Doctor of technical sciences ON THE. I swear, professor,
academician Russian Academy Technological Sciences, Moscow

AT recent decades the world is considering the direction of more efficient use of the energy of the deep heat of the Earth in order to partially replace natural gas, oil, coal. This will become possible not only in areas with high geothermal parameters, but also in any area of ​​the globe when drilling injection and production wells and creating circulation systems between them.

The interest in alternative energy sources that has grown in recent decades in the world is caused by the depletion of hydrocarbon fuel reserves and the need to solve a number of problems. environmental issues. Objective factors (reserves of fossil fuels and uranium, as well as changes in the environment caused by traditional fire and nuclear energy) allow us to assert that the transition to new methods and forms of energy production is inevitable.

The world economy is currently heading towards the transition to a rational combination of traditional and new energy sources. The heat of the Earth occupies one of the first places among them.

Geothermal energy resources are divided into hydrogeological and petrogeothermal. The first of them are represented by coolants (they make up only 1% of common resources geothermal energy) - groundwater, steam and steam-water mixtures. The second are geothermal energy contained in hot rocks.

The fountain technology (self-spill) used in our country and abroad for the extraction of natural steam and geothermal waters is simple, but inefficient. With a low flow rate of self-flowing wells, their heat production can recoup the cost of drilling only at a small depth of geothermal reservoirs with high temperature in areas of thermal anomalies. The service life of such wells in many countries does not even reach 10 years.

At the same time, experience confirms that in the presence of shallow collectors of natural steam, the construction of a Geothermal power plant is the most profitable option for using geothermal energy. The operation of such GeoTPPs has shown their competitiveness in comparison with other types of power plants. Therefore, the use of reserves of geothermal waters and steam hydrotherms in our country on the Kamchatka Peninsula and on the islands of the Kuril chain, in the regions of the North Caucasus, and also possibly in other areas, is expedient and timely. But steam deposits are a rarity, its known and predicted reserves are small. Much more common deposits of heat and power water are not always located close enough to the consumer - the heat supply object. This excludes the possibility of large scales of their effective use.

Often in difficult problem outgrow the issues of combating salinity. The use of geothermal, as a rule, mineralized sources as a heat carrier leads to overgrowth of borehole zones with iron oxide, calcium carbonate and silicate formations. In addition, the problems of erosion-corrosion and scaling adversely affect the operation of the equipment. The problem, also, is the discharge of mineralized and wastewater containing toxic impurities. Therefore, the simplest fountain technology cannot serve as the basis for the widespread development of geothermal resources.

According to preliminary estimates on the territory of the Russian Federation, the predicted reserves of thermal waters with a temperature of 40–250 °C, a salinity of 35–200 g/l and a depth of up to 3000 m are 21–22 million m3/day, which is equivalent to burning 30–40 million tons of water. .t. in year.

The predicted reserves of the steam-air mixture with a temperature of 150-250 ° C of the Kamchatka Peninsula and Kuril Islands is 500 thousand m3/day. and reserves of thermal waters with a temperature of 40-100 ° C - 150 thousand m3 / day.

The reserves of thermal waters with a flow rate of about 8 million m3/day, with a salinity of up to 10 g/l and a temperature above 50 °C are considered top priority for development.

Much greater value for the energy of the future is the extraction of thermal energy, practically inexhaustible petrogeothermal resources. This geothermal energy, enclosed in solid hot rocks, is 99% of the total resources of underground thermal energy. At a depth of up to 4-6 km, massifs with a temperature of 300-400 °C can be found only near the intermediate chambers of some volcanoes, but hot rocks with a temperature of 100-150 °C are distributed almost everywhere at these depths, and with a temperature of 180-200 °C in a fairly significant part territory of Russia.

For billions of years, nuclear, gravitational and other processes inside the Earth have generated and continue to generate thermal energy. Some of it is radiated into outer space, and heat is accumulated in the depths, i.e. the heat content of the solid, liquid and gaseous phases of terrestrial matter is called geothermal energy.

The continuous generation of intra-terrestrial heat compensates for it external losses, serves as a source of accumulation of geothermal energy and determines the renewable part of its resources. The total heat removal of the subsoil to earth's surface three times the current capacity of power plants in the world and is estimated at 30 TW.

However, it is clear that renewability matters only for limited natural resources, and overall potential geothermal energy is practically inexhaustible, since it should be defined as the total amount of heat available to the Earth.

It is no coincidence that in recent decades, the world has been considering the direction of more efficient use of the energy of the deep heat of the Earth in order to partially replace natural gas, oil, and coal. This will become possible not only in areas with high geothermal parameters, but also in any area of ​​the globe when drilling injection and production wells and creating circulation systems between them.

Of course, with low thermal conductivity of rocks, for the effective operation of circulation systems, it is necessary to have or create a sufficiently developed heat exchange surface in the heat extraction zone. Such a surface is often found in porous formations and zones of natural fracture resistance, which are often found at the above depths, the permeability of which makes it possible to organize forced filtration of the coolant with efficient extraction of rock energy, as well as the artificial creation of an extensive heat exchange surface in low-permeable porous massifs by hydraulic fracturing (see figure).

At present, hydraulic fracturing is used in oil and gas industry as a way to increase reservoir permeability to enhance oil recovery in the development of oil fields. Modern technology makes it possible to create a narrow but long crack, or a short but wide one. Examples of hydraulic fractures with fractures up to 2-3 km long are known.

The domestic idea of ​​extracting the main geothermal resources contained in solid rocks was expressed as early as 1914 by K.E. Obruchev.

In 1963, the first GCC was created in Paris to extract heat from porous formation rocks for heating and air conditioning in the premises of the Broadcasting Chaos complex. In 1985, 64 GCCs were already operating in France with a total thermal capacity of 450 MW, with an annual saving of approximately 150,000 tons of oil. In the same year, the first such GCC was created in the USSR in the Khankala valley near the city of Grozny.

In 1977, according to the project of the Los Alamos National Laboratory of the USA, tests of an experimental GCC with hydraulic fracturing of an almost impermeable massif began at the Fenton Hill site in the state of New Mexico. Cold fresh water injected through the well (injection) was heated due to heat exchange with a rock mass (185 OC) in a vertical fracture with an area of ​​8000 m2, formed by hydraulic fracturing at a depth of 2.7 km. In another well (production), also crossing this crack, superheated water came to the surface in the form of a steam jet. When circulating in a closed circuit under pressure, the temperature of superheated water on the surface reached 160-180 °C, and the thermal power of the system - 4-5 MW. Coolant leaks into the surrounding massif amounted to about 1% of the total flow. The concentration of mechanical and chemical impurities(up to 0.2 g / l) corresponded to the conditions of fresh drinking water. The hydraulic fracture did not require fixing and was kept open by the hydrostatic pressure of the fluid. The free convection developing in it ensured effective participation in the heat exchange of almost the entire surface of the outcrop of the hot rock mass.

The extraction of underground thermal energy from hot impermeable rocks, based on the methods of inclined drilling and hydraulic fracturing that have been mastered and practiced in the oil and gas industry for a long time, did not cause seismic activity, nor any other harmful effects on the environment.

In 1983, British scientists repeated the American experience by creating an experimental GCC with hydraulic fracturing of granites in Carnwell. Similar works were held in Germany, Sweden. More than 224 geothermal heating projects have been implemented in the USA. It is assumed, however, that geothermal resources can provide the bulk of the US's future non-electric thermal energy needs. In Japan, the capacity of GeoTPP in 2000 reached approximately 50 GW.

Currently, research and exploration of geothermal resources is carried out in 65 countries. In the world, based on geothermal energy, stations with a total capacity of about 10 GW have been created. The United Nations is actively supporting the development of geothermal energy.

