Earth energy. The warmth of the earth. Possible sources of internal heat
The warmth of the earth. Possible sources of internal heat
Geothermy- science that studies the thermal field of the Earth. The average surface temperature of the Earth 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 ) Earth's fields are internal and external processes. The heat of the Earth is caused by solar radiation and originates in the bowels of the planet. The values of heat influx from both sources are quantitatively extremely different and their roles in the life of the planet are different. Solar heating of the Earth is 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 the Earth and is concentrated mainly in places of manifestation of volcanism.
External source is solar radiation . Half of the solar energy is absorbed by the surface, vegetation and near-surface layer of the earth's crust. The other half is reflected into world space. Solar radiation maintains the temperature of the Earth's surface at an average of about 0 0 C. The Sun warms the near-surface layer of the Earth to an average depth of 8 - 30 m, with an average depth of 25 m, the effect of solar heat ceases and the temperature becomes constant (neutral layer). This depth is minimal in areas with a maritime climate and maximal in the Subpolar region. Below this boundary there is a belt of constant temperature corresponding to the average annual temperature of the area. So, for example, in Moscow on the territory of agricultural. academy. Timiryazev, at a depth of 20 m, the temperature has invariably remained equal to 4.2 ° C since 1882. In Paris, at a depth of 28 m, a thermometer has consistently shown 11.83 ° C for more than 100 years. The layer with a constant temperature is the deepest where perennial ( eternal Frost. Below the belt 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 melted, the heat of thermonuclear reactions occurring in the bowels of the Earth, the heat of the gravitational compression of the Earth under the action of gravity, the heat of chemical reactions and crystallization processes, etc. (for example, tidal friction). The heat from the bowels comes mainly from the 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 of rocks, proximity to volcanic chambers, etc.
Below the belt of 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 thermal field of the Earth. It is clear that these values are average and different in magnitude in different areas or zones of the Earth. The geothermal step 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, a temperature of 150 ° was assumed, in reality it turned out to be about 220 degrees. When drilling wells in the northern Caspian at a depth of 3000 m, the temperature was assumed to be 150 degrees, but it turned out to be 108 degrees.
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 step, the reasons lie in the following:
1) in the different thermal conductivity of the rocks that make up a particular area. Under the measure of thermal conductivity is understood the amount of heat in calories transferred in 1 second. Through a 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 step;
3) in different conditions of occurrence of rocks and the age of their occurrence; observations have shown that the temperature rises faster in the layers collected in folds, they often have violations (cracks), through which the access of heat from the depths is facilitated;
4) the nature of groundwater: hot groundwater flows warm rocks, cold ones cool;
5) remoteness from the ocean: near the ocean due to the cooling of rocks by a mass of water, the geothermal step is larger, and at the contact it is smaller.
Knowing 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 ° C is the limit for a person in dry air and 40 ° C in wet air); in others, it will be possible to work at great depths.
2. The assessment of temperature conditions during tunneling in mountainous areas is of great importance.
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 on natural heat in Kamchatka.
Using data on the size of the geothermal step, one can make some assumptions about the temperature conditions of the deep zones of the Earth. If we take the average value of the geothermal step as 33 m and assume that the increase in temperature with depth occurs evenly, then at a depth of 100 km there will be a temperature of 3000 ° C. This temperature exceeds the melting points of all substances known on Earth, therefore, at this depth there should be molten masses . But due to the huge pressure of 31,000 atm. Superheated masses do not have the characteristics of liquids, but are endowed with the characteristics of a solid body.
With depth, the geothermal step must apparently increase significantly. If we assume that the step does not change with depth, then the temperature in the center of the Earth should be about 200,000 degrees, and according to calculations, it cannot exceed 5000 - 10,000 degrees.
The main sources of thermal energy of the Earth are [ , ]:
To date, only the first four sources have been quantified. In our country, the main merit in this belongs to O.G. Sorokhtin and S.A. Ushakov. The following data is mainly based on the calculations of these scientists.
