Currently, geothermal energy is used in 51 countries in electricity generation technologies. Over five years (from 2010 to 2015), the total capacity of geothermal power plants increased by 16% and amounted to 12,635 MW. A significant increase in the capacity of geothermal power plants is due to environmental safety, significant economic efficiency and high utilization rates installed capacity.

Today geothermal power plants (GeoPPs) are operated in 26 countries with an annual electricity generation of about 73,549 GW. The expected growth in the installed capacity of geothermal power plants by 2020 is about 21,443 MW (Fig. 1). The United States has significant indicators in the field of geothermal energy: the total installed capacity of geothermal power plants is 3450 MW with an annual electricity generation of 16.6 MW / h. The Philippines is in second place with a total capacity of GeoPPs of 1,870 MW, and Indonesia is in third place with 1,340 MW. At the same time, the most significant increase in the capacity of GeoPPs over the past five years was noted in Turkey - from 91 to 397 MW, that is, by 336%. This is followed by Germany - by 280% (from 6.6 to 27 MW) and Kenya - by 194% (from 202 to 594 MW).

In modern geothermal energy, the most common are GeoPPs with a thermal scheme of a turbine plant, including an additional expansion of geothermal steam, the total capacity of which is 5079 MW. Power units of GeoPPs with a total capacity of 2863 MW operate on overheated geothermal steam. The total capacity of the power units of the GeoPP with two stages of steam expansion is 2544 MW.

Geothermal binary power units with an organic Rankine cycle are becoming more widespread, and today their total capacity exceeds 1800 MW. The average unit capacity of binary power units is 6.3 MW, power units with one separation pressure - 30.4 MW, with two separation pressures - 37.4 MW, and power units operating on superheated steam - 45.4 MW.

The main increase in the installed capacity of modern geothermal power plants in the world in recent years has been largely due to the construction of new geothermal power plants with binary cycle power units.

Technological schemes of modern GeoPPs can be classified according to the phase state of the geothermal coolant, the type of thermodynamic cycle and the turbines used (Fig. 2). Geothermal power plants operate on a geothermal coolant in the form of superheated steam, steam-water mixture and hot water... The direct cycle of a GeoPP is characterized by the use of a geothermal coolant as a working medium in the entire technological path.

GeoPPs with a binary cycle are mainly used in fields with low-temperature hot water(90-120 ° C), which are characterized by the use of a low-boiling working fluid in the second circuit. Double-circuit GeoPPs involve the use of binary and combined binary cycles. In the combined cycle of a geothermal power plant, a steam turbine operates on geothermal steam, and the heat recovery of the spent or waste geothermal coolant in the form of a liquid phase is carried out in a binary power plant of the secondary circuit.

Condensing turbines of single-circuit GeoPPs operate on geothermal superheated steam, as well as on saturated steam separated from the steam-water mixture. Backpressure turbines are used at single-circuit geothermal power plants, which, along with generating electricity, provide heat to the heat supply system.

At present, in Russia, power units with back pressure turbines are operated on the islands of Kunashir and Iturup (part of the Kuril ridge). The Kaluga Turbine Works developed the Omega-500, Tuman-2.0 and Tuman-2.5 power units.

Backpressure turbine plants are much simpler than condensing ones in their design, therefore their price is significantly lower.

Technological schemes of single-circuit GeoPPs with one, two and three separation pressures, the so-called SingleFlash, Double-Flash and Triple-Flash schemes, respectively, are quite often used. Thus, GeoPPs with two and three separation pressures assume the use of additional secondary steam obtained in the expander due to boiling up of the separator. This makes it possible to increase the utilization of the heat of the geothermal fluid in comparison with the GeoPP with one separation pressure.

Geothermal steam turbine units are manufactured by companies in Japan, the USA, Italy and Russia.

Table 1 shows the main manufacturers of modern steam turbine plants and equipment for geothermal power plants. The design of geothermal turbines has a number of features that are due to the use of low-grade geothermal saturated steam as a working medium, characterized by corrosiveness and tendency to form deposits.

Modern advanced technologies for increasing the efficiency of geothermal turbines include:

• in-channel moisture separation in the turbine flow path, including peripheral moisture separation, moisture removal through slots in hollow nozzle blades and a separator stage;
• systems for periodic flushing of the flow path and end seals on a running turbine;
• application of technology for controlling the physicochemical properties of the geothermal coolant by additives of surfactants;
• reduction of losses in turbine cascades by optimizing the geometry of nozzle and rotor blades, including the use of highly efficient saber blades.

Thus, in the design of the 25 MW geothermal steam turbine of KTZ OJSC for the Mutnovskaya GeoPP, special devices for moisture separation are used, which allow removing up to 80% of the liquid phase in the form of large drops and liquid films from the flow path. Starting from the fourth turbine stage, a developed system of peripheral moisture separation was used in the flow path. In the seventh and eighth stages of both turbine streams, in-channel moisture separation in nozzle grids is used. A fairly effective method of removing moisture is the use of a special turbine separator stage, which increases the efficiency of the turbine by almost 2%.

The salt content of the steam entering the flow path of the turbines of the GeoPP depends on the mineralization of the initial geothermal fluid and the efficiency of phase separation in the separation devices. The efficiency of separation devices largely determines the degree of drift of the turbine flow path by scale deposits, and also affects the intensity of drop impact erosion of turbine blades and corrosion cracking of the metal of the turbine flow path elements.

Vertical and horizontal separators are used in technological schemes of modern geothermal power plants. Vertical separators are used mainly at GeoPPs built with the participation of New Zealand specialists in New Zealand, the Philippines and other countries. Horizontal separators are used in geothermal power units in Russia, USA, Japan and Iceland. Moreover, up to 70% of GeoPPs in the world work with vertical separators. Vertical separators are capable of providing an average outlet steam dryness of up to 99.9%. Moreover, their efficiency significantly depends on the operating parameters: flow rate and pressure of wet steam, moisture content of the steam-water mixture (PVA), liquid level in the separator, etc.

In Russia, horizontal separators have been developed and are being operated at the power units of GeoPPs, which are distinguished by high efficiency and small-sized characteristics. The dryness of the steam at the outlet of the separator reaches 99.99%. These developments were based on research and technologies of enterprises producing equipment for nuclear power plants, shipbuilding and other industries. Such separators are installed and successfully operate in modular power units of the VerkhneMutnovskaya GeoPP and at the first stage of the Mutnovskaya GeoPP (Fig. 3).

The advantage of binary plants, which consists primarily in the ability to generate electricity based on a low-temperature heat source, has largely determined the main areas of their application. It is especially advisable to use binary installations for:

• power supply (also for autonomous) regions with low-temperature geothermal resources;
• increasing the capacity of operating geothermal power plants operating on a high-temperature geothermal coolant, without drilling additional wells;
• increasing the efficiency of using geothermal sources due to the use of binary plants in technological schemes of newly designed combined geothermal power plants.

Thermophysical, thermodynamic and other properties of organic low-boiling substances have a significant impact on the type and efficiency of the heat cycle, technological parameters, design and characteristics of equipment, operating modes, reliability and environmental friendliness of binary plants.

In practice, about 15 different low-boiling organic substances and mixtures are used as the working fluid of binary installations. In fact, at present, geothermal binary power units mainly operate on hydrocarbons - about 82.7% of the total installed capacity of binary power units in the world, fluorocarbons - 6.7%, chlorofluorocarbons - 2.0%, water-ammonia mixture - 0.5 %, there are no data on the working fluid for 8.2%.

Combined binary cycle geothermal power plants are distinguished by the fact that the primary geothermal fluid is not only a source of heat for the secondary circuit, but is also directly used to convert heat into mechanical work in a steam turbine.

