One of the best, most rational methods in the construction of permanent greenhouses is an underground thermos greenhouse.
Using this fact of the constancy of the earth's temperature at depth in the construction of a greenhouse provides enormous savings on heating costs in the cold season, makes maintenance easier, and makes the microclimate more stable..
Such a greenhouse works in the bitterest frosts, allowing you to produce vegetables and grow flowers all year round.
A properly equipped in-ground greenhouse makes it possible to grow, among other things, heat-loving southern crops. There are practically no restrictions. Citrus fruits and even pineapples can thrive in a greenhouse.
But in order for everything to function properly in practice, it is imperative to follow the time-tested technologies used to build underground greenhouses. After all, this idea is not new; even under the Tsar in Russia, sunken greenhouses produced pineapple harvests, which enterprising merchants exported for sale to Europe.
For some reason, the construction of such greenhouses has not become widespread in our country; by and large, it has simply been forgotten, although the design is ideal for our climate.
Probably, the need to dig a deep pit and pour the foundation played a role here. The construction of a buried greenhouse is quite expensive; it is far from being a greenhouse covered with polyethylene, but the return from the greenhouse is much greater.
The overall internal illumination is not lost from being buried in the ground; this may seem strange, but in some cases the light saturation is even higher than that of classic greenhouses.
It is impossible not to mention the strength and reliability of the structure; it is incomparably stronger than usual, it can more easily withstand hurricane gusts of wind, it resists hail well, and snow debris will not become a hindrance.
1. Pit
Creating a greenhouse begins with digging a pit. To use the heat of the earth to heat the interior, the greenhouse must be deep enough. The deeper you go, the warmer the earth becomes.
The temperature remains almost unchanged throughout the year at a distance of 2-2.5 meters from the surface. At a depth of 1 m, the soil temperature fluctuates more, but even in winter its value remains positive; usually in the middle zone the temperature is 4-10 C, depending on the time of year.
A recessed greenhouse is built in one season. That is, in winter it will be fully able to function and generate income. Construction is not cheap, but by using ingenuity and compromise materials, it is possible to save literally an order of magnitude by making a kind of economical version of a greenhouse, starting from the foundation pit.
For example, do without attracting construction equipment. Although the most labor-intensive part of the work - digging a pit - is, of course, better to give it to an excavator. Manually removing such a volume of soil is difficult and time-consuming.
The depth of the excavation pit must be at least two meters. At such a depth, the earth will begin to share its heat and work like a kind of thermos. If the depth is less, then in principle the idea will work, but noticeably less effectively. Therefore, it is recommended not to spare effort and money on deepening the future greenhouse.
Underground greenhouses can be any length, but it is better to keep the width within 5 meters; if the width is larger, the quality characteristics of heating and light reflection deteriorate.
On the sides of the horizon, underground greenhouses must be oriented, like ordinary greenhouses and greenhouses, from east to west, that is, so that one of the sides faces south. In this position, the plants will receive the maximum amount of solar energy.
2. Walls and roof
A foundation is poured or blocks are laid around the perimeter of the pit. The foundation serves as the basis for the walls and frame of the structure. It is better to make walls from materials with good thermal insulation characteristics; thermal blocks are an excellent option.
The roof frame is often made of wood, from bars impregnated with antiseptic agents. The roof structure is usually straight gable. A ridge beam is fixed in the center of the structure; for this, central supports are installed on the floor along the entire length of the greenhouse.
The ridge beam and the walls are connected by a series of rafters. The frame can be made without high supports. They are replaced with small ones, which are placed on transverse beams connecting opposite sides of the greenhouse - this design makes the internal space freer.
As a roof covering, it is better to take cellular polycarbonate - a popular modern material. The distance between the rafters during construction is adjusted to the width of the polycarbonate sheets. It is convenient to work with the material. The coating is obtained with a small number of joints, since the sheets are produced 12 m long.
They are attached to the frame with self-tapping screws; it is better to choose them with a washer-shaped cap. To avoid cracking of the sheet, you need to drill a hole of the appropriate diameter for each self-tapping screw. Using a screwdriver or a regular drill with a Phillips bit, the glazing work moves very quickly. In order to ensure that there are no gaps left, it is good to lay a sealant made of soft rubber or other suitable material along the top of the rafters in advance and only then screw the sheets. The peak of the roof along the ridge needs to be laid with soft insulation and pressed with some kind of corner: plastic, tin, or other suitable material.
For good thermal insulation, the roof is sometimes made with a double layer of polycarbonate. Although the transparency is reduced by about 10%, it is covered by excellent thermal insulation performance. It should be taken into account that snow on such a roof does not melt. Therefore, the slope must be at a sufficient angle, at least 30 degrees, so that snow does not accumulate on the roof. Additionally, an electric vibrator is installed for shaking; it will protect the roof if snow does accumulate.
Double glazing is done in two ways:
A special profile is inserted between two sheets, the sheets are attached to the frame from above;
First, the bottom layer of glazing is attached to the frame from the inside, to the underside of the rafters. The second layer of the roof is covered, as usual, from above.
