Geothermal resources represent a virtually inexhaustible, renewable and environmentally friendly source of energy that will play a significant role in the energy sector of the future. Since many extracted geothermal waters contain dissolved chemical elements that have a detrimental effect on pipelines (corrosion) and on the health of consumers, much attention is currently paid to the purification of this water and the separation of chemical elements from it. As one of the non-renewable energy sources, geothermal energy remains and will remain one of the leading places in the country's energy sector.

Geothermal energy

Geothermal energy refers to the physical heat of the deep layers of the earth, which have a temperature higher than the air temperature on the surface. Both liquid fluids (water and/or steam-water mixture) and dry rocks located at the appropriate depth can act as carriers of this energy. From the hot interior of the Earth, a heat flow constantly flows to its surface, the intensity of which, on average over the Earth’s surface, is about 0.03 W/m². Under the influence of this flow, depending on the properties of the rocks, a temperature gradient arises - the so-called geothermal step. In most places, the geothermal rate is no more than 2-3˚C/100m.

Today, it is economically feasible to use only thermal waters and hydrothermal steam as sources of geothermal energy for heat generation and/or electricity production. There are relatively few easily accessible geothermal deposits with temperatures above 100˚C on the globe. To produce electricity with acceptable technical and economic indicators, the temperature must be at least 100˚C. Currently, the total capacity of geothermal power plants operating in the world is about 10 GW(e). The total capacity of existing geothermal heating systems is estimated at approximately 20 GW(e).

The main problems of geothermal heat supply are related to salt deposition and corrosion resistance of materials and equipment operating in aggressive environments. In order to avoid pollution of the environment, rivers and reservoirs with mineral compounds extracted from the bowels of the earth, modern technologies for the use of geothermal energy provide for the reinjection of spent geothermal fluid into the formation.

Fig 1. Thermal diagram of the power plant

1-steam generator; 2- steam accumulator; 3- turbine; 4- ejector; 5- condenser; 6.7- pumps; ES - production well; NS - injection well

Hydrogeothermal resources, along with solar, wind, and tidal energy, are a new, renewable source of energy that in the future can actually occupy a significant place in the fuel and energy balance of a number of regions of our country. The diversity of natural conditions and the presence of natural manifestations of oil, gas and numerous sources of thermal mineral waters have attracted the attention of naturalists to the subsoil of Dagestan since ancient times.

At the same time, the local population widely used thermomineral springs not only to treat ailments, but also for the extraction of table salt, utility needs, baking bread, etc. The Talginsky, Akhtynsky, Kayakentsky, Karakaytagsky, Rychalsky, Istisu, Botlikhsky and many other thermomineral springs were widely popular among the local population.

The first printed information about the thermomineral waters of Dagestan belongs to the Russian doctor I. Lerikh, who visited Dagestan twice at the beginning of the 15th century. Following him, information about the groundwater of Dagestan is given in the works of S. G. Gmelin, G. V. Abikh, I. Berezin. A special impetus for the study of groundwater was given by the receipt of oil gushers in Berikey in 1894 and Kayakent in 1898. Following this, Dagestan was visited by such prominent geologists as N.I. Barbot-de-Marny, K.P. Lysenko, V.I. Meller, A. M. Konshin, A. A. Bulgakov, K. V. Kharichkov, I. N. Strizhov and others, whose works contain a number of interesting information and thoughts about the groundwater of Dagestan. However, all hydrogeological information before the 20s of the twentieth century. It is episodic and scattered in nature.

Fig 2. Basic integrated diagram of the use of geothermal waters

1 - production well; 2 - power generation; 3 - refrigeration processes; 4 - greenhouses; 5 - heat pump unit; 6 - industrial processes; 7 - sawmills; 8 - food production; 9 - dehydration; 10 - grain drying; 11 - livestock feed; 12 - central heating and hot water supply; 13 - soil heating and irrigation of farmland; 14 - fish farming; 15 - chemical production; 16 - balneotherapy and swimming pools; 17 - injection well

Research on a large scale began to be carried out only after the victory of the October Revolution. Much attention in these years has been paid to the study of mineral waters, medicinal mud and the development of resort construction on their basis. During this period, sources were studied that deserve special attention for their natural and balneological factors: Talginsky, Zuramakentsky, Kayakentsky, Istisu and brine iodine-bromine waters of the Berikeisky, Duzlaksky, Dagogninsky deposits, etc. With the release in 1963. Resolution of the Council of Ministers of the USSR "On the development of work on the use of the deep heat of the Earth in the national economy" in the city of Makhachkala, a qualitatively new stage in the development of geothermal resources begins.