Heat of the Earth's gravitational differentiation
One of the most important regularities in the development of the Earth is differentiation its substance, which continues at the present time. This differentiation resulted in the formation core and crust, change in the composition of the primary robes, while the separation of an initially homogeneous substance into fractions of different densities is accompanied by the release thermal energy, and the maximum heat release occurs when the terrestrial matter is divided into dense and heavy core and residual lighter silicate shell earth mantle. At present, most of this heat is generated at the border mantle - core.
Earth's Gravitational Differentiation Energies for the entire time of its existence stood out - 1.46 * 10 38 erg (1.46 * 10 31 J). Given energy for the most part first goes into kinetic energy convective currents of the mantle substance, and then in warmly; another part of it is spent on additional compression of the earth's interior, arising due to the concentration of dense phases in the central part of the Earth. From 1.46*10 38 erg energy of the Earth's gravitational differentiation went to its additional compression 0.23*10 38 erg (0.23*10 31 J), and in the form of heat released 1.23*10 38 erg (1.23*10 31 J). The magnitude of this thermal component significantly exceeds the total release in the Earth of all other types of energy. The time distribution of the total value and rate of release of the thermal component of gravitational energy is shown in Fig. 3.6 .
Rice. 3.6.
The current level of heat generation during the gravitational differentiation of the Earth - 3*10 20 erg/s (3*10 13W), which depends on the value of the modern heat flux passing through the surface of the planet in ( 4.2-4.3) * 10 20 erg / s ((4.2-4.3)*10 13W), is ~ 70%
.
radiogenic heat
Caused by the radioactive decay of unstable isotopes. The most energy-intensive and long-lived ( with a half-life commensurate with the age of the Earth) are isotopes 238 U, 235 U, 232Th and 40K. Most of them are concentrated in continental crust. Modern level of generation radiogenic heat:
- by American geophysicist V.Vakye - 1.14*10 20 erg/s (1.14*10 13W) ,
- according to Russian geophysicists O.G. Sorokhtin and S.A. Ushakov - 1.26*10 20 erg/s(1.26*10 13W) .
From the value of the modern heat flow, this is ~ 27-30%.
Of the total heat of radioactive decay in 1.26*10 20 erg/s (1.26*10 13W) in the earth's crust stands out - 0.91*10 20 erg/s, and in the mantle - 0.35*10 20 erg/s. It follows from this that the proportion of mantle radiogenic heat does not exceed 10% of the total modern heat loss of the Earth, and it cannot be the main source of energy for active tectono-magmatic processes, the depth of which can reach 2900 km; and the radiogenic heat released in the crust is relatively quickly lost through the earth's surface and practically does not participate in the heating of the deep interior of the planet.
In past geological epochs, the amount of radiogenic heat released in the mantle must have been higher. Its estimates at the time of the formation of the Earth ( 4.6 billion years ago) give - 6.95*10 20 erg/s. Since that time, there has been a steady decrease in the rate of release of radiogenic energy (Fig. 3.7 ).
For all the time in the Earth stood out ~4.27*10 37 erg(4.27*10 30 J) the thermal energy of radioactive decay, which is almost three times lower than the total value of the heat of gravitational differentiation.
Heat of tidal friction
It stands out during the gravitational interaction of the Earth, primarily with the Moon, as the nearest large cosmic body. Due to mutual gravitational attraction, tidal deformations occur in their bodies - swelling or humps. The tidal humps of the planets, with their additional attraction, influence their movement. Thus, the attraction of both tidal humps of the Earth creates a pair of forces acting both on the Earth itself and on the Moon. However, the influence of the near, moon-facing swelling is somewhat stronger than that of the far one. Due to the fact that the angular velocity of rotation of the modern Earth ( 7.27*10 -5 s -1) exceeds the orbital velocity of the Moon ( 2.66*10 -6 s -1), and the substance of the planets is not ideally elastic, then the tidal humps of the Earth are, as it were, carried away by its forward rotation and are noticeably ahead of the movement of the Moon. This leads to the fact that the maximum tides of the Earth always occur on its surface somewhat later than the moment climax Moon, and an additional moment of forces acts on the Earth and the Moon (Fig. 3.8 ) .
