply of buildings was the PC25 Model A manufactured by ONSI Corporation (now United Technologies, Inc.). This fuel cell with a nominal power of 200 kW belongs to the type of cells with an electrolyte based on phosphoric acid (Phosphoric Acid Fuel Cells, PAFC). The number "25" in the name of the model means the serial number of the design. Most of the previous models were experimental or test pieces, such as the 12.5 kW "PC11" model that appeared in the 1970s. The new models increased the power taken from a single fuel cell, and also reduced the cost per kilowatt of energy produced. Currently, one of the most efficient commercial models is the PC25 Model C fuel cell. Like model "A", this is a fully automatic fuel cell of the PAFC type with a power of 200 kW, designed to be installed directly on the serviced object as an independent source of heat and electricity. Such a fuel cell can be installed outside the building. Outwardly, it is a parallelepiped 5.5 m long, 3 m wide and 3 m high, weighing 18,140 kg. The difference from previous models is an improved reformer and a higher current density.

Table 1 Scope of fuel cells

Region applications Rated power Examples of using Stationary installations 5–250 kW and above Autonomous sources of heat and power supply for residential, public and industrial buildings, uninterruptible power supplies, backup and emergency power supplies Portable installations 1–50 kW Road signs, refrigerated trucks and railroads, wheelchairs, golf carts, spacecraft and satellites Mobile installations 25–150 kW Cars (prototypes were created, for example, by DaimlerCrysler, FIAT, Ford, General Motors, Honda, Hyundai, Nissan, Toyota, Volkswagen, VAZ), buses ( e.g. MAN, Neoplan, Renault) and other vehicles, warships and submarines Microdevices 1-500W Mobile phones, laptops, PDAs, various consumer electronic devices, modern military devices

In some types of fuel cells, the chemical process can be reversed: by applying a potential difference to the electrodes, water can be decomposed into hydrogen and oxygen, which are collected on porous electrodes. When a load is connected, such a regenerative fuel cell will begin to generate electrical energy.

A promising direction for the use of fuel cells is their use in conjunction with renewable energy sources, such as photovoltaic panels or wind turbines. This technology allows you to completely avoid air pollution. A similar system is planned to be created, for example, at the Adam Joseph Lewis Training Center in Oberlin (see ABOK, 2002, No. 5, p. 10). Currently, solar panels are used as one of the energy sources in this building. Together with NASA specialists, a project was developed to use photovoltaic panels to produce hydrogen and oxygen from water by electrolysis. The hydrogen is then used in fuel cells to generate electrical energy and hot water. This will allow the building to maintain the performance of all systems during cloudy days and at night.

The principle of operation of fuel cells

Let us consider the principle of operation of a fuel cell using the simplest element with a proton exchange membrane (Proton Exchange Membrane, PEM) as an example. Such an element consists of a polymer membrane placed between the anode (positive electrode) and the cathode (negative electrode) together with the anode and cathode catalysts. A polymer membrane is used as the electrolyte. The diagram of the PEM element is shown in fig. 5.

A proton exchange membrane (PEM) is a thin (approximately 2-7 sheets of plain paper thick) solid organic compound. This membrane functions as an electrolyte: it separates matter into positively and negatively charged ions in the presence of water.

An oxidative process occurs at the anode, and a reduction process occurs at the cathode. The anode and cathode in the PEM cell are made of a porous material, which is a mixture of particles of carbon and platinum. Platinum acts as a catalyst that promotes the dissociation reaction. The anode and cathode are made porous for free passage of hydrogen and oxygen through them, respectively.

The anode and cathode are placed between two metal plates, which supply hydrogen and oxygen to the anode and cathode, and remove heat and water, as well as electrical energy.

Hydrogen molecules pass through the channels in the plate to the anode, where the molecules decompose into individual atoms (Fig. 6).

	Figure 5 () Schematic diagram of a proton exchange membrane (PEM) fuel cell
	Figure 6 () Hydrogen molecules through the channels in the plate enter the anode, where the molecules are decomposed into individual atoms
	Figure 7 () As a result of chemisorption in the presence of a catalyst, hydrogen atoms are converted into protons
	Figure 8 () Positively charged hydrogen ions diffuse through the membrane to the cathode, and the electron flow is directed to the cathode through an external electrical circuit to which the load is connected.
	Figure 9 () Oxygen supplied to the cathode, in the presence of a catalyst, enters into a chemical reaction with hydrogen ions from the proton-exchange membrane and electrons from the external electrical circuit. Water is formed as a result of a chemical reaction

Then, as a result of chemisorption in the presence of a catalyst, hydrogen atoms, each donating one electron e - , are converted into positively charged hydrogen ions H +, i.e. protons (Fig. 7).

Positively charged hydrogen ions (protons) diffuse through the membrane to the cathode, and the electron flow is directed to the cathode through an external electrical circuit to which the load (consumer of electrical energy) is connected (Fig. 8).

Oxygen supplied to the cathode, in the presence of a catalyst, enters into a chemical reaction with hydrogen ions (protons) from the proton exchange membrane and electrons from the external electrical circuit (Fig. 9). As a result of a chemical reaction, water is formed.

The chemical reaction in a fuel cell of other types (for example, with an acidic electrolyte, which is a solution of phosphoric acid H 3 PO 4) is absolutely identical to the chemical reaction in a fuel cell with a proton exchange membrane.

In any fuel cell, part of the energy of a chemical reaction is released as heat.

The flow of electrons in an external circuit is a direct current that is used to do work. Opening the external circuit or stopping the movement of hydrogen ions stops the chemical reaction.

The amount of electrical energy produced by a fuel cell depends on the type of fuel cell, geometric dimensions, temperature, gas pressure. A single fuel cell provides an EMF of less than 1.16 V. It is possible to increase the size of the fuel cells, but in practice several cells are used, connected in batteries (Fig. 10).

Fuel cell device

Let's consider the fuel cell device on the example of the PC25 Model C model. The scheme of the fuel cell is shown in fig. eleven.

The fuel cell "PC25 Model C" consists of three main parts: the fuel processor, the actual power generation section and the voltage converter.

The main part of the fuel cell - the power generation section - is a stack composed of 256 individual fuel cells. The composition of the fuel cell electrodes includes a platinum catalyst. Through these cells, a direct electric current of 1,400 amperes is generated at a voltage of 155 volts. The dimensions of the battery are approximately 2.9 m in length and 0.9 m in width and height.

Since the electrochemical process takes place at a temperature of 177 ° C, it is necessary to heat the battery at the time of start-up and remove heat from it during operation. To do this, the fuel cell includes a separate water circuit, and the battery is equipped with special cooling plates.

The fuel processor allows you to convert natural gas into hydrogen, which is necessary for an electrochemical reaction. This process is called reforming. The main element of the fuel processor is the reformer. In the reformer, natural gas (or other hydrogen-containing fuel) reacts with steam at high temperature (900 °C) and high pressure in the presence of a nickel catalyst. The following chemical reactions take place:

CH 4 (methane) + H 2 O 3H 2 + CO

(reaction endothermic, with heat absorption);

CO + H 2 O H 2 + CO 2

(the reaction is exothermic, with the release of heat).

The overall reaction is expressed by the equation:

CH 4 (methane) + 2H 2 O 4H 2 + CO 2

(reaction endothermic, with heat absorption).

To provide the high temperature required for natural gas conversion, a portion of the spent fuel from the fuel cell stack is directed to a burner that maintains the reformer at the required temperature.

The steam required for reforming is generated from the condensate formed during the operation of the fuel cell. In this case, the heat removed from the fuel cell stack is used (Fig. 12).

The fuel cell stack generates an intermittent direct current, which is characterized by low voltage and high current. A voltage converter is used to convert it to industrial standard AC. In addition, the voltage converter unit includes various control devices and safety interlock circuits that allow the fuel cell to be turned off in the event of various failures.

In such a fuel cell, approximately 40% of the energy in the fuel can be converted into electrical energy. Approximately the same amount, about 40% of the fuel energy, can be converted into, which is then used as a heat source for heating, hot water supply and similar purposes. Thus, the total efficiency of such a plant can reach 80%.

An important advantage of such a source of heat and electricity is the possibility of its automatic operation. For maintenance, the owners of the facility on which the fuel cell is installed do not need to maintain specially trained personnel - periodic maintenance can be carried out by employees of the operating organization.

Fuel cell types

Currently, several types of fuel cells are known, which differ in the composition of the electrolyte used. The following four types are most widespread (Table 2):

1. Fuel cells with proton exchange membrane (Proton Exchange Membrane Fuel Cells, PEMFC).

2. Fuel cells based on orthophosphoric (phosphoric) acid (Phosphoric Acid Fuel Cells, PAFC).

3. Fuel cells based on molten carbonate (Molten Carbonate Fuel Cells, MCFC).

4. Solid oxide fuel cells (Solid Oxide Fuel Cells, SOFC). Currently, the largest fleet of fuel cells is built on the basis of PAFC technology.

One of the key characteristics of different types of fuel cells is the operating temperature. In many ways, it is the temperature that determines the scope of fuel cells. For example, high temperatures are critical for laptops, so proton exchange membrane fuel cells with low operating temperatures are being developed for this market segment.

For autonomous power supply of buildings, fuel cells of high installed capacity are required, and at the same time it is possible to use thermal energy, therefore, fuel cells of other types can also be used for these purposes.

Proton Exchange Membrane Fuel Cells (PEMFC)

These fuel cells operate at relatively low operating temperatures (60-160°C). They are characterized by high power density, allow you to quickly adjust the output power, and can be quickly turned on. The disadvantage of this type of elements is the high requirements for fuel quality, since contaminated fuel can damage the membrane. The nominal power of fuel cells of this type is 1-100 kW.

Proton exchange membrane fuel cells were originally developed by the General Electric Corporation in the 1960s for NASA. This type of fuel cell uses a solid state polymer electrolyte called a Proton Exchange Membrane (PEM). Protons can move through the proton exchange membrane, but electrons cannot pass through it, resulting in a potential difference between the cathode and anode. Due to their simplicity and reliability, such fuel cells were used as a power source on the Gemini manned spacecraft.

This type of fuel cell is used as a power source for a wide range of different devices, including prototypes and prototypes, from mobile phones to buses and stationary power systems. The low operating temperature allows such cells to be used to power various types of complex electronic devices. Less efficient is their use as a source of heat and power supply for public and industrial buildings, where large amounts of thermal energy are required. At the same time, such elements are promising as an autonomous source of power supply for small residential buildings such as cottages built in regions with a hot climate.

table 2 Fuel cell types

Item Type workers temperature, °С efficiency output electrical energy), % Total Efficiency, % Fuel cells with proton exchange membrane (PEMFC) 60–160 30–35 50–70 fuel cells based on orthophosphoric (phosphoric) acid (PAFC) 150–200 35 70–80 Fuel cells based molten carbonate (MCFC) 600–700 45–50 70–80 Solid state oxide fuel cells (SOFC) 700–1 000 50–60 70–80

Phosphoric Acid Fuel Cells (PAFC)

Tests of fuel cells of this type were already carried out in the early 1970s. Operating temperature range - 150-200 °C. The main area of ​​application is autonomous sources of heat and power supply of medium power (about 200 kW).

The electrolyte used in these fuel cells is a solution of phosphoric acid. The electrodes are made of paper coated with carbon, in which a platinum catalyst is dispersed.

The electrical efficiency of PAFC fuel cells is 37-42%. However, since these fuel cells operate at a sufficiently high temperature, it is possible to use the steam generated as a result of operation. In this case, the overall efficiency can reach 80%.

To generate energy, the hydrogen-containing feedstock must be converted to pure hydrogen through a reforming process. For example, if gasoline is used as a fuel, then sulfur compounds must be removed, since sulfur can damage the platinum catalyst.

PAFC fuel cells were the first commercial fuel cells to be economically justified. The most common model was the 200 kW PC25 fuel cell manufactured by ONSI Corporation (now United Technologies, Inc.) (Fig. 13). For example, these elements are used as a source of heat and electricity in a police station in New York's Central Park or as an additional source of energy for the Conde Nast Building & Four Times Square. The largest plant of this type is being tested as an 11 MW power plant located in Japan.

Fuel cells based on phosphoric acid are also used as an energy source in vehicles. For example, in 1994, H-Power Corp., Georgetown University, and the US Department of Energy equipped a bus with a 50 kW power plant.

Molten Carbonate Fuel Cells (MCFC)

Fuel cells of this type operate at very high temperatures - 600-700 °C. These operating temperatures allow the fuel to be used directly in the cell itself, without the need for a separate reformer. This process is called "internal reforming". It allows to significantly simplify the design of the fuel cell.

Fuel cells based on molten carbonate require a significant start-up time and do not allow to quickly adjust the output power, so their main area of ​​application is large stationary sources of heat and electricity. However, they are distinguished by high fuel conversion efficiency - 60% electrical efficiency and up to 85% overall efficiency.

In this type of fuel cell, the electrolyte consists of potassium carbonate and lithium carbonate salts heated to about 650 °C. Under these conditions, the salts are in a molten state, forming an electrolyte. At the anode, hydrogen interacts with CO 3 ions, forming water, carbon dioxide and releasing electrons that are sent to the external circuit, and at the cathode, oxygen interacts with carbon dioxide and electrons from the external circuit, again forming CO 3 ions.

