THEM. Kapitonov

Earth's nuclear heat

Earthly warmth

The earth is a fairly hot 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 it receives from the Sun. This self-energy of the Earth is believed to have the following origin. The Earth arose about 4.5 billion years ago following the formation of the Sun from a protoplanetary disk of gas and dust rotating around it and compacting it. At the early stage of its formation, the earth's substance was heated due to relatively slow gravitational compression. The energy released when small cosmic bodies fell on it also played a major role in the Earth’s thermal balance. Therefore, the young Earth was molten. Cooling down, it gradually came to its present state with a solid surface, a significant part of which is covered with oceanic and sea ​​waters. This hard outer layer is called earth's crust and on average, on land, 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 substance. Finally, the innermost part of the Earth is its core. 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, 2000-2500 km thick. Inner core with a radius of 1000-1500 km, it 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 under enormous (almost 4 million bar) pressure.
In addition to the internal heat of the Earth, which it inherited from the earliest hot stage of its formation, and the amount of which should decrease with time, there is another - long-term, associated with the radioactive decay of nuclei with a long half-life - primarily 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 - is constantly replenished thermal reserves 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 enormous heat contained within the Earth is constantly released 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 Watt, which is equivalent to the heat that 50 thousand can generate nuclear power plants(the average power of one nuclear power plant is about 10 9 Watt). The question arises: does radioactive energy play any significant role in the total thermal budget of the Earth and, if so, what role does it play? The answer to these questions remained unknown for a long time. There are now opportunities to answer these questions. The key role here belongs to neutrinos (antineutrinos), which are born in the processes of radioactive decay of nuclei that make up the Earth's matter 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, thanks to their unprecedented penetrating ability, recording them (and only them) with ground-based neutrino detectors can provide objective information about the radioactive decay processes occurring deep inside the Earth. An example of such a decay is the β − decay of the 228 Ra nucleus, which is a 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, 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 nuclei 232 Th, 235 U, 238 U are chains of successive decays, forming the so-called radioactive series. In such chains, α-decays are interspersed with β−-decays, since during α-decays the final nuclei are 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 series, stable nuclei are formed with a number of protons and neutrons close to or equal to the 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 double magic nucleus 208 Pb, and on the path 232 Th → 208 Pb six α-decays occur, interspersed with four β − decays (in the 238 U → 206 Pb chain there are eight α- and six β − - decays; in the 235 U → 207 Pb chain there are seven α- and four β − decays). Thus, the energy spectrum of antineutrinos from each radioactive series is a superposition of partial spectra from individual β − decays included in this series. The spectra of antineutrinos produced in the decays of 232 Th, 235 U, 238 U, 40 K are shown in Fig. 1. The 40 K decay is a single β − decay (see table). Antineutrinos reach their highest energy (up to 3.26 MeV) in decay
214 Bi → 214 Po, which is a link in the radioactive series 238 U. The total energy released during the passage of all decay links of the series 232 Th → 208 Pb is equal to 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 cores 232 Th, 235 U, 238 U, 40 K

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

An estimate of the geoneutrino flux, made on the basis of the decay of the 232 Th, 235 U, 238 U, 40 K nuclei contained in the Earth's matter, leads to a value of the order of 10 6 cm -2 sec -1. By registering these geo-neutrinos, it is possible to obtain information about the role of radioactive heat in the overall thermal balance of the Earth and test our ideas about the content of long-lived radioisotopes in the composition of the earth's 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 detect 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 produced in decay chains starting from the 232 Th and 238 U nuclei can be registered in the above reaction. Effective cross section there is very little reaction discussed: σ ≈ 10 -43 cm 2. 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, to reliably detect geo-neutrino fluxes, large-volume neutrino detectors are required, located in underground laboratories for maximum protection from the background. The idea of ​​using detectors designed to study solar and reactor neutrinos to register geoneutrinos arose in 1998. Currently, there are two large-volume neutrino detectors that use a liquid scintillator and are suitable for solving this problem. These are neutrino detectors from the KamLAND (Japan,) and Borexino (Italy,) experiments. Below we consider the design of the Borexino detector and the results obtained on this detector for registering geo-neutrinos.