The experience accumulated in many countries of the world in the use of geothermal coolants shows that under favorable conditions they are 2-5 times more profitable than thermal and nuclear power plants. Calculations show that one geothermal well can replace 158 thousand tons of coal per year.

Thus, the Earth's heat is perhaps the only major renewable energy resource, the rational development of which promises to reduce the cost of energy compared to modern fuel energy. With an equally inexhaustible energy potential, solar and thermonuclear installations, unfortunately, will be more expensive than existing fuel ones.

Despite the very long history of the development of the Earth's heat, today geothermal technology has not yet reached its high development. The development of the thermal energy of the Earth is experiencing great difficulties in the construction of deep wells, which are a channel for bringing the coolant to the surface. Due to the high temperature at the bottomhole (200-250 °C), traditional rock cutting tools are unsuitable for working in such conditions, there are special requirements for the choice of drill and casing pipes, cement slurries, drilling technology, well casing and completion. Domestic measuring equipment, serial operational fittings and equipment are produced in a design that allows temperatures not higher than 150-200 ° C. Traditional deep mechanical drilling of wells is sometimes delayed for years and requires significant financial costs. In the main production assets, the cost of wells is from 70 to 90%. This problem can and should be solved only by creating a progressive technology for the development of the main part of geothermal resources, i.e. extraction of energy from hot rocks.

Our group of Russian scientists and specialists has been dealing with the problem of extracting and using the inexhaustible, renewable deep thermal energy of the Earth's hot rocks on the territory of the Russian Federation for more than one year. The purpose of the work is to create on the basis of domestic, high technology technical means for deep penetration earth's crust. Currently, several variants of drilling tools (BS) have been developed, which have no analogues in world practice.

The operation of the first version of the BS is linked to the current conventional well drilling technology. Hard rock drilling speed (average density 2500-3300 kg/m3) up to 30 m/h, hole diameter 200-500 mm. The second variant of the BS performs drilling of wells in an autonomous and automatic mode. The launch is carried out from a special launch and acceptance platform, from which its movement is controlled. One thousand meters of BS in hard rocks will be able to pass within a few hours. Well diameter from 500 to 1000 mm. Reusable BS variants have great cost-effectiveness and huge potential value. The introduction of BS into production will open new stage in the construction of wells and provide access to inexhaustible sources of thermal energy of the Earth.

For the needs of heat supply, the required depth of wells throughout the country lies in the range of up to 3-4.5 thousand meters and does not exceed 5-6 thousand meters. The temperature of the heat carrier for housing and communal heat supply does not go beyond 150 °C. For industrial facilities, the temperature, as a rule, does not exceed 180-200 °C.

The purpose of creating the GCC is to provide constant, affordable, cheap heat to remote, hard-to-reach and undeveloped regions of the Russian Federation. The duration of operation of the GCS is 25-30 years or more. Payback period of stations (taking into account the latest technologies drilling) - 3-4 years.

The creation in the Russian Federation in the coming years of appropriate capacities for the use of geothermal energy for non-electric needs will replace about 600 million tons of equivalent fuel. Savings can be up to 2 trillion rubles.

Until 2030, it becomes possible to create energy capacities to replace fire energy by up to 30%, and until 2040 to almost completely eliminate organic raw materials as fuel from the energy balance of the Russian Federation.

Literature

1. Goncharov S.A. Thermodynamics. Moscow: MGTUim. N.E. Bauman, 2002. 440 p.

2. Dyadkin Yu.D. etc. Geothermal thermal physics. St. Petersburg: Nauka, 1993. 255 p.

3. Mineral resource base of the fuel and energy complex of Russia. Status and prognosis / V.K. Branchhugov, E.A. Gavrilov, V.S. Litvinenko and others. Ed. V.Z. Garipova, E.A. Kozlovsky. M. 2004. 548 p.

4. Novikov G. P. et al. Drilling wells for thermal waters. M.: Nedra, 1986. 229 p.

This energy belongs to alternative sources. Nowadays, more and more often they mention the possibilities of obtaining resources that the planet gives us. We can say that we live in an era of fashion for renewable energy. A multitude is created technical solutions, plans, theories in this area.

It is deep in the bowels of the earth and has the properties of renewal, in other words it is endless. Classical resources, according to scientists, are beginning to run out, oil, coal, gas will run out.

Nesjavellir Geothermal Power Plant, Iceland

Therefore, one can gradually prepare to adopt new alternative methods of energy production. Under the earth's crust is a powerful core. Its temperature ranges from 3000 to 6000 degrees. moving lithospheric plates demonstrates it tremendous power. It manifests itself in the form of volcanic sloshing of magma. In the depths, radioactive decay occurs, sometimes prompting such natural disasters.

Usually magma heats the surface without going beyond it. This is how geysers or warm pools of water are obtained. In this way, physical processes can be used for the right purposes for humanity.

Types of geothermal energy sources

It is usually divided into two types: hydrothermal and petrothermal energy. The first is formed by warm springs, and the second type is the temperature difference at the surface and in the depths of the earth. To put it in your own words, a hydrothermal spring is made up of steam and hot water, while a petrothermal spring is hidden deep underground.

Map of the development potential of geothermal energy in the world

For petrothermal energy, it is necessary to drill two wells, fill one with water, after which a soaring process will occur, which will come to the surface. There are three classes of geothermal areas:

• Geothermal - located near the continental plates. Temperature gradient over 80C/km. As an example, the Italian commune of Larderello. There is a power plant
• Semi-thermal - temperature 40 - 80 C / km. These are natural aquifers, consisting of crushed rocks. In some places in France, buildings are heated in this way.
• Normal - gradient less than 40 C/km. Representation of such areas is most common

They are an excellent source for consumption. They are in the rock, at a certain depth. Let's take a closer look at the classification:

• Epithermal - temperature from 50 to 90 s
• Mesothermal - 100 - 120 s
• Hypothermal - more than 200 s

These species are composed of different chemical composition. Depending on it, water can be used for various purposes. For example, in the production of electricity, heat supply (thermal routes), raw materials base.

Video: Geothermal energy

Heat supply process

The water temperature is 50 -60 degrees, which is optimal for heating and hot supply of a residential area. The need for heating systems depends on the geographical location and climatic conditions. And people constantly need the needs of hot water supply. For this process, GTS (geothermal thermal stations) are being built.

If for classical production thermal energy is used by a boiler house that consumes solid or gas fuel, then a geyser source is used in this production. The technical process is very simple, the same communications, thermal routes and equipment. It is enough to drill a well, clean it from gases, then send it to the boiler room with pumps, where the temperature schedule will be maintained, and then it will enter the heating main.

The main difference is that there is no need to use a fuel boiler. This significantly reduces the cost of thermal energy. In winter, subscribers receive heat and hot water supply, and in summer only hot water supply.

Power generation

Hot springs, geysers are the main components in the production of electricity. For this, several schemes are used, special power plants are being built. GTS device:

• DHW tank
• Pump
• Gas separator
• Steam separator
• generating turbine
• Capacitor
• booster pump
• Tank - cooler

As you can see, the main element of the circuit is a steam converter. This makes it possible to obtain purified steam, since it contains acids that destroy turbine equipment. It is possible to use a mixed scheme in the technological cycle, that is, water and steam are involved in the process. The liquid goes through the entire stage of purification from gases, as well as steam.

Circuit with binary source

The working component is a liquid with a low boiling point. Thermal water is also involved in the production of electricity and serves as a secondary raw material.