The new industrial stage of development of thermal waters aroused particularly high enthusiasm at first. This is explained by the fact that with the help of abandoned wells it was possible to sell thermal waters in significant quantities without significant costs. The volume of prospecting, exploration, drilling, repair and restoration work on gas and oil wells, as well as scientific research on predictive assessment of reserves, development of methods against corrosion and salt deposits, integrated use of thermal waters in heat and cold supply, balneology, etc., has increased sharply.

Introduction

In terms of thermal water reserves, Dagestan ranks first in the Russian Federation. Dagestan is a unique geothermal province of Russia. The large-scale development of geothermy here is facilitated by favorable geothermal and hydrogeological conditions of a large thermal aquifer basin of a multilayer type.

In terms of thermal intensity of the subsoil, the territory of Dagestan exceeds all known sedimentary basins of the CIS, with the exception of areas of modern volcanism.

Temperatures at depths of 3-6 km here are recorded at 140-210? C, which is 80-100? C higher than in Azerbaijan, Astrakhan and Rostov regions. In Dagestan, geothermal heat supply systems have been successfully operating for many years in the cities of Makhachkala, Kizlyar and Izberbash.

Geologically, Dagestan is located at the junction of two largest geological and tectonic structures (the Caucasian geosyncline and the Russian platform) and occupies the southeastern part of the Eastern Ciscaucasia.

Analysis of geological-tectonic, hydrodynamic, hydrogeological, geothermal, seismic and other natural conditions made it possible to identify four hydrogeothermal regions on the territory of Dagestan: Slantsevy, Limestone, Predgorny and Platform, which in turn are divided into smaller hydrogeological structures.

The objective of this work is to study the sources of geothermal energy potential in the Republic of Dagestan.

Geothermal energy

Geothermal energy refers to the physical heat of the deep layers of the earth, which have a temperature higher than the air temperature on the surface. Both liquid fluids (water and/or steam-water mixture) and dry rocks located at the appropriate depth can act as carriers of this energy. From the hot interior of the Earth, a heat flow constantly flows to its surface, the intensity of which, on average over the Earth’s surface, is about 0.03 W/mI. Under the influence of this flow, depending on the properties of the rocks, a temperature gradient arises - the so-called geothermal step. In most places, the geothermal stage is no more than 2-3ºC/100m.

Today, it is economically feasible to use only thermal waters and hydrothermal steam as sources of geothermal energy for heat generation and/or electricity production. There are relatively few easily accessible geothermal deposits with temperatures above 100°C on the globe.

To produce electricity with acceptable technical and economic indicators, the temperature must be at least 100? C.

Currently, the total capacity of geothermal power plants operating in the world is about 10 GW(e). The total capacity of existing geothermal heating systems is estimated at approximately 20 GW(e).

The main problems of geothermal heat supply are related to salt deposition and corrosion resistance of materials and equipment operating in aggressive environments.

In order to avoid pollution of the environment, rivers and reservoirs with mineral compounds extracted from the bowels of the earth, modern technologies for the use of geothermal energy provide for the reinjection of spent geothermal fluid into the formation.

Fig 1.

1-steam generator? 2- steam accumulator? 3-turbine? 4- ejector? 5- capacitor? 6.7 pumps? ES - production well? NS - injection well.

What is geothermal energy? This term refers to the production of heat energy and electricity, which uses energy from the bowels of the earth. This type of energy causes almost no harm to the environment. One kilowatt of electricity produced with the “assistance” of hot geothermal sources leads to the release of 13-380 grams of carbon dioxide, while in the case of coal, for example, the situation is much worse (1042 grams per kilowatt per hour).