Laboratory samples of fuel cells of this type were created in the late 1950s by the Dutch scientists G. H. J. Broers and J. A. A. Ketelaar. In the 1960s, engineer Francis T. Bacon, a descendant of a famous 17th-century English writer and scientist, worked with these elements, which is why MCFC fuel cells are sometimes referred to as Bacon elements. NASA's Apollo, Apollo-Soyuz, and Scylab programs used just such fuel cells as a power source (Fig. 14). In the same years, the US military department tested several samples of MCFC fuel cells manufactured by Texas Instruments, in which army grades of gasoline were used as fuel. In the mid-1970s, the US Department of Energy began research to develop a stationary molten carbonate fuel cell suitable for practical applications. In the 1990s, a number of commercial units rated up to 250 kW were put into operation, such as at the US Naval Air Station Miramar in California. In 1996, FuelCell Energy, Inc. commissioned a 2 MW pre-series plant in Santa Clara, California.

Solid state oxide fuel cells (SOFC)

Solid-state oxide fuel cells are simple in design and operate at very high temperatures - 700-1000 °C. Such high temperatures allow the use of relatively "dirty", unrefined fuel. The same features as in fuel cells based on molten carbonate determine a similar area of ​​application - large stationary sources of heat and electricity.

Solid oxide fuel cells are structurally different from fuel cells based on PAFC and MCFC technologies. The anode, cathode and electrolyte are made of special grades of ceramics. Most often, a mixture of zirconium oxide and calcium oxide is used as the electrolyte, but other oxides can be used. The electrolyte forms a crystal lattice coated on both sides with a porous electrode material. Structurally, such elements are made in the form of tubes or flat boards, which makes it possible to use technologies widely used in the electronics industry in their manufacture. As a result, solid-state oxide fuel cells can operate at very high temperatures, so they can be used to produce both electrical and thermal energy.

At high operating temperatures, oxygen ions are formed at the cathode, which migrate through the crystal lattice to the anode, where they interact with hydrogen ions, forming water and releasing free electrons. In this case, hydrogen is released from natural gas directly in the cell, i.e. there is no need for a separate reformer.

The theoretical foundations for the creation of solid-state oxide fuel cells were laid back in the late 1930s, when Swiss scientists Bauer (Emil Bauer) and Preis (H. Preis) experimented with zirconium, yttrium, cerium, lanthanum and tungsten, using them as electrolytes.

The first prototypes of such fuel cells were created in the late 1950s by a number of American and Dutch companies. Most of these companies soon abandoned further research due to technological difficulties, but one of them, Westinghouse Electric Corp. (now "Siemens Westinghouse Power Corporation"), continued work. The company is currently accepting pre-orders for a commercial model of tubular topology solid oxide fuel cell expected this year (Figure 15). The market segment of such elements is stationary installations for the production of heat and electric energy with a capacity of 250 kW to 5 MW.

SOFC type fuel cells have shown very high reliability. For example, a Siemens Westinghouse fuel cell prototype has logged 16,600 hours and continues to operate, making it the longest continuous fuel cell life in the world.

The high temperature, high pressure operating mode of SOFC fuel cells allows the creation of hybrid plants, in which fuel cell emissions drive gas turbines used to generate electricity. The first such hybrid plant is in operation in Irvine, California. The rated power of this plant is 220 kW, of which 200 kW from the fuel cell and 20 kW from the microturbine generator.

No one will be surprised by either solar panels or windmills, which generate electricity in all regions of the world. But the generation from these devices is not constant and it is necessary to install backup power sources, or connect to the grid to receive electricity during the period when renewable energy facilities do not generate electricity. However, there are plants developed in the 19th century that use "alternative" fuels to generate electricity, i.e. do not burn gas or oil products. Such installations are fuel cells.

HISTORY OF CREATION

Fuel cells (FC) or fuel cells were discovered as early as 1838-1839 by William Grove (Grow, Grove) when he was studying the electrolysis of water.

Reference: Electrolysis of water is the process of decomposition of water under the action of an electric current into hydrogen and oxygen molecules.

Disconnecting the battery from the electrolytic cell, he was surprised to find that the electrodes began to absorb the released gas and generate current. The discovery of the process of electrochemical "cold" combustion of hydrogen has become a significant event in the energy industry. Later he created the Grove accumulator. This device had a platinum electrode immersed in nitric acid and a zinc electrode in zinc sulfate. It generated a current of 12 amps and a voltage of 8 volts. Grow himself called this construction "wet battery". He then created a battery using two platinum electrodes. One end of each electrode was in sulfuric acid, while the other ends were sealed in containers of hydrogen and oxygen. There was a stable current between the electrodes, and the amount of water inside the containers increased. Grow was able to decompose and improve the water in this device.

"Grow's Battery"

(source: Royal Society of the National Museum of Natural History)

The term "fuel cell" (English "Fuel Cell") appeared only in 1889 by L. Mond and
Ch. Langer, who tried to create a device for generating electricity from air and coal gas.

HOW IT WORKS?

The fuel cell is a relatively simple device. It has two electrodes: an anode (negative electrode) and a cathode (positive electrode). A chemical reaction takes place on the electrodes. To speed it up, the surface of the electrodes is coated with a catalyst. Fuel cells are equipped with one more element - a membrane. The conversion of the chemical energy of the fuel directly into electricity occurs due to the work of the membrane. It separates the two chambers of the element into which fuel and oxidizer are supplied. The membrane allows only protons, which are obtained as a result of fuel splitting, to pass from one chamber to another on an electrode coated with a catalyst (electrons then run through the external circuit). In the second chamber, protons recombine with electrons (and oxygen atoms) to form water.

Working principle of a hydrogen fuel cell

At the chemical level, the process of converting fuel energy into electrical energy is similar to the usual combustion (oxidation) process.

During normal combustion in oxygen, organic fuel is oxidized, and the chemical energy of the fuel is converted into thermal energy. Let's see what happens when hydrogen is oxidized by oxygen in an electrolyte medium and in the presence of electrodes.

By supplying hydrogen to an electrode located in an alkaline environment, a chemical reaction proceeds:

2H 2 + 4OH - → 4H 2 O + 4e -

As you can see, we get electrons, which, passing through the external circuit, enter the opposite electrode, to which oxygen enters and where the reaction takes place:

4e- + O 2 + 2H 2 O → 4OH -

It can be seen that the resulting reaction 2H 2 + O 2 → H 2 O is the same as in conventional combustion, but the fuel cell generates electricity and some heat.

TYPES OF FUEL CELLS

FC is classified according to the type of electrolyte used for the reaction:

It should be noted that coal, carbon monoxide, alcohols, hydrazine, and other organic substances can also be used as fuel in fuel cells, and air, hydrogen peroxide, chlorine, bromine, nitric acid, etc. can be used as oxidizing agents.

FUEL CELL Efficiency

A feature of fuel cells is no hard limit on efficiency like a heat engine.

Help: efficiencyCarnot cycle is the maximum possible efficiency among all heat engines with the same minimum and maximum temperatures.

Therefore, the efficiency of fuel cells in theory can be higher than 100%. Many smiled and thought, "The perpetual motion machine has been invented." No, it's worth going back to the school chemistry course. The fuel cell is based on the conversion of chemical energy into electrical energy. This is where miracles happen. Certain chemical reactions in the process can absorb heat from the environment.

Reference: Endothermic reactions are chemical reactions accompanied by the absorption of heat. For endothermic reactions, the change in enthalpy and internal energy have positive values ​​(Δ H >0, Δ U >0), thus, the reaction products contain more energy than the original components.

An example of such a reaction is the oxidation of hydrogen, which is used in most fuel cells. Therefore, theoretically, the efficiency can be more than 100%. But today, fuel cells heat up during operation and cannot absorb heat from the environment.

Reference: This limitation is imposed by the second law of thermodynamics. The process of transferring heat from a "cold" body to a "hot" one is not possible.

Plus, there are losses associated with non-equilibrium processes. Such as: ohmic losses due to the specific conductivity of the electrolyte and electrodes, activation and concentration polarization, diffusion losses. As a result, part of the energy generated in fuel cells is converted into heat. Therefore, fuel cells are not perpetual motion machines and their efficiency is less than 100%. But their efficiency is greater than that of other machines. Today fuel cell efficiency reaches 80%.

Reference: In the forties, the English engineer T. Bacon designed and built a fuel cell battery with a total power of 6 kW and an efficiency of 80%, operating on pure hydrogen and oxygen, but the power-to-weight ratio of the battery turned out to be too small - such cells were unsuitable for practical use and too expensive (source: http://www.powerinfo.ru/).

FUEL CELL ISSUES

Almost all fuel cells use hydrogen as fuel, so the logical question is: “Where can I get it?”

It seems that a fuel cell was discovered as a result of electrolysis, so you can use the hydrogen released as a result of electrolysis. But let's take a closer look at this process.

According to Faraday's law: the amount of a substance that is oxidized at the anode or reduced at the cathode is proportional to the amount of electricity that has passed through the electrolyte. This means that to get more hydrogen, you need to spend more electricity. Existing methods of water electrolysis run with efficiency less than unity. Then we use the resulting hydrogen in fuel cells, where the efficiency is also less than unity. Therefore, we will spend more energy than we can generate.

Of course, hydrogen derived from natural gas can also be used. This method of hydrogen production remains the cheapest and most popular. Currently, about 50% of the hydrogen produced worldwide is obtained from natural gas. But there is a problem with the storage and transportation of hydrogen. Hydrogen has a low density ( one liter of hydrogen weighs 0.0846 grams), therefore, in order to transport it over long distances, it must be compressed. And this is additional energy and cash costs. Also, do not forget about safety.

However, there is also a solution here - liquid hydrocarbon fuel can be used as a source of hydrogen. For example, ethyl or methyl alcohol. True, a special additional device is already required here - a fuel converter, at a high temperature (for methanol it will be somewhere around 240 ° C) converting alcohols into a mixture of gaseous H 2 and CO 2. But in this case it is already more difficult to think about portability - such devices are good to use as stationary or car generators, but for compact mobile equipment you need something less bulky.

Catalyst

To enhance the reaction in a fuel cell, the anode surface is usually a catalyst. Until recently, platinum was used as a catalyst. Therefore, the cost of the fuel cell was high. Secondly, platinum is a relatively rare metal. According to experts, in the industrial production of fuel cells, the explored reserves of platinum will run out in 15-20 years. But scientists around the world are trying to replace platinum with other materials. By the way, some of them achieved good results. So Chinese scientists replaced platinum with calcium oxide (source: www.cheburek.net).

USING FUEL CELLS

For the first time, a fuel cell in automotive technology was tested in 1959. The Alice-Chambers tractor used 1008 batteries to operate. The fuel was a mixture of gases, mainly propane and oxygen.

Source: http://www.planetseed.com/

From the mid-60s, at the height of the "space race", the creators of spacecraft became interested in fuel cells. The work of thousands of scientists and engineers made it possible to reach a new level, and in 1965. The fuel cells were tested in the United States on the Gemini 5 spacecraft, and later on on the Apollo spacecraft for flights to the Moon and under the Shuttle program. In the USSR, fuel cells were developed at NPO Kvant, also for use in space (source: http://www.powerinfo.ru/).

Since the end product of hydrogen combustion in a fuel cell is water, they are considered the cleanest in terms of environmental impact. Therefore, fuel cells began to gain their popularity against the backdrop of a general interest in ecology.

Already at present, car manufacturers such as Honda, Ford, Nissan and Mercedes-Benz have created vehicles powered by hydrogen fuel cells.

Mercedes-Benz - Ener-G-Force powered by hydrogen

When using cars on hydrogen, the problem with hydrogen storage is solved. The construction of hydrogen filling stations will make it possible to refuel anywhere. Moreover, filling a car with hydrogen is faster than charging an electric car at a gas station. But when implementing such projects, they faced a problem like that of electric vehicles. People are ready to “transfer” to a hydrogen car if there is an infrastructure for them. And the construction of gas stations will begin if there is a sufficient number of consumers. Therefore, we again came to the dilemma of eggs and chicken.

Fuel cells are widely used in mobile phones and laptops. Gone are the days when the phone was charged once a week. Now the phone is charging, almost every day, and the laptop works without a network for 3-4 hours. Therefore, mobile technology manufacturers decided to synthesize a fuel cell with phones and laptops for charging and working. For example, Toshiba in 2003 demonstrated a finished prototype of a methanol fuel cell. It gives a power of about 100mW. One refill of 2 cubes of concentrated (99.5%) methanol is enough for 20 hours of MP3 player operation. Again, the same "Toshiba" demonstrated a 275x75x40mm laptop power supply element, which allows the computer to work for 5 hours on a single charge.

But some manufacturers have gone further. PowerTrekk has released a charger of the same name. PowerTrekk is the first water charger in the world. It is very easy to use it. The PowerTrekk needs water to be added to provide instant power through the USB cable. This fuel cell contains silicon powder and sodium silicide (NaSi) when mixed with water, this combination generates hydrogen. Hydrogen mixes with air in the fuel cell itself, and it converts the hydrogen into electricity through its membrane proton exchange, without fans or pumps. You can buy such a portable charger for 149 € (

Fuel cells (electrochemical generators) are a very efficient, durable, reliable and environmentally friendly method of generating energy. Initially, they were used only in the space industry, but today electrochemical generators are increasingly used in various fields: these are power supplies for mobile phones and laptops, vehicle engines, autonomous power supplies for buildings, and stationary power plants. Some of these devices work as laboratory prototypes, some are used for demonstration purposes or are undergoing pre-series testing. However, many models are already used in commercial projects and are mass-produced.

Device

Fuel cells are electrochemical devices capable of providing a high conversion rate of existing chemical energy into electrical energy.

