Nuclear heat of the earth. Disadvantages of obtaining geothermal energy

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 lot of technical solutions, plans, theories in this area are being created.

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. The movement of lithospheric plates demonstrates its 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 due to warm sources, and the second type is the temperature difference on 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 the classical production of thermal energy a boiler house is used 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 for heating. 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.

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

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.

The increased 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 (reserves of fossil fuels and uranium, as well as changes in the environment caused by traditional fire and nuclear power) 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 heat carriers (comprising only 1% of the total geothermal energy resources) - 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 shallow depth of geothermal reservoirs with high temperatures 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, the issues of combating scaling develop into a complex problem. 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, 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 .t. in year.

The predicted reserves of the steam-air mixture with a temperature of 150-250 °C in the Kamchatka Peninsula and the Kuril Islands are 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.

Of much greater importance 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 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 removal of heat from the interior 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 only matters 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 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).

Currently, hydraulic fracturing is used in the 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 or 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 work was carried out 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 selection of drill and casing pipes, cement slurries, drilling technology, casing and completion of wells. 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 technologies, technical means for deep penetration into the bowels of the 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 a 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. The payback period of 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-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.

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

Limited resources of fossil energy raw materials

The demand for organic energy raw materials is great in industrialized and developing countries (USA, Japan, states of united Europe, China, India, etc.). At the same time, their own hydrocarbon resources in these countries are either insufficient or reserved, and a country, such as 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, the economic needs for energy are still 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 1940s-1960s. The main oil-producing regions were the "Second Baku" in the Volga and Cis-Urals, then, starting from the 1970s, and to the present, Western Siberia has been such an area. But even here there is a significant decline in the production of fossil hydrocarbons. The era of "dry" Cenomanian gas is passing away. The previous stage of extensive development of natural gas production has come to an end. Its extraction from such giant deposits as Medvezhye, Urengoyskoye and Yamburgskoye amounted to 84, 65 and 50%, respectively. The proportion of oil reserves favorable for development also decreases over time.

Due to the active consumption of hydrocarbon fuels, onshore reserves of oil and natural gas have been significantly reduced. 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 the extraction of oil and gas in Russia in the required volumes, in the near future it will be provided to an increasing extent through the development of fields with complex mining and geological conditions. At the same time, the cost of hydrocarbon production will grow.

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

In Russia, 70% of electricity is generated at thermal power plants. Energy enterprises of the country annually burn about 500 million tons of c.e. tons for the purpose of generating 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 power requires ensuring environmental safety (to prevent a repeat of Chernobyl) and protecting it from possible terrorist attacks, as well as the safe and costly decommissioning of obsolete and spent nuclear power units. The proven recoverable reserves of uranium in the world are about 3 million 400 thousand tons. For the entire previous period (until 2007), about 2 million tons were mined.

RES as the future of global energy

The increased interest in the world in recent decades in alternative renewable energy sources (RES) 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 environmental changes 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 XXI 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 whole society and the more beneficial for the country, where decisive steps will be taken in this direction.

The world economy has 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 tons of fuel equivalent. tons, and energy consumption by 2025 may increase to 30–38 billion tons of fuel equivalent. tons, according to forecast data, by 2050 consumption at the level of 60 billion tons of fuel equivalent is possible. t. A characteristic trend in the development of the world economy in the period under review is 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 principle of operation of which is based on the consumption of low-potential thermal energy of the Earth.

Low-potential energy of the Earth's heat and heat pumps

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

The heat of the Earth can be used in various types of buildings and structures for heating, hot water supply, air conditioning (cooling), as well as for heating tracks in the winter season, preventing icing, heating fields in open stadiums, etc. In the English-language technical literature of the system utilizing the Earth's heat in heating and air conditioning systems are referred to as GHP - "geothermal heat pumps" (geothermal heat pumps). The climatic characteristics of the countries of Central and Northern Europe, which, together with the United States and Canada, are the main areas for the use of low-grade heat of the Earth, determine this mainly for heating purposes; cooling of the air, even in summer, is relatively rarely required. Therefore, unlike in the USA, heat pumps in European countries operate mainly in heating mode. In the US, they are more often used in air heating systems combined with ventilation, which allows both heating and cooling of the 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, floor heating systems are often used for heating buildings, in which a coolant of a relatively low temperature (35–40 ° C) circulates.

Types of systems for the use of low-potential energy of the Earth's heat

In the general case, two types of systems for using the low-potential energy of the Earth's heat can be distinguished:

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

- closed systems: heat exchangers are located in the soil massif; when a coolant with a temperature lower than the ground circulates through them, thermal energy is “taken off” from the ground and transferred to the heat pump evaporator (or when a coolant with a higher temperature relative to the ground is used, it is cooled).

The disadvantages of 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 water permeability of the soil, allowing replenishment of water reserves;

– good groundwater chemistry (e.g. low iron content) to avoid pipe scale and corrosion problems.

Closed systems for the use of low-potential energy of the Earth's heat

Closed systems are horizontal and 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 the countries of Western and Central Europe, horizontal ground heat exchangers are usually separate pipes laid relatively tightly and connected to each other in series or in parallel (Fig. 2).

Rice. 2. Horizontal ground heat exchangers with: a - sequential and

b - parallel connection.

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

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 by ocean and sea waters. This hard outer layer is called the earth's crust and on average, on land, its thickness is about 40 km, and under oceanic waters - 5-10 km. The deeper layer of the earth, called mantle also consists of a solid. 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 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 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, 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 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, due to the unprecedented penetrating ability, 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 forming 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 the 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). Antineutrinos reach their highest energy (up to 3.26 MeV) in the 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

Core	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 composition of 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 fluxes, 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.

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. The geothermal energy of the earth is obtained as follows: the lava and the 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 geothermal energy can be obtained industrially in almost any corner of the land: cold water will be pumped into the reservoir through one well, and hot water or steam will be extracted through the second. 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 extracted heat 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, 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 the 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 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 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 are used as energy sources in regions such as Kamchatka, Iceland, New Zealand and North America, and single geysers are found in several 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. In this natural way, the thermal energy of the earth is formed.

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, the potential energy of the Earth lies in its electric field. It is possible to obtain energy in this way based on the study of the basic laws of electrostatics and the features of the Earth's electric field. In fact, 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 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 role of such a generator is played by the Earth's magnetic field, which rotates together with our planet in the flow of the 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 are 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, but modern technologies allow 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: the sun's rays are reflected from the mirrors, which are sent to the central boiler with water. 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 significant gravitational energy was released. And the larger bodies 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 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 of the smallest particles of atomic matter. 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 a real man-made disaster will occur. We are 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 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 deep, 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 of the Earth's magnetic field or that which 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 environmental pollution remains, and it is growing catastrophically fast. The amount of 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 timely 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 make more active use of non-traditional energy sources.