After completing the work, it is advisable to seal all joints with tape. The finished roof looks very impressive: without unnecessary joints, smooth, without protruding parts.
3. Insulation and heating
Wall insulation is carried out as follows. First you need to carefully coat all the joints and seams of the wall with the solution; here you can also use polyurethane foam. The inside of the walls is covered with thermal insulation film.
In cold parts of the country, it is good to use thick foil film, covering the wall with a double layer.
The temperature deep in the soil of the greenhouse is above freezing, but colder than the air temperature necessary for plant growth. The top layer is heated by the sun's rays and the air of the greenhouse, but still the soil takes away heat, so often in underground greenhouses they use the technology of “warm floors”: the heating element - an electric cable - is protected with a metal grate or filled with concrete.
In the second case, soil for the beds is poured on top of concrete or greens are grown in pots and flowerpots.
The use of underfloor heating can be sufficient to heat the entire greenhouse, if there is enough power. But it is more effective and more comfortable for plants to use combined heating: warm floor + air heating. For good growth, they need an air temperature of 25-35 degrees with a ground temperature of approximately 25 C.
CONCLUSION
Of course, building a recessed greenhouse will cost more and require more effort than building a similar greenhouse of a conventional design. But the money invested in a thermos greenhouse pays off over time.
Firstly, it saves energy on heating. No matter how you heat the winter time an ordinary above-ground greenhouse, it will always be more expensive and more difficult than a similar heating method in an underground greenhouse. Secondly, saving on lighting. Foil thermal insulation of the walls, reflecting light, doubles the illumination. The microclimate in a deep greenhouse in winter will be more favorable for plants, which will certainly affect the yield. The seedlings will take root easily, and delicate plants will feel great. Such a greenhouse guarantees a stable, high yield of any plants all year round.
In our country, rich in hydrocarbons, geothermal energy is a kind of exotic resource, which, given the current state of affairs, is unlikely to compete with oil and gas. However, this alternative type of energy can be used almost everywhere and quite effectively.
Geothermal energy is the heat of the earth's interior. It is produced in the depths and reaches the surface of the Earth in different forms and with different intensities.
The temperature of the upper layers of the soil depends mainly on external (exogenous) factors - solar illumination and air temperature. In summer and during the day, the soil warms up to certain depths, and in winter and at night it cools down following changes in air temperature and with some delay that increases with depth. The influence of daily fluctuations in air temperature ends at depths from a few to several tens of centimeters. Seasonal fluctuations affect deeper layers of soil - up to tens of meters.
At some depth - from tens to hundreds of meters - the soil temperature remains constant, equal to the average annual air temperature at the Earth's surface. You can easily verify this by going down into a fairly deep cave.
When the average annual air temperature in a given area is below zero, it manifests itself as permafrost (more precisely, permafrost). In Eastern Siberia, the thickness, that is, the thickness, of year-round frozen soils in some places reaches 200–300 m.
From a certain depth (different for each point on the map), the action of the Sun and the atmosphere weakens so much that endogenous (internal) factors come first and the earth’s interior heats up from the inside, so that the temperature begins to rise with depth.
The heating of the deep layers of the Earth is associated mainly with the decay of radioactive elements located there, although other heat sources are also called, for example, physicochemical, tectonic processes in the deep layers earth's crust and robes. But whatever the reason, the temperature rocks and associated liquid and gaseous substances increases with depth. Miners face this phenomenon - it is always hot in deep mines. At a depth of 1 km, thirty-degree heat - normal phenomenon, and deeper the temperature is even higher.
The heat flow of the earth's interior reaching the Earth's surface is small - on average its power is 0.03–0.05 W/m2, or approximately 350 Wh/m2 per year. In the background heat flow from the Sun and the air heated by it, this is an imperceptible value: the Sun gives each square meter of the earth's surface about 4000 kWh annually, that is, 10,000 times more (of course, this is on average, with a huge spread between polar and equatorial latitudes and depending on other climatic and weather factors).
The insignificance of heat flow from the interior to the surface in most of the planet is associated with the low thermal conductivity of rocks and the peculiarities of the geological structure. But there are exceptions - places where the heat flow is high. These are, first of all, zones of tectonic faults, increased seismic activity and volcanism, where the energy of the earth’s interior finds an outlet. Such zones are characterized by thermal anomalies of the lithosphere; here the heat flow reaching the Earth’s surface can be several times and even orders of magnitude more powerful than “usual”. Volcanic eruptions and hot springs bring enormous amounts of heat to the surface in these zones.
These are the areas that are most favorable for the development of geothermal energy. On the territory of Russia, these are, first of all, Kamchatka, the Kuril Islands and the Caucasus.
At the same time, the development of geothermal energy is possible almost everywhere, since an increase in temperature with depth is a universal phenomenon, and the task is to “extract” heat from the depths, just as mineral raw materials are extracted from there.
On average, temperature increases with depth by 2.5–3°C for every 100 m. The ratio of the temperature difference between two points lying at different depths to the difference in depth between them is called the geothermal gradient.