Borexino detector and geo-neutrino registration

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 in height (Fig. 2).

Rice. 2. Layout 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. A nylon spherical vessel with a diameter of 8.5 m is filled with it (Fig. 3). The scintillator is pseudocumene (C 9 H 12) with the spectrum-shifting additive PPO (1.5 g/l). Light from the scintillator is collected by 2212 eight-inch photomultiplier tubes (PMTs) placed on a stainless steel sphere (SSS).

Rice. 3. Diagram of the Borexino detector

A nylon vessel with pseudocumene is an internal detector whose task is to register neutrinos (antineutrinos). The internal detector is surrounded by two concentric buffer zones that protect it from external gamma rays and neutrons. The internal zone is filled with a non-scintillating medium consisting of 900 tons of pseudocumene with dimethyl phthalate additives that quench scintillation. The outer zone is located on top of the SNS and is a water Cherenkov detector containing 2000 tons of ultrapure water and cuts off signals from muons entering the installation from the outside. For each interaction that occurs in the internal detector, the 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 detector of very high radiation purity. All materials have undergone strict selection, and the scintillator has been purified to minimize interior background. Due to its high radiation purity, Borexino is an excellent detector for detecting antineutrinos.
In reaction (1), a 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, creating a signal delayed relative to the first. In Boreksino, the neutron capture time is about 260 μs. The instantaneous and delayed signals are correlated in space and time, allowing precise 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 geoneutrinos from the decays of 40 K and 235 U are below this threshold, and only a part of the geoneutrinos produced in the decays of 232 Th and 238 U can be registered.
The Borexino detector first detected signals from geoneutrinos in 2010, and new results were recently published based on observations over 2056 days between December 2007 and March 2015. Below we present the data obtained and the results of their discussion, based on article.
As a result of the analysis of experimental data, 77 candidates for electron antineutrinos were identified that passed all selection criteria. The background from events simulating e was estimated as . Thus, the signal-to-background ratio was ≈100.
The main source of background were 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 compared to geo-neutrinos, which made it possible to separate these antineutrinos from the positron by the magnitude of the signal. The results of the analysis of the contributions of geoneutrinos and reactor antineutrinos to the total number of registered events from e are shown in Fig. 4. The number of registered geo-neutrinos given by this analysis (in Fig. 4 they correspond to the darkened area) is equal to . In the geo-neutrino spectrum 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.
The analysis discussed used the ratio of the masses of thorium and uranium in the Earth's matter
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. 4. Spectrum of 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.

For Russia, the Earth's heat energy can become a constant, reliable source of cheap and affordable electricity and heat using new high, environmentally friendly technologies for its extraction and supply to the consumer. This is especially true nowadays

Limited resources of fossil energy raw materials

The demand for organic energy raw materials is great in industrialized and developing countries (USA, Japan, countries of united Europe, China, India, etc.). At the same time, these countries’ own hydrocarbon resources are either insufficient or reserved, and a country, for example the United States, buys energy raw materials abroad or develops deposits in other countries.

In Russia, one of the richest countries in terms of energy resources, economic needs for energy are so far satisfied by the possibilities of using natural resources. However, the extraction of fossil hydrocarbons from the subsoil occurs at a very fast pace. If in the 1940–1960s. the main oil-producing areas were “Second Baku” in the Volga region and the Urals, then, from the 1970s to the present time, such an area has been Western Siberia. But here, too, there is a significant decrease in the production of fossil hydrocarbons. The era of “dry” Cenomanian gas is becoming a thing of the past. Previous stage of extensive mining development natural gas has come to an end. Its recovery from such giant deposits as Medvezhye, Urengoyskoye and Yamburgskoye amounted to 84, 65 and 50%, respectively. The share of oil reserves favorable for development is also decreasing over time.