Although, the heat that the earth’s depths conceal is not “concentrated” - in many areas it is possible to benefit from only a small part of the energy.

There are five types of geothermal energy sources:

Magma is rocks whose temperature is 1300 degrees Celsius, in a molten state;

Rocks heated to very high temperatures by magma, remaining in a dry state;

Geothermal water sources that contain water and steam, or only water (hot); they arise as follows: voids in the ground are filled with water as a result of precipitation, after which this water is heated by magma located nearby;

Wet steam deposits; the disadvantage of these deposits is that thermal power plants for them have to be organized in such a way as to prevent corrosion of the equipment, as well as to minimize the harmful impact on the environment;

Dry steam sources; There are relatively few of them, but they are quite easy to develop. 50% of the planet's geothermal power plants operate using dry steam sources.

Sources of hot water, as well as natural steam, are currently used more than others. Although, for full development geothermal energy in the future we will have to develop hot rocks. Their temperature is more than one hundred degrees at a depth of three to five kilometers.

Heat from the bowels of the earth can be “converted” into electricity provided that the coolant has a temperature of 150 degrees (or more). For this purpose, special structures called geoelectric power stations are erected. Energy at geoelectric power plants is “extracted” using one of the following methods:

Indirect scheme. The steam enters turbines, which are connected to electricity generators, by passing through pipes. In this case, the steam, before ending up in the pipes, undergoes “treatment” - gases that have a destructive effect on the pipe material are extracted from it.

Direct scheme. Everything happens in exactly the same way, with the difference that when using this scheme, the steam purification stage is skipped - the latter goes straight into the pipes.

Mixed scheme. It is similar to the previous scheme, but in this case, after condensation, the water is cleared of gases that are not dissolved in it.

At the moment, over eight dozen states are using the “thermal wealth” that the Earth conceals within itself. At the same time, seven dozen countries are using the capabilities of geothermal energy, building swimming pools, greenhouses, and improving the health of the population, and twenty-five countries have geothermal power plants at their disposal.

The geothermal power plants that humanity currently has are capable of providing electricity to one percent of the Earth's population (equal to 60 million people).

As for Russia, it cannot boast of the development of this area, although there are a lot of energy reserves in the earth's interior on its territory - even more than reserves of fossil fuel. At the same time, a larger number of “deposits” are located on the Kuril Islands, Kamchatka, Sakhalin, but few people live in these areas, the terrain is difficult and earthquakes often occur - in a word, the conditions are not the best.

More promising in this regard are the Kaliningrad region, Stavropol, Krasnodar territories - they can boast of the presence of reserves of thermal waters. Chukotka also has geothermal sources, and some of them are already providing energy to local settlements. For quite a long time, geothermal resources have been used in the North Caucasus, supplying heat and hot water to residents, using them in industry and agriculture. The benefits of geothermal energy are also available to people living in the West Siberian region, the Baikal region, and Primorye.

Experts say that recently Russia has been increasingly working towards the use of geothermal resources. It should be mentioned that, at the moment, the share of electricity obtained from geothermal energy in the total amount of energy “supplied” by alternative sources is negligible, and barely reaches 0.2%.

The rapid growth of energy consumption and the limited availability of non-renewable natural resources are forcing us to think about the use of alternative energy sources. In this regard, the use of geothermal resources deserves special attention.

Geothermal power plants (GeoPP) are structures for generating electrical energy from the natural heat of the Earth.

Geothermal energy has a history of more than a century. In July 1904, the first experiment was carried out in the Italian town of Larderello, which made it possible to obtain electricity from geothermal steam. A few years later, the first geothermal power plant was launched here, which is still operating.

Promising territories

For the construction of geothermal power plants, areas with geological activity, where natural heat is located at a relatively shallow depth, are considered ideal.

These include areas abounding in geysers, open thermal springs with water heated by volcanoes. This is where geothermal energy is developing most actively.

However, even in seismically inactive areas there are layers of the earth’s crust whose temperature is more than 100 °C.