The reciprocal is the geothermal step, or the depth interval at which the temperature rises by 1°C.
The higher the gradient and, accordingly, the lower the stage, the closer the heat of the Earth’s depths comes to the surface and the more promising this area is for the development of geothermal energy.
In different areas, depending on the geological structure and other regional and local conditions, the rate of temperature increase with depth can vary sharply. On an Earth scale, fluctuations in the magnitudes of geothermal gradients and steps reach 25 times. For example, in Oregon (USA) the gradient is 150°C per 1 km, and in South Africa- 6°C per 1 km.
The question is, what is the temperature at great depths - 5, 10 km or more? If the trend continues, temperatures at a depth of 10 km should average approximately 250–300°C. This is more or less confirmed by direct observations in ultra-deep boreholes, although the picture is much more complicated than a linear increase in temperature.
For example, in the Kola superdeep well, drilled in the Baltic crystalline shield, the temperature to a depth of 3 km changes at a rate of 10°C/1 km, and then the geothermal gradient becomes 2–2.5 times greater. At a depth of 7 km, a temperature of 120°C was already recorded, at 10 km - 180°C, and at 12 km - 220°C.
Another example is a well drilled in the Northern Caspian region, where at a depth of 500 m a temperature of 42°C was recorded, at 1.5 km - 70°C, at 2 km - 80°C, at 3 km - 108°C.
It is assumed that the geothermal gradient decreases starting from a depth of 20–30 km: at a depth of 100 km, the estimated temperatures are about 1300–1500°C, at a depth of 400 km - 1600°C, in the Earth's core (depths more than 6000 km) - 4000–5000° C.
At depths of up to 10–12 km, temperature is measured through drilled wells; where they are not present, it is determined by indirect signs in the same way as at greater depths. Such indirect signs may be the nature of the passage of seismic waves or the temperature of the pouring lava.
However, for the purposes of geothermal energy, data on temperatures at depths of more than 10 km are not yet of practical interest.
There is a lot of heat at depths of several kilometers, but how to raise it? Sometimes nature itself solves this problem for us with the help of a natural coolant - heated thermal waters that come to the surface or lie at a depth accessible to us. In some cases, the water in the depths is heated to the state of steam.
There is no strict definition of the concept of “thermal waters”. As a rule, they mean hot underground waters in a liquid state or in the form of steam, including those that come to the surface of the Earth with a temperature above 20°C, that is, as a rule, higher than the air temperature.
The heat of underground water, steam, steam-water mixtures is hydrothermal energy. Accordingly, energy based on its use is called hydrothermal.
The situation is more complicated with the extraction of heat directly from dry rocks - petrothermal energy, especially since fairly high temperatures, as a rule, begin from depths of several kilometers.
On the territory of Russia, the potential of petrothermal energy is one hundred times higher than that of hydrothermal energy - 3,500 and 35 trillion tons of standard fuel, respectively. This is quite natural - the warmth of the depths of the Earth is available everywhere, and thermal waters are found locally. However, due to obvious technical difficulties, thermal waters are currently mostly used to generate heat and electricity.
Waters with temperatures from 20–30 to 100°C are suitable for heating, temperatures from 150°C and above are suitable for generating electricity in geothermal power plants.
In general, geothermal resources in Russia, in terms of tons of equivalent fuel or any other unit of energy measurement, are approximately 10 times higher than fossil fuel reserves.
Theoretically, only geothermal energy could fully satisfy the country's energy needs. Almost on at the moment in most of its territory this is not feasible for technical and economic reasons.
In the world, the use of geothermal energy is most often associated with Iceland, a country located at the northern end of the Mid-Atlantic Ridge, in an extremely active tectonic and volcanic zone. Probably everyone remembers the powerful eruption of the Eyjafjallajökull volcano ( Eyjafjallajökull) in 2010.
It is thanks to this geological specificity that Iceland has huge reserves of geothermal energy, including hot springs that emerge on the surface of the Earth and even gush out in the form of geysers.
In Iceland, over 60% of all energy consumed currently comes from the Earth. Geothermal sources provide 90% of heating and 30% of electricity generation. Let us add that the rest of the country’s electricity is produced by hydroelectric power plants, that is, also using a renewable energy source, making Iceland look like a kind of global environmental standard.
The domestication of geothermal energy in the 20th century significantly helped Iceland in economically. Until the middle of the last century, it was a very poor country, now it ranks first in the world in terms of installed capacity and production of geothermal energy per capita and is in the top ten in absolute value of installed capacity of geothermal power plants. However, its population is only 300 thousand people, which simplifies the task of switching to environmentally friendly energy sources: the need for it is generally small.
In addition to Iceland, a high share of geothermal energy in the overall balance of electricity production is provided in New Zealand and the island states of Southeast Asia (Philippines and Indonesia), countries of Central America and East Africa, the territory of which is also characterized by high seismic and volcanic activity. For these countries, at their current level of development and needs, geothermal energy makes a significant contribution to socio-economic development.