Due to active consumption hydrocarbon fuels, oil and natural gas reserves on land have decreased significantly. Now their main reserves are concentrated on the continental shelf. And although the raw material base of the oil and gas industry is still sufficient for oil and gas production in Russia in required volumes, in the near future it will be ensured to an increasing extent through the development of deposits with complex mining and geological conditions. The cost of hydrocarbon production will increase.

Most of the non-renewable resources extracted from the subsoil are used as fuel for power plants. First of all, this is , whose share in the fuel structure is 64%.

In Russia, 70% of electricity is generated at thermal power plants. The country's energy enterprises burn about 500 million tons of coal annually. t. in order to generate electricity and heat, while the production of heat consumes 3–4 times more hydrocarbon fuel than the generation of electricity.

The amount of heat obtained from the combustion of these volumes of hydrocarbon raw materials is equivalent to the use of hundreds of tons of nuclear fuel - the difference is huge. However, nuclear energy requires ensuring environmental safety (to prevent a repeat of Chernobyl) and protecting it from possible terrorist acts, as well as the safe and costly decommissioning of obsolete and expired nuclear power plant units. Proven recoverable uranium reserves in the world are about 3 million 400 thousand tons. Over the entire previous period (until 2007), about 2 million tons were mined.

RES as the future of global energy

The growing interest in alternative renewable energy sources (RES) in the world in recent decades is caused not only by the depletion of hydrocarbon fuel reserves, but also by the need to solve environmental problems. Objective factors (fossil fuel and uranium reserves, as well as changes environment associated with the use of traditional fire and nuclear energy) and energy development trends suggest that the transition to new methods and forms of energy production is inevitable. Already in the first half of the 21st century. There will be a complete or almost complete transition to non-traditional energy sources.

The sooner a breakthrough is made in this direction, the less painful it will be for the entire society and the more beneficial for the country where decisive steps will be taken in this direction.

The world economy has now already set a course for the transition to a rational combination of traditional and new energy sources. Energy consumption in the world by 2000 amounted to more than 18 billion tce. t., and energy consumption by 2025 may increase to 30–38 billion tce. t., according to forecasts, by 2050 consumption at the level of 60 billion tce is possible. t. Characteristic trends in the development of the world economy in the period under review are a systematic decrease in the consumption of fossil fuels and a corresponding increase in the use of non-traditional energy resources. The thermal energy of the Earth occupies one of the first places among them.

Currently, the Ministry of Energy of the Russian Federation has adopted a program for the development of non-traditional energy, including 30 large projects for the use of heat pump units (HPU), the operating principle of which is based on the consumption of low-potential thermal energy of the Earth.

Low-grade heat energy of the Earth and heat pumps

The sources of low-potential heat energy of the Earth are solar radiation and thermal radiation heated interior of our planet. Currently, the use of such energy is one of the most dynamically developing areas of energy based on renewable energy sources.

The Earth's heat can be used in various types buildings and structures for heating, hot water supply, air conditioning (cooling), as well as for heating paths in the winter, preventing icing, heating fields in open stadiums, etc. In the English-language technical literature, systems that utilize the Earth’s heat in heat supply systems and air conditioning are designated as GHP - “geothermal heat pumps” (geothermal heat pumps). The climatic characteristics of the countries of Central and Northern Europe, which, together with the USA and Canada, are the main areas for the use of low-grade heat from the Earth, determine this mainly for heating purposes; Air cooling is required relatively rarely even in summer. Therefore, unlike the USA, heat pumps in European countries operate mainly in heating mode. In the USA, they are more often used in air heating systems combined with ventilation, which allows both heating and cooling of outside air. In European countries, heat pumps are usually used in water heating systems. Since their efficiency increases as the temperature difference between the evaporator and condenser decreases, systems are often used to heat buildings. underfloor heating, in which a coolant circulates at a relatively low temperature (35–40 o C).