The fuel cell device includes three main parts:

1. Power Generation Section;
2. CPU;
3. Voltage transformer.

The main part of the fuel cell is the power generation section, which is a battery made of individual fuel cells. A platinum catalyst is included in the structure of the fuel cell electrodes. With the help of these cells, a direct electric current is created.

One of these devices has the following characteristics: at a voltage of 155 volts, 1400 amperes are issued. The dimensions of the battery are 0.9 m in width and height, as well as 2.9 m in length. The electrochemical process in it is carried out at a temperature of 177 ° C, which requires heating the battery at the time of start-up, as well as heat removal during its operation. For this purpose, a separate water circuit is included in the composition of the fuel cell, including the battery is equipped with special cooling plates.

The fuel process converts natural gas into hydrogen, which is required for an electrochemical reaction. The main element of the fuel processor is the reformer. In it, natural gas (or other hydrogen-containing fuel) interacts at high pressure and high temperature (about 900 ° C) with water vapor under the action of a nickel catalyst.

There is a burner to maintain the required temperature of the reformer. The steam required for reforming is generated from the condensate. An unstable direct current is created in the fuel cell stack, and a voltage converter is used to convert it.

Also in the voltage converter unit there are:

• control devices.
• Safety interlock circuits that shut down the fuel cell on various faults.

Operating principle

The simplest element with a proton exchange membrane consists of a polymer membrane that is located between the anode and cathode, as well as cathode and anode catalysts. The polymer membrane is used as an electrolyte.

• The proton exchange membrane looks like a thin solid organic compound of small thickness. This membrane works as an electrolyte, in the presence of water it separates the substance into negatively as well as positively charged ions.
• Oxidation begins at the anode, and reduction occurs at the cathode. The cathode and anode in the PEM cell are made of a porous material; it is a mixture of platinum and carbon particles. Platinum acts as a catalyst, which promotes the dissociation reaction. The cathode and anode are made porous so that oxygen and hydrogen can freely pass through them.
• The anode and cathode are located between two metal plates, they supply oxygen and hydrogen to the cathode and anode, and remove electrical energy, heat and water.
• Through channels in the plate, hydrogen molecules enter the anode, where molecules are decomposed into atoms.
• As a result of chemisorption, when exposed to a catalyst, hydrogen atoms are converted into positively charged hydrogen ions H +, that is, protons.
• Protons diffuse to the cathode through the membrane, and the flow of electrons goes to the cathode through a special external electrical circuit. A load is connected to it, that is, a consumer of electrical energy.
• Oxygen, which is supplied to the cathode, when exposed, enters into a chemical reaction with electrons from the external electrical circuit and hydrogen ions from the proton-exchange membrane. The result of this chemical reaction is water.

The chemical reaction that occurs in fuel cells of other types (for example, with an acidic electrolyte in the form of phosphoric acid H3PO4) is completely identical to the reaction of a device with a proton exchange membrane.

Kinds

At the moment, several types of fuel cells are known, which differ in the composition of the electrolyte used:

• Fuel cells based on orthophosphoric or phosphoric acid (PAFC, Phosphoric Acid Fuel Cells).
• Devices with a proton exchange membrane (PEMFC, Proton Exchange Membrane Fuel Cells).
• Solid oxide fuel cells (SOFC, Solid Oxide Fuel Cells).
• Electrochemical generators based on molten carbonate (MCFC, Molten Carbonate Fuel Cells).

At the moment, electrochemical generators using PAFC technology have become more widespread.

Application

Today, fuel cells are used in the Space Shuttle, reusable space vehicles. They use 12W units. They generate all the electricity in the spacecraft. Water, which is formed during the electrochemical reaction, is used for drinking, including for cooling equipment.

Electrochemical generators were also used to power the Soviet Buran, a reusable ship.

Fuel cells are also used in the civilian sector.

• Stationary installations with a capacity of 5–250 kW and above. They are used as autonomous sources for heat and power supply of industrial, public and residential buildings, emergency and backup power supplies, uninterruptible power supplies.
• Portable units with a power of 1–50 kW. They are used for space satellites and ships. Instances are created for golf carts, wheelchairs, railway and freight refrigerators, road signs.
• Mobile units with a capacity of 25–150 kW. They are beginning to be used in warships and submarines, including cars and other vehicles. Prototypes have already been created by such automotive giants as Renault, Neoplan, Toyota, Volkswagen, Hyundai, Nissan, VAZ, General Motors, Honda, Ford and others.
• Microdevices with a power of 1–500 W. They find application in advanced handheld computers, laptops, consumer electronic devices, mobile phones, modern military devices.

Peculiarities

• Some of the energy of the chemical reaction in each fuel cell is released as heat. Cooling required. In an external circuit, the flow of electrons creates a direct current used to do work. The cessation of the movement of hydrogen ions or the opening of the external circuit leads to the termination of the chemical reaction.
• The amount of electricity that fuel cells create is determined by gas pressure, temperature, geometric dimensions, and type of fuel cell. To increase the amount of electricity generated by the reaction, it is possible to make the size of the fuel cells larger, but in practice, several elements are used, which are combined into batteries.
• The chemical process in some types of fuel cells can be reversed. That is, when a potential difference is applied to the electrodes, water can be decomposed into oxygen and hydrogen, which will be collected on porous electrodes. With the inclusion of the load, such a fuel cell will generate electrical energy.

prospects

Currently, electrochemical generators for use as the main source of energy require large initial costs. With the introduction of more stable membranes with high conductivity, efficient and cheap catalysts, alternative sources of hydrogen, fuel cells will become highly economically attractive and will be introduced everywhere.

• Cars will run on fuel cells, they will not have internal combustion engines at all. Water or solid-state hydrogen will be used as an energy source. Refueling will be easy and safe, and driving will be eco-friendly – ​​only water vapor will be generated.
• All buildings will have their own portable fuel cell power generators.
• Electrochemical generators will replace all batteries and will be in any electronics and household appliances.

Advantages and disadvantages

Each type of fuel cell has its own advantages and disadvantages. Some require high quality fuel, others have a complex design and need a high operating temperature.

In general, the following advantages of fuel cells can be indicated:

• safety for the environment;
• electrochemical generators do not need to be recharged;
• electrochemical generators can create energy constantly, they do not care about external conditions;
• flexibility in terms of scale and portability.

Among the disadvantages are:

• technical difficulties with fuel storage and transport;
• imperfect elements of the device: catalysts, membranes, and so on.

fuel cell ( fuel cell) is a device that converts chemical energy into electrical energy. It is similar in principle to a conventional battery, but differs in that its operation requires a constant supply of substances from the outside for an electrochemical reaction to occur. Hydrogen and oxygen are supplied to the fuel cells, and the output is electricity, water and heat. Their advantages include environmental friendliness, reliability, durability and ease of operation. Unlike conventional batteries, electrochemical converters can operate virtually indefinitely as long as fuel is available. They do not need to be charged for hours until fully charged. Moreover, the cells themselves can charge the battery while the car is parked with the engine off.

Proton membrane fuel cells (PEMFC) and solid oxide fuel cells (SOFC) are the most widely used in hydrogen vehicles.

A fuel cell with a proton exchange membrane operates as follows. Between the anode and cathode are a special membrane and a platinum-coated catalyst. Hydrogen enters the anode, and oxygen enters the cathode (for example, from air). At the anode, hydrogen is decomposed into protons and electrons with the help of a catalyst. Hydrogen protons pass through the membrane and enter the cathode, while electrons are given off to the external circuit (the membrane does not let them through). The potential difference thus obtained leads to the appearance of an electric current. On the cathode side, hydrogen protons are oxidized by oxygen. As a result, water vapor is produced, which is the main element of car exhaust gases. Possessing a high efficiency, PEM cells have one significant drawback - their operation requires pure hydrogen, the storage of which is a rather serious problem.

If such a catalyst is found that will replace expensive platinum in these cells, then a cheap fuel cell will immediately be created to generate electricity, which means that the world will get rid of oil dependence.

Solid oxide cells

Solid oxide SOFC cells are much less demanding on fuel purity. In addition, thanks to the use of a POX reformer (Partial Oxidation - partial oxidation), such cells can consume ordinary gasoline as fuel. The process of converting gasoline directly into electricity is as follows. In a special device - a reformer, at a temperature of about 800 ° C, gasoline evaporates and decomposes into its constituent elements.

This releases hydrogen and carbon dioxide. Further, also under the influence of temperature and with the help of SOFC itself (consisting of a porous ceramic material based on zirconium oxide), hydrogen is oxidized by oxygen in the air. After obtaining hydrogen from gasoline, the process proceeds further according to the scenario described above, with only one difference: the SOFC fuel cell, in contrast to devices operating on hydrogen, is less sensitive to foreign impurities in the original fuel. So the quality of gasoline should not affect the performance of the fuel cell.

The high operating temperature of SOFC (650-800 degrees) is a significant drawback, the warm-up process takes about 20 minutes. However, excess heat is not a problem, since it is completely removed by the remaining air and exhaust gases produced by the reformer and the fuel cell itself. This allows the SOFC system to be integrated into the vehicle as a stand-alone device in a thermally insulated housing.

The modular structure allows you to achieve the required voltage by connecting a set of standard cells in series. And, perhaps most importantly, from the point of view of the introduction of such devices, there are no very expensive platinum-based electrodes in SOFC. It is the high cost of these elements that is one of the obstacles in the development and dissemination of PEMFC technology.

Types of fuel cells

Currently, there are such types of fuel cells:

• A.F.C.– Alkaline Fuel Cell (alkaline fuel cell);
• PAFC– Phosphoric Acid Fuel Cell (phosphoric acid fuel cell);
• PEMFC– Proton Exchange Membrane Fuel Cell (fuel cell with a proton exchange membrane);
• DMFC– Direct Methanol Fuel Cell (fuel cell with direct methanol decomposition);
• MCFC– Molten Carbonate Fuel Cell (fuel cell of molten carbonate);
• SOFC– Solid Oxide Fuel Cell (solid oxide fuel cell).

Benefits of fuel cells/cells

A fuel cell/cell is a device that efficiently generates direct current and heat from a hydrogen-rich fuel through an electrochemical reaction.

A fuel cell is similar to a battery in that it generates direct current through a chemical reaction. The fuel cell includes an anode, a cathode and an electrolyte. However, unlike batteries, fuel cells/cells cannot store electrical energy, do not discharge, and do not require electricity to be recharged. Fuel cells/cells can continuously generate electricity as long as they have a supply of fuel and air.

Unlike other power generators such as internal combustion engines or turbines powered by gas, coal, oil, etc., fuel cells/cells do not burn fuel. This means no noisy high pressure rotors, no loud exhaust noise, no vibration. Fuel cells/cells generate electricity through a silent electrochemical reaction. Another feature of fuel cells/cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only products emitted during operation are water in the form of steam and a small amount of carbon dioxide, which is not emitted at all if pure hydrogen is used as fuel. Fuel cells/cells are assembled into assemblies and then into individual functional modules.

History of fuel cell/cell development

In the 1950s and 1960s, one of the biggest challenges for fuel cells was born out of the US National Aeronautics and Space Administration's (NASA) need for energy sources for long-duration space missions. NASA's Alkaline Fuel Cell/Cell uses hydrogen and oxygen as fuel, combining the two in an electrochemical reaction. The output is three by-products of the reaction useful in spaceflight - electricity to power the spacecraft, water for drinking and cooling systems, and heat to keep the astronauts warm.

The discovery of fuel cells dates back to the beginning of the 19th century. The first evidence of the effect of fuel cells was obtained in 1838.

In the late 1930s, work began on alkaline fuel cells, and by 1939 a cell using high pressure nickel-plated electrodes had been built. During the Second World War, fuel cells/cells for British Navy submarines were developed and in 1958 a fuel assembly consisting of alkaline fuel cells/cells just over 25 cm in diameter was introduced.

Interest increased in the 1950s and 1960s and also in the 1980s when the industrial world experienced a shortage of fuel oil. In the same period, world countries also became concerned about the problem of air pollution and considered ways to generate environmentally friendly electricity. At present, fuel cell/cell technology is undergoing rapid development.

How fuel cells/cells work

Fuel cells/cells generate electricity and heat through an ongoing electrochemical reaction using an electrolyte, a cathode and an anode.

The anode and cathode are separated by an electrolyte that conducts protons. After hydrogen enters the anode and oxygen enters the cathode, a chemical reaction begins, as a result of which electric current, heat and water are generated.

On the anode catalyst, molecular hydrogen dissociates and loses electrons. Hydrogen ions (protons) are conducted through the electrolyte to the cathode, while electrons are passed through the electrolyte and through an external electrical circuit, creating a direct current that can be used to power equipment. On the cathode catalyst, an oxygen molecule combines with an electron (which is supplied from external communications) and an incoming proton, and forms water, which is the only reaction product (in the form of vapor and / or liquid).

Below is the corresponding reaction:

Anode reaction: 2H 2 => 4H+ + 4e -
Reaction at the cathode: O 2 + 4H+ + 4e - => 2H 2 O
General element reaction: 2H 2 + O 2 => 2H 2 O

Types and variety of fuel cells/cells

Similar to the existence of different types of internal combustion engines, there are different types of fuel cells - the choice of the appropriate type of fuel cell depends on its application.

Fuel cells are divided into high temperature and low temperature. Low temperature fuel cells require relatively pure hydrogen as fuel. This often means that fuel processing is required to convert the primary fuel (such as natural gas) to pure hydrogen. This process consumes additional energy and requires special equipment. High temperature fuel cells do not need this additional procedure, as they can "internally convert" the fuel at elevated temperatures, which means there is no need to invest in hydrogen infrastructure.