The use of geothermal energy has a very long history. One of the first known examples is Italy, a place in the province of Tuscany, now called Larderello, where at the beginning of the 19th century local hot thermal waters, flowing naturally or extracted from shallow wells, were used for energy purposes.
Water from underground sources, rich in boron, was used here to obtain boric acid. Initially, this acid was obtained by evaporation in iron boilers, and ordinary wood from nearby forests was taken as fuel, but in 1827 Francesco Larderel created a system that worked on the heat of the waters themselves. At the same time, the energy of natural water vapor began to be used to operate drilling rigs, and at the beginning of the 20th century - for heating local houses and greenhouses. There, in Larderello, in 1904, thermal water vapor became an energy source for generating electricity.
The example of Italy was followed by several other countries at the end of the 19th and beginning of the 20th centuries. For example, in 1892, thermal waters were first used for local heating in the USA (Boise, Idaho), in 1919 in Japan, and in 1928 in Iceland.
In the USA, the first power plant operating on hydrothermal energy appeared in California in the early 1930s, in New Zealand - in 1958, in Mexico - in 1959, in Russia (the world's first binary GeoPP) - in 1965 .
Old principle on a new source
Electricity generation requires a higher hydrosource temperature than for heating - more than 150°C. The operating principle of a geothermal power plant (GeoPP) is similar to the operating principle of a conventional thermal power plant (CHP). In fact, a geothermal power plant is a type of thermal power plant.
At thermal power plants, the primary energy source is usually coal, gas or fuel oil, and the working fluid is water vapor. The fuel, when burned, heats the water into steam, which rotates steam turbine, and it generates electricity.
The difference between a GeoPP is that the primary source of energy here is the heat of the earth’s interior and the working fluid in the form of steam is supplied to the turbine blades of the electric generator in a “ready” form directly from the production well.
There are three main operating schemes for GeoPPs: direct, using dry (geothermal) steam; indirect, based on hydrothermal water, and mixed, or binary.
The use of one or another scheme depends on the state of aggregation and temperature of the energy carrier.
The simplest and therefore the first of the mastered schemes is direct, in which steam coming from the well is passed directly through the turbine. The world's first geoelectric power station in Larderello in 1904 also operated on dry steam.
GeoPPs with an indirect operating scheme are the most common in our time. They use hot underground water, which is pumped under high pressure into an evaporator, where part of it is evaporated, and the resulting steam rotates a turbine. In some cases it is required additional devices and circuits for purifying geothermal water and steam from aggressive compounds.
The exhaust steam enters the injection well or is used for heating the premises - in this case the principle is the same as when operating a thermal power plant.
At binary GeoPPs, hot thermal water interacts with another liquid that performs the functions of a working fluid with a lower boiling point. Both fluids are passed through a heat exchanger, where thermal water evaporates the working fluid, the vapors of which rotate the turbine.
This system is closed, which solves the problem of emissions into the atmosphere. In addition, working fluids with a relatively low boiling point make it possible to use not very hot thermal waters as a primary source of energy.
All three schemes use a hydrothermal source, but petrothermal energy can also be used to generate electricity.
The circuit diagram in this case is also quite simple. It is necessary to drill two interconnected wells - injection and production. Water is pumped into the injection well. At depth it is heated, then the heated water or steam formed as a result of strong heating is supplied to the surface through the production well. Then it all depends on how petrothermal energy is used - for heating or for generating electricity. A closed cycle is possible with pumping waste steam and water back into the injection well or another disposal method.
The disadvantage of such a system is obvious: to obtain a sufficiently high temperature of the working fluid, it is necessary to drill wells to great depths. And these are serious costs and the risk of significant heat losses when the fluid moves upward. Therefore, petrothermal systems are still less widespread compared to hydrothermal ones, although the potential of petrothermal energy is orders of magnitude higher.
Currently, the leader in the creation of so-called petrothermal circulation systems (PCS) is Australia. In addition, this area of geothermal energy is actively developing in the USA, Switzerland, Great Britain, and Japan.
Gift from Lord Kelvin
The invention of the heat pump in 1852 by physicist William Thompson (aka Lord Kelvin) provided humanity with real opportunity using low-grade heat from the upper layers of the soil. The heat pump system, or as Thompson called it, the heat multiplier, is based on physical process heat transfer from environment to the refrigerant. Essentially, it uses the same principle as petrothermal systems. The difference is in the heat source, which may raise a terminological question: to what extent can a heat pump be considered a geothermal system? The fact is that in the upper layers, to depths of tens to hundreds of meters, the rocks and the fluids they contain are heated not by the deep heat of the earth, but by the sun. Thus, it is the sun in this case that is the primary source of heat, although it is taken, as in geothermal systems, from the ground.
The operation of a heat pump is based on the delay in heating and cooling of the soil compared to the atmosphere, resulting in the formation of a temperature gradient between the surface and deeper layers, which retain heat even in winter, just as it happens in reservoirs. The main purpose of heat pumps is space heating. In essence, it is a “reverse refrigerator”. Both the heat pump and the refrigerator interact with three components: the internal environment (in the first case - a heated room, in the second - the cooled chamber of the refrigerator), the external environment - an energy source and a refrigerant (refrigerant), which is also a coolant that ensures heat transfer or cold.