For every 36 meters of depth, the temperature increases by 1 °C. In this case, a well is drilled and water is pumped into it.

The output is boiling water and steam, which can be used both for heating rooms and for producing electrical energy.

There are many territories where it is possible to obtain energy in this way, so geothermal power plants operate everywhere.

Sources of geothermal energy

Natural heat can be produced from the following sources.

Operating principles of geothermal power plants

Today, three methods are used to produce electricity using geothermal means, depending on the state of the medium (water or steam) and the temperature of the rock.

1. Direct (using dry steam). The steam directly impacts the turbine that powers the generator.
2. Indirect (use of water steam). This uses a hydrothermal solution that is pumped into an evaporator. The evaporation resulting from a decrease in pressure drives the turbine.
3. Mixed, or binary. In this case, hydrothermal water is used and an auxiliary fluid with a low boiling point, such as freon, which boils when exposed to hot water. The resulting steam from freon spins the turbine, then condenses and returns to the heat exchanger for heating. A closed system (circuit) is formed, practically eliminating harmful emissions into the atmosphere.

The first geothermal power plants ran on dry steam.

The indirect method is considered the most common today. Here, groundwater with a temperature of about 182 °C is used, which is pumped into generators located on the surface.

Advantages of GeoPP

• Reserves of geothermal resources are considered renewable, practically inexhaustible, but under one condition: A large amount of water cannot be pumped into an injection well in a short period of time.
• The station does not require external fuel to operate.
• The installation can operate autonomously, using its own generated electricity. An external power source is only required for the first start of the pump.
• The station does not require additional investments, with the exception of costs for maintenance and repair work.
• Geothermal power plants do not require sanitary areas.
• If the station is located on a sea or ocean shore, it can be used for natural desalination of water. This process can occur directly in the station’s operating mode - when heating water and cooling water evaporation.

Disadvantages of geothermal installations

• The initial investment in the development, design and construction of geothermal plants is large.
• Problems often arise in choosing a suitable location for a power plant and obtaining permission from the authorities and local residents.
• Through a working well, emissions of flammable and toxic gases and minerals contained in the earth's crust are possible. Technologies in some modern plants allow these emissions to be collected and processed into fuel.
• It happens that an operating power plant stops. This can happen due to natural processes in the rock or due to excessive injection of water into the well.

Largest producers of geothermal energy

The largest GeoPPs have been built in the USA and the Philippines. They represent entire geothermal complexes, consisting of dozens of individual geothermal stations.

The Geysers complex, located in California, is considered the most powerful. It consists of 22 two stations with a total capacity of 725 MW, sufficient to power a multimillion-dollar city.

• The Philippine Makiling-Banahau Power Plant has a capacity of about 500 MW.
• Another Philippine power plant named Tiwi has a capacity of 330 MW.
• Imperial Valley in the USA is a complex of ten geothermal power plants with a total capacity of 327 MW.
• Chronology of the development of domestic geothermal energy

Russian geothermal energy began its development in 1954, when it was adopted decision to create a laboratory for the study of natural thermal resources in Kamchatka.

1. 1966 – Pauzhetskaya geothermal power plant with a traditional cycle (dry steam) and a capacity of 5 MW was launched. After 15 years, its capacity was increased to 11 MW.
2. In 1967, the Paratunka station with a binary cycle began to operate. By the way, a patent for a unique binary cycle technology, developed and patented by Soviet scientists S. Kutateladze and L. Rosenfeld, was purchased by many countries.

High levels of hydrocarbon production in the 1970s and the critical economic situation in the 90s stopped the development of geothermal energy in Russia. However, now interest in it has reappeared for a number of reasons:

• Oil and gas prices on the domestic market are becoming close to world prices.
• Fuel reserves are rapidly depleting.
• Newly discovered hydrocarbon deposits on the Far Eastern shelf and Arctic coast are currently unprofitable.

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Prospects for the development of geothermal resources in Russia

The most promising areas of the Russian Federation in terms of the use of thermal energy to generate electricity are Kuril Islands and Kamchatka.

