Soil temperature at different depths. Thermal state of the inner parts of the globe. Minimum and maximum temperatures of the depths of the Earth

The biggest challenge is avoiding pathogenic microflora. And this is difficult to do in a moisture-saturated and warm enough environment. Even in the best cellars, there is always mold. Therefore, we need a system of regularly used pipe cleaning from any nasty things that accumulate on the walls. And it is not so easy to do this with a 3-meter deposit. First of all, a mechanical method comes to mind - a brush. As for cleaning chimneys. Using some kind of liquid chemistry. Or gas. If you pump phosgen through the pipe, for example, then everything will die and for a couple of months this may be enough. But any gas enters into the chemical. reactions with moisture in the pipe and, accordingly, settles in it, which makes airing for a long time. And long airing will lead to the recovery of pathogens. Here you need a competent approach with knowledge of modern cleaning products.

In general, I sign under each word! (I really don't know what to be happy about here).

In this system, I see several questions to be solved:

1. Is the length of this heat exchanger long enough for its effective use (some kind of effect will be, but it is not clear which one)
2. Condensation. In winter it will not be there, as cold air will be pumped through the pipe. Condensate will flow from the outside of the pipe - in the ground (it is warmer). But in the summer ... The problem is HOW to pump condensate from under a depth of 3m - I have already thought of making an airtight well-glass for collecting condensate on the side of the condensate intake. Install a pump in it, which will periodically pump out condensate ...
3. It is assumed that the sewer pipes (plastic) are sealed. If so, then the ground water around should not penetrate and should not affect the humidity of the air. Therefore, I suppose there will be no humidity (as in the basement). At least in winter. I think the basement is damp due to poor ventilation. Mold does not like sunshine and drafts (there will be drafts in the pipe). And now the question - HOW MANY sealed sewer pipes in the ground? How many years will they last for me? The fact is that this project is accompanying - a trench is dug for the sewage system (it will be at a depth of 1-1.2 m), then insulation (expanded polystyrene) and a dull earth battery). This means that this system is not repairable when it is depressurized - I will not bake it - I will just fill it with earth and that's it.
4. Pipe cleaning. I thought to make a viewing well at the lowest point. now there is less "intuzizism" on this matter - ground water - it may turn out that it will be flooded and there will be ZERO sense. There are not so many options without a well:
a. revisions are made on both sides (for each 110mm pipe), which go to the surface, a stainless cable is pulled through the pipe. For cleaning, we attach a kvach to it. Minus - a bunch of pipes enter the surface, which will affect the temperature and hydrodynamic conditions of the battery.
b. periodically flood the pipes with water and bleach, for example (or other disinfectant), pumping water out of the condensation well at the other end of the pipes. Then drying the pipes with air (perhaps in a revived mode - from the house to the outside, although I don't really like this idea).
5. There will be no mold (draft). but other microorganisms that live in the drink are very even. There is hope for a winter regime - cold dry air disinfects well. Option to protect - a filter at the input of the battery. Or ultraviolet (expensive)
6. How intense is it to drive air over such a structure?
Filter (fine mesh) at the inlet
-> rotate 90 degrees down
-> 4m 200mm pipe down
-> split flow into 4 110mm pipes
-> 10 meters horizontally
-> rotate 90 degrees down
-> 1 meter down
-> rotate 90 degrees
-> 10 meters horizontally
-> collection of flow in a 200mm pipe
-> 2 meters up
-> turn 90 degrees (into the house)
-> filter paper or cloth pocket
-> fan

We have 25m pipes, 6 turns at 90 degrees (turns can be done smoother - 2x45), 2 filters. I want 300-400m3 / h. Flow rate ~ 4m / s

To simulate temperature fields and for other calculations, it is necessary to know the temperature of the soil at a given depth.

The temperature of the soil at a depth is measured with the help of extraction soil-depth thermometers. These are planned surveys that are regularly carried out by meteorological stations. Research data serve as the basis for climate atlases and regulatory documents.

To obtain the ground temperature at a given depth, you can try, for example, two simple methods. Both methods involve using reference books:

1. For an approximate determination of the temperature, you can use the document CPI-22. "Crossings of railways with pipelines". Here, within the framework of the methodology for the thermal engineering calculation of pipelines, Table 1 is given, where for certain climatic regions the values ​​of soil temperatures are given depending on the depth of measurement. I present this table here below.

Table 1

1. Table of soil temperatures at different depths from a source "to help a worker in the gas industry" from the time of the USSR

Standard frost penetration depths for some cities:

The depth of soil freezing depends on the type of soil:

I think the easiest option is to use the above reference data and then interpolate.

The most reliable option for accurate calculations using ground temperatures is to use data from the meteorological services. Some online directories are based on the meteorological services. For example, http://www.atlas-yakutia.ru/.

Here it is enough to select the settlement, the type of soil and you can get the temperature map of the soil or its data in tabular form. In principle, it is convenient, but it looks like this resource is paid.

If you know more ways to determine the temperature of the soil at a given depth, then please write your comments.

You may be interested in the following material:

Temperature inside the Earth. Determination of temperature in the Earth's shells is based on various, often indirect, data. The most reliable temperature data refer to the uppermost part of the earth's crust, exposed by mines and boreholes to a maximum depth of 12 km (Kola well).

The rise in temperature in degrees Celsius per unit of depth is called geothermal gradient, and the depth in meters, during which the temperature increases by 1 0 С - geothermal step. The geothermal gradient and, accordingly, the geothermal stage vary from place to place, depending on geological conditions, endogenous activity in different regions, as well as heterogeneous thermal conductivity of rocks. At the same time, according to B. Gutenberg, the limits of fluctuations differ by more than 25 times. An example of this are two sharply different gradients: 1) 150 o per 1 km in Oregon (USA), 2) 6 o per 1 km is recorded in South Africa. According to these geothermal gradients, the geothermal step changes from 6.67 m in the first case to 167 m in the second. The most frequent fluctuations in the gradient are in the range of 20-50 o, and the geothermal step -15-45 m. The average geothermal gradient has long been taken at 30 o С per 1 km.

According to VN Zharkov, the geothermal gradient near the Earth's surface is estimated at 20 o C per 1 km. If we proceed from these two values ​​of the geothermal gradient and its invariability deep into the Earth, then at a depth of 100 km there should have been a temperature of 3000 or 2000 o C. However, this is at odds with the actual data. It is at these depths that magma chambers periodically originate, from which lava flows onto the surface, having a maximum temperature of 1200-1250 o. Taking into account this peculiar "thermometer", a number of authors (V. A. Lyubimov, V. A. Magnitsky) believe that at a depth of 100 km the temperature cannot exceed 1300-1500 o С.