A substance with a low boiling point acts as a refrigerant, which allows it to take heat from a source that has even a relatively low temperature.
In the refrigerator, liquid refrigerant flows through a throttle (pressure regulator) into the evaporator, where due to a sharp decrease in pressure, the liquid evaporates. Evaporation is an endothermic process requiring the absorption of heat from outside. As a result, heat is removed from the inner walls of the evaporator, which provides a cooling effect in the refrigerator chamber. Next, the refrigerant is drawn from the evaporator into the compressor, where it is returned to a liquid state. This is a reverse process leading to the release of removed heat into the external environment. As a rule, it is thrown indoors, and the back wall of the refrigerator is relatively warm.
A heat pump works in almost the same way, with the difference that heat is taken from the external environment and through the evaporator enters the internal environment - the room heating system.
In a real heat pump, water is heated, passing through an external circuit placed in the ground or reservoir, and then enters the evaporator.
In the evaporator, heat is transferred to an internal circuit filled with a low-boiling point refrigerant, which, passing through the evaporator, changes from a liquid to a gaseous state, taking away heat.
Next, the gaseous refrigerant enters the compressor, where it is compressed to high pressure and temperature, and enters the condenser, where heat exchange occurs between the hot gas and the coolant from the heating system.
The compressor requires electricity to operate, however, the transformation ratio (ratio of consumed and generated energy) in modern systems high enough to ensure their effectiveness.
Currently, heat pumps are quite widely used for space heating, mainly in economic developed countries.
Eco-correct energy
Geothermal energy is considered environmentally friendly, which is generally true. First of all, it uses a renewable and virtually inexhaustible resource. Geothermal energy does not require large areas, unlike large hydroelectric power stations or wind farms, and does not pollute the atmosphere, unlike hydrocarbon energy. On average, a GeoPP occupies 400 m 2 in terms of 1 GW of generated electricity. The same figure for a coal-fired thermal power plant, for example, is 3600 m2. The environmental advantages of GeoPP also include low water consumption - 20 liters fresh water per 1 kW, while thermal power plants and nuclear power plants require about 1000 liters. Note that these are the environmental indicators of the “average” GeoPP.
But there are still negative side effects. The most common among them is noise, thermal pollution atmosphere and chemical - water and soil, as well as the formation of solid waste.
The main source of chemical pollution of the environment is thermal water itself (with high temperature and mineralization), often containing large quantities toxic compounds, and therefore there is a problem of disposal of waste water and hazardous substances.
The negative effects of geothermal energy can be traced at several stages, starting with drilling wells. The same dangers arise here as when drilling any well: destruction of soil and vegetation cover, contamination of soil and groundwater.
At the stage of operation of the GeoPP, problems of environmental pollution remain. Thermal fluids - water and steam - usually contain carbon dioxide (CO 2), sulfur sulfide (H 2 S), ammonia (NH 3), methane (CH 4), table salt (NaCl), boron (B), arsenic (As ), mercury (Hg). When released into the external environment, they become sources of pollution. In addition, aggressive chemical environments can cause corrosion damage geothermal power plant designs.
At the same time, emissions of pollutants from GeoPPs are on average lower than from thermal power plants. For example, carbon dioxide emissions for each kilowatt-hour of electricity generated are up to 380 g at GeoPP, 1042 g at coal thermal power plants, 906 g - at fuel oil and 453 g - at gas thermal power plants.
The question arises: what to do with waste water? If the mineralization is low, after cooling it can be discharged into surface water. Another way is to pump it back into the aquifer through an injection well, which is preferably and predominantly used at present.
Extraction of thermal water from aquifers (as well as pumping out ordinary water) can cause subsidence and soil movements, other deformations of geological layers, and micro-earthquakes. The probability of such phenomena is, as a rule, low, although isolated cases have been recorded (for example, at the GeoPP in Staufen im Breisgau in Germany).
It should be emphasized that most GeoPPs are located in relatively sparsely populated areas and in third world countries, where environmental requirements are less stringent than in developed countries. In addition, at the moment the number of GeoPPs and their capacities are relatively small. With larger-scale development of geothermal energy, environmental risks may increase and multiply.
How much is the Earth's energy?
Investment costs for the construction of geothermal systems vary in a very wide range - from 200 to 5000 dollars per 1 kW of installed capacity, that is, the cheapest options are comparable to the cost of constructing a thermal power plant. They depend, first of all, on the conditions of occurrence of thermal waters, their composition, and the design of the system. Drilling to great depths, creating a closed system with two wells, and the need to purify water can increase the cost many times over.
For example, investments in the creation of a petrothermal circulation system (PCS) are estimated at 1.6–4 thousand dollars per 1 kW of installed capacity, which exceeds construction costs nuclear power plant and comparable to the costs of building wind and solar power plants.