Kamchatka has such potential geothermal resources with volcanic reserves of hydrothermal steam and energetic thermal waters that can meet the region's needs for 100 years. The Mutnovskoye field is considered promising, the known reserves of which can provide up to 300 MW of electricity. The history of the development of this area began with geoexploration, resource assessment, design and construction of the first Kamchatka GeoPPs (Pauzhetskaya and Paratunka), as well as the Verkhne-Mutnovskaya geothermal station with a capacity of 12 MW and Mutnovskaya, with a capacity of 50 MW.

There are two power plants operating on the Kuril Islands that use geothermal energy - on Kunashir Island (2.6 MW) and on Iturup Island (6 MW).

In comparison with the energy resources of individual Philippine and American GeoPPs, domestic alternative energy production facilities are losing significantly: their total capacity does not exceed 90 MW. But Kamchatka power plants, for example, provide 25% of the region’s electricity needs, which in the event of unexpected interruptions in fuel supplies will not allow residents of the peninsula to be left without electricity.

Russia has every opportunity to develop geothermal resources – both petrothermal and hydrogeothermal. However, they are used extremely little, and there are more than enough promising areas. In addition to the Kuril Islands and Kamchatka, practical application is possible in the North Caucasus, Western Siberia, Primorye, Baikal region, and the Okhotsk-Chukotka volcanic belt.

The geothermal energy industry owes its emergence to such a natural phenomenon as an increase in the temperature of underground rock in proportion to depth. For every 36 meters in depth, the temperature increases by an average of 1 °C. Access to heated groundwater can be obtained not only through wells - some hot springs are natural geysers. The coolant is used not only for heating needs, but also to produce electricity using geothermal stations that convert steam into electricity.

In addition, the use of hot rocks in which there is no groundwater is practiced. In this case, power engineers pump water into underground horizons with its further selection in a heated state. High “dry” horizons, the temperature of which, however, does not reach the boiling degree of water, are also found in a large number of territories where there is no volcanic activity at all, which gives geotherms the status of promising energy sources, regardless of their geographic location.

Hot Spring Energy: Distribution Factors

Geothermal energy is most widespread in two types of regions. First of all, it develops where, due to natural conditions, there are a large number of accessible hot springs. In addition, geotherms are used where there is a shortage of combustible minerals or the delivery of energy resources is complicated by the inaccessibility of the area. In a number of countries, heat or electricity produced using geothermal plants covers a significant share of energy costs.

Using this technology, consumers in American San Francisco receive about a third of their electricity. There are already four geothermal stations in Poland, one of which meets the needs of the resort town of Zakopane. Hot water supply in Lithuanian Klaipeda is provided entirely by the operation of a geothermal station. In the nineties, the total capacity of geothermal stations in the world was estimated at 5 GW; by the 2000s it exceeded 6 GW. A number of estimates suggest that geothermal energy production now exceeds 10 GW.

The situation in the birthplace of geothermal energy

Nature itself has decreed that Iceland has become a leading country in the use of geothermal sources. In this country, at a relatively shallow depth, the water temperature is sufficient to produce energy, which was made possible due to high volcanic activity. There are about a hundred volcanoes in the region, and the island itself is located at the junction of lithospheric plates.

Every nine out of ten houses in the country are heated with hot water from underground. The capital of Iceland, Reykjavik, has completely switched to geothermal heating since 1943, providing heat supply not only to the residential sector, but also to industrial enterprises. The state has almost completely abandoned traditional energy resources; 25% of the needs are met using geothermal sources, 70% are provided by hydroelectric power plants.

Its leading position in the industry gives Iceland the opportunity not only to be an energy self-sufficient country, but also to even export the energy generated by geothermal stations. In recent years, a project for organizing the supply of electricity generated at Icelandic geothermal power plants to the UK has been discussed. The British, in turn, are ready to lay a 750-mile sea cable. The project budget is estimated at billions of pounds. According to London's calculations, the implementation of the project will make it possible to provide a fifth of the country's electricity needs.

