Heat pump for heating: principle of operation and advantages of use. How to make a heat pump for heating a house with your own hands: operating principle and assembly diagrams How a heat pump for heating a house works

The situation is such that the most popular way to heat a home at the moment is the use of heating boilers - gas, solid fuel, diesel and much less often - electric. But such simple and at the same time high-tech systems as heat pumps have not become widespread, and for good reason. For those who love and know how to calculate everything in advance, their advantages are obvious. Heat pumps for heating do not burn irreplaceable reserves of natural resources, which is extremely important not only from the point of view of environmental protection, but also allows you to save on energy, as they become more expensive every year. In addition, with the help of heat pumps you can not only heat the room, but also heat hot water for household needs, and air condition the room in the summer heat.

Operating principle of a heat pump

Let's take a closer look at the principle of operation of a heat pump. Remember how a refrigerator works. The heat of the products placed in it is pumped out and thrown onto the radiator located on the rear wall. You can easily verify this by touching it. The principle of household air conditioners is approximately the same: they pump out heat from the room and throw it onto a radiator located on the outer wall of the building.

The operation of a heat pump, refrigerator and air conditioner is based on the Carnot cycle.

1. The coolant, moving along a source of low-temperature heat, for example, soil, heats up by several degrees.
2. It then enters a heat exchanger called an evaporator. In the evaporator, the coolant releases the accumulated heat to the refrigerant. Refrigerant is a special liquid that turns into steam at low temperatures.
3. Taking on the temperature from the coolant, the heated refrigerant turns into steam and enters the compressor. The compressor compresses the refrigerant, i.e. an increase in its pressure, due to which its temperature also increases.
4. The hot, compressed refrigerant enters another heat exchanger called a condenser. Here the refrigerant transfers its heat to another coolant, which is provided in the heating system of the house (water, antifreeze, air). This cools the refrigerant and turns it back into liquid.
5. Next, the refrigerant enters the evaporator, where it is heated by a new portion of the heated coolant, and the cycle repeats.

The heat pump requires electricity to operate. But it is still much more profitable than using only an electric heater. Since an electric boiler or electric heater spends exactly the same amount of electricity as it produces heat. For example, if a heater has a power rating of 2 kW, then it spends 2 kW per hour and produces 2 kW of heat. A heat pump produces 3 to 7 times more heat than it consumes electricity. For example, 5.5 kW/hour is used to operate the compressor and pump, and the heat produced is 17 kW/hour. It is this high efficiency that is the main advantage of a heat pump.

Advantages and disadvantages of the heat pump heating system

There are many legends and misconceptions surrounding heat pumps, despite the fact that they are not such an innovative or high-tech invention. All “warm” states in the USA, almost all of Europe and Japan, where the technology has been worked out almost to perfection for a long time, are heated with the help of heat pumps. By the way, you should not think that such equipment is a purely foreign technology and came to us quite recently. After all, back in the USSR such units were used at experimental facilities. An example of this is the Druzhba sanatorium in the city of Yalta. In addition to the futuristic architecture, reminiscent of a “hut on chicken legs,” this sanatorium is also famous for the fact that since the 80s of the 20th century it has used industrial heat pumps for heating. The source of heat is the nearby sea, and the pumping station itself not only heats all the premises of the sanatorium, but also provides hot water, heats the water in the pool and cools it during the hot season. So let's try to dispel the myths and determine whether it makes sense to heat your home in this way.

Advantages of heating systems with a heat pump:

• Energy savings. In connection with rising prices for gas and diesel fuel, this is a very relevant advantage. In the “monthly expenses” column, only electricity will appear, which, as we have already written, requires much less than the heat actually produced. When purchasing a unit, you need to pay attention to such a parameter as the heat transformation coefficient “ϕ” (may also be called the heat conversion coefficient, power or temperature transformation coefficient). It shows the ratio of the amount of heat output to the energy expended. For example, if ϕ=4, then at a consumption of 1 kW/hour we will receive 4 kW/hour of thermal energy.
• Maintenance savings. The heat pump does not require any special treatment. Its maintenance costs are minimal.
• Can be installed in any location. Sources of low-temperature heat for the operation of a heat pump can be soil, water or air. Wherever you build a house, even in a rocky area, there will always be an opportunity to find “food” for the unit. In areas remote from the gas main, this is one of the most optimal heating systems. And even in regions without power lines, you can install a gasoline or diesel engine to ensure the operation of the compressor.
• No need to monitor pump operation, add fuel, as is the case with a solid fuel or diesel boiler. The entire heating system with heat pump is automated.
• You can go away for a long time and not be afraid that the system will freeze. At the same time, you can save money by installing the pump to ensure a temperature of +10 °C in the living room.
• Safe for the environment. For comparison, when using traditional boilers that burn fuel, various oxides CO, CO2, NOx, SO2, PbO2 are always formed, as a result, phosphoric, nitrous, sulfuric acids and benzoic compounds settle around the house on the soil. When the heat pump operates, nothing is emitted. And the refrigerants used in the system are absolutely safe.
• It can also be noted here conservation of the planet's irreplaceable natural resources.
• Safety for people and property. Nothing in a heat pump gets hot enough to cause overheating or explosion. Besides, there is simply nothing to explode in it. So it can be classified as a completely fireproof unit.
• Heat pumps operate successfully even at an ambient temperature of -15 °C. So if someone thinks that such a system can only heat a house in regions with warm winters up to +5 °C, then they are mistaken.
• Heat pump reversibility. An undeniable advantage is the versatility of the installation, with which you can heat in winter and cool in summer. On hot days, the heat pump takes heat from the room and sends it to the ground for storage, from where it will be taken back in the winter. Please note that not all heat pumps have reverse capability, but only some models.
• Durability. With proper care, heat pumps in a heating system can last from 25 to 50 years without major repairs, and only once every 15 to 20 years will the compressor need to be replaced.