The steam phase of the geothermal two-phase heat carrier is used directly for generating electrical energy by expansion in a back pressure steam turbine, and the heat of condensation of the geothermal steam (as well as the separator) is sent to a second low-temperature circuit, in which an organic working fluid is used to generate electricity. The use of such a combined scheme of GeoPPs is especially advisable in cases where the initial geothermal fluid contains a large amount of non-condensable gases, since the energy consumption for removing them from the condenser can be significant.

The results of thermodynamic calculations show that with all the initial conditions being equal, the use of a binary power unit in combined cycle geothermal power plants can increase the capacity of Single-Flash GeoPPs by 15%, and DoubleFlash GeoPPs - by 5%. Currently, binary plants are produced at factories in the USA, Germany, Italy, Sweden, Russia and other countries. Information about some technical characteristics binary installations produced by various manufacturers are presented in table. 2.

In fig. 4 shows the data on the cost of the installed capacity of 1 kW during the construction of various GeoPPs with turbine installations on geothermal steam and a low-boiling organic working fluid, indicating the dependence of the GeoPP cost on the applied cycle and the temperature of the geothermal geofluid.

The most promising Russian geothermal energy projects are the expansion of the Mutnovskaya GeoPP (50 MW) and the Verkhne-Mutnovskaya GeoPP (12 MW) with combined (binary cycle) power units with a capacity of 10 and 6.5 MW, respectively, due to the heat recovery of their waste heat carrier without drilling additional wells, as well as the construction of the second stage of the Mutnovskaya GeoPP with a capacity of 50 MW.

conclusions

1. In the world geothermal energy, technological schemes are used with geothermal power plants of direct, binary and combined cycles, depending on the phase state and temperature of the geothermal heat carrier.
2. The main increase in the total installed capacity of GeoPPs in the world in recent years is due to the development of binary geothermal energy technologies.
3. The specific cost of the installed capacity of geothermal power units significantly depends on the temperature of the geothermal heat carrier and sharply decreases with its increase.

Geothermal energy

Annotation.

Introduction.

The cost of electricity generated by geothermal power plants.

Bibliography.

Annotation.

This work presents the history of the development of geothermal energy, both throughout the world and in our country of Russia. The analysis of the use of deep-seated heat of the Earth, for converting it into electrical energy, as well as for providing cities and villages with heat and hot water supply in such regions of our country as Kamchatka, Sakhalin, the North Caucasus, has been carried out. The economic feasibility study of the development of geothermal deposits, the construction of power plants and the terms of their recoupment have been made. Comparing the energies of geothermal sources with other types of energy sources, we obtain the prospects for the development of geothermal energy, which should take an important place in the overall balance of energy use. In particular, for the restructuring and re-equipment of the energy sector of the Kamchatka region and the Kuril Islands, partly of Primorye and the North Caucasus, it is necessary to use our own geothermal resources.

Introduction.

The main directions for the development of generating capacities in the country's energy sector in the near future are the technical re-equipment and reconstruction of power plants, as well as the commissioning of new generating capacities. First of all, this is the construction of combined cycle plants with an efficiency of 5560%, which will increase the efficiency of existing thermal power plants by 2540%. The next stage should be the construction of thermal power plants using new technologies for burning solid fuel and with supercritical steam parameters to achieve the TPP efficiency of 46-48%. Nuclear power plants with new types of thermal and fast neutron reactors will also receive further development.

An important place in the formation of Russia's energy sector is occupied by the country's heat supply sector, which is the largest in terms of the volume of consumed energy resources, more than 45% of their total consumption. District heating (DH) systems produce more than 71%, and decentralized sources about 29% of all heat. More than 34% of all heat is supplied by power plants, about 50% by boiler houses. In accordance with the energy strategy of Russia until 2020. it is planned to increase heat consumption in the country by at least 1.3 times, and the share of decentralized heat supply will increase from 28.6% in 2000. up to 33% in 2020

The increase in prices, which has occurred in recent years, for fossil fuel (gas, fuel oil, diesel fuel) and for its transportation to remote regions of Russia and, accordingly, an objective increase in selling prices for electric and thermal energy fundamentally change the attitude towards the use of renewable energy sources: geothermal, wind, solar.

So, the development of geothermal energy in certain regions of the country allows today to solve the problem of electricity and heat supply, in particular in Kamchatka, the Kuril Islands, as well as in the North Caucasus, in certain regions of Siberia and the European part of Russia.

Expansion of the use of local non-traditional renewable energy sources and, first of all, geothermal heat of the earth should become one of the main directions of improvement and development of heat supply systems. Already in the next 7-10 years, with the help of modern technologies of local heat supply, thanks to thermal heat, significant resources of fossil fuel can be saved.

In the last decade, the use of non-traditional renewable energy sources (RES) has experienced a real boom in the world. The scale of application of these sources has increased several times. This direction is developing most intensively in comparison with other areas of energy. There are several reasons for this phenomenon. First of all, it is obvious that the era of cheap traditional energy resources is irrevocably over. In this area, there is only one trend - an increase in prices for all types. No less significant is the desire of many countries deprived of their fuel base for energy independence. Environmental considerations, including the emission of harmful gases, play a significant role. The population of developed countries provides active moral support for the use of renewable energy sources.

For these reasons, the development of renewable energy sources in many states is a priority task of technical policy in the field of energy. In a number of countries, this policy is implemented through the adopted legislative and regulatory framework, which establishes the legal, economic and organizational framework for the use of renewable energy sources. In particular, the economic foundations consist in various measures to support renewable energy sources at the stage of their development of the energy market (tax and credit benefits, direct subsidies, etc.)

In Russia, the practical application of renewable energy sources lags significantly behind the leading countries. There is no legislative and regulatory framework, as well as state economic support. All this makes it extremely difficult to practice in this area. The main reason for the inhibiting factors is the lingering economic troubles in the country and, as a consequence, difficulties with investments, low effective demand, lack of funds for the necessary developments. Nevertheless, some work and practical measures for the use of renewable energy sources in our country are being carried out (geothermal energy). Steam-hydrothermal deposits in Russia are found only in Kamchatka and the Kuril Islands. Therefore, geothermal energy cannot and in the future take a significant place in the energy sector of the country as a whole. However, it is able to radically and on the most economic basis solve the problem of power supply to these regions, which use expensive imported fuel (fuel oil, coal, diesel fuel) and are on the verge of an energy crisis. The potential of steam-hydrothermal deposits in Kamchatka is capable of providing from various sources from 1000 to 2000 MW of installed electric power, which significantly exceeds the needs of this region for the foreseeable future. Thus, there are real prospects for the development of geothermal energy here.

The history of the development of geothermal energy.

Along with huge fossil fuel resources, Russia possesses significant reserves of the earth's heat, which can be multiplied by geothermal sources located at a depth of 300 to 2500 m, mainly in the fault zones of the earth's crust.

The territory of Russia is well explored, and today the main resources of the earth's heat are known, which have significant industrial potential, including energy. Moreover, almost everywhere there are heat reserves with temperatures ranging from 30 to 200 ° C.

Back in 1983. at VSEGINGEO, an atlas of the thermal water resources of the USSR was compiled. In our country, 47 geothermal deposits have been explored with reserves of thermal waters, which make it possible to obtain more than 240 · 10³m³ / day. Today in Russia specialists from almost 50 scientific organizations are engaged in the problems of using the heat of the earth.