At higher temperatures, the mantle rocks would be completely melted, which contradicts the free passage of shear seismic waves. Thus, the average geothermal gradient is traced only to a certain relatively shallow depth from the surface (20-30 km), and then it should decrease. But even in this case, in the same place, the temperature change with depth is uneven. This can be seen in the example of temperature changes with depth along the Kola well, located within the stable crystalline shield of the platform. When this well was laid, a geothermal gradient of 10 o per 1 km was calculated and, therefore, at the design depth (15 km), a temperature of about 150 o C was expected. However, such a gradient was only up to a depth of 3 km, and then it began to increase by 1.5 -2.0 times. At a depth of 7 km, the temperature was 120 o С, at 10 km -180 o С, at 12 km -220 o С. It is assumed that at the design depth the temperature will be close to 280 o С. Caspian region, in the region of a more active endogenous regime. In it, at a depth of 500 m, the temperature turned out to be 42.2 o C, at 1500 m - 69.9 o C, at 2000 m - 80.4 o C, at 3000 m - 108.3 o C.

What is the temperature in the deeper zones of the mantle and core of the Earth? More or less reliable data were obtained on the temperature of the base of layer B of the upper mantle (see Fig. 1.6). According to V.N. Zharkov, "detailed studies of the Mg 2 SiO 4 - Fe 2 SiO 4 phase diagram made it possible to determine the reference temperature at a depth corresponding to the first phase transition zone (400 km)" (ie, the transition of olivine to spinel). The temperature here, as a result of these studies, is about 1600 50 o C.

The problem of the distribution of temperatures in the mantle below layer B and in the core of the Earth has not yet been resolved, and therefore different ideas are expressed. It can only be assumed that the temperature increases with depth with a significant decrease in the geothermal gradient and an increase in the geothermal step. It is assumed that the temperature in the Earth's core is in the range of 4000-5000 o C.

Average chemical composition of the Earth. To judge the chemical composition of the Earth, data on meteorites are used, which are the most probable samples of protoplanetary material from which the terrestrial planets and asteroids were formed. To date, many meteorites that fell to the Earth at different times and in different places have been well studied. By composition, three types of meteorites are distinguished: 1) iron, consisting mainly of nickel iron (90-91% Fe), with a small amount of phosphorus and cobalt; 2) iron stone(siderolites), consisting of iron and silicate minerals; 3) stone, or aerolites, consisting mainly of ferrous-magnesian silicates and inclusions of nickel-iron.

The most widespread are stone meteorites - about 92.7% of all finds, iron stone 1.3% and iron 5.6%. Stone meteorites are subdivided into two groups: a) chondrites with small rounded grains - chondrules (90%); b) achondrites that do not contain chondrules. The composition of stony meteorites is close to that of ultrabasic igneous rocks. According to M. Bott, they contain about 12% of the iron-nickel phase.

Based on the analysis of the composition of various meteorites, as well as the obtained experimental geochemical and geophysical data, a number of researchers give a modern estimate of the gross elemental composition of the Earth, presented in table. 1.3.

As can be seen from the data in the table, the increased distribution refers to the four most important elements - O, Fe, Si, Mg, accounting for over 91%. The group of less common elements includes Ni, S, Ca, A1. The rest of the elements of the periodic system of Mendeleev on a global scale in terms of general distribution are of secondary importance. If we compare the data presented with the composition of the earth's crust, then we can clearly see a significant difference, consisting in a sharp decrease in O, A1, Si and a significant increase in Fe, Mg and the appearance in noticeable amounts of S and Ni.

The figure of the earth is called a geoid. The deep structure of the Earth is judged by longitudinal and transverse seismic waves, which, propagating inside the Earth, experience refraction, reflection and attenuation, which indicates the stratification of the Earth. There are three main areas:

Earth's crust;

mantle: upper to a depth of 900 km, lower to a depth of 2900 km;

the core of the Earth is external to a depth of 5120 km, internal to a depth of 6371 km.

The internal heat of the Earth is associated with the decay of radioactive elements - uranium, thorium, potassium, rubidium, etc. The average heat flux is 1.4-1.5 µcal / cm 2. s.

1. What is the shape and size of the Earth?

2. What are the methods of studying the internal structure of the Earth?

3. What is the internal structure of the Earth?

4. What seismic sections of the first order are clearly distinguished when analyzing the structure of the Earth?

5. What boundaries do the sections of Mohorovichich and Gutenberg correspond to?

6. What is the average density of the Earth and how does it change at the boundary between the mantle and the core?

7. How does the heat flow change in different zones? How is the change in the geothermal gradient and geothermal stage understood?

8. What data is used to determine the average chemical composition of the Earth?

Literature

• G.V. Voitkevich Foundations of the theory of the origin of the Earth. M., 1988.

• Zharkov V.N. Internal structure of the Earth and planets. M., 1978.

• Magnitsky V.A. Internal structure and physics of the Earth. M., 1965.

• Essays comparative planetology. M., 1981.

• Ringwood A.E. Composition and origin of the Earth. M., 1981.

"Use of low-grade thermal energy of the earth in heat pump systems"

Vasiliev G.P., Scientific Director of OJSC INSOLAR-INVEST, Doctor of Technical Sciences, Chairman of the Board of Directors of OJSC INSOLAR-INVEST
N.V. Shilkin, engineer, NIISF (Moscow)

Rational use of fuel and energy resources is today one of the global world problems, the successful solution of which, apparently, will be of decisive importance not only for the further development of the world community, but also for the preservation of its habitat. One of the promising ways to solve this problem is application of new energy-saving technologies using non-traditional renewable energy sources (NRES) The depletion of reserves of traditional fossil fuels and the environmental consequences of its combustion have resulted in a significant increase in interest in these technologies in almost all developed countries of the world in recent decades.

The advantages of heat supply technologies used in comparison with their traditional counterparts are associated not only with significant reductions in energy consumption in the life support systems of buildings and structures, but also with their environmental friendliness, as well as new opportunities in the field increasing the degree of autonomy of life support systems... Apparently, in the near future, it is these qualities that will play a decisive role in the formation of a competitive situation in the market of heat generating equipment.

Analysis of possible areas of application in the Russian economy of energy saving technologies using unconventional energy sources, shows that in Russia the most promising area of ​​their implementation is the life support systems of buildings. At the same time, a very effective direction for introducing the technologies under consideration into the practice of domestic construction seems to be the widespread use of heat pump heat supply systems (TST) using the soil of the surface layers of the Earth as a universally available low-potential heat source.

Using heat of the earth two types of heat energy can be distinguished - high-potential and low-potential. The source of high-potential thermal energy is hydrothermal resources - thermal waters heated as a result of geological processes to high temperatures, which allows them to be used for heating buildings. However, the use of the high-potential heat of the Earth is limited to areas with certain geological parameters. In Russia, this is, for example, Kamchatka, the region of the Caucasian mineral waters; in Europe, there are sources of high potential heat in Hungary, Iceland and France.

In contrast to the "direct" use of high-potential heat (hydrothermal resources), use of low-grade heat of the Earth by means of heat pumps is possible almost everywhere. It is currently one of the fastest growing areas of use. unconventional renewable energy sources.

Low-grade heat of the Earth can be used in various types of buildings and structures in many ways: for heating, hot water supply, air conditioning (cooling), heating paths in the winter season, to prevent icing, heating fields in open stadiums, etc. In the English-language technical literature, such systems designated as "GHP" - "geothermal heat pumps", ground source heat pumps.