With its help, low-boiling source steam is formed. GTS with such a cycle of work can be fully automated and do not require the presence of maintenance personnel. More powerful stations use a two-circuit scheme. This type of power plant allows reaching a capacity of 10 MW. Double circuit structure:

• steam generator
• Turbine
• Capacitor
• Ejector
• Feed pump
• Economizer
• Evaporator

Practical use

Huge reserves of sources are many times greater than the annual energy consumption. But only a small fraction is used by mankind. The construction of the stations dates back to 1916. In Italy, the first GeoTPP with a capacity of 7.5 MW was created. The industry is actively developing in such countries as: USA, Iceland, Japan, Philippines, Italy.

Active exploration of potential sites and more convenient methods of extraction are underway. The production capacity is growing from year to year. If we take into account the economic indicator, then the cost of such an industry is equal to coal-fired thermal power plants. Iceland almost completely covers the communal and housing stock with a GT source. 80% of homes use hot water from wells. Experts from the USA claim that, with proper development, GeoTPPs can produce 30 times more than annual consumption. If we talk about the potential, then 39 countries of the world will be able to fully provide themselves with electricity if they use the bowels of the earth to 100 percent.

With the development and formation of society, mankind began to look for more and more modern and at the same time economical ways to obtain energy. For this, various stations are being built today, but at the same time, the energy contained in the bowels of the earth is widely used. What is she like? Let's try to figure it out.

geothermal energy

Already from the name it is clear that it represents the heat of the earth's interior. Under the earth's crust is a layer of magma, which is a fiery-liquid silicate melt. According to research data, the energy potential of this heat is much higher than the energy of the world's natural gas reserves, as well as oil. Magma comes to the surface - lava. Moreover, the greatest activity is observed in those layers of the earth on which the boundaries of tectonic plates are located, as well as where the earth's crust is characterized by thinness. geothermal energy Earth is obtained as follows: the lava and water resources of the planet are in contact, as a result of which the water begins to heat up sharply. This leads to the eruption of the geyser, the formation of the so-called hot lakes and undercurrents. That is, precisely those phenomena of nature, the properties of which are actively used as energies.

Artificial geothermal sources

The energy contained in the bowels of the earth must be used wisely. For example, there is an idea to create underground boilers. To do this, you need to drill two wells of sufficient depth, which will be connected at the bottom. That is, it turns out that in almost any corner of the land you can get geothermal energy. industrial way: through one well will be injected cold water into the reservoir, and through the second - hot water or steam is extracted. Artificial heat sources will be beneficial and rational if the resulting heat will provide more energy. The steam can be sent to turbine generators that will generate electricity.

Of course, the heat taken away is only a fraction of what is available in general reserves. But it should be remembered that the deep heat will be constantly replenished due to the processes of compression of rocks, stratification of the bowels. According to experts, the earth's crust accumulates heat, the total amount of which is 5,000 times greater than the calorific value of all fossil interiors of the earth as a whole. It turns out that the operating time of such artificially created geothermal stations can be unlimited.

Source Features

The sources that make it possible to obtain geothermal energy are almost impossible to fully use. They exist in more than 60 countries of the world, with the largest number of terrestrial volcanoes on the territory of the Pacific volcanic ring of fire. But in practice, it turns out that geothermal sources in different regions worlds are completely different in their properties, namely the average temperature, mineralization, gas composition, acidity and so on.

Geysers are sources of energy on Earth, the peculiarities of which are that they spew boiling water at certain intervals. After the eruption, the pool becomes free of water, at its bottom you can see a channel that goes deep into the ground. Geysers as energy sources are used in regions such as Kamchatka, Iceland, New Zealand and North America, and single geysers are also found in some other areas.

Where does energy come from?

Uncooled magma is located very close to the earth's surface. Gases and vapors are released from it, which rise and pass through the cracks. Mixing with groundwater, they cause them to heat up, they themselves turn into hot water, in which many substances are dissolved. Such water is released to the surface of the earth in the form of various geothermal sources: hot springs, mineral springs, geysers, and so on. According to scientists, the hot bowels of the earth are caves or chambers connected by passages, cracks and channels. They are just filled with groundwater, and very close to them are magma chambers. This is how it naturally forms thermal energy earth.

Earth's electric field

There is another alternative energy source in nature, which is renewable, environmentally friendly, and easy to use. True, so far this source has only been studied and not applied in practice. So, potential energy The earth lies in its electric field. You can get energy in this way based on the study of the basic laws of electrostatics and features electric field Earth. In fact, our planet from an electrical point of view is a spherical capacitor charged up to 300,000 volts. Its inner sphere has negative charge, and the outer one - the ionosphere - is positive. is an insulator. Through it there is a constant flow of ionic and convective currents, which reach strengths of many thousands of amperes. However, the potential difference between the plates does not decrease in this case.

This suggests that in nature there is a generator, the role of which is to constantly replenish the leakage of charges from the capacitor plates. The magnetic field of the Earth acts as such a generator, rotating together with our planet in a stream solar wind. The energy of the Earth's magnetic field can be obtained just by connecting an energy consumer to this generator. To do this, you need to install a reliable ground.

Renewable sources

As the population of our planet is steadily growing, we need more and more energy to provide for the population. The energy contained in the bowels of the earth can be very different. For example, there are renewable sources: wind, solar and water energy. They are environmentally friendly, and therefore you can use them without fear of harming the environment.

water energy

This method has been used for many centuries. Today, a huge number of dams and reservoirs have been built, in which water is used to generate electrical energy. The essence of this mechanism is simple: under the influence of the flow of the river, the wheels of the turbines rotate, respectively, the energy of the water is converted into electrical energy.

Today there is a large number of hydroelectric power plants that convert the energy of the flow of water into electricity. The peculiarity of this method is that it is renewable, respectively, such designs have a low cost. That is why, despite the fact that the construction of hydroelectric power plants takes quite a long time, and the process itself is very costly, nevertheless, these facilities significantly outperform electric-intensive industries.

Solar energy: modern and promising

Solar energy is obtained using solar panels, however, modern technology allows the use of new methods for this. The largest system in the world is built in the California desert. It fully provides energy for 2,000 homes. The design works as follows: mirrors reflect Sun rays, which are sent to the central water boiler. It boils and turns into steam, which turns the turbine. It, in turn, is connected to an electric generator. The wind can also be used as the energy that the Earth gives us. The wind blows the sails, turns the windmills. And now with its help you can create devices that will generate electrical energy. By rotating the blades of the windmill, it drives the turbine shaft, which, in turn, is connected to an electric generator.

Internal energy of the Earth

It appeared as a result of several processes, the main of which are accretion and radioactivity. According to scientists, the formation of the Earth and its mass took place over several million years, and this happened due to the formation of planetesimals. They stuck together, respectively, the mass of the Earth became more and more. After our planet began to have a modern mass, but was still devoid of an atmosphere, meteoric and asteroid bodies fell on it without hindrance. This process is just called accretion, and it led to the fact that a significant amount of gravitational energy. And the larger bodies hit the planet, the more released the energy contained in the bowels of the Earth.

This gravitational differentiation led to the fact that substances began to separate: heavy substances simply sank, while light and volatile substances floated up. Differentiation also affected the additional release of gravitational energy.

Atomic Energy

The use of earth energy can occur in different ways. For example, with the help of the construction of nuclear power plants, when thermal energy is released due to the decay smallest particles matter of atoms. The main fuel is uranium, which is contained in the earth's crust. Many believe that this method of obtaining energy is the most promising, but its use is associated with a number of problems. First, uranium emits radiation that kills all living organisms. In addition, if this substance enters the soil or atmosphere, then there will be a real technological disaster. Sad consequences accidents on Chernobyl nuclear power plant we experience to this day. The danger lies in the fact that radioactive waste can threaten all living things very, very for a long time for millennia.