Fuel cells/cells on molten carbonate (MCFC)

Molten carbonate electrolyte fuel cells are high temperature fuel cells. The high operating temperature allows direct use of natural gas without a fuel processor and low calorific value fuel gas from process fuels and other sources.

The operation of RCFC is different from other fuel cells. These cells use an electrolyte from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of mobility of ions in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). The efficiency varies between 60-80%.

When heated to a temperature of 650°C, salts become a conductor for carbonate ions (CO 3 2-). These ions pass from the cathode to the anode where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electrical current and heat as a by-product.

Anode reaction: CO 3 2- + H 2 => H 2 O + CO 2 + 2e -
Reaction at the cathode: CO 2 + 1/2O 2 + 2e - => CO 3 2-
General element reaction: H 2 (g) + 1/2O 2 (g) + CO 2 (cathode) => H 2 O (g) + CO 2 (anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. At high temperatures, the natural gas is internally reformed, eliminating the need for a fuel processor. In addition, the advantages include the ability to use standard materials of construction, such as stainless steel sheet and nickel catalyst on the electrodes. The waste heat can be used to generate high pressure steam for various industrial and commercial purposes.

High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures takes a long time to reach optimal operating conditions, and the system reacts more slowly to changes in energy consumption. These characteristics allow the use of fuel cell systems with molten carbonate electrolyte in constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide.

Molten carbonate fuel cells are suitable for use in large stationary installations. Thermal power plants with an output electric power of 3.0 MW are industrially produced. Plants with an output power of up to 110 MW are being developed.

Fuel cells/cells based on phosphoric acid (PFC)

Fuel cells based on phosphoric (orthophosphoric) acid were the first fuel cells for commercial use.

Fuel cells based on phosphoric (orthophosphoric) acid use an electrolyte based on orthophosphoric acid (H 3 PO 4) with a concentration of up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, for this reason these fuel cells are used at temperatures up to 150–220°C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells, in which hydrogen supplied to the anode is split into protons and electrons. The protons pass through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are directed along an external electrical circuit, and an electric current is generated. Below are the reactions that generate electricity and heat.

Reaction at the anode: 2H 2 => 4H + + 4e -
Reaction at the cathode: O 2 (g) + 4H + + 4e - \u003d\u003e 2 H 2 O
General element reaction: 2H 2 + O 2 => 2H 2 O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. In the combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate steam at atmospheric pressure.

The high performance of thermal power plants on fuel cells based on phosphoric (orthophosphoric) acid in the combined production of heat and electricity is one of the advantages of this type of fuel cells. The plants use carbon monoxide at a concentration of about 1.5%, which greatly expands the choice of fuel. In addition, CO 2 does not affect the electrolyte and the operation of the fuel cell, this type of cell works with reformed natural fuel. Simple construction, low electrolyte volatility and increased stability are also advantages of this type of fuel cell.

Thermal power plants with an output electric power of up to 500 kW are industrially produced. Installations for 11 MW have passed the relevant tests. Plants with an output power of up to 100 MW are being developed.

Solid oxide fuel cells/cells (SOFC)

Solid oxide fuel cells are the fuel cells with the highest operating temperature. The operating temperature can vary from 600°C to 1000°C, which allows the use of various types of fuel without special pre-treatment. To handle these high temperatures, the electrolyte used is a thin ceramic-based solid metal oxide, often an alloy of yttrium and zirconium, which is a conductor of oxygen (O 2-) ions.

A solid electrolyte provides a hermetic gas transition from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O 2-). At the cathode, oxygen molecules are separated from the air into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen to form four free electrons. Electrons are directed through an external electrical circuit, generating electrical current and waste heat.

Reaction at the anode: 2H 2 + 2O 2- => 2H 2 O + 4e -
Reaction at the cathode: O 2 + 4e - \u003d\u003e 2O 2-
General element reaction: 2H 2 + O 2 => 2H 2 O

The efficiency of the generated electrical energy is the highest of all fuel cells - about 60-70%. High operating temperatures allow for combined heat and power generation to generate high pressure steam. Combining a high temperature fuel cell with a turbine creates a hybrid fuel cell to increase the efficiency of power generation up to 75%.

Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in a long time to reach optimal operating conditions, and the system is slower to respond to changes in power consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels from coal gasification or waste gases, and the like. Also, this fuel cell is excellent for high power applications, including industrial and large central power plants. Industrially produced modules with an output electrical power of 100 kW.

Fuel cells/cells with direct methanol oxidation (DOMTE)

The technology of using fuel cells with direct oxidation of methanol is undergoing a period of active development. It has successfully established itself in the field of powering mobile phones, laptops, as well as for creating portable power sources. what the future application of these elements is aimed at.

The structure of fuel cells with direct oxidation of methanol is similar to fuel cells with a proton exchange membrane (MOFEC), i.e. a polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. However, liquid methanol (CH 3 OH) is oxidized in the presence of water at the anode, releasing CO 2 , hydrogen ions and electrons, which are guided through an external electrical circuit, and an electric current is generated. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Reaction at the anode: CH 3 OH + H 2 O => CO 2 + 6H + + 6e -
Reaction at the cathode: 3/2O 2 + 6 H + + 6e - => 3H 2 O
General element reaction: CH 3 OH + 3/2O 2 => CO 2 + 2H 2 O

The advantage of this type of fuel cells is their small size, due to the use of liquid fuel, and the absence of the need to use a converter.

Alkaline fuel cells/cells (AFC)

Alkaline fuel cells are one of the most efficient elements used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, i.e. an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The concentration of potassium hydroxide may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in an SFC is a hydroxide ion (OH-) moving from the cathode to the anode where it reacts with hydrogen to produce water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxide ions there. As a result of this series of reactions taking place in the fuel cell, electricity is produced and, as a by-product, heat:

Reaction at the anode: 2H 2 + 4OH - => 4H 2 O + 4e -
Reaction at the cathode: O 2 + 2H 2 O + 4e - => 4 OH -
General reaction of the system: 2H 2 + O 2 => 2H 2 O

The advantage of SFCs is that these fuel cells are the cheapest to produce, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. SCFCs operate at relatively low temperatures and are among the most efficient fuel cells - such characteristics can respectively contribute to faster power generation and high fuel efficiency.

One of the characteristic features of SHTE is its high sensitivity to CO 2 , which can be contained in fuel or air. CO 2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SFCs is limited to closed spaces such as space and underwater vehicles, they must operate on pure hydrogen and oxygen. Moreover, molecules such as CO, H 2 O and CH4, which are safe for other fuel cells and even fuel for some of them, are detrimental to SFCs.

Polymer electrolyte fuel cells/cells (PETE)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which there is a conduction of water ions (H 2 O + (proton, red) attached to the water molecule). Water molecules present a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and on the exhaust electrodes, which limits the operating temperature to 100°C.

Solid acid fuel cells/cells (SCFC)

In solid acid fuel cells, the electrolyte (CsHSO 4 ) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO 4 2- oxy anions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two tightly compressed electrodes to ensure good contact. When heated, the organic component evaporates, leaving through the pores in the electrodes, retaining the ability of numerous contacts between the fuel (or oxygen at the other end of the cell), electrolyte and electrodes.

Various fuel cell modules. fuel cell battery

1. Fuel Cell Battery
2. Other high temperature equipment (integrated steam generator, combustion chamber, heat balance changer)
3. Heat resistant insulation

fuel cell module

Comparative analysis of types and varieties of fuel cells

Innovative energy-saving municipal heat and power plants are typically built on solid oxide fuel cells (SOFCs), polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PCFCs), proton exchange membrane fuel cells (MPFCs) and alkaline fuel cells (APFCs) . They usually have the following characteristics:

Solid oxide fuel cells (SOFC) should be recognized as the most suitable, which:

• operate at a higher temperature, which reduces the need for expensive precious metals (such as platinum)
• can operate on various types of hydrocarbon fuels, mainly on natural gas
• have a longer start-up time and therefore are better suited for long-term operation
• demonstrate high efficiency of power generation (up to 70%)
• due to high operating temperatures, the units can be combined with heat recovery systems, bringing the overall system efficiency up to 85%
• have near-zero emissions, operate silently and have low operating requirements compared to existing power generation technologies

Fuel cell type	Working temperature	Power Generation Efficiency	Fuel type	Application area
RKTE	550–700°C	50-70%		Medium and large installations
FKTE	100–220°C	35-40%	pure hydrogen	Large installations
MOPTE	30-100°C	35-50%	pure hydrogen	Small installations
SOFC	450–1000°C	45-70%	Most hydrocarbon fuels	Small, medium and large installations
POMTE	20-90°C	20-30%	methanol	portable
SHTE	50–200°C	40-70%	pure hydrogen	space research
PETE	30-100°C	35-50%	pure hydrogen	Small installations

Since small thermal power plants can be connected to a conventional gas supply network, fuel cells do not require a separate hydrogen supply system. When using small thermal power plants based on solid oxide fuel cells, the generated heat can be integrated into heat exchangers for heating water and ventilation air, increasing the overall efficiency of the system. This innovative technology is best suited for efficient power generation without the need for expensive infrastructure and complex instrument integration.

Fuel cell/cell applications

Application of fuel cells/cells in telecommunication systems

With the rapid spread of wireless communication systems around the world, as well as the growing social and economic benefits of mobile phone technology, the need for reliable and cost-effective backup power has become critical. Grid losses throughout the year due to bad weather, natural disasters or limited grid capacity are a constant challenge for grid operators.

Traditional telecom power backup solutions include batteries (valve-regulated lead-acid battery cell) for short-term backup power and diesel and propane generators for longer backup power. Batteries are a relatively cheap source of backup power for 1 to 2 hours. However, batteries are not suitable for longer backup periods because they are expensive to maintain, become unreliable after long use, are sensitive to temperatures, and are hazardous to the environment after disposal. Diesel and propane generators can provide continuous backup power. However, generators can be unreliable, require extensive maintenance, and release high levels of pollutants and greenhouse gases into the atmosphere.

In order to eliminate the limitations of traditional backup power solutions, an innovative green fuel cell technology has been developed. Fuel cells are reliable, quiet, contain fewer moving parts than a generator, have a wider operating temperature range than a battery from -40°C to +50°C and, as a result, provide extremely high levels of energy savings. In addition, the lifetime cost of such a plant is lower than that of a generator. Lower fuel cell costs are the result of only one maintenance visit per year and significantly higher plant productivity. After all, the fuel cell is an environmentally friendly technology solution with minimal environmental impact.

Fuel cell units provide backup power for critical communications network infrastructures for wireless, permanent and broadband communications in the telecommunications system, ranging from 250W to 15kW, they offer many unrivaled innovative features:

• RELIABILITY– Few moving parts and no standby discharge
• ENERGY SAVING
• SILENCE– low noise level
• STABILITY– operating range from -40°C to +50°C
• ADAPTABILITY– outdoor and indoor installation (container/protective container)
• HIGH POWER– up to 15 kW
• LOW MAINTENANCE NEED– minimum annual maintenance
• ECONOMY- attractive total cost of ownership
• CLEAN ENERGY– low emissions with minimal environmental impact

The system senses the DC bus voltage all the time and smoothly accepts critical loads if the DC bus voltage drops below a user-defined setpoint. The system runs on hydrogen, which enters the fuel cell stack in one of two ways - either from a commercial source of hydrogen, or from a liquid fuel of methanol and water, using an on-board reformer system.

Electricity is produced by the fuel cell stack in the form of direct current. The DC power is sent to a converter that converts the unregulated DC power from the fuel cell stack into high quality, regulated DC power for the required loads. A fuel cell installation can provide backup power for many days, as the duration is limited only by the amount of hydrogen or methanol/water fuel available in stock.

Fuel cells offer superior energy efficiency, increased system reliability, more predictable performance in a wide range of climates, and reliable service life compared to industry standard valve regulated lead acid battery packs. Lifecycle costs are also lower due to significantly less maintenance and replacement requirements. Fuel cells offer the end user environmental benefits as disposal costs and liability risks associated with lead acid cells are a growing concern.

The performance of electric batteries can be adversely affected by a wide range of factors such as charge level, temperature, cycles, life and other variables. The energy provided will vary depending on these factors and is not easy to predict. The performance of a proton exchange membrane fuel cell (PEMFC) is relatively unaffected by these factors and can provide critical power as long as fuel is available. Increased predictability is an important benefit when moving to fuel cells for mission-critical backup power applications.

Fuel cells generate energy only when fuel is supplied, like a gas turbine generator, but do not have moving parts in the generation zone. Therefore, unlike a generator, they are not subject to rapid wear and do not require constant maintenance and lubrication.

The fuel used to drive the Extended Duration Fuel Converter is a mixture of methanol and water. Methanol is a widely available, commercial fuel that currently has many uses, including windshield washer, plastic bottles, engine additives, and emulsion paints. Methanol is easy to transport, miscible with water, has good biodegradability and is sulfur free. It has a low freezing point (-71°C) and does not decompose during long storage.

Application of fuel cells/cells in communication networks

Security networks require reliable backup power solutions that can last for hours or days in an emergency if the power grid becomes unavailable.

With few moving parts and no standby power reduction, the innovative fuel cell technology offers an attractive solution compared to currently available backup power systems.

The most compelling reason for using fuel cell technology in communications networks is the increased overall reliability and security. During events such as power outages, earthquakes, storms, and hurricanes, it is important that systems continue to operate and have a reliable backup power supply for an extended period of time, regardless of the temperature or age of the backup power system.