The obvious economic advantage of GeoTES is free energy. For comparison, in the cost structure of an operating thermal power plant or nuclear power plant, fuel accounts for 50–80% or even more, depending on current energy prices. Hence, another advantage of the geothermal system: operating costs are more stable and predictable, since they do not depend on external energy price conditions. In general, the operating costs of geothermal power plants are estimated at 2–10 cents (60 kopecks–3 rubles) per 1 kWh of power produced.
The second largest expense item after energy (and very significant) is, as a rule, wages plant personnel, which can vary dramatically across countries and regions.
On average, the cost of 1 kWh of geothermal energy is comparable to that for thermal power plants (in Russian conditions- about 1 rub./1 kWh) and ten times higher than the cost of generating electricity at a hydroelectric power station (5–10 kopecks/1 kWh).
Part of the reason high cost is that, unlike thermal and hydraulic power plants, geothermal power plants have relatively low power. In addition, it is necessary to compare systems located in the same region and under similar conditions. For example, in Kamchatka, according to experts, 1 kWh of geothermal electricity costs 2–3 times less than electricity produced at local thermal power plants.
Indicators economic efficiency the operation of a geothermal system depends, for example, on whether waste water needs to be disposed of and in what ways this is done, and whether combined use of the resource is possible. Thus, chemical elements and compounds extracted from thermal water can provide additional income. Let us recall the example of Larderello: the primary thing there was precisely chemical production, and the use of geothermal energy was initially of an auxiliary nature.
Geothermal energy forwards
Geothermal energy is developing somewhat differently than wind and solar. Currently, it depends to a much greater extent on the nature of the resource itself, which varies sharply by region, and the highest concentrations are associated with narrow zones of geothermal anomalies, usually associated with areas of tectonic faults and volcanism.
In addition, geothermal energy is less technologically intensive compared to wind and, especially, solar energy: geothermal station systems are quite simple.
IN general structure The geothermal component accounts for less than 1% of global electricity production, but in some regions and countries its share reaches 25–30%. Due to the connection to geological conditions, a significant part of geothermal energy capacity is concentrated in third world countries, where there are three clusters of the greatest development of the industry - the islands of Southeast Asia, Central America and East Africa. The first two regions are included in the Pacific “belt of fire of the Earth”, the third is tied to the East African Rift. It is most likely that geothermal energy will continue to develop in these belts. A more distant prospect is the development of petrothermal energy, using the heat of the layers of the earth lying at a depth of several kilometers. This is an almost ubiquitous resource, but its extraction requires high costs, so petrothermal energy is developing primarily in the most economically and technologically powerful countries.
In general, given the widespread distribution of geothermal resources and an acceptable level of environmental safety, there is reason to believe that geothermal energy has good development prospects. Especially with the growing threat of a shortage of traditional energy resources and rising prices for them.
From Kamchatka to the Caucasus
In Russia, the development of geothermal energy has a fairly long history, and in a number of positions we are among the world leaders, although in the overall energy balance of the huge country the share of geothermal energy is still negligible.
Two regions became pioneers and centers for the development of geothermal energy in Russia - Kamchatka and North Caucasus, and if in the first case we are talking primarily about electricity, then in the second - about the use of thermal energy of thermal water.
In the North Caucasus - in the Krasnodar Territory, Chechnya, Dagestan - the heat of thermal waters was used for energy purposes even before the Great Patriotic War. In the 1980–1990s, the development of geothermal energy in the region, for obvious reasons, stalled and has not yet emerged from the state of stagnation. Nevertheless, geothermal water supply in the North Caucasus provides heat to about 500 thousand people, and, for example, the city of Labinsk in the Krasnodar Territory with a population of 60 thousand people is completely heated by geothermal waters.
In Kamchatka, the history of geothermal energy is connected, first of all, with the construction of GeoPPs. The first of them, the still operating Pauzhetskaya and Paratunka stations, were built back in 1965–1967, while the Paratunka GeoPP with a capacity of 600 kW became the first station in the world with a binary cycle. This was the development of Soviet scientists S.S. Kutateladze and A.M. Rosenfeld from the Institute of Thermophysics SB RAS, who in 1965 received an author's certificate for the extraction of electricity from water with a temperature of 70°C. This technology subsequently became the prototype for more than 400 binary GeoPPs in the world.
The capacity of the Pauzhetskaya GeoPP, commissioned in 1966, was initially 5 MW and was subsequently increased to 12 MW. Currently, a binary unit is being built at the station, which will increase its capacity by another 2.5 MW.
The development of geothermal energy in the USSR and Russia was hampered by the availability of traditional energy resources - oil, gas, coal, but never stopped. The largest geothermal energy facilities at the moment are the Verkhne-Mutnovskaya GeoPP with a total power unit capacity of 12 MW, commissioned in 1999, and the Mutnovskaya GeoPP with a capacity of 50 MW (2002).