New time - new ideas

Of course, people do not stop there, and every year more and more attempts are made to find new ways to get energy. If the energy of the earth's heat is obtained quite simply, then some methods are not so simple. For example, as an energy source, it is quite possible to use biological gas, which is obtained during the decay of waste. It can be used for heating houses and heating water.

Increasingly, they are being built when dams and turbines are installed across the mouths of reservoirs, which are driven by ebbs and flows, respectively, electricity is obtained.

Burning garbage, we get energy

Another method that is already being used in Japan is the creation of incinerators. Today they are built in England, Italy, Denmark, Germany, France, the Netherlands and the USA, but only in Japan these enterprises began to be used not only for their intended purpose, but also for generating electricity. At local factories, 2/3 of all garbage is burned, while the factories are equipped with steam turbines. Accordingly, they supply heat and electricity to nearby areas. At the same time, in terms of costs, building such an enterprise is much more profitable than building a thermal power plant.

More tempting is the prospect of using the Earth's heat where volcanoes are concentrated. In this case, it will not be necessary to drill the Earth too deeply, since already at a depth of 300-500 meters the temperature will be at least twice as high as the boiling point of water.

There is also such a way to generate electricity, as Hydrogen - the simplest and lightest chemical element - can be considered an ideal fuel, because it is where there is water. If you burn hydrogen, you can get water, which decomposes into oxygen and hydrogen. The hydrogen flame itself is harmless, that is, there will be no harm to the environment. The peculiarity of this element is that it has a high calorific value.

What's in the future?

Of course the energy magnetic field Earth or the one that is obtained at nuclear power plants cannot fully satisfy all the needs of mankind, which are growing every year. However, experts say that there is no reason to worry, since the planet's fuel resources are still enough. Moreover, more and more new sources are being used, environmentally friendly and renewable.

The problem of pollution remains environment, and it is growing exponentially fast. Quantity harmful emissions goes off scale, respectively, the air we breathe is harmful, the water has dangerous impurities, and the soil is gradually depleted. That is why it is so important to start studying such a phenomenon as energy in the bowels of the Earth in a timely manner in order to look for ways to reduce the need for fossil fuels and make more active use of non-traditional energy sources.

THEM. Kapitonov

Earth's nuclear heat

Earth heat

The earth is a rather strongly heated body and is a source of heat. It heats up primarily due to the solar radiation it absorbs. But the Earth also has its own thermal resource comparable to the heat received from the Sun. It is believed that this own energy of the Earth has the following origin. The Earth arose about 4.5 billion years ago following the formation of the Sun from a protoplanetary gas-dust disk rotating around it and condensing. At an early stage of its formation, the earth's substance was heated up due to relatively slow gravitational compression. An important role in the heat balance of the Earth was also played by the energy released during the fall of small cosmic bodies on it. Therefore, the young Earth was molten. Cooling down, it gradually came to its current state with a solid surface, a significant part of which is covered with oceanic and sea ​​waters. This hard outer layer called the earth's crust and on average on land plots its thickness is about 40 km, and under ocean waters- 5-10 km. The deeper layer of the earth, called mantle, also consists of solid matter. It extends to a depth of almost 3000 km and contains the bulk of the Earth's matter. Finally, the innermost part of the Earth is its nucleus. It consists of two layers - external and internal. outer core this is a layer of molten iron and nickel at a temperature of 4500-6500 K with a thickness of 2000-2500 km. inner core with a radius of 1000-1500 km is a solid iron-nickel alloy heated to a temperature of 4000-5000 K with a density of about 14 g / cm 3, which arose at a huge (almost 4 million bar) pressure.
In addition to the internal heat of the Earth, inherited from the earliest hot stage of its formation, and the amount of which should decrease with time, there is another one - long-term, associated with the radioactive decay of nuclei with a long half-life - first of all, 232 Th, 235 U , 238 U and 40 K. The energy released in these decays - they account for almost 99% of the earth's radioactive energy - constantly replenishes the thermal reserves of the Earth. The above nuclei are contained in the crust and mantle. Their decay leads to heating of both the outer and inner layers of the Earth.
Part of the huge heat contained inside the Earth constantly comes out to its surface, often in very large-scale volcanic processes. The heat flow flowing from the depths of the Earth through its surface is known. It is (47±2)·10 12 watts, which is equivalent to the heat that can be generated by 50 thousand nuclear power plants (the average power of one nuclear power plant is about 10 9 watts). The question arises whether radioactive energy plays any significant role in the total thermal budget of the Earth, and if so, what role? The answer to these questions remained unknown for a long time. Now there are opportunities to answer these questions. The key role here belongs to neutrinos (antineutrinos), which are produced in the processes radioactive decay nuclei that make up the substance of the Earth and which are called geo-neutrino.

Geo-neutrino

Geo-neutrino is the combined name for neutrinos or antineutrinos, which are emitted as a result of the beta decay of nuclei located under the earth's surface. Obviously, due to the unprecedented penetrating ability, the registration of these (and only them) by ground-based neutrino detectors can provide objective information about the processes of radioactive decay occurring deep inside the Earth. An example of such a decay is the β - decay of the 228 Ra nucleus, which is the product of the α decay of the long-lived 232 Th nucleus (see table):

The half-life (T 1/2) of the 228 Ra nucleus is 5.75 years, and the released energy is about 46 keV. The energy spectrum of antineutrinos is continuous with an upper limit close to the released energy.
The decays of 232 Th, 235 U, 238 U nuclei are chains of successive decays that form the so-called radioactive series. In such chains, α-decays are interspersed with β − -decays, since in α-decays the final nuclei turn out to be shifted from the β-stability line to the region of nuclei overloaded with neutrons. After a chain of successive decays at the end of each row, stable nuclei are formed with the number of protons and neutrons close to or equal to magic numbers (Z = 82,N= 126). Such final nuclei are stable isotopes of lead or bismuth. Thus, the decay of T 1/2 ends with the formation of a doubly magic nucleus 208 Pb, and on the path 232 Th → 208 Pb, six α-decays occur, alternating with four β - decays (in the chain 238 U → 206 Pb, eight α- and six β - - decays; there are seven α- and four β − decays in the 235 U → 207 Pb chain). Thus, the energy spectrum of antineutrinos from each radioactive series is a superposition of partial spectra from individual β − decays that make up this series. The spectra of antineutrinos produced in 232 Th, 235 U, 238 U, 40 K decays are shown in Figs. 1. The 40 K decay is a single β − decay (see table). the greatest energy(up to 3.26 MeV) antineutrinos reach in decay
214 Bi → 214 Po, which is a link in the 238 U radioactive series. The total energy released during the passage of all decay links in the 232 Th → 208 Pb series is 42.65 MeV. For the radioactive series 235 U and 238 U, these energies are 46.39 and 51.69 MeV, respectively. Energy released in decay
40 K → 40 Ca is 1.31 MeV.

Characteristics of 232 Th, 235 U, 238 U, 40 K nuclei

Nucleus	Share in % in a mixture isotopes	Number of cores relates. Si nuclei	T 1/2 billion years	First links decay
232Th	100	0.0335	14.0
235 U	0.7204	6.48 10 -5	0.704
238 U	99.2742	0.00893	4.47
40K	0.0117	0.440	1.25

The estimate of the geo-neutrino flux, made on the basis of the decay of the 232 Th, 235 U, 238 U, 40 K nuclei contained in the composition of the Earth's matter, leads to a value of the order of 10 6 cm -2 sec -1 . By registering these geo-neutrinos, one can obtain information about the role of radioactive heat in the total heat balance of the Earth and test our ideas about the content of long-lived radioisotopes in the terrestrial matter.