The range of fuel cell power supplies is ideal for supporting secure communications networks. Thanks to their energy saving design principles, they provide an environmentally friendly, reliable backup power with extended duration (up to several days) for use in the power range from 250 W to 15 kW.

Application of fuel cells/cells in data networks

Reliable power supply for data networks, such as high-speed data networks and fiber optic backbones, is of key importance throughout the world. Information transmitted over such networks contains critical data for institutions such as banks, airlines or medical centers. A power outage in such networks not only poses a danger to the transmitted information, but also, as a rule, leads to significant financial losses. Reliable, innovative fuel cell installations that provide standby power provide the reliability you need to ensure uninterrupted power.

Fuel cell units operating on a liquid fuel mixture of methanol and water provide a reliable backup power supply with extended duration, up to several days. In addition, these units feature significantly reduced maintenance requirements compared to generators and batteries, requiring only one maintenance visit per year.

Typical application characteristics for the use of fuel cell installations in data networks:

• Applications with power inputs from 100 W to 15 kW
• Applications with battery life requirements > 4 hours
• Repeaters in fiber optic systems (hierarchy of synchronous digital systems, high speed internet, voice over IP…)
• Network nodes of high-speed data transmission
• WiMAX Transmission Nodes

Fuel cell standby installations offer numerous advantages for critical data network infrastructures over traditional battery or diesel generators, allowing for increased on-site utilization:

1. Liquid fuel technology solves the problem of hydrogen storage and provides virtually unlimited backup power.
2. Due to their quiet operation, low weight, resistance to temperature extremes and virtually vibration-free operation, fuel cells can be installed outdoors, in industrial premises/containers or on rooftops.
3. On-site preparations for using the system are quick and economical, and the cost of operation is low.
4. The fuel is biodegradable and represents an environmentally friendly solution for the urban environment.

Application of fuel cells/cells in security systems

The most carefully designed building security and communication systems are only as reliable as the power that powers them. While most systems include some type of back-up uninterruptible power system for short-term power losses, they do not provide for the longer power outages that can occur after natural disasters or terrorist attacks. This could be a critical issue for many corporate and government agencies.

Vital systems such as CCTV monitoring and access control systems (ID card readers, door closing devices, biometric identification technology, etc.), automatic fire alarm and fire extinguishing systems, elevator control systems and telecommunication networks, are at risk in the absence of a reliable alternative source of continuous power supply.

Diesel generators are noisy, hard to locate, and are well aware of their reliability and maintenance issues. In contrast, a fuel cell back-up installation is quiet, reliable, has zero or very low emissions, and is easy to install on a rooftop or outside a building. It does not discharge or lose power in standby mode. It ensures the continued operation of critical systems, even after the institution ceases operations and the building is abandoned by people.

Innovative fuel cell installations protect expensive investments in critical applications. They provide environmentally friendly, reliable backup power with extended duration (up to many days) for use in the power range from 250 W to 15 kW, combined with numerous unsurpassed features and, especially, a high level of energy saving.

Fuel cell power backup units offer numerous advantages for mission critical applications such as security and building management systems over traditional battery or diesel generators. Liquid fuel technology solves the problem of hydrogen storage and provides virtually unlimited backup power.

Application of fuel cells/cells in domestic heating and power generation

Solid oxide fuel cells (SOFCs) are used to build reliable, energy-efficient and emission-free thermal power plants to generate electricity and heat from widely available natural gas and renewable fuel sources. These innovative units are used in a wide variety of markets, from domestic power generation to power supply to remote areas, as well as auxiliary power sources.

Application of fuel cells/cells in distribution networks

Small thermal power plants are designed to operate in a distributed power generation network consisting of a large number of small generator sets instead of one centralized power plant.

The figure below shows the loss in efficiency of electricity generation when it is generated by CHP and transmitted to homes through the traditional transmission networks currently in use. Efficiency losses in district generation include losses from the power plant, low and high voltage transmission, and distribution losses.

The figure shows the results of the integration of small thermal power plants: electricity is generated with a generation efficiency of up to 60% at the point of use. In addition, the household can use the heat generated by the fuel cells for water and space heating, which increases the overall efficiency of fuel energy processing and improves energy savings.

Using Fuel Cells to Protect the Environment - Utilization of Associated Petroleum Gas

One of the most important tasks in the oil industry is the utilization of associated petroleum gas. The existing methods of utilization of associated petroleum gas have a lot of disadvantages, the main one being that they are not economically viable. Associated petroleum gas is flared, which causes great harm to the environment and human health.

Innovative fuel cell heat and power plants using associated petroleum gas as a fuel open the way to a radical and cost-effective solution to the problems of associated petroleum gas utilization.

1. One of the main advantages of fuel cell installations is that they can operate reliably and sustainably on variable composition associated petroleum gas. Due to the flameless chemical reaction underlying the operation of a fuel cell, a reduction in the percentage of, for example, methane only causes a corresponding reduction in power output.
2. Flexibility in relation to the electrical load of consumers, differential, load surge.
3. For the installation and connection of thermal power plants on fuel cells, their implementation does not require capital expenditures, because The units are easily mounted on unprepared sites near fields, are easy to operate, reliable and efficient.
4. High automation and modern remote control do not require the constant presence of personnel at the plant.
5. Simplicity and technical perfection of the design: the absence of moving parts, friction, lubrication systems provides significant economic benefits from the operation of fuel cell installations.
6. Water consumption: none at ambient temperatures up to +30 °C and negligible at higher temperatures.
7. Water outlet: none.
8. In addition, fuel cell thermal power plants do not make noise, do not vibrate, do not emit harmful emissions into the atmosphere

Hydrogen fuel cells convert the chemical energy of the fuel into electricity, bypassing the inefficient, lossy combustion processes and the conversion of thermal energy into mechanical energy. The hydrogen fuel cell is electrochemical the device as a result of highly efficient "cold" combustion of fuel directly generates electricity. The proton exchange membrane hydrogen-air fuel cell (PEMFC) is one of the most promising fuel cell technologies.

Eight years ago six liquid diesel pumps were opened in Western Europe; they must be two hundred to the end. We are far from the thousands of fast charging terminals that are hatching everywhere to stimulate the spread of electric movement. And that's where the rub hurts. And we better announce graphene.

The Batteries Haven't Had Their Last Word

It's more than autonomy, so limiting charging time is slowing down the spread of the electric car. However, he recalled this month a note addressed to his customers that batteries have a limitation limited to this type of probe at very high voltage. Thomas Brachman will be told that a hydrogen distribution network still needs to be built. The argument that he sweeps his hand, recalling that the multiplication of fast charge terminals is also very expensive, due to the high cross-section of high-voltage copper cables. "It's easier and cheaper to transport liquefied hydrogen by truck from buried tanks near production sites."

A proton-conducting polymer membrane separates two electrodes, an anode and a cathode. Each electrode is a carbon plate (matrix) coated with a catalyst. On the anode catalyst, molecular hydrogen dissociates and donates electrons. Hydrogen cations are conducted through the membrane to the cathode, but electrons are given off to the external circuit, since the membrane does not allow electrons to pass through.

Hydrogen is not yet a pure electricity vector

As for the cost of the battery itself, which is very sensitive information, Thomas Brachmann has no doubt that it can be significantly reduced as efficiency increases. "Platinum is the element that costs more." Unfortunately, almost all hydrogen comes from fossil energy sources. Moreover, dihydrogen is just a vector of energy, and not a source from which, during its production, not a negligible part is consumed, its liquefaction, and then its conversion into electricity.

On the cathode catalyst, an oxygen molecule combines with an electron (which is supplied from the electrical circuit) and an incoming proton and forms water, which is the only reaction product (in the form of vapor and / or liquid).

Membrane-electrode blocks are made from hydrogen fuel cells, which are the key generating element of the energy system.

The car of the future behaves like a real one

The battery balance is about three times higher, despite losses due to heating in the drivers. Alas, the miracle car will not pierce our roads, except as part of public demonstrations. Brachmann, who recalls that the natural silence of an electric car enhances the impression of living in a noisy world. Against all odds, the steering and brake pedal delivers natural consistency.

Tiny battery but improved performance

The gadget is noticeable, the central screen scatters the images of the camera placed in the right mirror as soon as the turn signal is activated. Most of our US customers no longer require, and this allows us to keep prices down - justifies the chief engineer, who offers a lower rate than. It's really worth talking about a fuel cell stack, as there are 358 that work together. The main tank with a capacity of 117 liters, pressed against the back wall of the bench, prohibits folding it, and the second - 24 liters, is hidden under the seat.

Advantages of hydrogen fuel cells compared to traditional solutions:

- increased specific energy intensity (500 ÷ 1000 W*h/kg),

- extended operating temperature range (-40 0 C / +40 0 C),

- absence of a thermal spot, noise and vibration,

- cold start reliability

- practically unlimited energy storage period (lack of self-discharge),

First two-stroke fuel cell

Despite its compact size, this new fuel cell converts dihydrogen into electricity faster and better than its predecessor. It delivers the pile elements into oxygen at a rate previously considered inconsistent with their durability. Excess water, which previously limited the flow rate, is best evacuated. As a result, the power per element is increased by half, and the efficiency reaches 60%.

This is due to the presence of a 1.7 kWh lithium-ion battery - located under the front seats, which allows additional current to be delivered during strong accelerations. Either the autonomy of the forecast is 460 km, which perfectly corresponds to what the manufacturer claims.

- the ability to change the energy intensity of the system by changing the number of fuel cartridges, which provides almost unlimited autonomy,

The ability to provide almost any reasonable energy intensity of the system by changing the capacity of the hydrogen storage,

- high energy consumption

- tolerance to impurities in hydrogen,

But a thousand parts facilitate airflow and optimize cooling. Even more than its predecessor, this electric vehicle demonstrates that the fuel cell is in the spotlight. A big challenge for the industry and our leaders. Meanwhile, very smart, who will know which of the fuel cell or battery will prevail.

A fuel cell is an electrochemical energy conversion device that can generate electricity in the form of direct current by combining a fuel and an oxidizer in a chemical reaction to produce a waste product, typically fuel oxide.

- long service life,

- environmental friendliness and noiselessness of work.

Power supply systems based on hydrogen fuel cells for UAVs:

Installation of fuel cells on unmanned aerial vehicles instead of traditional batteries, it multiplies the flight duration, the payload weight, makes it possible to increase the reliability of the aircraft, expand the temperature range for launching and operating the UAV, lowering the limit to -40 0С. Compared to internal combustion engines, fuel cell systems are quiet, vibration-free, operate at low temperatures, are difficult to detect during flight, do not produce harmful emissions, and can efficiently perform tasks from video surveillance to payload delivery.

Each fuel cell has two electrodes, one positive and one negative, and the reaction that produces electricity takes place at the electrodes in the presence of an electrolyte that carries charged particles from electrode to electrode while electrons circulate in external wires located between the electrodes to create electricity.

The fuel cell can generate electricity continuously as long as the required flow of fuel and oxidizer is maintained. Some fuel cells produce only a few watts while others can produce several hundred kilowatts, while smaller batteries are likely to be found in laptops and cell phones, but fuel cells are too expensive to be small generators used to generate electricity for homes and businesses.

The composition of the power supply system for the UAV:

Economic dimensions of fuel cells

The use of hydrogen as a fuel source entails significant costs. For this reason, hydrogen is now a non-economic source, in particular because other less expensive sources can be used. Hydrogen production costs can vary as they reflect the cost of the resources from which it is extracted.

Battery Fuel Sources

Fuel cells are generally classified into the following categories: hydrogen fuel cells, organic fuel cells, metal fuel cells, and redox batteries. When hydrogen is used as a fuel source, the chemical energy is converted into electricity during the reverse hydrolysis process to give only water and heat as waste. The hydrogen fuel cell is very low, but can be more or less high in hydrogen production, especially if it is produced from fossil fuels.

• - fuel cell battery,
• - Li-Po buffer battery to cover short-term peak loads,
• - electronic control system ,
• - fuel system consisting of a cylinder with compressed hydrogen or a solid source of hydrogen.

The fuel system uses high-strength lightweight cylinders and reducers to ensure the maximum supply of compressed hydrogen on board. It is allowed to use various standard sizes of cylinders (from 0.5 to 25 liters) with reducers that provide the necessary hydrogen flow.

Hydrogen batteries are divided into two categories: low temperature batteries and high temperature batteries, where high temperature batteries can also use fossil fuels directly. The latter are composed of hydrocarbons such as oil or gasoline, alcohol or biomass.

Other fuel sources in batteries include, but are not limited to, alcohols, zinc, aluminum, magnesium, ionic solutions, and many hydrocarbons. Other oxidizing agents include, but are not limited to, air, chlorine, and chlorine dioxide. Currently, there are several types of fuel cells.

Characteristics of the power supply system for the UAV:

Portable chargers based on hydrogen fuel cells:

Portable chargers based on hydrogen fuel cells are compact devices comparable in weight and dimensions to existing and widely used battery chargers in the world.

The ubiquitous portable technology in the modern world regularly needs to be recharged. Traditional portable systems are practically useless at negative temperatures, and after performing their function, they also require recharging using (electrical networks), which also reduces their efficiency and autonomy of the device.

Each dihydrogen molecule has 2 electrons. The H ion passes from the anode to the cathode and induces an electric current when an electron is transferred. What might fuel cells for aircraft look like? Today, tests are being carried out on aircraft to try and fly them using a fuel cell lithium-ion hybrid battery. The true gain of the fuel cell lies in its low weight integrity: it is lighter, which helps to reduce the weight of the aircraft and, therefore, fuel consumption.