The absolute values of the forces of tidal interaction in the Earth-Moon system are now relatively small and the tidal deformations of the lithosphere caused by them can reach only a few tens of centimeters, but they lead to a gradual deceleration of the Earth's rotation and, conversely, to the acceleration of the orbital motion of the Moon and its removal from the Earth. The kinetic energy of the movement of the earth's tidal humps is converted into thermal energy due to the internal friction of matter in the tidal humps.
At present, the rate of release of tidal energy by G. McDonald is ~0.25*10 20 erg/s (0.25*10 13W), while its main part (about 2/3) is presumably dissipates(dispersed) in the hydrosphere. Consequently, the fraction of tidal energy caused by the interaction of the Earth with the Moon and dissipated in the solid Earth (primarily in the asthenosphere) does not exceed 2 %
total thermal energy generated in its depths; and the fraction of solar tides does not exceed 20 %
from the influence of the lunar tides. Therefore, solid tides now play practically no role in feeding tectonic processes with energy, but in some cases they can act as "triggers", for example, earthquakes.
The magnitude of tidal energy is directly related to the distance between space objects. And if the distance between the Earth and the Sun does not assume any significant changes in the geological time scale, then in the Earth-Moon system this parameter is a variable. Regardless of ideas about, almost all researchers admit that in the early stages of the development of the Earth, the distance to the Moon was significantly less than the modern one, while in the process of planetary development, according to most scientists, it gradually increases, and according to Yu.N. Avsyuku this distance experiences long-term changes in the form of cycles "arrival - departure" of the moon. This implies that in past geological epochs the role of tidal heat in the overall heat balance of the Earth was more significant. In general, for the entire time of the development of the Earth, it has stood out ~3.3*10 37 erg (3.3*10 30 J) tidal heat energy (this is subject to the successive removal of the Moon from the Earth). The change in time of the rate of release of this heat is shown in Fig. 3.10 .
More than half of the total tidal energy was released in katarchee (hellea)) - 4.6-4.0 billion years ago, and at that time, only due to this energy, the Earth could additionally warm up by ~ 500 0 С. energy-intensive endogenous processes .
accretion heat
This is the heat stored by the Earth since its formation. During accretions, which lasted for several tens of millions of years, due to the collision planetesimals The earth has experienced significant heating. At the same time, there is no consensus on the magnitude of this heating. Currently, researchers are inclined to believe that in the process of accretion, the Earth experienced, if not complete, then significant partial melting, which led to the initial differentiation of the Proto-Earth into a heavy iron core and a light silicate mantle, and to the formation "magma ocean" on its surface or at shallow depths. Although even before the 1990s, the model of a relatively cold primary Earth was considered practically universally recognized, which gradually warmed up due to the above processes, accompanied by the release of a significant amount of thermal energy.
An accurate estimate of the primary accretionary heat and its share that has survived to the present time is associated with significant difficulties. By O.G. Sorokhtin and S.A. Ushakov, who are supporters of a relatively cold primary Earth, the value of the accretion energy converted into heat is - 20.13*10 38 erg (20.13*10 31 J). This energy in the absence of heat loss would be enough for complete evaporation terrestrial matter, because temperature could rise to 30 000 0 С. But the accretion process was relatively long, and the energy of planetesimal impacts was released only in the near-surface layers of the growing Earth and was quickly lost with thermal radiation, so the initial heating of the planet was not large. The magnitude of this thermal radiation, which goes in parallel with the formation (accretion) of the Earth, is estimated by the indicated authors as 19.4*10 38 erg (19.4*10 31 J)
.
In the modern energy balance of the Earth, accretion heat most likely plays an insignificant role.