Rice. 1. Energy spectra of antineutrinos from nuclear decay

232 Th, 235 U, 238 U, 40 K normalized to one decay of the parent nucleus

The reaction is used to register electron antineutrinos

P → e + + n, (1)

in which this particle was actually discovered. The threshold for this reaction is 1.8 MeV. Therefore, only geo-neutrinos formed in decay chains starting from 232 Th and 238 U nuclei can be registered in the above reaction. The effective cross section of the reaction under discussion is extremely small: σ ≈ 10 -43 cm 2. Hence it follows that a neutrino detector with a sensitive volume of 1 m 3 will register no more than a few events per year. Obviously, for reliable fixation of geo-neutrino flows, large-volume neutrino detectors are needed, located in underground laboratories for maximum protection from the background. The idea to use detectors designed to study solar and reactor neutrinos for registration of geo-neutrinos arose in 1998. Currently, there are two large volume neutrino detectors using a liquid scintillator and suitable for solving the problem. These are the neutrino detectors of the KamLAND experiments (Japan, ) and Borexino (Italy, ). Below we consider the device of the Borexino detector and the results obtained on this detector on the registration of geo-neutrinos.

Borexino detector and registration of geo-neutrinos

The Borexino neutrino detector is located in central Italy in an underground laboratory under the Gran Sasso mountain range, whose mountain peaks reach 2.9 km (Fig. 2).

Rice. Fig. 2. Location diagram of the neutrino laboratory under the Gran Sasso mountain range (central Italy)

Borexino is a non-segmented massive detector whose active medium is
280 tons of organic liquid scintillator. It filled a nylon spherical vessel 8.5 m in diameter (Fig. 3). The scintillator was pseudocumene (C 9 H 12) with a spectrum-shifting PPO additive (1.5 g/l). The light from the scintillator is collected by 2212 eight-inch photomultipliers (PMTs) placed on a stainless steel sphere (SSS).

Rice. 3. Scheme of the device of the Borexino detector

A nylon vessel with pseudocumene is an internal detector whose task is to register neutrinos (antineutrinos). The inner detector is surrounded by two concentric buffer zones that protect it from external gamma rays and neutrons. The inner zone is filled with a non-scintillating medium consisting of 900 tons of pseudocumene with dimethyl phthalate additives to quench scintillations. The outer zone is located on top of the SNS and is a water Cherenkov detector containing 2000 tons of ultrapure water and cutting off signals from muons entering the facility from outside. For each interaction occurring in the internal detector, energy and time are determined. Calibration of the detector using various radioactive sources made it possible to very accurately determine its energy scale and the degree of reproducibility of the light signal.
Borexino is a very high radiation purity detector. All materials were rigorously selected, and the scintillator was cleaned to minimize the internal background. Because of its high radiation purity, Borexino is an excellent detector for detecting antineutrinos.
In reaction (1), the positron gives an instantaneous signal, which after some time is followed by the capture of a neutron by a hydrogen nucleus, which leads to the appearance of a γ-quantum with an energy of 2.22 MeV, which creates a signal delayed relative to the first one. In Borexino, the neutron capture time is about 260 μs. The instantaneous and delayed signals are correlated in space and time, providing accurate recognition of the event caused by e .
The threshold for reaction (1) is 1.806 MeV and, as can be seen from Fig. 1, all geo-neutrinos from the decays of 40 K and 235 U are below this threshold, and only a part of the geo-neutrinos that originated in the decays of 232 Th and 238 U can be detected.
The Borexino detector first detected signals from geo-neutrinos in 2010 and recently published new results based on observations over 2056 days from December 2007 to March 2015. Below we present the obtained data and the results of their discussion, based on article.
As a result of the analysis of experimental data, 77 candidates for electron antineutrinos that passed all the selection criteria were identified. The background from events simulating e was estimated by . Thus, the signal/background ratio was ≈100.
The main background source was reactor antineutrinos. For Borexino, the situation was quite favorable, since there are no nuclear reactors near the Gran Sasso laboratory. In addition, reactor antineutrinos are more energetic than geo-neutrinos, which made it possible to separate these antineutrinos from the positron by signal strength. The results of the analysis of the contributions of geo-neutrinos and reactor antineutrinos to the total number of recorded events from e are shown in Figs. 4. The number of registered geo-neutrinos given by this analysis (the shaded area corresponds to them in Fig. 4) is equal to . In the spectrum of geo-neutrinos extracted as a result of the analysis, two groups are visible - less energetic, more intense and more energetic, less intense. The authors of the described study associate these groups with the decays of thorium and uranium, respectively.
In the analysis under discussion, we used the ratio of the masses of thorium and uranium in the matter of the Earth
m(Th)/m(U) = 3.9 (in the table this value is ≈3.8). This figure reflects the relative content of these chemical elements in chondrites - the most common group of meteorites (more than 90% of meteorites that fell to Earth belong to this group). It is believed that the composition of chondrites, with the exception of light gases (hydrogen and helium), repeats the composition of the solar system and the protoplanetary disk from which the Earth was formed.

Rice. Fig. 4. Spectrum of the light output from positrons in units of the number of photoelectrons for antineutrino candidate events (experimental points). The shaded area is the contribution of geo-neutrinos. The solid line is the contribution of reactor antineutrinos.

In our country, rich in hydrocarbons, geothermal energy is a kind of exotic resource that, in the current state of affairs, is unlikely to compete with oil and gas. However, this alternative view energy can be used almost everywhere and quite efficiently.

Geothermal energy is the heat of the earth's interior. It is produced in the depths and comes to the surface of the Earth in different forms and with different intensity.

The temperature of the upper layers of the soil depends mainly on external (exogenous) factors - sunlight and air temperature. In summer and during the day, the soil warms up to certain depths, and in winter and at night it cools down following the change in air temperature and with some delay, increasing with depth. The influence of daily fluctuations in air temperature ends at depths from a few to several tens of centimeters. seasonal fluctuations capture deeper layers of soil - up to tens of meters.

At a certain depth - from tens to hundreds of meters - the temperature of the soil is kept constant, equal to the average annual air temperature near the Earth's surface. This is easy to verify by going down into a fairly deep cave.

When the average annual air temperature in a given area is below zero, this manifests itself as permafrost (more precisely, permafrost). In Eastern Siberia, the thickness, that is, the thickness, of year-round frozen soils reaches 200–300 m in places.

From a certain depth (its own for each point on the map), the effect of the Sun and the atmosphere weakens so much that endogenous (internal) factors come first and the earth's interior is heated from the inside, so that the temperature begins to rise with depth.

The heating of the deep layers of the Earth is associated mainly with the decay of the radioactive elements located there, although other sources of heat are also called, for example, physicochemical, tectonic processes in deep layers earth's crust and mantle. But whatever the cause, the temperature of rocks and associated liquid and gaseous substances increases with depth. Miners face this phenomenon - it is always hot in deep mines. At a depth of 1 km, thirty-degree heat is normal, and deeper the temperature is even higher.

The heat flow of the earth's interior, reaching the surface of the Earth, is small - on average, its power is 0.03–0.05 W / m 2, or approximately 350 W h / m 2 per year. On the background heat flow from the Sun and the air heated by it, this is an imperceptible value: the Sun gives each square meter of the earth's surface about 4000 kWh annually, that is, 10,000 times more (of course, this is on average, with a huge spread between polar and equatorial latitudes and depending on other climatic and weather factors).

The insignificance of the heat flow from the depths to the surface in most of the planet is associated with the low thermal conductivity of rocks and the peculiarities of the geological structure. But there are exceptions - places where the heat flow is high. These are, first of all, zones of tectonic faults, increased seismic activity and volcanism, where the energy of the earth's interior finds a way out. Such zones are characterized by thermal anomalies of the lithosphere, here the heat flow reaching the Earth's surface can be many times and even orders of magnitude more powerful than the "usual" one. A huge amount of heat is brought to the surface in these zones by volcanic eruptions and hot springs of water.