But for now, flying a fuel cell aircraft is not possible because it still has many drawbacks. Image of a fuel cell. What are the disadvantages of a fuel cell? First of all, if hydrogen were common, its use in large quantities would be problematic. Indeed, it is available not only on Earth. It is found in oxygen-containing water, ammonia. Therefore, it is necessary to carry out electrolysis of water to obtain it, and this is not yet a widely used method.

Hydrogen fuel cell systems require only the replacement of a compact fuel cartridge, after which the device is immediately ready for operation.

Features of portable chargers:

Uninterruptible power supplies based on hydrogen fuel cells:

Uninterruptible power supply systems based on hydrogen fuel cells are designed to organize backup power supply and temporary power supply. Uninterruptible power supply systems based on hydrogen fuel cells offer significant advantages over traditional solutions for organizing temporary and backup power supply, using batteries and diesel generators.

Hydrogen is a gas and therefore difficult to contain and transport. Another risk associated with the use of hydrogen is the risk of explosion as it is a highly flammable gas. what supplies the battery for its production on a large scale requires a different source of energy, whether it be oil, gas or coal, or nuclear power, which makes its environmental balance significantly worse than kerosene and make heap, platinum, metal, which is even rarer and more valuable than gold.

The fuel cell provides energy by oxidizing the fuel at the anode and reducing the oxidizer at the cathode. The discovery of the fuel cell principle and the first laboratory implementations using sulfuric acid as an electrolyte are credited to the chemist William Grove.

Characteristics of the uninterruptible power supply system:

fuel cell- this is an electrochemical device similar to a galvanic cell, but differs from it in that the substances for the electrochemical reaction are fed into it from the outside - in contrast to the limited amount of energy stored in a galvanic cell or battery.

Indeed, fuel cells have some advantages: those using dihydrogen and dioxide only emit water vapor: so it is a clean technology. There are several types of fuel cells, depending on the nature of the electrolyte, the nature of the fuel, direct or indirect oxidation, operating temperature.

The following table summarizes the main characteristics of these various devices. Several European programs are looking for other polymers, such as polybenzimidazole derivatives, that are more stable and cheaper. Battery compactness is also a constant challenge with membranes on the order of 15-50 µm, porous carbon anodes and stainless steel bipolar plates. Lifespan can also be improved since, on the one hand, traces of carbon monoxide on the order of a few parts per million in hydrogen are real poisons for the catalyst, and on the other hand, control of the water in the polymer is indispensable.

Rice. one. Some fuel cells

Fuel cells convert the chemical energy of the fuel into electricity, bypassing the inefficient combustion processes that occur with large losses. As a result of a chemical reaction, they convert hydrogen and oxygen into electricity. As a result of this process, water is formed and a large amount of heat is released. A fuel cell is very similar to a battery that can be charged and then used to store electrical energy. The inventor of the fuel cell is considered to be William R. Grove, who invented it back in 1839. In this fuel cell, a solution of sulfuric acid was used as an electrolyte, and hydrogen was used as a fuel, which combined with oxygen in an oxidizer medium. Until recently, fuel cells were used only in laboratories and on spacecraft.

Unlike other power generators such as internal combustion engines or turbines powered by gas, coal, oil, etc., fuel cells do not burn fuel. This means no noisy high pressure rotors, no loud exhaust noise, no vibrations. Fuel cells generate electricity through a silent electrochemical reaction. Another feature of fuel cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only products emitted by fuel cells are water in the form of steam and a small amount of carbon dioxide, which is not emitted at all if pure hydrogen is used as fuel. Fuel cells are assembled into assemblies and then into individual functional modules.

Fuel cells don't have moving parts (at least not inside the cell itself), and so they don't obey Carnot's law. That is, they will have more than 50% efficiency and are especially effective at low loads. Thus, fuel cell vehicles can be (and have already been proven to be) more fuel efficient than conventional vehicles in real-life driving conditions.

The fuel cell generates DC electrical current that can be used to drive an electric motor, lighting fixtures, and other electrical systems in a vehicle.

There are several types of fuel cells, differing in the chemical processes used. Fuel cells are usually classified according to the type of electrolyte they use.

Some types of fuel cells are promising for use as power plants in power plants, while others are for portable devices or for driving cars.

1. Alkaline fuel cells (AFC)

Alkaline fuel cell- This is one of the very first developed elements. Alkaline fuel cells (ALFCs) are one of the most studied technologies used since the mid-1960s by NASA in the Apollo and Space Shuttle programs. On board these spacecraft, fuel cells produce electricity and drinking water.

Alkaline fuel cells are one of the most efficient elements used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, i.e. an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The concentration of potassium hydroxide may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in the SFC is a hydroxide ion (OH-) moving from the cathode to the anode, where it reacts with hydrogen to produce water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxide ions there. As a result of this series of reactions taking place in the fuel cell, electricity is produced and, as a by-product, heat:

Anode reaction: 2H2 + 4OH- => 4H2O + 4e

Reaction at the cathode: O2 + 2H2O + 4e- => 4OH

General reaction of the system: 2H2 + O2 => 2H2O

The advantage of SFCs is that these fuel cells are the cheapest to manufacture, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. In addition, SFCs operate at relatively low temperatures and are among the most efficient.

One of the characteristic features of SFC is its high sensitivity to CO2, which can be contained in fuel or air. CO2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SFCs is limited to closed spaces such as space and underwater vehicles, they operate on pure hydrogen and oxygen.

2. Carbonate melt fuel cells (MCFC)

Fuel cells with molten carbonate electrolyte are high temperature fuel cells. The high operating temperature allows direct use of natural gas without a fuel processor and low calorific value fuel gas from process fuels and other sources. This process was developed in the mid-1960s. Since that time, manufacturing technology, performance and reliability have been improved.

The operation of RCFC is different from other fuel cells. These cells use an electrolyte from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of mobility of ions in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). The efficiency varies between 60-80%.

When heated to a temperature of 650°C, the salts become a conductor for carbonate ions (CO32-). These ions travel from the cathode to the anode where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electrical current and heat as a by-product.

Anode reaction: CO32- + H2 => H2O + CO2 + 2e

Reaction at the cathode: CO2 + 1/2O2 + 2e- => CO32-

General element reaction: H2(g) + 1/2O2(g) + CO2(cathode) => H2O(g) + CO2(anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. The advantage is the ability to use standard materials (stainless steel sheet and nickel catalyst on the electrodes). The waste heat can be used to produce high pressure steam. High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures takes a long time to reach optimal operating conditions, and the system reacts more slowly to changes in energy consumption. These characteristics allow the use of fuel cell systems with molten carbonate electrolyte in constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide, "poisoning", etc.

Molten carbonate fuel cells are suitable for use in large stationary installations. Thermal power plants with an output electric power of 2.8 MW are industrially produced. Plants with an output power of up to 100 MW are being developed.

3. Fuel cells based on phosphoric acid (PFC)

Fuel cells based on phosphoric (orthophosphoric) acid became the first fuel cells for commercial use. This process was developed in the mid-60s of the XX century, tests have been carried out since the 70s of the XX century. As a result, stability and performance have been increased and cost has been reduced.

Fuel cells based on phosphoric (orthophosphoric) acid use an electrolyte based on orthophosphoric acid (H3PO4) with a concentration of up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, so these fuel cells are used at temperatures up to 150-220°C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells (MEFCs), in which hydrogen supplied to the anode is split into protons and electrons. The protons pass through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are directed along an external electrical circuit, and an electric current is generated. Below are the reactions that generate electricity and heat.

Anode reaction: 2H2 => 4H+ + 4e

Reaction at the cathode: O2(g) + 4H+ + 4e- => 2H2O

General element reaction: 2H2 + O2 => 2H2O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. In the combined production of heat and electricity, the overall efficiency is about 85%. In addition, given the operating temperatures, the waste heat can be used to heat water and generate steam at atmospheric pressure.

The high performance of thermal power plants on fuel cells based on phosphoric (orthophosphoric) acid in the combined production of heat and electricity is one of the advantages of this type of fuel cells. The plants use carbon monoxide at a concentration of about 1.5%, which greatly expands the choice of fuel. Simple construction, low electrolyte volatility, and increased stability are also advantages of such fuel cells.

Thermal power plants with an output electric power of up to 400 kW are industrially produced. Installations with a capacity of 11 MW have passed the relevant tests. Plants with an output power of up to 100 MW are being developed.

4. Fuel cells with a proton exchange membrane (MOFEC)

Fuel cells with proton exchange membrane are considered to be the best type of fuel cells for vehicle power generation, which can replace gasoline and diesel internal combustion engines. These fuel cells were first used by NASA for the Gemini program. Installations on MOPFC with power from 1 W to 2 kW are developed and shown.

The electrolyte in these fuel cells is a solid polymer membrane (thin plastic film). When impregnated with water, this polymer passes protons, but does not conduct electrons.

The fuel is hydrogen, and the charge carrier is a hydrogen ion (proton). At the anode, the hydrogen molecule is separated into a hydrogen ion (proton) and electrons. The hydrogen ions pass through the electrolyte to the cathode, while the electrons move around the outer circle and produce electrical energy. Oxygen, which is taken from the air, is fed to the cathode and combines with electrons and hydrogen ions to form water. The following reactions occur on the electrodes: Anode reaction: 2H2 + 4OH- => 4H2O + 4eCathode reaction: O2 + 2H2O + 4e- => 4OHTotal cell reaction: 2H2 + O2 => 2H2O Compared to other types of fuel cells, fuel cells with a proton exchange membrane produce more energy for a given volume or weight of the fuel cell. This feature allows them to be compact and lightweight. In addition, the operating temperature is less than 100°C, which allows you to quickly start operation. These characteristics, as well as the ability to rapidly change energy output, are just some of the features that make these fuel cells a prime candidate for use in vehicles.

Another advantage is that the electrolyte is a solid rather than a liquid. It is easier to keep gases at the cathode and anode with a solid electrolyte, so such fuel cells are cheaper to manufacture. When using a solid electrolyte, there are no difficulties such as orientation, and fewer problems due to the occurrence of corrosion, which increases the durability of the cell and its components.

5. Solid oxide fuel cells (SOFC)

Solid oxide fuel cells are the fuel cells with the highest operating temperature. The operating temperature can vary from 600°C to 1000°C, which allows the use of various types of fuel without special pre-treatment. To handle these high temperatures, the electrolyte used is a thin ceramic-based solid metal oxide, often an alloy of yttrium and zirconium, which is a conductor of oxygen (O2-) ions. The technology of using solid oxide fuel cells has been developing since the late 1950s and has two configurations: planar and tubular.

A solid electrolyte provides a hermetic gas transition from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (О2-). At the cathode, oxygen molecules are separated from the air into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen to form four free electrons. The electrons are directed through an external electrical circuit, generating electrical current and waste heat.

Anode reaction: 2H2 + 2O2- => 2H2O + 4e

Reaction at the cathode: O2 + 4e- => 2O2-

General element reaction: 2H2 + O2 => 2H2O

The efficiency of electrical energy production is the highest of all fuel cells - about 60%. In addition, high operating temperatures allow for combined heat and power generation to generate high pressure steam. Combining a high-temperature fuel cell with a turbine creates a hybrid fuel cell to increase the efficiency of electrical power generation by up to 70%.

Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in a significant time to reach optimum operating conditions, and the system is slower to respond to changes in power consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels from coal gasification or waste gases, and the like. Also, this fuel cell is excellent for high power applications, including industrial and large central power plants. Industrially produced modules with an output electrical power of 100 kW.

6. Fuel cells with direct methanol oxidation (DOMTE)

Fuel cells with direct methanol oxidation are successfully used in the field of powering mobile phones, laptops, as well as to create portable power sources, which is what the future use of such elements is aimed at.

The structure of fuel cells with direct oxidation of methanol is similar to the structure of fuel cells with a proton exchange membrane (MOFEC), i.e. a polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. But liquid methanol (CH3OH) is oxidized in the presence of water at the anode, releasing CO2, hydrogen ions and electrons, which are sent through an external electrical circuit, and an electric current is generated. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Anode reaction: CH3OH + H2O => CO2 + 6H+ + 6eCathode reaction: 3/2O2 + 6H+ + 6e- => 3H2O Total element reaction: CH3OH + 3/2O2 => CO2 + 2H2O 1990s and their specific power and efficiency were increased up to 40%.

These elements were tested in the temperature range of 50-120°C. Due to low operating temperatures and no need for a converter, these fuel cells are the best candidate for applications in mobile phones and other consumer products, as well as in car engines. Their advantage is also small dimensions.

7. Polymer electrolyte fuel cells (PETE)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which the conduction of water ions H2O+ (proton, red) is attached to the water molecule. Water molecules present a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and on the exhaust electrodes, which limits the operating temperature to 100°C.

8. Solid acid fuel cells (SCFC)

In solid acid fuel cells, the electrolyte (CsHSO4) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO42-oxyanions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two tightly compressed electrodes to ensure good contact. When heated, the organic component evaporates, leaving through the pores in the electrodes, retaining the ability of numerous contacts between the fuel (or oxygen at the other end of the cell), electrolyte and electrodes.