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, 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, 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.
geothermal energy- this is the energy of heat that is released from the inner zones of the Earth over hundreds of millions of years. According to geological and geophysical studies, the temperature in the Earth's core reaches 3,000-6,000 °C, gradually decreasing in the direction from the center of the planet to its surface. The eruption of thousands of volcanoes, the movement of blocks of the earth's crust, earthquakes testify to the action of the powerful internal energy of the Earth. Scientists believe that the thermal field of our planet is due to radioactive decay in its depths, as well as the gravitational separation of the core matter.
The main sources of heating the bowels of the planet are uranium, thorium and radioactive potassium. The processes of radioactive decay on the continents occur mainly in the granitic layer of the earth's crust at a depth of 20-30 km or more, in the oceans - in the upper mantle. It is assumed that at the bottom of the earth's crust at a depth of 10-15 km, the probable temperature value on the continents is 600-800 ° C, and in the oceans - 150-200 ° C.
A person can use geothermal energy only where it manifests itself close to the Earth's surface, i.e. in areas of volcanic and seismic activity. Now geothermal energy is effectively used by such countries as the USA, Italy, Iceland, Mexico, Japan, New Zealand, Russia, the Philippines, Hungary, El Salvador. Here, the internal heat of the earth rises to the very surface in the form of hot water and steam with a temperature of up to 300 ° C and often breaks out as the heat of gushing sources (geysers), for example, the famous geysers of Yellowstone Park in the USA, the geysers of Kamchatka, Iceland.
Geothermal energy sources divided into dry hot steam, wet hot steam and hot water. The well, which is an important source of energy for the electric railway in Italy (near Larderello), has been powered by dry hot steam since 1904. Two other well-known places in the world with hot dry steam are the Matsukawa field in Japan and the geyser field near San Francisco, where geothermal energy has also been used effectively for a long time. Most of the wet hot steam in the world is located in New Zealand (Wairakei), geothermal fields of a slightly lower capacity - in Mexico, Japan, El Salvador, Nicaragua, Russia.
Thus, four main types of geothermal energy resources can be distinguished:
surface heat of the earth used by heat pumps;
energy resources of steam, hot and warm water near the earth's surface, which are now used in the production of electrical energy;
heat concentrated deep below the surface of the earth (perhaps in the absence of water);
magma energy and heat that accumulates under volcanoes.
Geothermal heat reserves (~ 8 * 1030J) are 35 billion times the annual global energy consumption. Only 1% of the geothermal energy of the earth's crust (depth of 10 km) can provide an amount of energy that is 500 times greater than all the world's oil and gas reserves. However, today only a small part of these resources can be used, and this is due primarily to economic reasons. The beginning of the industrial development of geothermal resources (energy of hot deep waters and steam) was laid in 1916, when the first geothermal power plant with a capacity of 7.5 MW was put into operation in Italy. Over the past time, considerable experience has been accumulated in the field of practical development of geothermal energy resources. The total installed capacity of operating geothermal power plants (GeoTPP) was: 1975 - 1,278 MW, in 1990 - 7,300 MW. The United States, the Philippines, Mexico, Italy, and Japan have achieved the greatest progress in this matter.
The technical and economic parameters of the GeoTPP vary over a fairly wide range and depend on the geological characteristics of the area (depth of occurrence, parameters of the working fluid, its composition, etc.). For the majority of commissioned GeoTPPs, the cost of electricity is similar to the cost of electricity produced at coal-fired TPPs, and amounts to 1200 ... 2000 US dollars / MW.
In Iceland, 80% of residential buildings are heated with hot water extracted from geothermal wells under the city of Reykjavik. In the western United States, about 180 homes and farms are heated by geothermal hot water. According to experts, between 1993 and 2000, global electricity generation from geothermal energy more than doubled. There are so many reserves of geothermal heat in the United States that it could theoretically provide 30 times more energy than the state currently consumes.
In the future, it is possible to use the heat of magma in those areas where it is located close to the Earth's surface, as well as the dry heat of heated crystalline rocks. In the latter case, wells are drilled for several kilometers, cold water is pumped down, and hot water is returned back.
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 of 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.