The climatic characteristics of the countries of Central and Northern Europe, which, together with the USA and Canada, are the main regions for the use of low-potential heat of the Earth, determine mainly the need for heating; cooling the air even in summer is relatively rare. Therefore, unlike the United States, heat pumps in European countries they operate mainly in heating mode. IN THE USA heat pumps are more often used in air heating systems combined with ventilation, which allows both heating and cooling the outside air. In European countries heat pumps usually used in hot water heating systems. Insofar as heat pump efficiency increases with a decrease in the temperature difference between the evaporator and the condenser, often underfloor heating systems are used for heating buildings, in which a coolant circulates at a relatively low temperature (35–40 oC).

Majority heat pumps in Europe, designed to use the low-grade heat of the Earth, equipped with electrically driven compressors.

Over the past ten years, the number of systems that use the low-grade heat of the Earth for heating and cooling buildings through heat pumps, has increased significantly. The largest number of such systems are in use in the United States. A large number of such systems operate in Canada and the countries of central and northern Europe: Austria, Germany, Sweden and Switzerland. Switzerland is the leader in terms of the use of low-grade thermal energy of the Earth per capita. In Russia, over the past ten years, according to technology and with the participation of OJSC INSOLAR-INVEST, specializing in this area, only a few objects have been built, the most interesting of which are presented in.

In Moscow, in the Nikulino-2 microdistrict, it was actually built for the first time heat pump hot water system multi-storey residential building. This project was implemented in 1998-2002 by the Ministry of Defense of the Russian Federation jointly with the Government of Moscow, the Ministry of Industry and Science of Russia, the Association of NP "AVOK" and within the framework of "Long-term energy saving program in Moscow".

The heat of the soil of the surface layers of the Earth, as well as the heat of the removed ventilation air, is used as a low-potential source of thermal energy for the evaporators of heat pumps. The hot water treatment plant is located in the basement of the building. It includes the following main elements:

• vapor compression heat pump units (HPU);
• hot water storage tanks;
• systems for collecting low-grade thermal energy of the soil and low-grade heat of the removed ventilation air;
• circulation pumps, instrumentation

The main heat exchange element of the system for collecting low-potential soil heat are vertical ground coaxial heat exchangers located outside along the perimeter of the building. These heat exchangers represent 8 wells with a depth of 32 to 35 m each, arranged near the house. Since the operating mode of heat pumps using warmth of the earth and the heat of the exhaust air, constant, and the consumption of hot water is variable, the hot water supply system is equipped with storage tanks.

Data assessing the global level of use of low-grade thermal energy of the Earth by means of heat pumps are given in the table.

Table 1. World level of use of low-grade thermal energy of the Earth by means of heat pumps

Soil as a source of low-grade thermal energy

As a source of low-grade thermal energy, groundwater with a relatively low temperature or the soil of the surface (up to 400 m deep) layers of the Earth can be used.... The heat content of the soil mass is generally higher. The thermal regime of the soil of the surface layers of the Earth is formed under the influence of two main factors - the solar radiation falling on the surface and the flux of radiogenic heat from the earth's interior.... Seasonal and daily changes in the intensity of solar radiation and the temperature of the outside air cause fluctuations in the temperature of the upper layers of the soil. The penetration depth of daily fluctuations in the outside air temperature and the intensity of the incident solar radiation, depending on the specific soil and climatic conditions, ranges from several tens of centimeters to one and a half meters. The penetration depth of seasonal fluctuations in the outside air temperature and the intensity of the incident solar radiation does not exceed, as a rule, 15–20 m.

The temperature regime of soil layers located below this depth ("neutral zone") is formed under the influence of thermal energy coming from the bowels of the Earth and practically does not depend on seasonal, and even more so daily, changes in the parameters of the external climate (Fig. 1).

Rice. 1. Graph of soil temperature changes depending on depth

With increasing depth, the temperature of the soil increases in accordance with the geothermal gradient (approximately 3 degrees C for every 100 m). The magnitude of the flux of radiogenic heat coming from the earth's interior differs for different areas. For Central Europe, this value is 0.05–0.12 W / m2.

During the operational period, the soil mass located within the zone of thermal influence of the register of pipes of the ground heat exchanger of the system for collecting low-potential soil heat (heat collection system), due to seasonal changes in the parameters of the external climate, as well as under the influence of operational loads on the heat collection system, as a rule, is subjected to repeated freezing and thawing. In this case, naturally, there is a change in the aggregate state of moisture contained in the pores of the soil and in the general case both in the liquid and in the solid and gaseous phases simultaneously. In other words, the soil massif of the heat collection system, regardless of what state it is in (frozen or thawed), is a complex three-phase polydisperse heterogeneous system, the skeleton of which is formed by a huge amount of solid particles of various shapes and sizes and can be both rigid and and mobile, depending on whether the particles are firmly bound together or they are separated from each other by matter in the mobile phase. The gaps between the solid particles can be filled with mineralized moisture, gas, steam and ice, or both. Modeling heat and mass transfer processes that form the thermal regime of such a multicomponent system is an extremely difficult task, since it requires taking into account and mathematical description of various mechanisms of their implementation: thermal conductivity in an individual particle, heat transfer from one particle to another during their contact, molecular thermal conductivity in a medium filling the gaps. between particles, convection of steam and moisture contained in the pore space, and many others.

Special attention should be paid to the influence of the moisture content of the soil massif and the migration of moisture in its pore space on thermal processes that determine the characteristics of the soil as a source of low-potential thermal energy.

In capillary-porous systems, which is the soil mass of the heat collection system, the presence of moisture in the pore space has a noticeable effect on the heat propagation process. The correct accounting of this influence today is associated with significant difficulties, which are primarily associated with the lack of clear ideas about the nature of the distribution of solid, liquid and gaseous phases of moisture in a particular structure of the system. Until now, the nature of the forces of connection of moisture with particles of the skeleton, the dependence of the forms of connection of moisture with the material at various stages of moisture, the mechanism of movement of moisture in the pore space have not been clarified.

In the presence of a temperature gradient in the thickness of the soil massif, vapor molecules move to places with a reduced temperature potential, but at the same time, under the action of gravitational forces, an oppositely directed flow of moisture occurs in the liquid phase. In addition, the temperature regime of the upper layers of the soil is influenced by the moisture of atmospheric precipitation, as well as groundwater.

The main factors under the influence of which the temperature regime of the soil massif of the systems for collecting low-potential soil heat is formed are shown in Fig. 2.

Rice. 2. Factors under the influence of which the temperature regime of the soil is formed

Types of systems for the use of low-potential thermal energy of the Earth

Ground heat exchangers connect heat pump equipment with a soil massif. In addition to "extracting" the Earth's heat, ground heat exchangers can also be used to accumulate heat (or cold) in the ground mass.

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

• open systems: groundwater supplied directly to heat pumps is used as a source of low-grade thermal energy;
• closed systems: heat exchangers are located in the soil mass; when a coolant circulates through them with a temperature low relative to the ground, heat energy is "taken" from the ground and transferred to the evaporator heat pump(or, when using a heat carrier with an elevated temperature relative to the ground, its cooling).