Types of systems for using low-potential heat energy from the Earth

IN general case Two types of systems for using low-potential heat energy from the Earth can be distinguished:

– open systems: groundwater supplied directly to heat pumps is used as a source of low-grade thermal energy;

– closed systems: heat exchangers are located in the soil mass; when a coolant with a lower temperature relative to the ground circulates through them, thermal energy is “selected” from the ground and transferred to the evaporator of the heat pump (or when using a coolant with a higher temperature relative to the ground, it is cooled).

Cons open systems are that wells require maintenance. In addition, the use of such systems is not possible in all areas. The main requirements for soil and groundwater are as follows:

– sufficient permeability of the soil, allowing water reserves to be replenished;

- good chemical composition groundwater(e.g. low iron content), avoiding problems associated with the formation of deposits on pipe walls and corrosion.

Closed systems for using low-potential heat energy from the Earth

Closed systems can be horizontal or vertical (Figure 1).

Rice. 1. Scheme of a geothermal heat pump installation with: a – horizontal

and b – vertical ground heat exchangers.

Horizontal ground heat exchanger

In Western and Central Europe, horizontal ground heat exchangers are usually individual pipes laid relatively tightly and connected to each other in series or parallel (Fig. 2).

Rice. 2. Horizontal ground heat exchangers with: a – serial and

b – parallel connection.

To save the area where heat is removed, improved types of heat exchangers have been developed, for example, heat exchangers in the shape of a spiral (Fig. 3), located horizontally or vertically. This form of heat exchangers is common in the USA.

Warmth of the Earth. Probable sources internal warmth

Geothermy- a science that studies the Earth's thermal field. The average temperature of the Earth's surface has a general tendency to decrease. Three billion years ago, the average temperature on the Earth's surface was 71 o, now it is 17 o. Sources of heat (thermal ) The Earth's fields are internal and external processes. The Earth's heat is caused by solar radiation and originates in the bowels of the planet. The magnitudes of heat influx from both sources are quantitatively extremely unequal and their roles in the life of the planet are different. Solar heating of the Earth accounts for 99.5% of the total amount of heat received by its surface, and internal heating accounts for 0.5%. In addition, the influx of internal heat is very unevenly distributed on Earth and is concentrated mainly in places where volcanism occurs.

External source- this is solar radiation . Half solar energy absorbed by the surface, vegetation and subsurface layer of the earth's crust. The other half is reflected into the world space. Solar radiation maintains the temperature of the Earth's surface on average about 0 0 C. The sun warms up the near-surface layer of the Earth to a depth of an average of 8 - 30 m, with an average depth of 25 m, the influence of solar heat ceases and the temperature becomes constant (neutral layer). This depth is minimal in zones with a marine climate and maximum in the Subpolar region. Below this boundary there is a zone of constant temperature corresponding to the average annual temperature of the area. For example, in Moscow, on agricultural territory. Academy named after Timiryazev, at a depth of 20 m, the temperature since 1882 has invariably remained equal to 4.2 o C. In Paris, at a depth of 28 m, the thermometer has consistently shown 11.83 o C for more than 100 years. The layer with a constant temperature is the deepest where perennial ( permafrost. Below the zone of constant temperature is the geothermal zone, which is characterized by heat generated by the Earth itself.

Internal sources are the bowels of the Earth. The Earth radiates more heat into space than it receives from the Sun. Internal sources include residual heat from the time when the planet was molten, the heat of thermonuclear reactions occurring in the bowels of the Earth, the heat of the gravitational compression of the Earth under the influence of gravity, the heat of chemical reactions and crystallization processes, etc. (for example, tidal friction). Heat from the interior comes mainly from moving zones. The increase in temperature with depth is associated with the existence of internal heat sources - the decay of radioactive isotopes - U, Th, K, gravitational differentiation of matter, tidal friction, exothermic redox chemical reactions, metamorphism and phase transitions. The rate of temperature increase with depth is determined by a number of factors - thermal conductivity, permeability rocks, proximity to volcanic centers, etc.