9. Comparison of the most important characteristics of fuel cells

Fuel Cell Characteristics

Fuel cell type	Working temperature	Power Generation Efficiency	Fuel type	Scope
				Medium and large installations
			pure hydrogen	installations
			pure hydrogen	Small installations
			Most hydrocarbon fuels	Small, medium and large installations
				portable installations
			pure hydrogen	Space explored
			pure hydrogen	Small installations

10. Use of fuel cells in cars

Ecology of knowledge. Science and technology: Mobile electronics are improving every year, becoming more widespread and more accessible: PDAs, laptops, mobile and digital devices, photo frames, etc. All of them are constantly replenished

DIY fuel cell at home

Mobile electronics are improving every year, becoming more widespread and more accessible: PDAs, laptops, mobile and digital devices, photo frames, etc. All of them are constantly updated with new features, larger monitors, wireless communications, stronger processors, while decreasing in size. . Power technologies, unlike semiconductor technology, do not go by leaps and bounds.

The available batteries and accumulators to power the achievements of the industry are becoming insufficient, so the issue of alternative sources is very acute. Fuel cells are by far the most promising direction. The principle of their operation was discovered back in 1839 by William Grove, who generated electricity by changing the electrolysis of water.

What are fuel cells?

Video: Documentary, Fuel Cells for Transportation: Past, Present, Future

Fuel cells are of interest to car manufacturers, and the creators of spacecraft are also interested in them. In 1965, they were even tested by America on the Gemini 5 launched into space, and later on the Apollo. Millions of dollars are being invested in fuel cell research even today, when there are problems associated with environmental pollution, increasing greenhouse gas emissions from the combustion of fossil fuels, the reserves of which are also not endless.

A fuel cell, often referred to as an electrochemical generator, operates in the manner described below.

Being, like accumulators and batteries, a galvanic cell, but with the difference that active substances are stored in it separately. They come to the electrodes as they are used. On the negative electrode, natural fuel or any substance obtained from it burns, which can be gaseous (hydrogen, for example, and carbon monoxide) or liquid, like alcohols. At the positive electrode, as a rule, oxygen reacts.

But a simple-looking principle of action is not easy to translate into reality.

DIY fuel cell

Unfortunately, we do not have photos of what this fuel element should look like, we hope for your imagination.

A low-power fuel cell with your own hands can be made even in a school laboratory. It is necessary to stock up on an old gas mask, several pieces of plexiglass, alkali and an aqueous solution of ethyl alcohol (more simply, vodka), which will serve as “fuel” for the fuel cell.

First of all, you need a housing for the fuel cell, which is best made from plexiglass, at least five millimeters thick. Internal partitions (five compartments inside) can be made a little thinner - 3 cm. For gluing plexiglass, glue of the following composition is used: six grams of plexiglass chips are dissolved in one hundred grams of chloroform or dichloroethane (they work under a hood).

In the outer wall, it is now necessary to drill a hole into which you need to insert a drain glass tube with a diameter of 5-6 centimeters through a rubber stopper.

Everyone knows that in the periodic table in the lower left corner there are the most active metals, and the high-activity metalloids are in the table in the upper right corner, i.e. the ability to donate electrons increases from top to bottom and from right to left. Elements that can, under certain conditions, manifest themselves as metals or metalloids are in the center of the table.

Now, in the second and fourth compartments, we pour activated carbon from the gas mask (between the first partition and the second, as well as the third and fourth), which will act as electrodes. So that coal does not spill out through the holes, it can be placed in a nylon fabric (women's nylon stockings will do).

The fuel will circulate in the first chamber, in the fifth there should be an oxygen supplier - air. There will be an electrolyte between the electrodes, and in order to prevent it from leaking into the air chamber, it is necessary to soak it with a solution of paraffin in gasoline (the ratio of 2 grams of paraffin to half a glass of gasoline) before filling the fourth chamber with coal for air electrolyte. On a layer of coal you need to put (slightly pressing) copper plates, to which the wires are soldered. Through them, the current will be diverted from the electrodes.

It remains only to charge the element. For this, vodka is needed, which must be diluted with water in 1: 1. Then carefully add three hundred to three hundred and fifty grams of caustic potassium. For electrolyte, 70 grams of caustic potassium are dissolved in 200 grams of water.

The fuel cell is ready for testing. Now you need to simultaneously pour fuel into the first chamber, and electrolyte into the third. A voltmeter attached to the electrodes should show from 07 volts to 0.9. To ensure continuous operation of the element, it is necessary to drain the spent fuel (drain into a glass) and add new fuel (through a rubber tube). The feed rate is controlled by squeezing the tube. This is how the operation of a fuel cell looks in laboratory conditions, the power of which is understandably small.

To make the power greater, scientists have been working on this problem for a long time. Methanol and ethanol fuel cells are located on the active development steel. But, unfortunately, so far there is no way to put them into practice.

Why the fuel cell is chosen as an alternative power source

A fuel cell was chosen as an alternative power source, since the end product of hydrogen combustion in it is water. The problem is only in finding an inexpensive and efficient way to produce hydrogen. The colossal funds invested in the development of hydrogen generators and fuel cells cannot fail to bear fruit, so a technological breakthrough and their real use in everyday life is only a matter of time.

Already today, the monsters of the automotive industry: General Motors, Honda, Dreimler Coisler, Ballard, demonstrate buses and cars that run on fuel cells with a power of up to 50 kW. But, the problems associated with their safety, reliability, cost - have not yet been resolved. As already mentioned, unlike traditional power sources - batteries and batteries, in this case, the oxidizer and fuel are supplied from the outside, and the fuel cell is only an intermediary in the ongoing reaction to burn the fuel and convert the released energy into electricity. “Burning” occurs only if the element gives current to the load, like a diesel electric generator, but without a generator and diesel, and also without noise, smoke and overheating. At the same time, the efficiency is much higher, since there are no intermediate mechanisms.

Great hopes are placed on the use of nanotechnologies and nanomaterials, which will help to miniaturize fuel cells, while increasing their power. There have been reports that ultra-efficient catalysts have been created, as well as fuel cell designs that do not have membranes. In them, together with the oxidizer, fuel (methane, for example) is supplied to the element. Solutions are interesting, where oxygen dissolved in water is used as an oxidizing agent, and organic impurities accumulating in polluted waters are used as fuel. These are the so-called biofuel cells.

Fuel cells, according to experts, can enter the mass market in the coming years. published

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The owners of the patent RU 2379795:

The invention relates to direct-acting alcohol fuel cells using solid acid electrolytes and internal reforming catalysts. The technical result of the invention is increased specific power and voltage of the element. According to the invention, the fuel cell includes an anode, a cathode, a solid acid electrolyte, a gas diffusion layer and an internal reforming catalyst. The internal reforming catalyst may comprise any suitable reformer and is adjacent to the anode. In this configuration, the heat generated in the exothermic reactions on the catalyst in the fuel cell and the ohmic heating of the fuel cell electrolyte are the driving force for the endothermic fuel reforming reaction to convert the alcohol fuel into hydrogen. It is possible to use any alcohol fuel, such as methanol or ethanol. 5 n. and 20 z.p. f-ly, 4 ill.

Technical field

The invention relates to direct-acting alcohol fuel cells using solid acid electrolytes.

State of the art

Alcohols have recently come under intense scrutiny as potential fuels. Alcohols such as methanol and ethanol are particularly desirable as fuels because they have specific energies five to seven times that of standard compressed hydrogen. For example, one liter of methanol is energetically equivalent to 5.2 liters of hydrogen compressed to 320 atm. In addition, one liter of ethanol is energetically equivalent to 7.2 liters of hydrogen compressed to 350 atm. Such alcohols are also desirable because they are easy to handle, store and transport.

Methanol and ethanol have been the subject of much research in terms of alcohol fuels. Ethanol can be obtained from the fermentation of plants containing sugar and starch. Methanol can be obtained from the gasification of wood or waste wood/cereals (straw). However, methanol synthesis is more efficient. These alcohols, among other things, are renewable resources and therefore they are expected to play an important role in both reducing greenhouse gas emissions and reducing dependence on fossil fuels.

Fuel cells have been proposed as devices that convert the chemical energy of such alcohols into electrical energy. In this regard, direct-acting alcohol fuel cells with polymer electrolyte membranes have been subjected to intensive research. Specifically, direct methanol fuel cells and direct ethanol fuel cells have been studied. However, research on direct ethanol fuel cells has been limited due to the relative difficulty of oxidizing ethanol compared to oxidizing methanol.

Despite these extensive research efforts, the performance of direct alcohol fuel cells remains unsatisfactory, mainly due to the kinetic limitations imposed by electrode catalysts. For example, typical direct-acting methanol fuel cells have a power density of approximately 50 mW/cm 2 . Higher specific power levels have been obtained, for example 335 mW/cm 2 , but only under extremely harsh conditions (Nafion®, 130°C, oxygen 5 atm and methanol 1 M for a flow rate of 2 cc/min at a pressure of 1.8 atm). Similarly, a direct ethanol fuel cell has a power density of 110 mW/cm 2 under similar extremely harsh conditions (Nafion® silica, 140° C., anode 4 atm, oxygen 5.5 atm). Accordingly, there is a need for direct-acting alcohol fuel cells having high power densities in the absence of such extreme conditions.

Brief summary of the invention

The present invention relates to alcohol fuel cells containing solid acid electrolytes and using an internal reforming catalyst. A fuel cell generally includes an anode, a cathode, a solid acid electrolyte, and an internal reformer. The reformer provides for the reforming of alcohol fuel to produce hydrogen. The driving force behind the reforming reaction is the heat generated during the exothermic reactions in the fuel cell.

The use of solid acid electrolytes in the fuel cell makes it possible to place the reformer directly adjacent to the anode. This was not previously considered possible due to the elevated temperatures required for effective functioning of known reforming materials and the heat sensitivity of typical polymer electrolyte membranes. However, compared to conventional polymer electrolyte membranes, solid acid electrolytes can withstand much higher temperatures, which makes it possible to place the reformer adjacent to the anode and therefore close to the electrolyte. In this configuration, the waste heat generated by the electrolyte is absorbed by the reformer and drives the endothermic reforming reaction.

Brief description of the drawings

These and other features and advantages of the present invention will be better understood upon reading the following detailed description, taken in conjunction with the accompanying drawings, where:

Figure 1 is a schematic representation of a fuel cell according to one embodiment of the present invention;

Figure 2 is a graphical comparison of curves between power density and cell voltage for fuel cells obtained according to Examples 1 and 2 and Comparative Example 1;

Figure 3 is a graphical comparison of curves between power density and cell voltage for fuel cells obtained according to Examples 3, 4 and 5 and Comparative Example 2; and

Figure 4 is a graphical comparison of the curves between power density and cell voltage for fuel cells obtained in accordance with Comparative Examples 2 and 3.

Detailed description of the invention

The present invention relates to direct alcohol fuel cells containing solid acid electrolytes and using an internal reforming catalyst in physical contact with a membrane electrode assembly (MEA) designed to reform an alcohol fuel to produce hydrogen. As noted above, fuel cell performance that converts chemical energy in alcohols directly into electrical power remains unsatisfactory due to kinetic limitations imposed by fuel cell electrode catalysts. However, it is well known that these kinetic limits are greatly reduced when hydrogen fuel is used. Accordingly, the present invention uses a reforming catalyst or reformer for reforming an alcohol fuel into hydrogen, thereby reducing or eliminating the kinetic limitations associated with the alcohol fuel. Alcohol fuels are steam reformed according to the following reaction examples:

Methanol to hydrogen: CH 3 OH+H 2 O→3H 2 +CO 2 ;

Ethanol to hydrogen: C 2 H 5 OH+3H 2 O→6H 2 +2CO 2 .

However, the reforming reaction is highly endothermic. Therefore, the reformer must be heated to obtain the driving force for the reforming reaction. The amount of heat required is typically about 59 kJ per mole of methanol (equivalent to burning about 0.25 moles of hydrogen) and about 190 kJ per mole of ethanol (equivalent to burning about 0.78 moles of hydrogen).

As a result of the passage of electric current during operation of the fuel cells, waste heat is generated, the effective removal of which is problematic. However, the generation of this waste heat makes placing the reformer directly next to the fuel cell a natural choice. Such a configuration makes it possible to supply hydrogen from the reformer to the fuel cell and cool the fuel cell, and allows the fuel cell to heat the reformer and generate a driving force for reactions therein. This configuration is used in molten carbonate fuel cells and for methane reforming reactions at a temperature of approximately 650°C. However, alcohol reforming reactions generally proceed at temperatures ranging from about 200° C. to about 350° C., and no suitable alcohol reforming fuel cell has yet been developed.

The present invention relates to such a fuel cell using alcohol reforming. As illustrated in FIGURE 1, a fuel cell 10 according to the present invention generally includes a first current collector/gas diffusion layer 12, an anode 12a, a second current collector/gas diffusion layer 14, a cathode 14a, an electrolyte 16, and an internal reforming catalyst 18. Internal reforming catalyst 18 placed adjacent to the anode 12a. More specifically, the reforming catalyst 18 is placed between the first gas diffusion layer 12 and the anode 12a. Any known suitable reforming catalyst 18 may be used. Non-limiting examples of suitable reforming catalysts include mixtures of Cu-Zn-Al oxides, mixtures of Cu-Co-Zn-Al oxides, and mixtures of Cu-Zn-Al-Zr oxides.

Any alcohol fuel such as methanol, ethanol and propanol can be used. In addition, dimethyl ether can be used as a fuel.