Popularity in Asia

Currently, geothermal energy is literally undergoing a rebirth in China. The industry has been abandoned in this country for forty years. Interest in it was renewed with the coming to power of the country's leader Xi Jinping. Thanks to the efforts of the Secretary General, the city of Xianyang can rightfully be considered the world capital of green energy. In the country as a whole, during the three years of Jinping's rule, the volume of geothermal energy production increased from 28 to 100 MW.

The industry development plan was included in the 13th Five-Year Plan program. To a large extent, the dynamic development of this area is facilitated by engineers from Iceland invited to work in China. According to preliminary calculations, the geothermal potential in China is comparable to the energy that can be obtained by burning 853 billion tons of coal.

It is with the overconsumption of the latter that attempts to find alternative resources are associated, since 66% of the energy received in the country is generated using coal. The geothermal strategy is expected to be implemented in a maximum of 10 years. Already, China accounts for 15% of global geothermal energy production. The PRC plans to achieve a generation volume of 2 GW.

The share of geothermal energy in Japan reaches 21%. However, its development is actively hampered by environmental social movements due to the fact that the use of geothermal sources leads to an increase in the threat of environmental pollution. However, we will dwell on the dangers of geothermal energy below.

Foreign experts believe that the industry has great prospects in Kazakhstan. In a number of regions of the country, the temperature of groundwater reaches the boiling point, which, along with the rising cost of traditional electricity, makes geotherms an attractive investment. Graham Norman, a professor at the University of Michigan who visited the republic, believes that Kazakhstan’s potential is no worse than Turkey’s, where geothermal energy is developing outside areas with high intensity hot springs.

Environmental and technical problems of the industry

The development of geothermal energy is significantly hampered by a number of problems inherent in this industry. Among the most serious obstacles is the need for a complex process of reinjecting waste coolant (water) containing toxic substances - arsenic, cadmium, zinc, lead, boron - into aquifers. This eliminates the possibility of releasing such water into the surface layers. In addition, the problem of hydrogen sulfide emissions into the atmosphere is acute.

For geothermal stations, among other things, unlike thermal power plants and even hydroelectric power plants, there is a strict binding of the construction site to certain areas depending on the geology. Often (except perhaps Iceland), such places are located in hard-to-reach areas, mountainous areas. One should not discount the high mineralization of groundwater, which over time leads to clogging of wells.

It is necessary to take into account the main development factor inherent in any industry - market demand. OPEC calculated that, despite the overall increase in demand for renewable energy resources, including geothermal, by 7.6% per year, by 2040 the share of such sources in energy production will be only 4.3%, inferior to traditional methods generation. Currently, the share of alternative energy is only 0.9% on the world market.

International recognition and future forecasts

However, at the international level, geothermal energy is considered a fairly promising area. The focus on developing this segment is confirmed by the decision of the recent Climate Summit in Paris. Representatives from 38 countries voted to increase geothermal energy production by 500%. The initiative to make such a decision belongs to the International Renewable Energy Agency (IRENA). It is expected that the development of the industry will provide an opportunity to curb adverse climate change.

The summit resolution stated that this type of energy remains one of the cheapest, but the degree of development of the industry is extremely insufficient. About 90 states have potential for development in this area. Summit members recognized that the main obstacle to the implementation of geothermal projects is not the environment at all, but the need for significant investments in drilling operations. At the same time, sales of electricity can be carried out as sources are developed, without waiting for the projects to be fully implemented.

The use of geothermal sources can partially solve the problem of hunger in disadvantaged regions. Pronedra previously wrote that the UN believes that the introduction of geothermal energy will make it possible to reduce food shortages in a number of developing countries where there is simply no electricity to ensure food storage, and, as a result, to create conditions for the accumulation of food reserves.

Probably, taking into account the targeted international energy policy in this direction, cheap and effective methods will be introduced aimed at overcoming the risks of contamination of underground horizons and eliminating the technical problems that inevitably accompany geothermal energy. If the main obstacles to the development of the geothermal segment disappear, the industry will definitely begin to experience dynamic growth and over time will become a significant energy source for many countries around the world.