It is these areas that are most favorable for the development of geothermal energy. On the territory of Russia, these are, first of all, Kamchatka, the Kuril Islands and the Caucasus.

At the same time, the development of geothermal energy is possible almost everywhere, since the increase in temperature with depth is a ubiquitous phenomenon, and the task is to “extract” heat from the bowels, just as mineral raw materials are extracted from there.

On average, the temperature increases with depth by 2.5–3°C for every 100 m. The ratio of the temperature difference between two points lying at different depths to the difference in depth between them is called the geothermal gradient.

The reciprocal is the geothermal step, or the depth interval at which the temperature rises by 1°C.

The higher the gradient and, accordingly, the lower the step, the closer the heat of the Earth's depths approaches the surface and the more promising this area is for the development of geothermal energy.

AT different areas, depending on the geological structure and other regional and local conditions, the rate of temperature increase with depth can vary dramatically. On the scale of the Earth, fluctuations in the values ​​of geothermal gradients and steps reach 25 times. For example, in the state of Oregon (USA) the gradient is 150°C per 1 km, and in South Africa it is 6°C per 1 km.

The question is, what is the temperature at great depths - 5, 10 km or more? If the trend continues, temperatures at a depth of 10 km should average around 250–300°C. This is more or less confirmed by direct observations in ultradeep wells, although the picture is much more complicated than the linear increase in temperature.

For example, in the Kola superdeep well drilled in the Baltic Crystalline Shield, the temperature changes at a rate of 10°C/1 km to a depth of 3 km, and then the geothermal gradient becomes 2–2.5 times greater. At a depth of 7 km, a temperature of 120°C has already been recorded, at 10 km - 180°C, and at 12 km - 220°C.

Another example is a well laid in the Northern Caspian, where at a depth of 500 m a temperature of 42°C was recorded, at 1.5 km - 70°C, at 2 km - 80°C, at 3 km - 108°C.

It is assumed that the geothermal gradient decreases starting from a depth of 20–30 km: at a depth of 100 km, the estimated temperatures are about 1300–1500°C, at a depth of 400 km - 1600°C, in the Earth's core (depths of more than 6000 km) - 4000–5000° C.

At depths up to 10–12 km, temperature is measured through drilled wells; where they do not exist, it is determined by indirect signs in the same way as at greater depths. Such indirect signs may be the nature of the passage seismic waves or the temperature of the erupting lava.

However, for the purposes of geothermal energy, data on temperatures at depths of more than 10 km are not yet of practical interest.

There is a lot of heat at depths of several kilometers, but how to raise it? Sometimes nature itself solves this problem for us with the help of a natural coolant - heated thermal waters that come to the surface or lie at a depth accessible to us. In some cases, the water in the depths is heated to the state of steam.

There is no strict definition of the concept of "thermal waters". As a rule, they mean hot groundwater in a liquid state or in the form of steam, including those that come to the Earth's surface with a temperature above 20 ° C, that is, as a rule, higher than the air temperature.

The heat of groundwater, steam, steam-water mixtures is hydrothermal energy. Accordingly, energy based on its use is called hydrothermal.

The situation is more complicated with the production of heat directly from dry rocks - petrothermal energy, especially since sufficiently high temperatures, as a rule, begin from depths of several kilometers.

On the territory of Russia, the potential of petrothermal energy is a hundred times higher than that of hydrothermal energy - 3,500 and 35 trillion tons of standard fuel, respectively. This is quite natural - the warmth of the Earth's depths is everywhere, and thermal waters are found locally. However, due to obvious technical difficulties, heat and electricity are currently used for the most part thermal waters.

Water temperatures from 20-30 to 100°C are suitable for heating, temperatures from 150°C and above - and for the generation of electricity in geothermal power plants.

In general, geothermal resources on the territory of Russia, in terms of tons of reference fuel or any other unit of energy measurement, are approximately 10 times higher than fossil fuel reserves.

Theoretically, only geothermal energy could fully meet the energy needs of the country. In practice, at the moment, in most of its territory, this is not feasible for technical and economic reasons.

In the world, the use of geothermal energy is most often associated with Iceland - a country located at the northern end of the Mid-Atlantic Ridge, in an extremely active tectonic and volcanic zone. Probably everyone remembers the powerful eruption of the volcano Eyyafyatlayokudl ( Eyjafjallajokull) in 2010 year.

It is thanks to this geological specificity that Iceland has huge reserves of geothermal energy, including hot springs that come to the surface of the Earth and even gushing in the form of geysers.

In Iceland, more than 60% of all energy consumed is currently taken from the Earth. Including due to geothermal sources, 90% of heating and 30% of electricity generation are provided. We add that the rest of the electricity in the country is produced by hydroelectric power plants, that is, also using a renewable energy source, thanks to which Iceland looks like a kind of global environmental standard.

The "taming" of geothermal energy in the 20th century helped Iceland significantly in economic terms. Until the middle of the last century, it was a very poor country, now it ranks first in the world in terms of installed capacity and production of geothermal energy per capita, and is in the top ten in terms of absolute installed capacity of geothermal power plants. However, its population is only 300 thousand people, which simplifies the task of switching to environmentally friendly energy sources: the need for it is generally small.

In addition to Iceland, a high share of geothermal energy in the total balance of electricity production is provided in New Zealand and the island states of Southeast Asia (Philippines and Indonesia), the countries of Central America and East Africa, whose territory is also characterized by high seismic and volcanic activity. For these countries, at their current level of development and needs, geothermal energy makes a significant contribution to socio-economic development.

The use of geothermal energy has a very long history. One of the first famous examples- Italy, a place in the province of Tuscany, now called Larderello, where else in early XIX centuries, local hot thermal waters, flowing naturally or extracted from shallow wells, were used for energy purposes.

Water from underground sources, rich in boron, was used here to obtain boric acid. Initially, this acid was obtained by evaporation in iron boilers, and ordinary firewood was taken as fuel from nearby forests, but in 1827 Francesco Larderel created a system that worked on the heat of the waters themselves. At the same time, the energy of natural water vapor began to be used for the operation of drilling rigs, and at the beginning of the 20th century, for heating local houses and greenhouses. In the same place, in Larderello, in 1904, thermal water vapor became an energy source for generating electricity.

The example of Italy at the end of the 19th and beginning of the 20th century was followed by some other countries. For example, in 1892, thermal waters were first used for local heating in the United States (Boise, Idaho), in 1919 - in Japan, in 1928 - in Iceland.

In the United States, the first hydrothermal power plant appeared in California in the early 1930s, in New Zealand - in 1958, in Mexico - in 1959, in Russia (the world's first binary GeoPP) - in 1965 .

An old principle at a new source

Electricity generation requires a higher water source temperature than heating, over 150°C. The principle of operation of a geothermal power plant (GeoES) is similar to the principle of operation of a conventional thermal power plant (TPP). In fact, a geothermal power plant is a type of thermal power plant.

At thermal power plants, as a rule, coal, gas or fuel oil act as the primary source of energy, and water vapor serves as the working fluid. The fuel, burning, heats the water to a state of steam, which rotates the steam turbine, and it generates electricity.

The difference between the GeoPP is that the primary source of energy here is the heat of the earth's interior and working body in the form of steam enters the turbine blades of the electric generator in a "ready" form directly from the production well.

There are three main schemes of GeoPP operation: direct, using dry (geothermal) steam; indirect, based on hydrothermal water, and mixed, or binary.