Below the belt constant temperatures There is an increase in temperature, on average 1 o per 33 m ( geothermal stage) or 3 o every 100 m ( geothermal gradient). These values ​​are indicators of the Earth's thermal field. It is clear that these values ​​are average and vary in magnitude in various areas or zones of the Earth. The geothermal stage is different at different points on the Earth. For example, in Moscow - 38.4 m, in Leningrad 19.6, in Arkhangelsk - 10. So, when drilling a deep well on the Kola Peninsula at a depth of 12 km, the temperature was assumed to be 150 o, in reality it turned out to be about 220 degrees. When drilling wells in the northern Caspian region at a depth of 3000 m, the temperature was assumed to be 150 o degrees, but it turned out to be 108 o.

It should be noted that the climatic features of the area and the average annual temperature do not affect the change in the value of the geothermal stage; the reasons lie in the following:

1) in different thermal conductivities rocks that make up a particular region. The measure of thermal conductivity is the amount of heat in calories transferred in 1 second. Through a cross section of 1 cm 2 with a temperature gradient of 1 o C;

2) in the radioactivity of rocks, the greater the thermal conductivity and radioactivity, the lower the geothermal stage;

3) in different conditions of occurrence of rocks and the age of disturbance of their occurrence; observations have shown that the temperature increases faster in layers collected in folds; they often contain irregularities (cracks), through which the access of heat from the depths is facilitated;

4) the nature of groundwater: flows of hot groundwater warm up rocks, cold ones cool them;

5) distance from the ocean: near the ocean due to the cooling of rocks by the mass of water, the geothermal step is greater, and at the contact it is less.

Knowledge of the specific value of the geothermal step is of great practical importance.

1. This is important when designing mines. In some cases, it will be necessary to take measures to artificially lower the temperature in deep workings (temperature - 50 o C is the limit for humans in dry air and 40 o C in humid air); in others, it will be possible to carry out work at great depths.

2. Great value has an assessment of temperature conditions during tunneling in mountainous areas.

3. The study of the geothermal conditions of the Earth's interior makes it possible to use steam and hot springs emerging on the Earth's surface. Underground heat is used, for example, in Italy, Iceland; In Russia, an experimental industrial power plant was built using natural heat in Kamchatka.

Using data on the magnitude of the geothermal step, we can make some assumptions about temperature conditions deep zones of the Earth. If we accept average value geothermal stage for 33 m and assume that the temperature increases uniformly with depth, then at a depth of 100 km there will be a temperature of 3000 o C. This temperature exceeds the melting points of all substances known on Earth, therefore at this depth there must be molten masses. But due to the enormous pressure of 31,000 atm. Superheated masses do not have the characteristics of liquids, but are endowed with the characteristics of a solid.

With depth, the geothermal stage apparently should increase significantly. If we assume that the level does not change with depth, then the temperature in the center of the Earth should be about 200,000 o degrees, and according to calculations it cannot exceed 5,000 - 10,000 o.

Doctor of Technical Sciences N.A. I hate it, professor,
academician Russian Academy Technological Sciences, Moscow

In recent decades, the world has been considering the direction of more effective use energy of the Earth's deep heat 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.

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

The world economy is currently heading towards a transition to a rational combination of traditional and new energy sources. The warmth 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 (accounting for only 1% of the total geothermal energy resources) - groundwater, steam and steam-water mixtures. The latter represent geothermal energy contained in hot rocks.

The fountain technology (self-flowing) used in our country and abroad for the extraction of natural steam and geothermal waters is simple, but ineffective. 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 natural steam reservoirs, the construction of a geothermal power plant is the most profitable option for using geothermal energy. The operation of such geothermal power plants has shown their competitiveness compared to other types of power plants. Therefore, the use of reserves of geothermal waters and hydrothermal steam in our country on the Kamchatka Peninsula and on the islands of the Kuril ridge, in the regions of the North Caucasus, and also possibly in other areas is advisable and timely. But steam deposits are rare; its known and predicted reserves are small. Much more common deposits of thermal energy water are not always located close enough to the consumer - the heat supply object. This excludes the possibility of their effective use on a large scale.