The main part of open systems are wells, which allow to extract groundwater from aquifers of the soil and return water back to the same aquifers. Usually, paired wells are arranged for this. A diagram of such a system is shown in Fig. 3.

Rice. 3. Diagram of an open system for the use of low-potential thermal energy of groundwater

The advantage of open systems is the ability to obtain a large amount of thermal energy at relatively low costs. However, the wells require maintenance. In addition, the use of such systems is not possible in all areas. The main requirements for soil and groundwater are as follows:

• sufficient water permeability of the soil, allowing replenishment of water supplies;
• good groundwater chemistry (eg low iron content) to avoid problems associated with pipe wall deposits and corrosion.

Open systems are more often used for heating or cooling large buildings. The world's largest geothermal heat pump system uses groundwater as a source of low-grade thermal energy. This system is located in Louisville, Kentucky, USA. The system is used for heat and cold supply of the hotel-office complex; its capacity is approximately 10 MW.

Sometimes systems that use the heat of the Earth include systems for using low-grade heat from open water bodies, natural and artificial. This approach has been adopted, in particular, in the United States. Systems using low-grade heat from water bodies are classified as open systems, as are systems using low-grade heat from groundwater.

Closed systems, in turn, are divided into horizontal and vertical.

Horizontal ground heat exchanger(in the English-language literature, the terms “ground heat collector” and “horizontal loop” are also used) is usually located near the house at a shallow depth (but below the level of soil freezing in winter). The use of horizontal ground heat exchangers is limited by the size of the site available.

In the countries of Western and Central Europe, horizontal ground heat exchangers are usually separate pipes, laid relatively tightly and connected in series or in parallel (Fig. 4a, 4b). To save the area of ​​the site, improved types of heat exchangers were developed, for example, heat exchangers in the form of a spiral, located horizontally or vertically (Fig. 4e, 4f). This form of heat exchanger is common in the United States.

Rice. 4. Types of horizontal ground heat exchangers
a - a heat exchanger of pipes connected in series;
b - heat exchanger made of parallel-connected pipes;
в - horizontal collector laid in a trench;
d - a heat exchanger in the form of a loop;
e - a heat exchanger in the form of a spiral, located horizontally (the so-called "slinky" collector;
e - a heat exchanger in the form of a spiral, located vertically

If a system with horizontal heat exchangers is used only for generating heat, its normal operation is possible only if there is sufficient heat input from the earth's surface due to solar radiation. For this reason, the surface above the heat exchangers must be exposed to sunlight.

Vertical ground heat exchangers(in the English-language literature, the designation "BHE" - "borehole heat exchanger" is accepted) allow the use of low-potential thermal energy of the soil mass lying below the "neutral zone" (10–20 m from the ground level). Systems with vertical ground heat exchangers do not require large areas and do not depend on the intensity of solar radiation falling on the surface. Vertical ground heat exchangers work effectively in almost all types of geological environments, with the exception of soils with low thermal conductivity, such as dry sand or dry gravel. Systems with vertical ground heat exchangers are very widespread.

The scheme of heating and hot water supply of a single-family residential building by means of a heat pump installation with a vertical ground heat exchanger is shown in Fig. 5.

Rice. 5. Scheme of heating and hot water supply of a single-family residential building by means of a heat pump installation with a vertical ground heat exchanger

The coolant circulates through pipes (most often polyethylene or polypropylene) laid in vertical wells with a depth of 50 to 200 m. Usually, two types of vertical ground heat exchangers are used (Fig. 6):

• U-shaped heat exchanger, which are two parallel pipes connected at the bottom. One well contains one or two (rarely three) pairs of such pipes. The advantage of this arrangement is the relatively low manufacturing cost. Double U-shaped heat exchangers are the most widely used type of vertical ground heat exchangers in Europe.
• Coaxial (concentric) heat exchanger. The simplest coaxial heat exchanger consists of two pipes of different diameters. A pipe with a smaller diameter is located inside another pipe. Coaxial heat exchangers can be of more complex configurations.

Rice. 6. Section of various types of vertical ground heat exchangers

To increase the efficiency of the heat exchangers, the space between the borehole walls and the pipes is filled with special heat-conducting materials.

Systems with vertical ground heat exchangers can be used to heat and cool buildings of various sizes. For a small building, one heat exchanger is sufficient; for large buildings, it may be necessary to install a whole group of wells with vertical heat exchangers. The largest number of wells in the world is used in the heating and cooling system of Richard Stockton College in the USA in the state of New Jersey. The college's vertical ground heat exchangers are located in 400 boreholes 130 m deep. In Europe, the largest number of boreholes (154 boreholes 70 m deep) are used in the heating and cooling system of the headquarters of the German Air Traffic Service (Deutsche Flug-sicherung).

A particular case of vertical closed systems is the use of building structures as ground heat exchangers, for example, foundation piles with monolithic pipelines. The section of such a pile with three contours of a ground heat exchanger is shown in Fig. 7.

Rice. 7. Diagram of ground heat exchangers embedded in the foundation piles of the building and the cross-section of such a pile

The ground massif (in the case of vertical ground heat exchangers) and building structures with ground heat exchangers can be used not only as a source, but also as a natural accumulator of thermal energy or "cold", for example, the heat of solar radiation.

There are systems that cannot be unambiguously classified as open or closed. For example, one and the same deep (100 to 450 m deep) well filled with water can be both production and injection. The diameter of the well is usually 15 cm. A pump is placed in the lower part of the well, through which water from the well is supplied to the evaporators of the heat pump. Return water is returned to the top of the water column in the same well. There is a constant replenishment of the well with groundwater, and an open system works like a closed one. Systems of this type in the English-language literature are called "standing column well system" (Fig. 8).

Rice. 8. Scheme of a "standing column well"

Typically, wells of this type are also used to supply the building with drinking water.... However, such a system can only work effectively in soils that provide constant water replenishment of the well, which prevents it from freezing. If the aquifer is too deep, a powerful pump will be required for the normal operation of the system, which requires increased energy consumption. The great depth of the well determines the rather high cost of such systems, so they are not used for heat and cooling supply of small buildings. Now in the world there are several such systems in the USA, Germany and Europe.

One of the promising areas is the use of water from mines and tunnels as a source of low-grade thermal energy. The temperature of this water is constant throughout the year. Water from mines and tunnels is readily available.