Mutnovskaya and Verkhne-Mutnovskaya GeoPPs are unique objects not only for Russia, but also on a global scale. The stations are located at the foot of the Mutnovsky volcano, at an altitude of 800 meters above sea level, and operate in extreme climatic conditions, where there is winter for 9–10 months of the year. The equipment of the Mutnovsky GeoPPs, currently one of the most modern in the world, was entirely created at domestic power engineering enterprises.
Currently, the share of Mutnovsky stations in the overall energy consumption structure of the Central Kamchatka energy hub is 40%. There are plans to increase capacity in the coming years.
Special mention should be made about Russian petrothermal developments. We don’t have large drilling centers yet, but we have advanced technologies for drilling to great depths (about 10 km), which also have no analogues in the world. Their further development will radically reduce the costs of creating petrothermal systems. The developers of these technologies and projects are N. A. Gnatus, M. D. Khutorskoy (Geological Institute of the Russian Academy of Sciences), A. S. Nekrasov (Institute of National Economic Forecasting of the Russian Academy of Sciences) and specialists from the Kaluga Turbine Plant. Currently, the petrothermal circulation system project in Russia is at the experimental stage.
Geothermal energy has prospects in Russia, although they are relatively distant: at the moment the potential is quite large and the position of traditional energy is strong. At the same time, in a number of remote areas of the country, the use of geothermal energy is economically profitable and is already in demand. These are territories with high geoenergy potential (Chukotka, Kamchatka, the Kuril Islands - the Russian part of the Pacific “Fire Belt of the Earth”, the mountains of Southern Siberia and the Caucasus) and at the same time remote and cut off from the centralized energy supply.
Probably, in the coming decades, geothermal energy in our country will develop precisely in such regions.
This might seem fantastic if it weren't true. It turns out that in harsh Siberian conditions you can get heat directly from the ground. The first facilities with geothermal heating systems appeared in the Tomsk region last year, and although they can reduce the cost of heat compared to traditional sources by about four times, there is no mass going “underground” yet. But the trend is noticeable and, most importantly, it is gaining momentum. In fact, this is the most affordable alternative source energy for Siberia, where, for example, solar panels or wind generators cannot always demonstrate their effectiveness. Geothermal energy is essentially just lying under our feet.
“The depth of soil freezing is 2–2.5 meters. The temperature of the earth below this mark remains the same in winter and summer, ranging from plus one to plus five degrees Celsius. The operation of the heat pump is based on this property, says the power engineer of the Education Department of the Tomsk District Administration Roman Alekseenko. - Connecting pipes are buried into the earthen contour to a depth of 2.5 meters, at a distance of about one and a half meters from each other. The coolant, ethylene glycol, circulates in the pipe system. The external horizontal earth circuit communicates with the refrigeration unit, in which the refrigerant circulates - freon, a gas with a low boiling point. At plus three degrees Celsius, this gas begins to boil, and when the compressor sharply compresses the boiling gas, the temperature of the latter rises to plus 50 degrees Celsius. The heated gas is sent to a heat exchanger in which ordinary distilled water circulates. The liquid heats up and spreads heat throughout the heating system laid in the floor.”
Pure physics and no miracles
A kindergarten equipped with a modern Danish geothermal heating system opened in the village of Turuntaevo near Tomsk last summer. According to the director of the Tomsk company “Ekoklimat” Georgy Granin, an energy-efficient system made it possible to reduce heat supply fees several times. Over the course of eight years, this Tomsk enterprise has already equipped about two hundred facilities in different regions of Russia with geothermal heating systems and continues to do so in the Tomsk region. So there is no doubt about Granin’s words. A year before the opening of the kindergarten in Turuntaevo, Ecoclimate equipped another kindergarten“Sunny Bunny” in the “Green Hills” microdistrict of Tomsk. In fact, this was the first experience of this kind. And it turned out to be quite successful.
Back in 2012, during a visit to Denmark organized under the program of the Euro Info Correspondent Center (EICC-Tomsk Region), the company managed to agree on cooperation with the Danish company Danfoss. And today, Danish equipment helps extract heat from the depths of Tomsk, and, as experts say without undue modesty, it turns out quite effectively. The main indicator of efficiency is efficiency. “The heating system of a kindergarten building with an area of 250 square meters in Turuntaevo cost 1.9 million rubles,” says Granin. “And the heating fee is 20–25 thousand rubles a year.” This amount is not comparable to what the kindergarten would pay for heat using traditional sources.
The system worked without problems in the Siberian winter. Compliance calculation was carried out thermal equipment SanPiN standards, according to which it must maintain a temperature in the kindergarten building of at least +19°C at an outside air temperature of -40°C. In total, about four million rubles were spent on redevelopment, repair and re-equipment of the building. Including the heat pump, the amount was just under six million. Thanks to heat pumps, today the heating of a kindergarten is completely insulated and independent system. The building now has no traditional radiators, and the room is heated using a “warm floor” system.