More than 3,000 wells have been drilled to use geothermal resources. The cost of geothermal research and drilling operations already performed in this area, in modern prices is more than 4 billion. dollars. So in Kamchatka, on geothermal fields, 365 wells have already been drilled with a depth of 225 to 2266 m and about 300 mln. dollars (in modern prices).

The first geothermal power plant was commissioned in Italy in 1904. The first geothermal power plant in Kamchatka, and the first in the USSR, the Pauzhetskaya Geothermal Power Plant, was put into operation in 1967. and had a power of 5 mW, subsequently increased to 11 mW. A new impetus to the development of geothermal energy in Kamchatka was given in the 90s with the emergence of organizations and firms (JSC Geotherm, JSC Intergeotherm, JSC Nauka), which in cooperation with industry (primarily with the Kaluga Turbine Plant) developed new progressive schemes, technologies and types of equipment for converting geothermal energy into electrical energy and obtained loans from the European Bank for Reconstruction and Development. As a result, in 1999. in Kamchatka, the Verkhne-Mutnovskaya Geothermal Power Plant (three modules of 4 MW each) was commissioned. The first 25mW unit is commissioned. the first stage of the Mutnovskaya Geothermal Power Plant with a total capacity of 50 MW.

The second stage with a capacity of 100 MW can be commissioned in 2004

Thus, the nearest and quite real prospects for geothermal energy in Kamchatka have been determined, which is a positive, undoubted example of the use of renewable energy sources in Russia, despite the serious economic difficulties in the country. The potential of steam-hydrothermal fields in Kamchatka is capable of providing 1000 MW of installed electric power, which significantly exceeds the needs of this region for the foreseeable future.

According to the Institute of Volcanology of the Far Eastern Branch of the Russian Academy of Sciences, the already identified geothermal resources make it possible to fully provide Kamchatka with electricity and heat for more than 100 years. Along with the high-temperature Mutnovskoye field with a capacity of 300 MW (e) in the south of Kamchatka, significant reserves of geothermal resources are known at Koshelevskoye, Bolshe Bannom, and in the north at the Kireunskoye fields. The heat reserves of geothermal waters in Kamchatka are estimated at 5000 MW (t).

Chukotka also has significant reserves of geothermal heat (on the border with the Kamchatka region), some of them have already been discovered and can be actively used for nearby cities and villages.

The Kuril Islands are also rich in the reserves of the earth's heat, they are quite enough for heat and electricity supply of this territory for 100-200 years. On the island of Iturup, reserves of a two-phase geothermal coolant were discovered, the capacity of which (30 MW (e)) is sufficient to meet the energy requirements of the entire island in the next 100 years. Wells have already been drilled here at the Okeanskoye geothermal field and a GeoPP is under construction. On the southern island of Kunashir there are reserves of geothermal heat, which are already used to generate electricity and heat supply to the city of Yuzhno Kurilsk. The bowels of the northern island of Paramushir are less studied, however, it is known that this island also has significant reserves of geothermal water with a temperature of 70 to 95 ° C; a GeoTS with a capacity of 20 MW (t) is also being built here.

Deposits of thermal waters with a temperature of 100-200 ° C are much more widespread. At this temperature, it is advisable to use low-boiling working fluids in a steam-turbine cycle. The use of double-circuit geothermal power plants on thermal water is possible in a number of regions of Russia, primarily in the North Caucasus. Geothermal deposits with temperatures in the reservoir from 70 to 180 ° C, which are located at a depth of 300 to 5000 m, are well studied here. Geothermal water has been used here for a long time for heating and hot water supply. In Dagestan, more than 6 million cubic meters of geothermal water are produced annually. In the North Caucasus, about 500 thousand people use geothermal water supply.

Primorye, the Baikal region, the West Siberian region also have reserves of geothermal heat suitable for large-scale use in industry and agriculture.

Converting geothermal energy into electricity and heat.

One of the promising areas of using the heat of highly mineralized underground thermal waters is its conversion into electrical energy. For this purpose, a technological scheme for the construction of a geothermal power plant was developed, consisting of a geothermal circulation system (GCS) and a steam turbine unit (STU), the diagram of which is shown in Fig. 1. Distinctive feature Such a technological scheme from the known is that in it the role of an evaporator and a superheater is performed by a downhole vertical counter-flow heat exchanger located in the upper part of the injection well, where the produced high-temperature thermal water is supplied through the surface pipeline, which, after heat transfer to the secondary heat carrier, is pumped back into the formation. The secondary coolant from the condenser of the steam turbine unit flows by gravity into the heating zone through a pipe run down inside the heat exchanger to the bottom.

The work of vocational schools is based on the Rankine cycle; t, s diagram of this cycle and the nature of the change in the temperatures of the heat carriers in the heat exchanger-evaporator.

The most important point in the construction of a geothermal power plant is the choice of a working fluid in the secondary circuit. The working fluid chosen for the geothermal installation must have favorable chemical, physical and operational properties under the given operating conditions, i.e. to be stable, non-flammable, explosion-proof, non-toxic, inert with respect to construction materials and cheap. It is advisable to choose a working fluid with a lower coefficient of dynamic viscosity (less hydraulic losses) and with a higher coefficient of thermal conductivity (better heat transfer).

It is practically impossible to fulfill all these requirements at the same time, therefore it is always necessary to optimize the choice of one or another working fluid.

Low initial parameters of the working bodies of geothermal power plants lead to the search for low-boiling working bodies with a negative curvature of the right boundary curve in the t, s diagram, since the use of water and steam leads in this case to a deterioration in thermodynamic parameters and to a sharp increase in the dimensions of steam turbine plants, which is essential. increases their value.

It is proposed to use a mixture of isobutane + isopentane in the supercritical state as a supercritical agent in the secondary circuit of binary energy cycles. The use of supercritical mixtures is convenient because the critical properties, i.e. critical temperature tк (x), critical pressure pк (x) and critical density qc (x) depend on the composition of the mixture x. This will make it possible, by selecting the composition of the mixture, to select the supercritical agent with the most favorable critical parameters for the corresponding temperature of thermal water of a particular geothermal field.

Low-boiling hydrocarbon isobutane is used as a secondary heat carrier, the thermodynamic parameters of which correspond to the required conditions. Critical parameters of isobutane: tc = 134.69 ° C; pk = 3.629 MPa; qк = 225.5 kg / m³. In addition, the choice of isobutane as a secondary coolant is due to its relatively low cost and environmental friendliness (in contrast to freons). Isobutane as a working fluid has found wide distribution abroad, and it is also proposed to use it in a supercritical state in binary geothermal energy cycles.

The energy characteristics of the installation are calculated for a wide range of temperatures of the produced water and various modes of its operation. In this case, it was assumed in all cases that the condensation temperature of isobutane tcon = 30 ° C.

The question arises about the choice of the smallest temperature difference êtfig. 2. On the one hand, a decrease in êt leads to an increase in the surface of the evaporator heat exchanger, which may not be economically justified. On the other hand, an increase in êt at a given temperature of thermal water tt leads to the need to lower the evaporation temperature tg (and, consequently, pressure), which will negatively affect the efficiency of the cycle. In most practical cases, it is recommended to take êt = 10 ÷ 25 ° C.

The results obtained show that there are optimal parameters for the operation of the steam power plant, which depend on the temperature of the water entering the primary circuit of the heat exchanger steam generator. With an increase in the evaporation temperature of isobutane tg, the power N generated by the turbine increases by 1 kg / s of the secondary coolant flow rate. At the same time, as tz increases, the amount of isobutane evaporated decreases by 1 kg / s of thermal water consumption.

As the temperature of the thermal water rises, the optimum temperature evaporation.

Figure 3 shows the graphs of the dependence of the power N generated by the turbine on the evaporation temperature tf of the secondary coolant at different temperatures of thermal water.