"Stability" of systems for the use of low-grade heat of the Earth

During the operation of the ground heat exchanger, a situation may arise when during the heating season the temperature of the soil near the ground heat exchanger decreases, and in the summer period the ground does not have time to warm up to the initial temperature - its temperature potential decreases. Energy consumption during the next heating season causes an even greater decrease in ground temperature, and its temperature potential is further reduced. This forces the design of systems use of low-grade heat of the Earth consider the problem of “sustainability” of such systems. Often, energy resources are used very intensively to reduce the payback period of equipment, which can lead to their rapid depletion. Therefore, it is necessary to maintain such a level of energy production that would allow exploiting the source of energy resources for a long time. This ability of systems to maintain the required level of heat production for a long time is called “sustainability”. For systems using low-grade heat of the earth the following definition of sustainability is given: “For each system of using the low-grade heat of the Earth and for each mode of operation of this system, there is a certain maximum level of energy production; energy production below this level can be maintained for a long time (100-300 years). "

Conducted in OJSC "INSOLAR-INVEST" Studies have shown that the consumption of thermal energy from the soil mass by the end of the heating season causes a decrease in the temperature of the soil near the register of pipes of the heat collection system, which in the soil and climatic conditions of most of the territory of Russia does not have time to be compensated for in the summer period of the year, and by the beginning of the next heating season the soil comes out with reduced temperature potential. The consumption of thermal energy during the next heating season causes a further decrease in ground temperature, and by the beginning of the third heating season, its temperature potential is even more different from the natural one. Etc. However, the envelopes of the thermal effect of the long-term operation of the heat collection system on the natural temperature regime of the soil have a pronounced exponential character, and by the fifth year of operation, the soil enters a new regime, close to the periodic one, that is, starting from the fifth year of operation, the long-term consumption of thermal energy from the soil massif heat collection system is accompanied by periodic changes in its temperature. Thus, when designing heat pump heat supply systems it seems necessary to take into account the drop in the temperatures of the soil mass, caused by the long-term operation of the heat collection system, and use the temperatures of the soil mass expected for the 5th year of operation of the TST as design parameters.

In combined systems used for both heat and cold supply, the heat balance is established "automatically": in winter (heat supply is required) the soil massif is cooled, in summer (cold supply is required) - the soil massif is heated. Systems that use low-grade groundwater heat are constantly replenishing water reserves from water seeping from the surface and water coming from deeper layers of the ground. Thus, the heat content of groundwater increases both "from above" (due to the heat of the atmospheric air) and "from below" (due to the heat of the Earth); the amount of heat input "from above" and "from below" depends on the thickness and depth of the aquifer. Due to these heat inputs, the groundwater temperature remains constant throughout the season and changes little during operation.

The situation is different in systems with vertical ground heat exchangers. When heat is removed, the temperature of the soil around the ground heat exchanger decreases. The decrease in temperature is influenced by both the design features of the heat exchanger and the mode of its operation. For example, in systems with high values ​​of heat dissipated (several tens of watts per meter of heat exchanger length) or in systems with a ground heat exchanger located in soil with low thermal conductivity (for example, in dry sand or dry gravel), a decrease in temperature will be especially noticeable and can lead to to freezing of the soil mass around the soil heat exchanger.

German experts have measured the temperature of the soil massif, in which a vertical soil heat exchanger with a depth of 50 m is arranged, located near Frankfurt am Main. For this, 9 wells of the same depth were drilled around the main well at a distance of 2.5, 5 and 10 m from. In all ten wells, sensors were installed every 2 m to measure temperature - a total of 240 sensors. In fig. 9 shows diagrams showing the temperature distribution in the soil mass around the vertical soil heat exchanger at the beginning and at the end of the first heating season. At the end of the heating season, a decrease in the temperature of the soil mass around the heat exchanger is clearly noticeable. There is a heat flow directed to the heat exchanger from the surrounding soil mass, which partially compensates for the decrease in soil temperature caused by the “extraction” of heat. The magnitude of this flux, in comparison with the magnitude of the heat flux from the earth's interior in a given area (80–100 mW / m2), is estimated to be quite high (several watts per square meter).

Rice. 9. Schemes of temperature distribution in the soil mass around the vertical soil heat exchanger at the beginning and at the end of the first heating season

Since the relatively widespread use of vertical heat exchangers began to receive about 15–20 years ago, there is a lack of experimental data all over the world, obtained with long (several tens of years) service life of systems with heat exchangers of this type. The question arises about the stability of these systems, about their reliability for long periods of operation. Is the Earth's low-grade heat a renewable energy source? What is the "renewal" period for this source?

When operating a rural school in the Yaroslavl region, equipped heat pump system using a vertical ground heat exchanger, the average values ​​of specific heat output were at the level of 120-190 W / linear. m length of the heat exchanger.

Since 1986, studies have been carried out on a system with vertical ground heat exchangers in Switzerland near Zurich. A vertical ground coaxial heat exchanger with a depth of 105 m was installed in the soil massif. This heat exchanger was used as a source of low-grade thermal energy for a heat pump system installed in a single-family residential building. The vertical ground heat exchanger provided a peak power of approximately 70 watts per meter of length, which created a significant thermal load on the surrounding soil mass. Annual heat production is about 13 MWh

At a distance of 0.5 and 1 m from the main well, two additional wells were drilled, in which temperature sensors were installed at a depth of 1, 2, 5, 10, 20, 35, 50, 65, 85 and 105 m, after which the wells were filled clay-cement mixture. The temperature was measured every thirty minutes. In addition to the soil temperature, other parameters were also recorded: the speed of movement of the coolant, energy consumption by the drive of the compressor of the heat pump, air temperature, etc.

The first observation period lasted from 1986 to 1991. Measurements have shown that the influence of the heat of the outside air and solar radiation is observed in the surface layer of the soil at a depth of 15 m. Below this level, the thermal regime of the soil is formed mainly due to the heat of the earth's interior. For the first 2-3 years of operation soil temperature The temperature surrounding the vertical heat exchanger dropped sharply, but every year the temperature decrease decreased, and after a few years the system entered a mode close to constant, when the temperature of the soil mass around the heat exchanger became 1–2 ° C lower than the initial one.

In the fall of 1996, ten years after the start of operation of the system, measurements were resumed. These measurements showed that the soil temperature did not change significantly. In subsequent years, slight fluctuations in ground temperature were recorded in the range of 0.5 degrees C, depending on the annual heating load. Thus, the system reached a quasi-stationary regime after the first few years of operation.

Based on the experimental data, mathematical models of the processes taking place in the soil massif were built, which made it possible to make a long-term forecast of changes in the temperature of the soil massif.

Mathematical modeling showed that the annual decrease in temperature will gradually decrease, and the volume of the soil mass around the heat exchanger, subject to a decrease in temperature, will increase every year. At the end of the operating period, the regeneration process begins: the soil temperature begins to rise. The nature of the process of regeneration is similar to the nature of the process of "extraction" of heat: in the first years of operation there is a sharp increase in the temperature of the soil, and in subsequent years the rate of increase in temperature decreases. The length of the "regeneration" period depends on the length of the operating period. These two periods are approximately the same. In this case, the period of operation of the ground heat exchanger was thirty years, and the period of "regeneration" is also estimated at thirty years.

Thus, heating and cooling systems for buildings that use the low-grade heat of the Earth are a reliable source of energy that can be used everywhere. This source can be used for a sufficiently long time, and can be renewed at the end of the period of operation.