The Turuntaevsky kindergarten is insulated, as they say, “from” to “to” - the building is equipped with additional thermal insulation: a 10-centimeter layer of insulation, equivalent to two to three bricks, is installed on top of the existing wall (three bricks thick). Behind the insulation there is an air layer, and then there is metal siding. The roof is also insulated in the same way. The main focus of the builders was on the “warm floor” - the heating system of the building. It turned out several layers: a concrete floor, a layer of foam plastic 50 mm thick, a system of pipes in which the hot water and linoleum. Although the water temperature in the heat exchanger can reach +50°C, the maximum heating of the actual floor covering does not exceed +30°C. The actual temperature of each room can be adjusted manually - automatic sensors allow you to set the floor temperature so that the kindergarten room warms up to the degrees required by sanitary standards.
The pump power in the Turuntaevsky kindergarten is 40 kW of generated thermal energy, for the production of which the heat pump requires 10 kW of electrical power. Thus, out of 1 kW consumed electrical energy The heat pump produces 4 kW of heat. “We were a little afraid of winter - we didn’t know how the heat pumps would behave. But even in severe frosts, the kindergarten was consistently warm - from plus 18 to 23 degrees Celsius, says the director of the Turuntaevskaya secondary school Evgeniy Belonogov. - Of course, it’s worth considering here that the building itself was well insulated. The equipment is unpretentious in maintenance, and despite the fact that this is a Western development, it has proven to be quite effective in our harsh Siberian conditions.”
A comprehensive project to exchange experience in the field of resource conservation was implemented by the EICC-Tomsk Region of the Tomsk Chamber of Commerce and Industry. Its participants were small and medium-sized enterprises developing and implementing resource-saving technologies. In May last year, Danish experts visited Tomsk as part of the Russian-Danish project, and the result was, as they say, obvious.
Innovation comes to school
A new school in the village of Vershinino, Tomsk region, built by a farmer Mikhail Kolpakov, is the third facility in the region that uses earth heat as a heat source for heating and hot water supply. The school is also unique because it has the highest energy efficiency category - “A”. The heating system was designed and launched by the same company “Ekoklimat”.
“When we made a decision on what kind of heating to install in the school, we had several options - a coal boiler house and heat pumps,” says Mikhail Kolpakov. - We studied the experience of an energy-efficient kindergarten in Zeleny Gorki and calculated that heating the old fashioned way, using coal, would cost us more than 1.2 million rubles per winter, and we also need hot water. And with heat pumps, the costs will be about 170 thousand for the whole year, including hot water.”
The system only needs electricity to produce heat. Consuming 1 kW of electricity, the heat pumps in the school produce about 7 kW of thermal energy. In addition, unlike coal and gas, the heat of the earth is a self-renewing source of energy. The installation of a modern heating system at the school cost approximately 10 million rubles. For this purpose, 28 wells were drilled on the school grounds.
“The arithmetic here is simple. We calculated that servicing a coal boiler house, taking into account the salary of the stoker and the cost of fuel, would cost more than a million rubles per year,” notes the head of the education department Sergey Efimov. - When using heat pumps, you will have to pay about fifteen thousand rubles per month for all resources. The undoubted advantages of using heat pumps are their efficiency and environmental friendliness. The heat supply system allows you to regulate the heat supply depending on the weather outside, which eliminates the so-called “underheating” or “overheating” of the room.”
According to preliminary calculations, expensive Danish equipment will pay for itself in four to five years. The service life of Danfoss heat pumps, with which Ekoklimat LLC works, is 50 years. By receiving information about the air temperature outside, the computer determines when to heat the school and when not to do so. Therefore, the question of the date of turning the heating on and off disappears altogether. Regardless of the weather outside the windows inside the school, climate control will always work for children.
“When the Ambassador Extraordinary and Plenipotentiary of the Kingdom of Denmark came to the all-Russian meeting last year and visited our kindergarten in Green Gorki, he was pleasantly surprised that those technologies that are considered innovative even in Copenhagen are applied and work in the Tomsk region,” speaks commercial director Ecoclimate company Alexander Granin.
In general, the use of local renewable energy sources in various sectors of the economy, in this case in the social sphere, which includes schools and kindergartens, is one of the main directions implemented in the region as part of the program for energy saving and increasing energy efficiency. The development of renewable energy is actively supported by the regional governor Sergey Zhvachkin. And three budgetary institutions with a geothermal heating system are just the first steps towards the implementation of a large and promising project.
The kindergarten in Green Hills was recognized as the best energy-efficient facility in Russia at a competition in Skolkovo. Then the Vershininskaya school with geothermal heating also appeared highest category energy efficiency. The next facility, no less significant for the Tomsk region, is a kindergarten in Turuntaevo. This year, the companies Gazkhimstroyinvest and Stroygarant have already begun construction of kindergartens for 80 and 60 children in the villages of the Tomsk region Kopylovo and Kandinka, respectively. Both new facilities will be heated by geothermal heating systems - from heat pumps. In total, this year the district administration intends to spend almost 205 million rubles on the construction of new kindergartens and renovation of existing ones. There is a need to reconstruct and re-equip the building for a kindergarten in the village of Takhtamyshevo. In this building, heating will also be implemented using heat pumps, since the system has proven itself well.