For high-temperature water (tt = 180 ° C), supercritical cycles are considered, when the initial steam pressure is pH = 3.8; 4.0; 4.2; and 5.0MPa. Of these, the most effective from the point of view of obtaining maximum power is the supercritical cycle, which is close to the so-called "triangular" cycle with an initial pressure of pH = 5.0 MPa. In this cycle, due to the minimum temperature difference between the coolant and the working fluid, the temperature potential of thermal water is used most fully. Comparison of this cycle with the subcritical one (pH = 3.4 MPa) shows that the power generated by the turbine during the supercritical cycle increases by 11%, the density of the flow of matter entering the turbine is 1.7 times higher than in the cycle with pH = 3 , 4 MPa, which will lead to an improvement in the transport properties of the coolant and a decrease in the size of the equipment (supply pipelines and turbines) of the steam turbine plant. In addition, in the cycle with pH = 5.0 MPa, the temperature of the waste thermal water tn, injected back into the reservoir, is 42 ° C, while in the subcritical cycle with pH = 3.4 MPa, the temperature is tn = 55 ° C.

At the same time, an increase in the initial pressure to 5.0 MPa in the supercritical cycle affects the cost of equipment, in particular, the cost of the turbine. Although the size of the flow path of the turbine decreases with increasing pressure, the number of turbine stages simultaneously increases, a more developed end seal is required and, most importantly, the thickness of the casing walls increases.

To create a supercritical cycle in the technological scheme of the GeoTPP, it is necessary to install a pump on the pipeline connecting the condenser with the heat exchanger.

However, factors such as an increase in power, a decrease in the size of the supply pipelines and turbines, and a more complete response of the temperature potential of thermal water, speak in favor of a supercritical cycle.

In the future, it is necessary to look for coolants with a lower critical temperature, which will allow creating supercritical cycles when using thermal waters with a lower temperature, since the thermal potential of the vast majority of explored deposits in Russia does not exceed 100 ÷ 120 ° C. In this respect, the most promising is R13B1 (trifluorobromomethane) with the following critical parameters: tc = 66.9 ° C; pk = 3.946MPa; qк = 770kg / m³.

The results of estimated calculations show that the use of thermal water with a temperature of tc = 120 ° C in the primary circuit of the Geothermal power plant and the creation of a supercritical cycle with an initial pressure of pн = 5.0 MPa in the secondary circuit on R13B1 freon, also allow increasing the turbine power up to 14% compared to the subcritical cycle with initial pressure pн = 3.5 MPa.

For the successful operation of the geothermal power plant, it is necessary to solve the problems associated with the occurrence of corrosion and scale deposits, which, as a rule, are aggravated with an increase in the mineralization of thermal water. The most intense scale deposits are formed due to the degassing of thermal water and the violation as a result of this carbon dioxide equilibrium.

In the proposed technological scheme, the primary coolant circulates in a closed loop: reservoir - production well - onshore pipeline - pump - injection well - reservoir where conditions for water degassing are minimized. At the same time, it is necessary to adhere to such temperature and pressure conditions in the onshore part of the primary circuit, which prevent degassing and precipitation of carbonate deposits (depending on temperature and salinity, the pressure must be maintained at a level of 1.5 MPa and higher).

A decrease in the temperature of thermal water leads to the precipitation of non-carbonate salts, which was confirmed by studies carried out at the Kayasulinsky geothermal test site. Part of the precipitated salts will be deposited on the inner surface of the injection well, and the bulk will be carried out to the bottomhole zone. Salt deposition at the bottom of the injection well will contribute to a decrease in injectivity and a gradual decrease in the circular flow rate, up to a complete shutdown of the GVC.

To prevent corrosion and scale deposits in the GVC circuit, an effective reagent OEDPA (hydroxyethyl-dendiphosphonic acid) can be used, which has a long-term anticorrosive and antiscale effect of surface passivation. Restoration of the passivating layer of OEDPhK is carried out by periodic impulse injection of the reagent solution into the thermal water at the production wellhead.

To dissolve salt sludge, which will accumulate in the bottomhole zone, and, therefore, to restore the injectivity of the injection well, a very effective reagent is NMC (concentrate of low molecular weight acids), which can also be periodically introduced into the circulating thermal water in the area before the injection pump.

Consequently, from the above, it can be suggested that one of the promising directions for the development of thermal energy of the earth's interior is its transformation into electrical energy through the construction of double-circuit geothermal power plants on low-boiling working agents. The efficiency of such a conversion depends on many factors, in particular, on the choice of the working fluid and the parameters of the thermodynamic cycle of the secondary circuit of the Geothermal power plant.

The results of the calculated analysis of the cycles using various coolants in the secondary circuit show that the most optimal are supercritical cycles, which make it possible to increase the turbine power and cycle efficiency, improve the transport properties of the coolant and more fully operate the temperature of the initial thermal water circulating in the primary circuit of the Geothermal power plant.

It was also found that for high-temperature thermal water (180 ° C and above) the most promising is the creation of supercritical cycles in the secondary circuit of a Geothermal power plant using isobutane, while for waters with a lower temperature (100 ÷ 120 ° C and above), when creating the same cycles, the most suitable coolant is freon R13B1.

Depending on the temperature of the produced thermal water, there is an optimal evaporation temperature of the secondary heat carrier corresponding to the maximum power generated by the turbine.

In the future, it is necessary to study supercritical mixtures, the use of which as a working agent for geothermal energy cycles is the most convenient, since by selecting the mixture composition one can easily change their critical properties depending on external conditions.

Another direction is the use of geothermal energy, geothermal heat supply, which has long found application in Kamchatka and the North Caucasus for heating greenhouses, heating and hot water supply in the housing and communal sector. The analysis of the world and domestic experience shows that geothermal heat supply is promising. Currently, geothermal heat supply systems with a total capacity of 17,175 MW are in operation in the world, more than 200 thousand geothermal installations are operated in the United States alone. According to the plans of the European Union, the capacity of geothermal heating systems, including heat pumps, should increase from 1300 MW in 1995 to 5000 MW in 2010.

In the USSR, geothermal waters were used in Krasnodar and Stavropol Territories, Kabardino-Balkaria, North Ossetia, Checheno-Ingushetia, Dagestan, Kamchatka Oblast, Crimea, Georgia, Azerbaijan and Kazakhstan. In 1988, 60.8 million m³ of geothermal water was extracted, now in Russia it is extracted up to 30 million. m³ per year, which is equivalent to 150 ÷ ​​170 thousand tons of standard fuel. At the same time, the technical potential of geothermal energy, according to the Ministry of Energy of the Russian Federation, is 2,950 million tons of fuel equivalent.

Over the past 10 years, the system of exploration, development and exploitation of geothermal resources has disintegrated in our country. In the USSR, scientific research work on this problem was carried out by the institutes of the Academy of Sciences, the ministries of geology and the gas industry. Exploration, assessment and approval of reserves of deposits were carried out by institutes and regional divisions of the Ministry of Geology. Drilling of productive wells, field development, development of re-injection technologies, geothermal water treatment, operation of geothermal heat supply systems were carried out by subdivisions of the Ministry of the Gas Industry. It included five regional operational departments, the research and production association "Soyuzgeotherm" (Makhachkala), which developed a scheme for the prospective use of geothermal waters in the USSR. The design of systems and equipment for geothermal heat supply was carried out by the Central Research and Development Institute of Engineering Equipment.