The use of one or another scheme depends on the state of aggregation and the temperature of the energy carrier.

The simplest and therefore the first of the mastered schemes is the direct one, in which the steam coming from the well is passed directly through the turbine. The world's first GeoPP in Larderello in 1904 also operated on dry steam.

GeoPPs with an indirect scheme of operation are the most common in our time. They use hot underground water, which is injected under high pressure into the evaporator, where part of it is evaporated, and the resulting steam rotates the turbine. In some cases, additional devices and circuits are required to purify geothermal water and steam from aggressive compounds.

The exhaust steam enters the injection well or is used for space heating - in this case, the principle is the same as during the operation of a CHP.

At binary GeoPPs, hot thermal water interacts with another liquid that acts as a working fluid with a lower boiling point. Both liquids are passed through a heat exchanger, where thermal water evaporates the working liquid, the vapors of which rotate the turbine.

The principle of operation of a binary GeoPP. Hot thermal water interacts with another liquid that acts as a working fluid and has a lower boiling point. Both liquids are passed through a heat exchanger, where thermal water evaporates the working liquid, the vapors of which, in turn, rotate the turbine.

This system is closed, which solves the problem of emissions into the atmosphere. In addition, working fluids with a relatively low boiling point make it possible to use not very hot thermal waters as a primary source of energy.

All three schemes use a hydrothermal source, but petrothermal energy can also be used to generate electricity.

The circuit diagram in this case is also quite simple. It is necessary to drill two interconnected wells - injection and production. Water is pumped into the injection well. At depth, it heats up, then heated water or steam formed as a result of strong heating is supplied to the surface through a production well. Further, it all depends on how the petrothermal energy is used - for heating or for the production of electricity. A closed cycle is possible with the pumping of exhaust steam and water back into the injection well or another method of disposal.

Scheme of the petrothermal system. The system is based on the use of a temperature gradient between the earth's surface and its interior, where the temperature is higher. Water from the surface is pumped into the injection well and heated at depth, then the heated water or the steam formed as a result of heating is supplied to the surface through the production well.

The disadvantage of such a system is obvious: in order to obtain a sufficiently high temperature of the working fluid, it is necessary to drill wells to a great depth. And this is a serious cost and the risk of significant heat loss when the fluid moves up. Therefore, petrothermal systems are still less common than hydrothermal ones, although the potential of petrothermal energy is orders of magnitude higher.

Currently, the leader in the creation of the so-called petrothermal circulating systems (PCS) is Australia. In addition, this direction of geothermal energy is actively developing in the USA, Switzerland, Great Britain, and Japan.

Gift from Lord Kelvin

The invention of the heat pump in 1852 by physicist William Thompson (aka Lord Kelvin) provided humanity with a real opportunity to use low-grade heat upper layers of soil. The heat pump system, or heat multiplier as Thompson called it, is based on physical process heat transfer from the environment to the refrigerant. In fact, it uses the same principle as in petrothermal systems. The difference is in the source of heat, in connection with which a terminological question may arise: to what extent can a heat pump be considered a geothermal system? The fact is that in the upper layers, to depths of tens or hundreds of meters, the rocks and the fluids contained in them are heated not by the deep heat of the earth, but by the sun. Thus, it is the sun this case- the primary source of heat, although it is taken, as in geothermal systems, from the ground.

The operation of a heat pump is based on the delay in the heating and cooling of the soil compared to the atmosphere, as a result of which a temperature gradient is formed between the surface and deeper layers, which retain heat even in winter, similar to how it happens in reservoirs. The main purpose of heat pumps is space heating. In fact, it is a “refrigerator in reverse”. Both the heat pump and the refrigerator interact with three components: internal environment(in the first case - a heated room, in the second - a cooled refrigerator chamber), the external environment - a source of energy and a refrigerant (refrigerant), it is also a coolant that provides heat or cold transfer.

A substance with a low boiling point acts as a refrigerant, which allows it to take heat from a source that has even a relatively low temperature.

In the refrigerator, the liquid refrigerant enters the evaporator through a throttle (pressure regulator), where, due to a sharp decrease in pressure, the liquid evaporates. Evaporation is an endothermic process requiring heat to be absorbed from outside. As a result, heat is taken from the inner walls of the evaporator, which provides a cooling effect in the refrigerator chamber. Further from the evaporator, the refrigerant is sucked into the compressor, where it returns to the liquid state of aggregation. This is the reverse process, leading to the release of the extracted heat during external environment. As a rule, it is thrown into the room, and the back wall of the refrigerator is relatively warm.

The heat pump works in almost the same way, with the difference that heat is taken from the external environment and enters the internal environment through the evaporator - the room heating system.

In a real heat pump, water is heated, passing through an external circuit laid in the ground or a reservoir, then enters the evaporator.

In the evaporator, heat is transferred to an internal circuit filled with a refrigerant with a low boiling point, which, passing through the evaporator, changes from a liquid state to a gaseous state, taking heat.

Further, the gaseous refrigerant enters the compressor, where it is compressed to high pressure and temperature, and enters the condenser, where heat exchange takes place between the hot gas and the heat carrier from the heating system.

The compressor requires electricity to operate, however, the transformation ratio (the ratio of consumed and generated energy) in modern systems high enough to be effective.

Currently, heat pumps are widely used for space heating, mainly in economically developed countries.

Eco-correct energy

Geothermal energy is considered environmentally friendly, which is generally true. First of all, it uses a renewable and practically inexhaustible resource. Geothermal energy does not require large areas, unlike large hydroelectric power plants or wind farms, and does not pollute the atmosphere, unlike hydrocarbon energy. On average, GeoPP occupies 400 m 2 in terms of 1 GW of electricity generated. The same figure for a coal-fired thermal power plant, for example, is 3600 m 2. The environmental benefits of GeoPPs also include low water consumption - 20 liters of fresh water per 1 kW, while thermal power plants and nuclear power plants require about 1000 liters. Note that these are the environmental indicators of the "average" GeoPP.

But negative side effects yet there are. Among them, noise is most often distinguished, thermal pollution atmosphere and chemical - water and soil, as well as the formation of solid waste.

The main source of chemical pollution of the environment is thermal water itself (with high temperature and mineralization), often containing large quantities toxic compounds, in connection with which there is a problem of disposal of waste water and hazardous substances.

The negative effects of geothermal energy can be traced at several stages, starting with drilling wells. Here, the same dangers arise as when drilling any well: destruction of the soil and vegetation cover, pollution of the soil and groundwater.

At the stage of operation of the GeoPP, the problems of environmental pollution persist. Thermal fluids - water and steam - typically contain carbon dioxide (CO 2), sulfur sulfide (H 2 S), ammonia (NH 3), methane (CH 4), common salt (NaCl), boron (B), arsenic (As ), mercury (Hg). When released into the environment, they become sources of pollution. In addition, an aggressive chemical environment can cause corrosion damage to GeoTPP structures.

At the same time, pollutant emissions at GeoPPs are on average lower than at TPPs. For example, emissions carbon dioxide for each kilowatt-hour of electricity generated, they amount to 380 g at GeoPPs, 1042 g - at coal-fired thermal power plants, 906 g - at fuel oil and 453 g - at gas thermal power plants.

The question arises: what to do with waste water? With low salinity, after cooling, it can be discharged into surface waters. The other way is to pump it back into the aquifer through an injection well, which is the preferred and predominant practice at present.

The extraction of thermal water from aquifers (as well as pumping out ordinary water) can cause subsidence and ground movements, other deformations of geological layers, and micro-earthquakes. The probability of such phenomena is usually low, although individual cases have been recorded (for example, at the GeoPP in Staufen im Breisgau in Germany).