Literature

1. Rybach L. Status and prospects of geothermal heat pumps (GHP) in Europe and worldwide; sustainability aspects of GHPs. International course of geothermal heat pumps, 2002

2. Vasiliev G.P., Krundyshev N.S. Energy efficient rural school in the Yaroslavl region. AVOK No. 5, 2002

3. Sanner B. Ground Heat Sources for Heat Pumps (classification, characteristics, advantages). 2002

4. Rybach L. Status and prospects of geothermal heat pumps (GHP) in Europe and worldwide; sustainability aspects of GHPs. International course of geothermal heat pumps, 2002

5. ORKUSTOFNUN Working Group, Iceland (2001): Sustainable production of geothermal energy - suggested definition. IGA News no. 43, January-March 2001, 1-2

6. Rybach L., Sanner B. Ground-source heat pump systems - the European experience. GeoHeat- Center Bull. 21/1, 2000

7. Saving energy with Residential Heat Pumps in Cold Climates. Maxi Brochure 08. CADDET, 1997

8. Atkinson Schaefer L. Single Pressure Absorption Heat Pump Analysis. A Dissertation Presented to The Academic Faculty. Georgia Institute of Technology, 2000

9. Morley T. The reversed heat engine as a means of heating buildings, The Engineer 133: 1922

10. Fearon J. The history and development of the heat pump, Refrigeration and Air Conditioning. 1978

11. Vasiliev G.P. Energy efficient buildings with heat pump heating systems. Journal "Housing and communal services", No. 12, 2002

12. Guidelines for the use of heat pumps using secondary energy resources and non-traditional renewable energy sources. Moskomarkhitektura. State Unitary Enterprise "NIATs", 2001

13. Energy efficient residential building in Moscow. AVOK No. 4, 1999

14. Vasiliev G.P. An energy-efficient experimental residential building in the Nikulino-2 microdistrict. AVOK No. 4, 2002

Description:

In contrast to the “direct” use of high-potential geothermal heat (hydrothermal resources), the use of the soil of the surface layers of the Earth as a source of low-potential thermal energy for geothermal heat pump heat supply systems (GTST) is possible almost everywhere. At present, it is one of the most dynamically developing areas of the use of non-traditional renewable energy sources in the world.

Geothermal heat pump heat supply systems and the efficiency of their application in the climatic conditions of Russia

G.P. Vasiliev, Scientific Supervisor of OJSC "INSOLAR-INVEST"

In contrast to the “direct” use of high-potential geothermal heat (hydrothermal resources), the use of soil of the surface layers of the Earth as a source of low-potential thermal energy for geothermal heat pump heat supply systems (GTSS) is possible almost everywhere. At present, it is one of the most dynamically developing areas of the use of non-traditional renewable energy sources in the world.

The soil of the surface layers of the Earth is actually a heat accumulator of unlimited power. The thermal regime of the soil is formed under the influence of two main factors - the solar radiation falling on the surface and the flux of radiogenic heat from the earth's interior. Seasonal and daily changes in the intensity of solar radiation and the temperature of the outside air cause fluctuations in the temperature of the upper layers of the soil. The penetration depth of daily fluctuations in the outside air temperature and the intensity of the incident solar radiation, depending on specific soil and climatic conditions, ranges from several tens of centimeters to one and a half meters. The penetration depth of seasonal fluctuations in the outside air temperature and the intensity of the incident solar radiation does not exceed, as a rule, 15–20 m.

The thermal regime of soil layers located below this depth ("neutral zone") is formed under the influence of thermal energy coming from the bowels of the Earth and practically does not depend on seasonal, and even more so daily, changes in the parameters of the external climate (Fig. 1). With increasing depth, the ground temperature also increases in accordance with the geothermal gradient (about 3 ° C for every 100 m). The magnitude of the flux of radiogenic heat coming from the earth's interior differs for different areas. As a rule, this value is 0.05–0.12 W / m 2.

During the operation of the GTSS, the soil mass, located within the zone of thermal influence of the register of pipes of the soil heat exchanger of the system for collecting low-potential soil heat (heat collection system), due to seasonal changes in the parameters of the external climate, as well as under the influence of operational loads on the heat collection system, as a rule, is subjected to repeated freezing and thawing. In this case, of course, there is a change in the aggregate state of moisture contained in the pores of the soil and in the general case both in the liquid and in the solid and gaseous phases simultaneously. At the same time, in capillary-porous systems, which is the soil mass of the heat collection system, the presence of moisture in the pore space has a noticeable effect on the process of heat propagation. Correct accounting of this influence today is associated with significant difficulties, which are primarily associated with the lack of clear ideas about the nature of the distribution of solid, liquid and gaseous phases of moisture in a particular structure of the system. In the presence of a temperature gradient in the thickness of the soil massif, water vapor molecules move to places with a reduced temperature potential, but at the same time, under the action of gravitational forces, an oppositely directed flow of moisture occurs in the liquid phase. In addition, the temperature regime of the upper layers of the soil is influenced by the moisture of atmospheric precipitation, as well as groundwater.

The characteristic features of the thermal regime of soil heat collection systems as a design object should also include the so-called "informative uncertainty" of mathematical models describing such processes, or, in other words, the lack of reliable information about the impacts on the environment system (atmosphere and soil mass located outside the zone of thermal influence of the soil heat exchanger of the heat collection system) and the extreme complexity of their approximation. Indeed, if the approximation of the impacts on the outdoor climate system, although complex, can still be realized with a certain expenditure of "computer time" and the use of existing models (for example, a "typical climatic year"), then the problem of taking into account the influence on the system of atmospheric impacts (dew, fog, rain, snow, etc.), as well as an approximation of the thermal effect on the soil mass of the system of heat collection of the underlying and surrounding soil layers is practically not solvable today and could be the subject of separate studies. So, for example, the lack of knowledge of the processes of formation of filtration flows of groundwater, their speed regime, as well as the impossibility of obtaining reliable information about the heat and humidity regime of soil layers located below the zone of thermal influence of a ground heat exchanger, significantly complicates the task of constructing a correct mathematical model of the thermal regime of a system for collecting low-potential heat. soil.

To overcome the described difficulties arising in the design of the GTST, the created and tested in practice method of mathematical modeling of the thermal regime of soil heat collection systems and the method of accounting for the phase transitions of moisture in the pore space of the soil massif of heat collection systems can be recommended.

The essence of the method is to consider the difference between two problems when constructing a mathematical model: the “basic” problem describing the thermal regime of the soil in its natural state (without the influence of the soil heat exchanger of the heat collection system), and the problem being solved, describing the thermal regime of the soil mass with heat sinks (sources). As a result, the method makes it possible to obtain a solution with respect to a certain new function, which is a function of the effect of heat sinks on the natural thermal regime of the soil and the equal temperature difference between the soil massif in its natural state and the soil massif with drains (heat sources) - with the soil heat storage unit of the heat collection system. The use of this method in the construction of mathematical models of the thermal regime of systems for collecting low-potential soil heat made it possible not only to bypass the difficulties associated with the approximation of external influences on the heat collection system, but also to use in the models the information about the natural thermal regime of the soil, experimentally obtained by meteorological stations. This makes it possible to partially take into account the entire complex of factors (such as the presence of groundwater, their speed and thermal regimes, the structure and location of soil layers, the "thermal" background of the Earth, atmospheric precipitation, phase transformations of moisture in the pore space, and much more), which significantly affect the formation of the thermal regime of the heat collection system and the joint accounting of which in the strict formulation of the problem is practically impossible.