Often in complex problem issues of combating salt deposits are growing. The use of geothermal, usually mineralized, sources as a coolant leads to overgrowing of well zones with iron oxide, calcium carbonate and silicate formations. In addition, problems of erosion-corrosion and scale deposits negatively affect the operation of equipment. The problem also becomes the discharge of mineralized waste water 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 forecast 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 hydrocarbons. .T. per year.

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

The priority for development is considered to be thermal water reserves 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.

Of much greater importance for the energy sector of the future is the extraction of thermal energy, practically inexhaustible petrogeothermal resources. This geothermal energy, contained in solid hot rocks, accounts for 99% of the total underground thermal energy resources. At a depth of 4-6 km, massifs with a temperature of 300-400 °C can be found only near the intermediate centers 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 large part territory of Russia.

For billions of years, nuclear, gravitational and other processes inside the Earth have generated and are generating thermal energy. Some of it is emitted into outer space, and the heat is accumulated in the depths, i.e. The heat content of the solid, liquid and gaseous phases of earthly matter is called geothermal energy.

The continuous generation of intraterrestrial heat compensates for its external losses, serves as a source of accumulation of geothermal energy and determines the renewable part of its resources. The total transfer of heat from the subsoil to the earth's surface is three times higher than 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 the total potential of 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 Earth's deep heat with the aim of partially replacing 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 efficient work circulation systems must have or create a sufficiently developed heat exchange surface in the heat extraction zone. Such a surface is possessed by porous strata and zones of natural fracture resistance that are often found at the above depths, the permeability of which makes it possible to organize forced filtration of the coolant with the effective extraction of energy from rocks, as well as the artificial creation of an extensive heat exchange surface in low-permeability porous massifs by hydraulic fracturing (see figure).

Currently, hydraulic fracturing is used in the oil and gas industry as a way to increase the permeability of formations to increase oil recovery during development oil fields. Modern technology allows you to create a narrow but long crack, or a short but wide one. There are known examples of hydraulic fracturing with cracks up to 2-3 km long.

The domestic idea of ​​extracting the main geothermal resources contained in solid rocks was expressed back in 1914 by K.E. Tsiolkovsky, and in 1920 the geothermal circulation system (GCS) in a hot granite massif was described by V.A. Obruchev.

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

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

Extraction of underground thermal energy from hot impermeable rocks, based on the methods of inclined drilling and hydraulic fracturing developed and long practiced in the oil and gas industry, did not cause seismic activity or any other harmful effects on the environment.

In 1983, British scientists repeated the American experience by creating an experimental GCS with hydraulic fracturing of granites in Carnwell. Similar work was carried out in Germany and Sweden. There are more than 224 geothermal heating projects in the United States. It is assumed that geothermal resources can provide the bulk of the US's future needs for thermal energy for non-electrical needs. In Japan, the capacity of geothermal power plants in 2000 reached approximately 50 GW.

Currently, research and exploration of geothermal resources is carried out in 65 countries. In the world, stations with a total capacity of about 10 GW have been created based on geothermal energy. The UN provides active support for the development of geothermal energy.