At present, comprehensive research work in the field of geothermal has ceased: from geological and hydrogeological research to the problems of purifying geothermal waters. Exploratory drilling, development of previously explored fields is not being carried out, equipment of existing geothermal heat supply systems is not being modernized. The role of government in the development of geothermal energy is insignificant. Geothermal specialists are scattered, their experience is not in demand. The analysis of the current situation and development prospects in the new economic conditions of Russia is carried out using the example of the Krasnodar Territory.

For this region, of all the renewable energy sources, the most promising is the use of geothermal waters. Figure 4 shows the priorities for the use of renewable energy sources for heat supply to facilities in the Krasnodar Territory.

The Krasnodar Territory annually produces up to 10 million m³ / year of geothermal water with a temperature of 70 ÷ 100 ° C, which replaces 40 ÷ 50 thousand tons of organic fuel (in terms of conventional fuel). There are 10 fields in operation with 37 wells, 6 fields with 23 wells are under development. Total number of geothermal wells 77. Geothermal waters heat 32 hectares. greenhouses, 11 thousand apartments in eight settlements, hot water supply is provided to 2 thousand people. The explored exploitable reserves of geothermal waters of the region are estimated at 77.7 thousand. m³ / day, or during operation during the heating season - 11.7 mln. m³ per season, forecasted reserves are 165 thous. m³ / day and 24.7 mln. m³ per season.

One of the most developed Mostovskoye geothermal field, 240 km from Krasnodar in the foothills of the Caucasus, where 14 wells were drilled with a depth of 1650-1850 m with flow rates of 1500-3,300 m³ / day, a temperature at the mouth of 67-78 ° C, a total salinity of 0.9-1. 9g / l. In terms of chemical composition, geothermal water almost meets the standards for drinking water. The main consumer of geothermal water from this deposit is a greenhouse complex with a greenhouse area of ​​up to 30 hectares, on which 8 wells previously worked. Currently, 40% of the greenhouse area is heated here.

For heating residential and administrative buildings pos. Mostovoy in the 80s was built a geothermal central heating station (CHP) with an estimated thermal power of 5 MW, the diagram of which is shown in Fig. 5. Geothermal water in the central heating station is supplied from two wells with a flow rate of 45 ÷ 70 m³ / h each and a temperature of 70 ÷ 74 ºС into two storage tanks with a capacity of 300 m³ each. To utilize the heat of waste geothermal water, two steam compressor heat pumps with an estimated thermal power of 500 kW were installed. The geothermal water spent in heating systems with a temperature of 30 ÷ 35 ° C in front of the heat pump unit (HPU) is divided into two streams, one of which is cooled to 10 ° C and drained into the reservoir, and the second is heated to 50 ° C and returned to the storage tanks. Heat pump units were manufactured by the Moscow plant "Compressor" on the basis of refrigeration machines A-220-2-0.

Heat power regulation geothermal heating in the absence of peak reheating, it is carried out in two ways: by passages of the coolant and cyclically. At last way the systems are periodically filled with geothermal heat carrier with simultaneous discharge of the cooled one. With a daily heating period Z, the heating time Zн is determined by the formula

Zн = 48j / (1 + j), where the coefficient of supply heat; calculated air temperature in the room, ° С; and actual and calculated outdoor air temperature, ° С.

The capacity of storage tanks of geothermal systems is determined from the condition of ensuring the normalized amplitude of air temperature fluctuations in heated residential premises (± 3 ° C) according to the formula.

where kF is the heat transfer of the heating system per 1 ° C of the temperature head, W / ° C; Z = Zн + Zperiod of geothermal heating operation; Zpp pause duration, h; Qp and Qp is the estimated and seasonally average thermal power of the building heating system, W; c · volumetric heat capacity of geothermal water, J / (m³ · ºС); nnumber of geothermal heating starts per day; k1 is the coefficient of heat loss in the geothermal heat supply system; A1amplitude of temperature fluctuations in the heated building, ºС; Rnomsum total indicator of heat absorption of heated premises; Vс and Vтс capacity of heating systems and heating networks, m³.

When heat pumps are operating, the ratio of the flow rates of geothermal water through the evaporator Gi and the condenser Gk is determined by the formula:

Where tk, to, t is the temperature of geothermal water after the condenser, building heating system and HPU evaporators, ºС.

It should be noted the low reliability of the applied designs of heat pumps, since the conditions of their operation significantly differed from those of the refrigerating machines. The ratio of the discharge and suction pressures of the compressors when operating in the heat pump mode is 1.5 ÷ 2 times higher than the analogous ratio in refrigeration machines. Failures of the connecting rod-piston group, oil industry, automation led to the premature failure of these machines.

As a result of the lack of control over the hydrological regime, the operation of the Mostovskoye geothermal field decreased by 2 times within 10 years. In order to restore the reservoir pressure of the field in 1985. three injection wells were drilled, a pumping station was built, but their work did not give a positive result due to the low injectivity of the reservoirs.

For the most promising use of geothermal resources in Ust-Labinsk with a population of 50 thousand people, located 60 km from Krasnodar, a geothermal heat supply system with an estimated thermal capacity of 65 MW has been developed. Eocene-Paleocene sediments with a depth of 2200-2600 m with a reservoir temperature of 97-100 ° C and a salinity of 17-24 g / l were selected from three water-pumping horizons.

As a result of the analysis of existing and prospective heat loads in accordance with the city heat supply development scheme, the optimal, calculated, heat capacity of the geothermal heat supply system was determined. Feasibility comparison four options(three of them without peak boiler houses with a different number of wells and one with heating in the boiler house) showed that the scheme with the peak boiler house has the minimum payback period, Fig. 6.

The geothermal heat supply system provides for the construction of the western and central thermal water intakes with seven injection wells. Operating mode of thermal water intakes with reverse injection of the cooled heat carrier. The heat supply system is double-circuit with peak heating in the boiler room and dependent connection of the existing heating systems of buildings. Capital investments in the construction of this geothermal system amounted to 5.14 million. rub. (in 1984 prices), the payback period is 4.5 years, the estimated economy of the replaced fuel is 18.4 thousand tons of standard fuel per year.

The cost of electricity generated by geothermal power plants.

The costs of research and development (drilling) of geothermal fields account for up to 50% of the total cost of a geothermal power plant, and therefore the cost of electricity generated at a geothermal power plant is quite significant. Thus, the cost of the entire pilot industrial (OP) of the Verkhnee-Mutnovskaya GeoPP [capacity 12 (3 × 4) MW] was about 300 million rubles. However, the absence of transportation costs for fuel, the renewability of geothermal energy and the environmental friendliness of electricity and heat production allow geothermal energy to compete successfully in the energy market and in some cases produce cheaper electricity and heat than traditional IES and CHPs. For remote areas (Kamchatka, Kuril Islands) GeoPPs have an unconditional advantage over CHP and diesel power plants operating on imported fuel.

If we consider Kamchatka as an example, where more than 80% of electricity is produced at CHPP-1 and CHPP-2, operating on imported fuel oil, then the use of geothermal energy is more profitable. Even today, when the process of construction and development of new GeoPPs at the Mutnovsky geothermal field is still underway, the cost of electricity at the Verkhne-Mutnovskaya GeoPP is more than two times lower than at the TPP in Petropavlovsk Kamchatsky. The cost of 1 kW × h (e) at the old Pauzhetskaya GeoPP is 2-3 times lower than at CHPP-1 and CHPP-2.

The prime cost of 1 kWh of electricity in Kamchatka in July 1988 was from 10 to 25 cents, and the average electricity tariff was set at 14 cents. In June 2001. in the same region, the electricity tariff for 1 kWh ranged from 7 to 15 cents. At the beginning of 2002. the average tariff at OJSC Kamchatskenergo was 3.6 rubles. (12 cents). It is absolutely clear that the economy of Kamchatka cannot develop successfully without reducing the cost of consumed electricity, and this can only be achieved through the use of geothermal resources.