Historically, this configuration has not been considered possible for alcohol fuel cells due to the endothermic nature of the reforming reaction and the sensitivity of the electrolyte to heat. Typical alcohol fuel cells use polymer electrolyte membranes that cannot withstand the heat required to drive the reforming catalyst. However, the electrolytes used in the fuel cells of the present invention contain solid acid electrolytes such as those described in US Pat. pending U.S. Patent Application 10/139043, entitled PROTON CONDUCTING MEMBRANE USING A SOLID ACID, the entire contents of which are also incorporated herein by reference. One non-limiting example of a solid acid suitable for use as an electrolyte in the present invention is CsH 2 PO 4 . The solid acid electrolytes used in the fuel cells of this invention can withstand much higher temperatures, which makes it possible to place the reforming catalyst directly adjacent to the anode. In addition, the endothermic reforming reaction consumes the heat generated in the exothermic reactions in the fuel cell, forming a thermally balanced system.

These solid acids are used in their superprotonic phases and act as proton conducting membranes in the temperature range from about 100°C to about 350°C. The upper end of this temperature range is ideal for methanol reforming. In order to generate enough heat to generate a driving force for the reforming reaction and to provide proton conductivity of the solid acidic electrolyte, the fuel cell of the present invention is preferably operated at temperatures ranging from about 100°C to about 500°C. However, it is more preferred to operate the fuel cell at temperatures ranging from about 200°C to about 350°C. In addition to greatly improving the performance of alcohol fuel cells, the relatively high operating temperatures of the alcohol fuel cells of the invention may allow the replacement of expensive metal catalysts such as Pt/Ru and Pt at the anode and cathode, respectively, with less expensive catalyst materials.

The following examples and comparative examples illustrate the superior performance of the alcohol fuel cells of the invention. However, these examples are presented for purposes of illustration only and should not be taken as limiting the invention to these examples.

Example 1 Methanol Fuel Cell

13 mg/cm2 Pt/Ru was used as an anode electrocatalyst. Cu (30% wt.) - Zn (20% wt.) - Al was used as an internal reforming catalyst. 15 mg/cm2 Pt was used as the cathodic electrocatalyst. The electrolyte used was a CsH 2 PO 4 membrane with a thickness of 160 μm. Steamed mixtures of methanol and water were fed into the anode space at a flow rate of 100 μl/min. 30% humidified oxygen was applied to the cathode at a flow rate of 50 cm 3 /min (standard temperature and pressure). The methanol:water ratio was 25:75. The temperature of the element was set equal to 260°C.

Example 2 Ethanol Fuel Cell

13 mg/cm2 Pt/Ru was used as an anode electrocatalyst. Cu (30% wt.) - Zn (20% wt.) - Al was used as an internal reforming catalyst. 15 mg/cm2 Pt was used as the cathode electrocatalyst. The electrolyte used was a CsH 2 PO 4 membrane with a thickness of 160 μm. Steamed mixtures of ethanol and water were fed into the anode space at a flow rate of 100 μl/min. 30% humidified oxygen was applied to the cathode at a flow rate of 50 cm 3 /min (standard temperature and pressure). The ratio of ethanol: water was 15:85. The temperature of the element was set equal to 260°C.

Comparative Example 1 Fuel Cell Using Pure H 2

13 mg/cm2 Pt/Ru was used as an anode electrocatalyst. 15 mg/cm2 Pt was used as the cathode electrocatalyst. The electrolyte used was a CsH 2 PO 4 membrane with a thickness of 160 μm. 3% humidified hydrogen was supplied to the anode space at a flow rate of 100 µl/min. 30% humidified oxygen was applied to the cathode at a flow rate of 50 cm 3 /min (standard temperature and pressure). The temperature of the element was set equal to 260°C.

Figure 2 shows the power density versus cell voltage curves for Examples 1 and 2 and Comparative Example 1. As shown, the methanol fuel cell (Example 1) achieves a peak power density of 69 mW/cm cell achieves a peak power density of 53 mW/cm 2 and a hydrogen fuel cell (Comparative Example 1) achieves a peak power density of 80

mW / cm 2. These results show that the fuel cells obtained according to Example 1 and Comparative Example 1 are very similar, indicating that the methanol fuel cell having the reformer exhibits performance almost as good as that of the hydrogen fuel cell, which is a significant improvement. However, as shown in the following Examples and Comparative Examples, by reducing the thickness of the electrolyte, an additional increase in power density is achieved.

The fuel cell was made by slurry deposition of CsH 2 PO 4 onto a porous stainless steel support that served as both a gas diffusion layer and a current collector. The cathode electrocatalyst layer was first deposited on the gas diffusion layer and then pressed before the electrolyte layer was deposited. After that, a layer of anode electrocatalyst was deposited, followed by placement of a second gas diffusion electrode as the final layer of the structure.

As an anode electrode, a mixture of CsH 2 PO 4 , Pt (50 atomic wt.%) Ru, Pt (40 wt. %) - Ru (20 wt. %) deposited on C (40 wt. %), and naphthalene was used. The ratio of components in a mixture of CsH 2 PO 4:Pt-Ru:Pt-Ru-C:naphthalene was 3:3:1:0.5 (wt.). The mixture was used in a total amount of 50 mg. Download Pt and Ru were 5.6 mg/cm 2 and 2.9 mg/cm 2 respectively. The area of ​​the anode electrode was equal to 1.74 cm 2 .

As the cathode electrode used a mixture of CsH 2 PO 4 , Pt, Pt (50% wt.), deposited on C (50% wt.), and naphthalene. The ratio of components in a mixture of CsH 2 PO 4:Pt:Pt-C:naphthalene was 3:3:1:1 (wt.). The mixture was used in a total amount of 50 mg. Pt loadings were 7.7 mg/cm 2 . The area of ​​the cathode was equal to 2.3-2.9 cm 1 .

As a reforming catalyst used CuO (30% wt.) - ZnO (20% wt.) - Al 2 O 3 ie CuO (31% mol.) - ZnO (16% mol.) - Al 2 O 3 . The reforming catalyst was prepared by a co-precipitation method using a solution of copper, zinc, and aluminum nitrate (total metal concentration was 1 mol/l) and an aqueous solution of sodium carbonates (1.1 mol/l). The precipitate was washed with deionized water, filtered off, and dried in air at 120°C for 12 hours. The dried powder in an amount of 1 g was lightly pressed to a thickness of 3.1 mm and a diameter of 15.6 mm, and then calcined at 350° C. for 2 hours.

The electrolyte used was a CsH 2 PO 4 membrane with a thickness of 47 μm.

A methanol-water solution (43% vol. or 37% wt. or 25% mol. or 1.85 M methanol) was fed through a glass evaporator (200°C) at a flow rate of 135 μl/min. The temperature of the element was set equal to 260°C.

The fuel cell was prepared in accordance with the above example 3, except that through the evaporator (200°C) at a flow rate of 114 μl/min was fed not a mixture of methanol-water, but a mixture of ethanol-water (36% vol. or 31% of the mass or 15% mol., or 0.98 M ethanol).

The fuel cell was prepared in accordance with Example 3 above, except that at a flow rate of 100 μl/min, vodka (Absolut Vodka, Sweden) (40% vol. or 34% wt., or 17% mol.) was supplied instead of methanol-water. . ethanol).

Comparative Example 2

A fuel cell was prepared in accordance with Example 3 above, except that dried hydrogen at 100 sccm moistened with hot water (70° C.) was used instead of methanol-water.

Comparative Example 3

A fuel cell was prepared in accordance with Example 3 above except that no reforming catalyst was used and the cell temperature was set to 240°C.

Comparative Example 4

A fuel cell was prepared in accordance with Comparative Example 2, except that the cell temperature was set to 240°C.

Figure 3 shows curves between power density and cell voltage for Examples 3, 4 and 5 and Comparative Example 2. As shown, the methanol fuel cell (Example 3) achieves a peak power density of 224 mW/cm 2 , which is a significant increase specific power compared to the fuel cell obtained in accordance with example 1 and having a much thicker electrolyte. This methanol fuel cell also shows a dramatic improvement in performance over methanol fuel cells that do not use an internal reformer, which is better demonstrated in Figure 4. The ethanol fuel cell (Example 4) also shows increased power density and cell voltage compared to an ethanol fuel cell. having a thicker electrolyte membrane (example 2). However, as shown, the methanol fuel cell (Example 3) performs better than the ethanol fuel cell (Example 4). For a vodka fuel cell (Example 5), specific powers are achieved that are comparable to those of an ethanol fuel cell. As shown in Figure 3, the methanol fuel cell (Example 3) exhibits performance that is about as good as that of the hydrogen fuel cell (Comparative Example 2).

Figure 4 shows the power density versus cell voltage curves for Comparative Examples 3 and 4. As shown, a methanol fuel cell without a reformer (Comparative Example 3) achieves significantly lower power densities than those achieved with hydrogen fuel cell (comparative example 4). In addition, Figures 2, 3 and 4 show that compared to a methanol fuel cell without a reformer (Comparative Example 3), significantly higher power densities are achieved for methanol fuel cells with reformers (Examples 1 and 3).

The foregoing description has been presented to introduce the currently preferred embodiments of the invention. Those skilled in the relevant art and technology to which this invention relates should understand that changes and modifications may be made to the described embodiments without substantially deviating from the principles, scope and spirit of this invention. Accordingly, the foregoing description should not be taken as referring only to the specific embodiments described, but rather should be understood to be consistent with and substantiating the following claims, which contain the fullest and most objective scope of the invention.

1. A fuel cell comprising: an anode electrocatalytic layer, a cathode electrocatalytic layer, an electrolyte layer containing a solid acid, a gas diffusion layer, and an internal reforming catalyst disposed adjacent to the anode electrocatalytic layer such that the internal reforming catalyst is located between the anode electrocatalytic layer and the gas diffusion layer and is in physical contact with the anode electrocatalytic layer.

2. The fuel cell of claim 1, wherein the solid acidic electrolyte contains CsH 2 PO 4 .

3. The fuel cell of claim 1 wherein the reforming catalyst is selected from the group consisting of Cu-Zn-Al oxide mixtures, Cu-Co-Zn-Al oxide mixtures, and Cu-Zn-Al-Zr oxide mixtures.

4. A method of operating a fuel cell, including:





fuel supply; and operating the fuel cell at a temperature in the range of about 100°C to about 500°C.

5. The method of claim 4, wherein the fuel is alcohol.

6. The method of claim 4 wherein the fuel is selected from the group consisting of methanol, ethanol, propanol and dimethyl ether.

7. The method of claim 4 wherein the fuel cell is operated at a temperature in the range of about 200°C to about 350°C.

8. The process of claim 4 wherein the reforming catalyst is selected from the group consisting of Cu-Zn-Al oxide mixtures, Cu-Co-Zn-Al oxide mixtures, and Cu-Zn-Al-Zr oxide mixtures.

9. The method of claim 4, wherein the electrolyte contains a solid acid.

10. The method according to claim 9, where the solid acid contains CsH 2 PO 4 .

11. A method of operating a fuel cell, including:
formation of an anode electrocatalytic layer;
formation of a cathode electrocatalytic layer;
forming an electrolyte layer containing a solid acid;
formation of a gas diffusion layer and
forming an internal reforming catalyst near the anode electrocatalytic layer such that the internal reforming catalyst is located between the anode electrocatalytic layer and the gas diffusion layer and is in physical contact with the anode electrocatalytic layer;
fuel supply; and operating the fuel cell at a temperature in the range of about 200°C to about 350°C.

12. The method of claim 11 wherein the fuel is alcohol.

13. The method of claim 11 wherein the fuel is selected from the group consisting of methanol, ethanol, propanol and dimethyl ether.

14. The process of claim 11 wherein the reforming catalyst is selected from the group consisting of Cu-Zn-Al oxide mixtures, Cu-Co-Zn-Al oxide mixtures, and Cu-Zn-Al-Zr oxide mixtures.

15. The method of claim 11 wherein the electrolyte contains a solid acid.

16. The method of claim 15 wherein the solid acid contains CsH 2 PO 4 .

17. A method of operating a fuel cell, including:
formation of an anode electrocatalytic layer;
formation of a cathode electrocatalytic layer;
forming an electrolyte layer containing a solid acid;
formation of a gas diffusion layer and
forming an internal reforming catalyst near the anode electrocatalytic layer such that the internal reforming catalyst is located between the anode electrocatalytic layer and the gas diffusion layer and is in physical contact with the anode electrocatalytic layer;
supply of alcohol fuel; and operating the fuel cell at a temperature in the range of about 100°C to about 500°C.

18. The method of claim 17 wherein the fuel is selected from the group consisting of methanol, ethanol, propanol and dimethyl ether.

19. The method of claim 17 wherein the fuel cell is operated at a temperature in the range of about 200°C to about 350°C.

20. The process of claim 17 wherein the reforming catalyst is selected from the group consisting of Cu-Zn-Al oxide mixtures, Cu-Co-Zn-Al oxide mixtures, and Cu-Zn-Al-Zr oxide mixtures.

21. The method of claim 17, wherein the solid acidic electrolyte contains CsH 2 PO 4 .

22. A method of operating a fuel cell, including:
formation of an anode electrocatalytic layer;
formation of a cathode electrocatalytic layer;
forming an electrolyte layer containing a solid acid;
formation of a gas diffusion layer and
forming an internal reforming catalyst near the anode electrocatalytic layer such that the internal reforming catalyst is located between the anode electrocatalytic layer and the gas diffusion layer and is in physical contact with the anode electrocatalytic layer;
supply of alcohol fuel; and operating the fuel cell at a temperature in the range of about 200°C to about 350°C.

The invention relates to direct-acting alcohol fuel cells using solid acid electrolytes and internal reforming catalysts