The method of accounting for the phase transitions of moisture in the pore space of the soil massif in the design of the GTST is based on the new concept of the “equivalent” thermal conductivity of the soil, which is determined by replacing the problem of the thermal regime of the soil cylinder frozen around the pipes of the soil heat exchanger with an “equivalent” quasi-stationary problem with a close temperature field and the same boundary conditions, but with a different "equivalent" thermal conductivity.

The most important task solved in the design of geothermal heat supply systems for buildings is a detailed assessment of the energy capabilities of the climate in the construction area and, on this basis, drawing up a conclusion on the effectiveness and appropriateness of using one or another GTST circuit solution. The calculated values ​​of climatic parameters given in the current regulatory documents do not give a complete characteristic of the outdoor climate, its variability by months, as well as in certain periods of the year - the heating season, the overheating period, etc. Therefore, when deciding on the temperature potential of geothermal heat, assessing the possibility combination with other natural sources of heat of low potential, assessment of their (sources) temperature level in the annual cycle, it is necessary to attract more complete climatic data, cited, for example, in the Handbook on the climate of the USSR (Leningrad: Gidromethioizdat. Issues 1–34).

Among such climatic information, in our case, it should be highlighted, first of all:

- data on the average monthly soil temperature at different depths;

- data on the arrival of solar radiation on variously oriented surfaces.

Table Figures 1–5 show data on average monthly ground temperatures at different depths for some cities of Russia. Table 1 shows the average monthly soil temperatures in 23 cities of the Russian Federation at a depth of 1.6 m, which seems to be the most rational from the point of view of the temperature potential of the soil and the possibility of mechanizing the work on laying horizontal ground heat exchangers.

The information presented in the tables on the natural course of soil temperatures at a depth of 3.2 m (ie, in the "working" soil layer for a GTS with a horizontal arrangement of a ground heat exchanger) clearly illustrates the possibilities of using soil as a low-potential heat source. Obvious is the relatively small interval of variation in the temperature of layers located at the same depth on the territory of Russia. For example, the minimum soil temperature at a depth of 3.2 m from the surface in Stavropol is 7.4 ° C, and in Yakutsk - (–4.4 ° C); accordingly, the interval of soil temperature change at a given depth is 11.8 degrees. This fact makes it possible to count on the creation of a sufficiently unified heat pump equipment suitable for operation practically throughout the entire territory of Russia.

As can be seen from the tables presented, a characteristic feature of the natural temperature regime of the soil is the lag of the minimum soil temperatures relative to the time of arrival of the minimum outside air temperatures. The minimum outside air temperatures are observed everywhere in January, the minimum temperatures in the ground at a depth of 1.6 m in Stavropol are observed in March, in Yakutsk - in March, in Sochi - in March, in Vladivostok - in April. ... Thus, it is obvious that by the time the minimum temperatures in the ground occur, the load on the heat pump heat supply system (the heat loss of the building) decreases. This moment opens up quite serious opportunities for reducing the installed capacity of the GTST (saving capital costs) and must be taken into account when designing.

To assess the effectiveness of the use of geothermal heat pump systems for heat supply in the climatic conditions of Russia, the territory of the Russian Federation was zoned according to the efficiency of using geothermal heat of low potential for heat supply purposes. The zoning was carried out on the basis of the results of numerical experiments on modeling the operating modes of the GTST in the climatic conditions of various regions of the territory of the Russian Federation. Numerical experiments were carried out on the example of a hypothetical two-story cottage with a heated area of ​​200 m 2, equipped with a geothermal heat pump system for heat supply. The external enclosing structures of the house in question have the following reduced heat transfer resistances:

- external walls - 3.2 m 2 h ° C / W;

- windows and doors - 0.6 m 2 h ° C / W;

- coverings and floors - 4.2 m 2 h ° C / W.

When carrying out numerical experiments, the following were considered:

- a system for collecting soil heat with a low density of geothermal energy consumption;

- horizontal heat collection system made of polyethylene pipes with a diameter of 0.05 m and a length of 400 m;

- a system for collecting soil heat with a high density of geothermal energy consumption;

- vertical heat collection system from one thermal well with a diameter of 0.16 m and a length of 40 m.

Studies have shown that the consumption of thermal energy from the soil mass by the end of the heating season causes a decrease in the temperature of the soil near the register of pipes of the heat collection system, which in the soil and climatic conditions of most of the territory of the Russian Federation does not have time to compensate in the summer period of the year, and by the beginning of the next heating season, the soil comes out with a reduced temperature potential. The consumption of thermal energy during the next heating season causes a further decrease in ground temperature, and by the beginning of the third heating season, its temperature potential is even more different from the natural one. And so on. operation, long-term consumption of thermal energy from the soil massif of the heat collection system is accompanied by periodic changes in its temperature. Thus, when carrying out zoning of the territory of the Russian Federation, it was necessary to take into account the drop in the temperatures of the soil massif caused by the long-term operation of the heat collection system, and use the soil temperatures expected for the 5th year of operation of the GTST as the calculated parameters of the temperatures of the soil massif. Considering this circumstance, when carrying out zoning of the territory of the Russian Federation in terms of the efficiency of the GTST application, the average heat transformation coefficient K p tr was chosen as a criterion for the efficiency of the geothermal heat pump heat supply system for the 5th year of operation, which is the ratio of the useful thermal energy generated by the GTST to the energy spent on its drive, and determined for the ideal thermodynamic Carnot cycle as follows:

K tr = T about / (T about - T u), (1)

where T about - the temperature potential of heat removed to the heating or heat supply system, K;

T and is the temperature potential of the heat source, K.

The transformation coefficient of the heat pump heat supply system Ktr is the ratio of the useful heat removed to the consumer's heat supply system to the energy spent on the operation of the GTST, and is numerically equal to the amount of useful heat received at temperatures T o and T and per unit of energy spent on the drive of the GTST ... The actual transformation ratio differs from the ideal one described by formula (1) by the value of the coefficient h, which takes into account the degree of thermodynamic perfection of the GTST and irreversible energy losses during the cycle.

Numerical experiments were carried out using the program created at INSOLAR-INVEST, which ensures the determination of the optimal parameters of the heat collection system depending on the climatic conditions of the construction area, the heat-shielding qualities of the building, the operational characteristics of the heat pump equipment, circulation pumps, heating devices of the heating system, as well as their modes. exploitation. The program is based on the previously described method of constructing mathematical models of the thermal regime of systems for collecting low-potential soil heat, which made it possible to bypass the difficulties associated with the informative uncertainty of models and the approximation of external influences, due to the use of experimentally obtained information about the natural thermal regime of the soil in the program, which allows partially taking into account the whole complex of factors (such as the presence of groundwater, their speed and thermal regimes, the structure and location of soil layers, the "thermal" background of the Earth, atmospheric precipitation, phase transformations of moisture in the pore space, and much more) that significantly affect the formation of the thermal regime of the system heat collection, and the joint accounting of which in the strict formulation of the problem is practically impossible today. As a solution to the "basic" problem, we used the data of the USSR Climate Handbook (Leningrad: Gidromethioizdat. Issue 1–34).