Now, when restructuring the energy sector, it is very important to proceed from real prices for fuel and equipment, as well as energy prices for different consumers. V otherwise you can come to erroneous conclusions and predictions. So, in the strategy of economic development of the Kamchatka region, developed in 2001 in "Dalsetproekt", without sufficient justification for 1000m³ of gas, the price of 50 USD was included, although it is clear that the real cost of gas will not be less than 100 USD, and the duration of the development of gas fields will be 5 ÷ 10 years. At the same time, according to the proposed strategy, gas reserves are calculated for a service life of no more than 12 years. Therefore, the prospects for the development of the Kamchatka region's energy sector should be associated primarily with the construction of a series of geothermal power plants at the Mutnovskoye field [up to 300 MW (e)], the re-equipment of the Pauzhetskaya GeoPP, the capacity of which should be increased to 20 MW, and the construction of new GeoPPs. The latter will ensure the energy independence of Kamchatka for many years (at least 100 years) and will reduce the cost of electricity sold.

According to the assessment of the World Energy Council, of all renewable energy sources, the lowest price per 1 kWh is at the GeoPP (see table).

	power	use power			Price installed		in the last
	10200	55 ÷ 95 (84)	2 ÷ 10	1 ÷ 8	800 ÷ 3000	70,2	22
Wind	12500	20 ÷ 30 (25)	5 ÷ 13	3 ÷ 10	1100 ÷ 1700	27,1	30
	50	8 ÷ 20	25 ÷ 125	5 ÷ 25	5000 ÷ 10000	2,1	30
Tides	34	20 ÷ 30	8 ÷ 15	8 ÷ 15	1700 ÷ 2500	0,6

From the experience of operating large GeoPPs in the Philippines, New Zealand, Mexico and the USA, it follows that the cost of 1 kWh of electricity often does not exceed 1 cent, while it should be borne in mind that the power utilization factor at GeoPP reaches 0.95.

Geothermal heat supply is most beneficial in the direct use of geothermal hot water, as well as in the introduction of heat pumps, which can effectively use the heat of the earth with a temperature of 10-30 ° C, i.e. low grade geothermal heat. In the current economic conditions of Russia, the development of geothermal heat supply is extremely difficult. Fixed assets must be invested in well drilling. In the Krasnodar Territory, the cost of drilling 1m of wells is 8 thousand rubles, and its depth is 1800m, the costs are 14.4 million rubles. With an estimated well flow rate of 70m³ / h, a triggered temperature head of 30 ° C, round-the-clock operation for 150 days. per year, the utilization rate of the estimated flow rate during the heating season is 0.5, the amount of heat supplied is 4385 MWh, or in value terms, 1.3 million rubles. at a rate of 300 rubles / (MWh). With this rate, well drilling will pay off in 11 years. At the same time, in the future, the need to develop this direction in the energy sector is beyond doubt.

Conclusions.

1. Practically throughout the entire territory of Russia there are unique reserves of geothermal heat with coolant temperatures (water, two-phase flow and steam) from 30 to 200 ° C.

2.In recent years, geothermal technologies have been created in Russia on the basis of large fundamental research, which can quickly provide effective use heat of the earth at GeoPP and GeoTS for generating electricity and heat.

3. Geothermal energy should take an important place in the overall balance of energy use. In particular, for the restructuring and re-equipment of the power industry of the Kamchatka region and the Kuril Islands and partly of Primorye, Siberia and the North Caucasus, one should use its own geothermal resources.

4. Large-scale introduction of new heat supply schemes with heat pumps using low-potential heat sources will reduce the consumption of fossil fuel by 20-25%.

5. To attract investments and loans in the energy sector, it is necessary to carry out effective projects and guarantee the timely return of borrowed funds, which is possible only with full and timely payment of electricity and heat supplied to consumers.

Bibliography.

1. Conversion of geothermal energy into electrical energy using a supercritical cycle in the secondary circuit. Abdulagatov I.M., Alkhasov A.B. "Heat power engineering. -1988№4-p. 53-56 ".

2. Salamov A.A. "Geothermal power plants in the world power engineering" Heat power engineering2000№1-p. 79-80 "

3. Heat of the Earth: From the report "Prospects for the development of geothermal technologies" Ecology and Life-2001-№6-p49-52.

4. Tarnizhevsky B.V. "State and prospects for the use of renewable energy sources in Russia" Industrial power engineering-2002-№1-p. 52-56.

5. Kuznetsov V.A. "Mutnovskaya geothermal power plant" Power plants-2002-№1-p. 31-35.

6. Butuzov V.A. "Geothermal heat supply systems in the Krasnodar Territory" Energy Manager-2002-No. 1-p. 14-16.

7. Butuzov V.A. "Analysis of geothermal heat supply systems in Russia" Industrial energy-2002-№6-p.53-57.

8. Dobrokhotov V.I. "The use of geothermal resources in the energy sector of Russia" Heat power engineering-2003-No. 1-p. 2-11.

9. Alkhasov A.B. "Increasing the efficiency of using geothermal heat" Heat power engineering-2003-No.3-p.52-54.

3.4 CALCULATION OF A GEOTHERMAL POWER PLANT

We will calculate the thermal diagram of a binary type geothermal power plant, according to.

Our geothermal power plant consists of two turbines:

The first one operates on saturated water vapor obtained in the expander. Electric power - ;

The second runs on saturated steam of R11 freon, which evaporates due to the heat of the water removed from the expander.

Water from geothermal wells with pressure pgw and temperature tgw enters the expander. The expander produces dry saturated steam with a pressure of pp. This steam is directed to a steam turbine. The remaining water from the expander goes to the evaporator, where it is cooled down and ends back into the well. Temperature head in the evaporator unit = 20 ° C. The working fluids expand in turbines and enter the condensers, where they are cooled with water from the river with a temperature of thw. Water heating in the condenser = 10 ° С, and underheating to saturation temperature = 5 ° С.

Relative internal efficiency of turbines. Electromechanical efficiency of turbine generators = 0.95.

Initial data are shown in table 3.1.

Tab. 3.1. Initial data for calculating GeoPP

Schematic diagram of a binary type GeoPP (Fig. 3.2).

Rice. 3.2. Schematic diagram of GeoPP.

According to the diagram in Fig. 3.2 and the initial data, we carry out calculations.

Calculation of the scheme of a steam turbine operating on dry saturated steam

Steam temperature at the inlet to the turbine condenser:

where is the temperature of the cooling water at the inlet to the condenser; - heating water in the condenser; - temperature head in the condenser.

The steam pressure in the turbine condenser is determined from the tables of properties of water and steam:

Available heat drop per turbine:

where is the enthalpy of dry saturated steam at the turbine inlet; is the enthalpy at the end of the theoretical process of steam expansion in the turbine.

Steam consumption from the expander to the steam turbine:

where is the relative internal efficiency of the steam turbine; - electromechanical efficiency of turbine generators.

Geothermal water expander calculation

Expander heat balance equation

where is the flow rate of geothermal water from the well; - enthalpy of geothermal water from the well; - water flow from the expander to the evaporator; is the enthalpy of geothermal water at the outlet of the expander. It is determined from the tables of properties of water and steam as the enthalpy of boiling water.

Expander material balance equation

Solving these two equations together, it is necessary to determine and.