The experience accumulated in many countries around the world in the use of geothermal coolants shows that in favorable conditions they turn out to be 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 heat of the Earth is perhaps the only large, 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 harnessing the Earth’s heat, today geothermal technology has not yet reached its high development. Developing the Earth's thermal energy experiences great difficulties during construction deep wells, which are a channel for bringing the coolant to the surface. Due to the high temperature at the bottom (200-250 °C), traditional rock cutting tools are unsuitable for working in such conditions; special requirements are imposed on the selection of drilling and casing pipes, cement slurries, drilling technology, casing and completion of wells. Domestic measuring equipment, serial operational fittings and equipment are produced in versions that allow temperatures not higher than 150-200 °C. Traditional deep mechanical drilling of wells sometimes takes years and requires significant financial costs. In fixed production assets, the cost of wells ranges from 70 to 90%. This problem can and should be solved only by creating a progressive technology for developing the main part of geothermal resources, i.e. extracting 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 hot rocks of the Earth on the territory of the Russian Federation for many years. The goal of the work is to create, based on domestic, high technology technical means for deep penetration into the bowels of the earth's crust. Currently, several variants of drilling assemblies (DS) have been developed, which have no analogues in world practice.

The operation of the first version of the BS is linked to the current traditional well drilling technology. Drilling speed for hard rocks (average density 2500-3300 kg/m3) up to 30 m/h, hole diameter 200-500 mm. The second version of the BS drills wells in an autonomous and automatic mode. The launch is carried out from a special launching and acceptance platform, from which its movement is controlled. One thousand meters of BS in hard rock can be covered within a few hours. Well diameter is from 500 to 1000 mm. Reusable BS options have a large economic efficiency and enormous potential value. The introduction of BS into production will open a new stage in the construction of wells and provide access to the Earth's inexhaustible sources of thermal energy.

For heat supply needs, the required depth of wells throughout the country ranges from up to 3-4.5 thousand m and does not exceed 5-6 thousand m. The coolant temperature 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 a GCS is to provide constant, accessible, cheap heat to remote, hard-to-reach and undeveloped areas of the Russian Federation. The duration of operation of the GCS is 25-30 years or more. The payback period for the stations (taking into account the latest drilling technologies) is 3-4 years.

The creation in the Russian Federation in the coming years of appropriate capacities for the use of geothermal energy for non-electrical needs will make it possible to replace about 600 million tons of fuel equivalent. Savings could amount to up to 2 trillion rubles.

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

Literature

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

2. Dyadkin Yu.D. and others. Geothermal thermophysics. St. Petersburg: Nauka, 1993. 255 p.

3. Mineral resource base of the fuel and energy complex of Russia. Condition and prognosis / V.K. Branchugov, 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.

As society developed and became established, humanity began to look for more and more modern and at the same time economical ways to obtain energy. For this purpose, 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 it 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 there is a layer of magma, which is a fiery liquid silicate melt. According to research data, energy potential This heat is much higher than the energy of the world's reserves of natural gas, as well as oil. Magma - lava - comes to the surface. 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 land turns out as follows: lava and water resources The planets touch, causing the water to heat up sharply. This leads to the eruption of the geyser, the formation of so-called hot lakes and underwater currents. That is, precisely those natural phenomena whose properties are actively used as energy.

Artificial geothermal springs

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 it is possible to obtain geothermal energy using an industrial method: through one well it will be pumped cold water into the formation, and through the second - hot water or steam is extracted. Artificial heat sources will be profitable and rational if the resulting heat produces more energy. The steam can be sent to turbine generators, which will generate electricity.

Of course, the heat removed is only a fraction of what is available in the total reserves. But it should be remembered that the deep heat will be constantly replenished due to the processes of compression of rocks and stratification of the subsoil. As experts say, the earth's crust accumulates heat, the total amount of which is 5000 times greater than the calorific value of all the fossil subsoil of the earth as a whole. It turns out that the operating time of such artificially created geothermal stations can be unlimited.

Features of sources

The sources that make it possible to obtain geothermal energy are almost impossible to fully utilize. They exist in more than 60 countries around 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 of the world are completely different in their properties, namely average temperature, salinity, gas composition, acidity and so on.

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

Where does the 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 its heating and 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 being filled with underground waters, and very close to them there are pockets of magma. This is how it is formed naturally thermal energy land.