The program actually allows solving the problem of multi-parameter optimization of the GTST configuration for a specific building and construction area. In this case, the target function of the optimization problem is the minimum annual energy costs for the operation of the GTST, and the optimization criteria are the radius of the pipes of the ground heat exchanger, its (heat exchanger) length and depth.

The results of numerical experiments and zoning of the territory of Russia in terms of the efficiency of using low-potential geothermal heat for the purposes of heating buildings are presented graphically in Fig. 2-9.

In fig. 2 shows the values ​​and isolines of the transformation coefficient of geothermal heat pump heat supply systems with horizontal heat collection systems, and in Fig. 3 - for GTST with vertical heat collection systems. As can be seen from the figures, the maximum values ​​of Kp tr 4.24 for horizontal heat collection systems and 4.14 for vertical systems can be expected in the south of the territory of Russia, and the minimum values, respectively, are 2.87 and 2.73 in the north, in Uelen. For central Russia, the values ​​of K ptr for horizontal heat collection systems are in the range of 3.4–3.6, and for vertical systems, in the range of 3.2–3.4. Sufficiently high values ​​of Кррт (3.2-3.5) for the regions of the Far East, regions with traditionally difficult conditions of fuel supply attract themselves. Apparently, the Far East is the region of the priority implementation of the GTST.

In fig. 4 shows the values ​​and isolines of specific annual energy consumption for the drive of "horizontal" GTST + PD (peak closer), including energy consumption for heating, ventilation and hot water supply, reduced to 1 m 2 of the heated area, and in Fig. 5 - for GTST with vertical heat collection systems. As can be seen from the figures, the annual specific energy consumption for the drive of horizontal GTST, reduced to 1 m2 of heated building area, varies from 28.8 kWh / (year m2) in the south of Russia to 241 kWh / (year m2) in St. Yakutsk, and for vertical GTST, respectively, from 28.7 kWh / / (year m2) in the south and up to 248 kWh / / (year m2) in Yakutsk. If we multiply the value of annual specific energy consumption for the drive of the GTST presented in the figures for a particular area by the value for this area K r tr, reduced by 1, then we get the amount of energy saved by the GTST from 1 m 2 of the heated area per year. For example, for Moscow for a vertical GTST, this value will be 189.2 kWh from 1 m 2 per year. For comparison, we can cite the values ​​of specific energy consumption established by the Moscow standards for energy conservation MGSN 2.01–99 for low-rise buildings at 130, and for multi-storey buildings at 95 kWh / (year m 2). At the same time, the standardized MGSN 2.01–99 energy costs include only energy costs for heating and ventilation, in our case, energy costs for hot water supply are also included in energy costs. The fact is that the approach to the assessment of energy costs for the operation of a building existing in the current standards allocates into separate items the energy costs for heating and ventilation of the building and the energy costs for its hot water supply. At the same time, energy consumption for hot water supply is not standardized. This approach does not seem to be correct, since the energy costs for hot water supply are often commensurate with the energy costs for heating and ventilation.

In fig. 6 shows the values ​​and isolines of the rational ratio of the thermal power of the peak closer (PD) and the installed electric power of horizontal GTSS in fractions of a unit, and in Fig. 7 - for GTST with vertical heat collection systems. The criterion for the rational ratio of the thermal power of the peak closer and the installed electrical power of the GTST (excluding PD) was the minimum annual electricity consumption for the GTST + PD drive. As can be seen from the figures, the rational ratio of the capacities of the thermal DP and electric GTST (without DP) varies from 0 in the south of Russia, to 2.88 - for horizontal GTST and 2.92 for vertical systems in Yakutsk. In the central zone of the territory of the Russian Federation, the rational ratio of the thermal power of the closer and the installed electrical power of the GTST + PD is in the range of 1.1–1.3 for both horizontal and vertical GTST. At this point, you need to dwell in more detail. The fact is that when replacing, for example, electric heating in the Central zone of Russia, we actually have the opportunity to reduce the capacity of the electrical equipment installed in the heated building by 35-40% and, accordingly, reduce the electric power requested from RAO UES, which today “costs »About 50 thousand rubles. for 1 kW of electric power installed in the house. So, for example, for a cottage with an estimated heat loss in the coldest five-day period equal to 15 kW, we will save 6 kW of installed electrical power and, accordingly, about 300 thousand rubles. or ≈ 11.5 thousand US dollars. This figure is practically equal to the cost of a GTST of such heat capacity.

Thus, if we correctly take into account all the costs associated with connecting a building to a centralized power supply, it turns out that with the current tariffs for electricity and connecting to centralized power supply networks in the central zone of the Russian Federation, even at a one-time cost, the GTST turns out to be more profitable than electric heating, not to mention 60 % energy saving.

In fig. 8 shows the values ​​and isolines of the specific weight of thermal energy generated during the year by the peak closer (PD) in the total annual energy consumption of the horizontal GTST + PD system in percent, and in Fig. 9 - for GTST with vertical heat collection systems. As can be seen from the figures, the specific weight of thermal energy generated during the year by the peak closer (PD) in the total annual energy consumption of the horizontal GTST + PD system varies from 0% in the south of Russia to 38–40% in Yakutsk and Tura, and for vertical GTST + PD - respectively, from 0% in the south and up to 48.5% in Yakutsk. In Central Russia, these values ​​are about 5–7% for both vertical and horizontal GTST. This is a small energy consumption, and in this regard, you need to be careful when choosing a peak closer. The most rational from the point of view of both specific capex in 1 kW of power and automation are peak electrodes. The use of pellet boilers deserves attention.

In conclusion, I would like to dwell on a very important issue: the problem of choosing a rational level of thermal protection of buildings. This problem is today a very serious task, for the solution of which a serious numerical analysis is required, taking into account both the specifics of our climate, and the features of the utilized engineering equipment, infrastructure of centralized networks, as well as the ecological situation in cities, which is literally worsening before our eyes, and much more. It is obvious that today it is already incorrect to formulate any requirements for the shell of a building without taking into account its (building) relationships with the climate and the energy supply system, utilities, etc. As a result, in the very near future, the solution to the problem of choosing a rational level of thermal protection will be possible only based on the consideration of the building + energy supply system + climate + environment complex as a single eco-energy system, and with this approach, the competitive advantages of the GTST in the domestic market can hardly be overestimated.

Literature

1. Sanner B. Ground Heat Sources for Heat Pumps (classification, characteristics, advantages). Course on geothermal heat pumps, 2002.

2. Vasiliev GP Economically reasonable level of thermal protection of buildings. Energosberezhenie. - 2002. - No. 5.

3. Vasiliev GP Heat and cold supply of buildings and structures using low-potential thermal energy of the surface layers of the Earth: Monograph. Publishing house "Granitsa". - M.: Krasnaya Zvezda, 2006.