It should be emphasized that most of GeoPP is located in relatively sparsely populated areas and in third world countries, where environmental requirements are less stringent than in developed countries. In addition, at the moment the number of GeoPPs and their capacities are relatively small. With a larger development of geothermal energy environmental risks can grow and multiply.

How much is the energy of the Earth?

Investment costs for the construction of geothermal systems vary greatly. wide range- from 200 to 5000 dollars per 1 kW of installed capacity, that is, the cheapest options are comparable to the cost of building a thermal power plant. They depend, first of all, on the conditions of occurrence of thermal waters, their composition, and the design of the system. Drilling to great depths, creating a closed system with two wells, the need for water treatment can multiply the cost.

For example, investments in the creation of a petrothermal circulation system (PTS) are estimated at 1.6–4 thousand dollars per 1 kW of installed capacity, which exceeds the costs of building a nuclear power plant and is comparable to the costs of building wind and solar power plants.

The obvious economic advantage of GeoTPP is a free energy carrier. For comparison, in the cost structure of an operating thermal power plant or nuclear power plant, fuel accounts for 50–80% or even more, depending on current energy prices. Hence, another advantage of the geothermal system: operating costs are more stable and predictable, since they do not depend on the external conjuncture of energy prices. In general, the operating costs of the GeoTPP are estimated at 2–10 cents (60 kopecks–3 rubles) per 1 kWh of generated capacity.

The second largest (and very significant) item of expenditure after the energy carrier is, as a rule, wage plant personnel, which can vary dramatically across countries and regions.

On average, the cost of 1 kWh of geothermal energy is comparable to that for thermal power plants (in Russian conditions- about 1 ruble/1 kWh) and ten times higher than the cost of electricity generation at HPPs (5–10 kopecks/1 kWh).

Part of the reason for the high cost is that, unlike thermal and hydraulic power plants, GeoTPP has a relatively small capacity. In addition, it is necessary to compare systems located in the same region and in similar conditions. So, for example, in Kamchatka, according to experts, 1 kWh of geothermal electricity costs 2-3 times cheaper than electricity produced at local thermal power plants.

Indicators economic efficiency The work of a geothermal system depends, for example, on whether it is necessary to dispose of the waste water and in what ways this is done, whether the combined use of the resource is possible. So, chemical elements and compounds extracted from thermal water can provide additional income. Recall the example of Larderello: it was chemical production that was primary there, and the use of geothermal energy was initially of an auxiliary nature.

Geothermal Energy Forwards

Geothermal energy is developing somewhat differently than wind and solar. At present, it largely depends on the nature of the resource itself, which differs sharply by region, and the highest concentrations are tied to narrow zones of geothermal anomalies, usually associated with areas of tectonic faults and volcanism.

In addition, geothermal energy is less technologically capacious compared to wind and even more so with solar energy: the systems of geothermal stations are quite simple.

In the overall structure of world electricity production, the geothermal component accounts for less than 1%, but in some regions and countries its share reaches 25–30%. Due to the linkage to geological conditions, a significant part of the geothermal energy capacity is concentrated in third world countries, where there are three clusters of the industry's greatest development - the islands of Southeast Asia, Central America and East Africa. The first two regions are part of the Pacific "Fire Belt of the Earth", the third is tied to the East African Rift. With the greatest probability, geothermal energy will continue to develop in these belts. A more distant prospect is the development of petrothermal energy, using the heat of the earth's layers lying at a depth of several kilometers. This is an almost ubiquitous resource, but its extraction requires high costs, so petrothermal energy is developing primarily in the most economically and technologically powerful countries.

In general, given the ubiquity of geothermal resources and an acceptable level environmental safety, there is reason to believe that geothermal energy has good development prospects. Especially with the growing threat of a shortage of traditional energy carriers and rising prices for them.

From Kamchatka to the Caucasus

In Russia, the development of geothermal energy has a fairly long history, and in a number of positions we are among the world leaders, although the share of geothermal energy in the overall energy balance of a huge country is still negligible.

The pioneers and centers for the development of geothermal energy in Russia were two regions - Kamchatka and the North Caucasus, and if in the first case we are talking primarily about the electric power industry, then in the second - about the use of thermal energy of thermal water.

In the North Caucasus, in Krasnodar Territory, Chechnya, Dagestan - the heat of thermal waters for energy purposes was used even before the Great Patriotic War. In the 1980s–1990s, the development of geothermal energy in the region, for obvious reasons, stalled and has not yet recovered from the state of stagnation. Nevertheless, geothermal water supply in the North Caucasus provides heat for about 500 thousand people, and, for example, the city of Labinsk in the Krasnodar Territory with a population of 60 thousand people is completely heated by geothermal waters.

In Kamchatka, the history of geothermal energy is associated primarily with the construction of the GeoPP. The first of them, still operating Pauzhetskaya and Paratunskaya stations, were built back in 1965–1967, while the Paratunskaya GeoPP with a capacity of 600 kW became the first station in the world with a binary cycle. It was the development of Soviet scientists S. S. Kutateladze and A. M. Rosenfeld from the Institute of Thermal Physics of the Siberian Branch of the Russian Academy of Sciences, who received in 1965 a copyright certificate for extracting electricity from water with a temperature of 70 ° C. This technology subsequently became the prototype for more than 400 binary GeoPPs in the world.

The capacity of the Pauzhetskaya GeoPP, commissioned in 1966, was initially 5 MW and subsequently increased to 12 MW. Currently, the station is under construction of a binary block, which will increase its capacity by another 2.5 MW.

The development of geothermal energy in the USSR and Russia was hindered by the availability of traditional energy sources - oil, gas, coal, but never stopped. The largest geothermal power facilities at the moment are the Verkhne-Mutnovskaya GeoPP with a total capacity of 12 MW power units, commissioned in 1999, and the Mutnovskaya GeoPP with a capacity of 50 MW (2002).

Mutnovskaya and Verkhne-Mutnovskaya GeoPP are unique objects not only for Russia, but also on a global scale. The stations are located at the foot of the Mutnovsky volcano, at an altitude of 800 meters above sea level, and operate in extreme climatic conditions, where it is winter for 9-10 months a year. The equipment of the Mutnovsky GeoPPs, currently one of the most modern in the world, was completely created at domestic enterprises of power engineering.

At present, the share of Mutnovsky stations in the overall structure of energy consumption of the Central Kamchatka energy hub is 40%. An increase in capacity is planned in the coming years.

Separately, it should be said about Russian petrothermal developments. We do not yet have large PDS, however, there are advanced technologies for drilling to great depths (about 10 km), which also have no analogues in the world. Them further development will drastically reduce the cost of creating petrothermal systems. The developers of these technologies and projects are N. A. Gnatus, M. D. Khutorskoy (Geological Institute of the Russian Academy of Sciences), A. S. Nekrasov (Institute of Economic Forecasting of the Russian Academy of Sciences) and specialists from the Kaluga Turbine Plant. Currently, the petrothermal circulation system project in Russia is at the pilot stage.

There are prospects for geothermal energy in Russia, although they are relatively distant: at the moment, the potential is quite large and the position of traditional energy is strong. At the same time, in a number of remote regions of the country, the use of geothermal energy is economically profitable and is in demand even now. These are territories with high geoenergy potential (Chukotka, Kamchatka, the Kuriles - the Russian part of the Pacific "Fire Belt of the Earth", the mountains of Southern Siberia and the Caucasus) and at the same time remote and cut off from centralized energy supply.

It is likely that in the coming decades, geothermal energy in our country will develop precisely in such regions.

Kirill Degtyarev,
Researcher, Moscow State University M. V. Lomonosov
"Science and Life" No. 9, No. 10 2013