The temperature of the geothermal water leaving the expander is determined from the tables of properties of water and steam as the saturation temperature at the pressure in the expander:

Determination of parameters at characteristic points of the thermal circuit of a turbine operating in freon

Freon vapor temperature at the turbine inlet:

Freon vapor temperature at the turbine outlet:

The enthalpy of freon vapor at the turbine inlet is determined from the p-h diagram for freon on the saturation line at:

240 kJ / kg.

The enthalpy of freon vapor at the turbine outlet is determined from the p-h diagram for freon at the intersection of the lines and the temperature line:

220 kJ / kg.

The enthalpy of boiling freon at the exit from the condenser is determined by the p-h diagram for freon on the curve for boiling liquid in temperature:

215 kJ / kg.

Evaporator calculation

Geothermal water temperature at the outlet of the evaporator:

Evaporator heat balance equation:

where is the heat capacity of water. Take = 4.2 kJ / kg.

It is necessary to determine from this equation.

Calculation of the power of a turbine running on freon

where is the relative internal efficiency of the freon turbine; - electromechanical efficiency of turbine generators.

Determination of pump power for pumping geothermal water into a well

where is the efficiency of the pump, taken as 0.8; is the average specific volume of geothermal water.

Electric power of GeoPP

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CALCULATION OF A GEOTHERMAL POWER PLANT

We will calculate the thermal diagram of a binary type geothermal power plant, according to.

Our geothermal power plant consists of two turbines:

The first one operates on saturated water vapor obtained in the expander. Electric power - ;

The second runs on saturated steam of R11 freon, which evaporates due to the heat of the water removed from the expander.

Water from geothermal wells with pressure pgw and temperature tgw enters the expander. The expander produces dry saturated steam with a pressure of pp. This steam is directed to a steam turbine. The remaining water from the expander goes to the evaporator, where it is cooled down and ends back into the well. Temperature head in the evaporator unit = 20 ° C. The working fluids expand in turbines and enter the condensers, where they are cooled with water from the river with a temperature of thw. Water heating in the condenser = 10 ° С, and underheating to saturation temperature = 5 ° С.

Relative internal efficiency of turbines. Electromechanical efficiency of turbine generators = 0.95.

Initial data are shown in table 3.1.

Tab. 3.1. Initial data for calculating GeoPP

Schematic diagram of a binary type GeoPP (Fig. 3.2).

Rice. 3.2.

According to the diagram in Fig. 3.2 and the initial data, we carry out calculations.

Calculation of the scheme of a steam turbine operating on dry saturated steam

Steam temperature at the inlet to the turbine condenser:

where is the temperature of the cooling water at the inlet to the condenser; - heating water in the condenser; - temperature head in the condenser.

The steam pressure in the turbine condenser is determined from the tables of properties of water and steam:

Available heat drop per turbine:

where is the enthalpy of dry saturated steam at the turbine inlet; is the enthalpy at the end of the theoretical process of steam expansion in the turbine.

Steam consumption from the expander to the steam turbine:

where is the relative internal efficiency of the steam turbine; - electromechanical efficiency of turbine generators.

Geothermal water expander calculation

Expander heat balance equation

where is the flow rate of geothermal water from the well; - enthalpy of geothermal water from the well; - water flow from the expander to the evaporator; is the enthalpy of geothermal water at the outlet of the expander. It is determined from the tables of properties of water and steam as the enthalpy of boiling water.

Expander material balance equation

Solving these two equations together, it is necessary to determine and.

The temperature of the geothermal water leaving the expander is determined from the tables of properties of water and steam as the saturation temperature at the pressure in the expander:

Determination of parameters at characteristic points of the thermal circuit of a turbine operating in freon

Freon vapor temperature at the turbine inlet:

Freon vapor temperature at the turbine outlet:

The enthalpy of freon vapor at the turbine inlet is determined from the p-h diagram for freon on the saturation line at:

240 kJ / kg.

The enthalpy of freon vapor at the turbine outlet is determined from the p-h diagram for freon at the intersection of the lines and the temperature line:

220 kJ / kg.

The enthalpy of boiling freon at the exit from the condenser is determined by the p-h diagram for freon on the curve for boiling liquid in temperature:

215 kJ / kg.

Evaporator calculation

Geothermal water temperature at the outlet of the evaporator:

Evaporator heat balance equation:

where is the heat capacity of water. Take = 4.2 kJ / kg.

It is necessary to determine from this equation.

Calculation of the power of a turbine running on freon

where is the relative internal efficiency of the freon turbine; - electromechanical efficiency of turbine generators.

Determination of pump power for pumping geothermal water into a well

where is the efficiency of the pump, taken as 0.8; is the average specific volume of geothermal water.

GEOTHERMAL ENERGY

Skotarev Ivan Nikolaevich

2nd year student, department physics StSAU, Stavropol

Khashchenko Andrey Alexandrovich

scientific advisor, can. phys.-mat. sciences, Associate Professor StSAU, Stavropol

Now humanity does not really think about what it will leave for future generations. People thoughtlessly pump out and dig up minerals. Every year the population of the planet is growing, and therefore the need for more more energy carriers such as gas, oil and coal. This cannot last long. Therefore, now, in addition to the development of the nuclear industry, the use of alternative energy sources is becoming relevant. One of the promising areas in this area is geothermal energy.

Most of the surface of our planet has significant reserves of geothermal energy due to significant geological activity: active volcanic activity in the initial periods of the development of our planet and also to this day, radioactive decay, tectonic shifts and the presence of magma in the earth's crust. In some places on our planet, a particularly large amount of geothermal energy accumulates. These are, for example, various geyser valleys, volcanoes, underground accumulations of magma, which in turn heat the upper rocks.

In simple terms, geothermal energy is the energy of the interior of the Earth. For example, volcanic eruptions clearly indicate the enormous temperature inside the planet. This temperature gradually decreases from the hot inner core to the Earth's surface ( picture 1).

Figure 1. Temperature in different layers of the earth

Geothermal energy has always attracted people with the possibilities of its useful applications... After all, a person in the process of his development came up with many useful technologies and looked for profit and profit in everything. This is what happened with coal, oil, gas, peat, etc.

For example, in some geographic areas, the use of geothermal sources can significantly increase energy production, since geothermal power plants (Geothermal power plants) are one of the cheapest alternative energy sources, because the upper three-kilometer layer of the Earth contains more than 1020 J of heat suitable for generating electricity. Nature itself gives a person a unique source of energy in his hands, it is only necessary to use it.

In total, there are now 5 types of sources of geothermal energy:

1. Deposits of geothermal dry steam.

2. Sources of wet steam. (a mixture of hot water and steam).

3. Deposits of geothermal water (contain hot water or steam and water).

4. Dry hot rocks heated by magma.

5. Magma (molten rocks heated to 1300 ° C).

Magma transfers its heat to rocks, and their temperature rises with increasing depth. According to available data, the temperature of rocks rises by an average of 1 ° C for every 33 m depth (geothermal step). There is a great variety in the world temperature conditions geothermal energy sources that will determine technical means to use it.

Geothermal energy can be used in two main ways - to generate electricity and to heat various objects. Geothermal heat can be converted into electricity if the temperature of the heating medium reaches more than 150 ° C. It is the use of the inner regions of the Earth for heating that is the most profitable and efficient as well as very affordable. Direct geothermal heat, depending on the temperature, can be used for heating buildings, greenhouses, swimming pools, drying agricultural and fish products, evaporating solutions, growing fish, mushrooms, etc.

All geothermal installations existing today are divided into three types:

1. Stations based on dry steam deposits - this is a direct scheme.

Dry steam power plants appeared earlier than anyone else. In order to obtain the required energy, steam is passed through a turbine or generator ( picture 2).