Earth's electric field

There is another alternative source of energy in nature, which is renewable, environmentally friendly, and easy to use. True, this source is still only being studied and not used in practice. So, the potential energy of the Earth lies in its electric field. Energy can be obtained in this way by studying the basic laws of electrostatics and features electric field Earth. In essence, our planet, from an electrical point of view, is a spherical capacitor charged up to 300,000 volts. Its inner sphere has a negative charge, and its outer sphere - the ionosphere - has a positive charge. is an insulator. Through it there is a constant flow of ionic and convective currents, which reach a force of many thousands of amperes. However, the potential difference between the plates does not decrease.

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 role of such a generator is the Earth’s magnetic field, rotating together with our planet in the flow of solar wind. The energy of the Earth's magnetic field can be obtained precisely by connecting an energy consumer to this generator. To do this, you need to install reliable grounding.

Renewable sources

As our planet's population grows steadily, we need more and more energy to power our 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 can be used 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 the operation of this mechanism is simple: under the influence of the river flow, the wheels of the turbines rotate, and accordingly, the water energy is converted into electricity.

Today there are a large number of hydroelectric power plants that convert the energy of water flow into electricity. The peculiarity of this method is that they are renewed, and, accordingly, such structures have a low cost. That is why, despite the fact that the construction of hydroelectric power stations takes quite a long time, and the process itself is very expensive, these structures still have a significant advantage over electricity-intensive industries.

Solar energy: modern and promising

Solar energy is obtained using solar panels, however modern technologies allow the use of new methods for this. The largest system in the world is built in the California desert. It fully supplies energy to 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 rotates the turbine. It, in turn, is connected to an electric generator. Wind can also be used as energy that the Earth gives us. The wind inflates the sails and turns the mills. And now, with its help, you can create devices that will produce electrical energy. By rotating the windmill blades, 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 ones being accretion and radioactivity. According to scientists, the formation of the Earth and its mass occurred over several million years, and this happened due to the formation of planetesimals. They stuck together, and accordingly, the mass of the Earth became more and more. After our planet began to have its modern mass, but was still devoid of an atmosphere, meteoroid and asteroid bodies fell unhindered on it. This process is precisely called accretion, and it led to the release of significant gravitational energy. And the larger the bodies that hit the planet, the greater the amount of energy contained in the bowels of the Earth was released.

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

Atomic energy

Using the earth's energy can occur in different ways. For example, through the construction of nuclear power plants, when thermal energy is released due to the decay of the smallest particles of atomic matter. The main fuel is uranium, which is contained in earth's crust. Many believe that this particular method of generating 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 gets into the soil or atmosphere, then a real man-made disaster. We are still experiencing the sad consequences of the accident at the Chernobyl nuclear power plant to this day. The danger lies in the fact that radioactive waste can threaten all living things for a very, very 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 obtain energy. If the earth's heat energy is obtained quite simply, then some methods are not so simple. For example, it is quite possible to use biological gas, which is obtained by rotting waste, as an energy source. 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 the ebb and flow of the tides, respectively, producing electricity.

By burning garbage we get energy

Another method, which is already used in Japan, is the creation of waste incineration plants. Today they are built in England, Italy, Denmark, Germany, France, the Netherlands and the USA, but only in Japan did these enterprises begin to be used not only for their intended purpose, but also to generate electricity. Local factories burn 2/3 of all waste, and the factories are equipped steam turbines. Accordingly, they supply heat and electricity to nearby areas. Moreover, in terms of costs, building such an enterprise is much more profitable than building a thermal power plant.

The prospect of using the Earth's heat where volcanoes are concentrated looks more tempting. In this case, there will be no need 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 easiest chemical element- can be considered an ideal fuel, because it exists 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, it will not cause harm to the environment. The peculiarity of this element is that it has a high calorific value.

What's next?

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

The problem of environmental pollution remains, and it is growing catastrophically quickly. Quantity harmful emissions goes off scale, accordingly, 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 promptly study such a phenomenon as energy in the bowels of the Earth in order to look for ways to reduce the need for fossil fuels and more actively use non-traditional energy sources.