Figure 2. Geothermal power plant of direct scheme

2. Separator stations using pressurized hot water deposits. Sometimes a pump is used for this, which provides the required volume of the incoming energy carrier - an indirect scheme.

It is the most common type of geothermal power plant in the world. Here the waters are pumped under high pressure into generating sets. The hydrothermal solution is pumped into the evaporator to reduce the pressure, resulting in the evaporation of part of the solution. Further, steam is formed, which makes the turbine work. The leftover liquid can also be beneficial. Usually it is passed through another evaporator and get additional power ( picture 3).

Figure 3. Indirect Geothermal Power Plant

They are characterized by the absence of interaction of the generator or turbine with steam or water. Their principle of operation is based on the judicious use of moderate temperature groundwater.

Usually the temperature should be below two hundred degrees. The binary cycle itself consists in the use of two types of water - hot and temperate. Both streams are passed through a heat exchanger. The hotter liquid evaporates the colder one, and the vapors generated as a result of this process drive the turbines,,.

Figure 4. Diagram of a geothermal power plant with a binary cycle

As for our country, geothermal energy ranks first in terms of the potential for its use due to the unique landscape and natural conditions. Found reserves of geothermal waters with a temperature of 40 to 200 ° C and a depth of 3500 m on its territory can provide approximately 14 million m3 of hot water per day. Large reserves of underground thermal waters are found in Dagestan, North Ossetia, Checheno-Ingushetia, Kabardino-Balkaria, Transcaucasia, Stavropol and Krasnodar Territories, Kazakhstan, Kamchatka and in a number of other regions of Russia. For example, in Dagestan, thermal waters have been used for heat supply for a long time.

The first geothermal power plant was built in 1966 at the Pauzhetskoye field on the Kamchatka Peninsula to supply power to the surrounding villages and fish processing plants, which contributed to local development. The local geothermal system can provide power to power plants with a capacity of up to 250-350 MW. But this potential is used only by a quarter.

The territory of the Kuril Islands has a unique and at the same time complex landscape. The power supply of the cities located there costs great difficulties: the need to deliver livelihoods to the islands by sea or air, which is quite costly and takes a lot of time. The geothermal resources of the islands currently allow receiving 230 MW of electricity, which can meet all the needs of the region for energy, heat, and hot water supply.

On the island of Iturup, resources of a two-phase geothermal coolant have been found, the capacity of which is sufficient to meet the energy requirements of the entire island. On the southern island of Kunashir, a 2.6 MW GeoPP operates, which is used to generate electricity and heat supply to the city of Yuzhno-Kurilsk. It is planned to build several more GeoPPs with a total capacity of 12-17 MW.

The most promising regions for the use of geothermal sources in Russia are the south of Russia and the Far East. The Caucasus, Stavropol Territory and Krasnodar Territory have a huge potential for geothermal energy.

The use of geothermal waters in the central part of Russia is costly due to the deep bedding of thermal waters.

In the Kaliningrad region, there are plans to implement a pilot project for geothermal heat and power supply to the city of Svetly on the basis of a binary GeoPP with a capacity of 4 MW.

Geothermal energy in Russia is focused both on the construction of large facilities and on the use of geothermal energy for individual houses, schools, hospitals, private shops and other facilities using geothermal circulation systems.

In the Stavropol Territory, at the Kayasulinskoye field, the construction of an expensive experimental Stavropol Geothermal Power Plant with a capacity of 3 MW has been started and suspended.

In 1999, the Verkhne-Mutnovskaya GeoPP ( picture 5).

Figure 5. Verkhne-Mutnovskaya GeoPP

It has a capacity of 12 MW (3x4 MW) and is an experimental and industrial stage of the Mutnovskaya GeoPP with a design capacity of 200 MW, created to supply the industrial region of Petropavlovsk-Kamchatsk.

But despite the big advantages in this direction, there are also disadvantages:

1. The main one is the need to pump waste water back into the underground aquifer. Thermal waters contain a large amount of salts of various toxic metals (boron, lead, zinc, cadmium, arsenic) and chemical compounds(ammonia, phenols), which makes it impossible to discharge these waters into natural water systems located on the surface.

2. Occasionally, a geothermal power plant in operation may be suspended due to natural changes in the earth's crust.

3. Finding a suitable site for the construction of a geothermal power plant and obtaining permission from local authorities and the consent of residents to build it can be problematic.

4. Construction of a GeoPP can negatively affect land stability in the surrounding region.

Most of these shortcomings are insignificant and more completely solvable.

People in the world today do not think about the consequences of their decisions. After all, what will they do if they run out of oil, gas and coal? People are used to living in comfort. They will not be able to heat their houses with firewood for a long time, because a large population will need huge number wood, which by itself will lead to large-scale deforestation and leave the world without oxygen. Therefore, in order to prevent this from happening, it is necessary to use the resources available to us economically, but with maximum efficiency... One of the ways to solve this problem is the development of geothermal energy. Of course, it has its pros and cons, but its development will greatly facilitate the further existence of mankind and will play a big role in its further development.

Now this direction is not very popular, because the world is dominated by the oil and gas industry and large companies are in no hurry to invest in the development of a much-needed industry. Therefore, for the further progression of geothermal energy, investments and state support are needed, without which it is simply impossible to implement anything on a national scale. The introduction of geothermal energy into the country's energy balance will allow:

1. to increase energy security, on the other hand, to reduce the harmful effect on the environmental situation in comparison with traditional sources.

2. to develop the economy, because the freed up funds can be invested in other industries, the social development of the state, etc.

In the last decade, the use of non-traditional renewable energy sources has experienced a real boom in the world. The scale of application of these sources has increased several times. It is able to radically and on the most economic basis solve the problem of energy supply to these regions, which use expensive imported fuel and are on the verge of an energy crisis, improve the social situation of the population of these regions, etc. This is exactly what we observe in Western Europe (Germany, France, Great Britain), Northern Europe (Norway, Sweden, Finland, Iceland, Denmark). This is due to the fact that they have high economic development and are very dependent on fossil resources, and therefore the heads of these states, together with business, are trying to minimize this dependence. In particular, the development of geothermal energy in the Nordic countries is favored by the presence of a large number geysers and volcanoes. It's not for nothing that Iceland is called the land of volcanoes and geysers.

Now humanity is beginning to understand the importance of this industry and is trying to develop it as much as possible. The use of a wide range of various technologies makes it possible to reduce energy consumption by 40-60% and at the same time ensure real economic development. And the remaining demand for electricity and heat can be covered due to its more efficient production, due to restoration, due to the combination of heat and electricity generation, as well as due to the use of renewable resources, which makes it possible to abandon some types of power plants and reduce carbon dioxide emissions. gas by about 80%.

Bibliography:

1. Baeva A.G., Moskvichyova V.N. Geothermal energy: problems, resources, use: ed. Moscow: SO AN SSSR, Institute of Thermophysics, 1979 .-- 350 p.

2. Berman E., Mavritsky B.F. Geothermal Energy: ed. M .: Mir, 1978 - 416 pages.

3. Geothermal energy. [Electronic resource] - Access mode - URL: http://ustoj.com/Energy_5.htm(date of treatment 08/29/2013).

4. Geothermal energy of Russia. [Electronic resource] - Access mode - URL: http://www.gisee.ru/articles/geothermic-energy/24511/(date of treatment 09/07/2013).

5. Dvorov I.M. Deep warmth of the Earth: ed. Moscow: Nauka, 1972 .-- 208 p.

6. Power engineering. From Wikipedia, the free encyclopedia. [Electronic resource] - Access mode - URL: http://ru.wikipedia.org/wiki/Geothermal_energy(date of treatment 09/07/2013).