Disadvantages of heat pump heating systems:

• Large initial investment. In addition to the fact that prices for heat pumps for heating are quite high (from 3,000 to 10,000 USD), you will also need to spend no less on the installation of a geothermal system than on the pump itself. An exception is the air source heat pump, which does not require additional work. The heat pump will not pay for itself soon (in 5 - 10 years). So the answer to the question of whether or not to use a heat pump for heating rather depends on the preferences of the owner, his financial capabilities and construction conditions. For example, in a region where supplying a gas main and connecting to it costs the same as a heat pump, it makes sense to give preference to the latter.

• In regions where winter temperatures drop below -15 °C, additional heat source must be used. It is called bivalent heating system, in which the heat pump provides heat while the street is down to -20 ° C, and when it cannot cope, for example, an electric heater or a gas boiler, or a heat generator is connected.

• It is most advisable to use a heat pump in systems with low-temperature coolant, such as "warm floor" system(+35 °C) and fan coil units(+35 - +45 °C). Fan coil units They are a fan convector in which heat/cold is transferred from water to air. To install such a system in an old house, a complete redevelopment and reconstruction will be required, which will entail additional costs. This is not a disadvantage when building a new home.
• Environmental friendliness of heat pumps, taking heat from water and soil, somewhat relative. The fact is that during operation, the space around the coolant pipes cools, and this disrupts the established ecosystem. After all, even in the depths of the soil, anaerobic microorganisms live, ensuring the vital functions of more complex systems. On the other hand, compared to gas or oil production, the damage from a heat pump is minimal.

Heat sources for heat pump operation

Heat pumps take heat from those natural sources that accumulate solar radiation during the warm period. Heat pumps vary depending on the heat source.

Priming

Soil is the most stable source of heat that accumulates over the season. At a depth of 5 - 7 m, the soil temperature is almost always constant and equal to approximately +5 - +8 ° C, and at a depth of 10 m it is always constant +10 ° C. There are two ways to collect heat from the ground.

Horizontal ground collector It is a horizontally laid pipe through which coolant circulates. The depth of the horizontal collector is calculated individually depending on the conditions, sometimes it is 1.5 - 1.7 m - the depth of soil freezing, sometimes lower - 2 - 3 m to ensure greater temperature stability and less difference, and sometimes only 1 - 1.2 m - here the soil begins to warm up faster in the spring. There are cases when a two-layer horizontal collector is installed.

Horizontal collector pipes can have different diameters: 25 mm, 32 mm and 40 mm. The shape of their layout can also be different - snake, loop, zigzag, various spirals. The distance between the pipes in the snake must be at least 0.6 m, and is usually 0.8 - 1 m.

Specific heat removal per linear meter of pipe depends on the soil structure:

• Dry sand - 10 W/m;
• Dry clay - 20 W/m;
• Clay is wetter - 25 W/m;
• Clay with a very high water content - 35 W/m.

To heat a house with an area of ​​100 m2, provided that the soil is wet clay, you will need 400 m2 of land area for the collector. This is quite a lot - 4 - 5 acres. And taking into account the fact that there should be no buildings on this site and only a lawn and flower beds with annual flowers are allowed, not everyone can afford to equip a horizontal collector.

A special liquid flows through the collector pipes, it is also called "brine" or antifreeze, for example, a 30% solution of ethylene glycol or propylene glycol. The “brine” collects the heat from the ground and is sent to the heat pump, where it transfers it to the refrigerant. The cooled “brine” flows again into the ground collector.

Vertical soil probe is a system of pipes buried to 50 - 150 m. This can be just one U-shaped pipe, lowered to a greater depth of 80 - 100 m and filled with concrete mortar. Or maybe a system of U-shaped pipes lowered 20 m to collect energy from a larger area. Carrying out drilling work to a depth of 100 - 150 m is not only expensive, but also requires obtaining a special permit, which is why they often resort to cunning and equip several probes of shallow depth. The distance between such probes is 5 - 7 m.

Specific heat removal from a vertical collector also depends on the rock:

• Dry sedimentary rocks - 20 W/m;
• Sedimentary rocks saturated with water and rocky soil - 50 W/m;
• Rocky soil with a high thermal conductivity coefficient - 70 W/m;
• Underground (groundwater) water - 80 W/m.

The area required for a vertical collector is very small, but the cost of their installation is higher than that of a horizontal collector. The advantage of a vertical collector is also a more stable temperature and greater heat removal.

Water

Water can be used as a heat source in different ways.

Collector at the bottom of an open, non-freezing reservoir- rivers, lakes, seas - represents pipes with “brine”, submerged with the help of a weight. Due to the high temperature of the coolant, this method is the most profitable and economical. Only those from whom the reservoir is located no further than 50 m can install a water collector, otherwise the efficiency of the installation is lost. As you understand, not everyone has such conditions. But not using heat pumps for coastal residents is simply short-sighted and stupid.

Collector in sewer drains or waste water from technical installations can be used for heating houses and even high-rise buildings and industrial enterprises within the city, as well as for preparing hot water. What is being done successfully in some cities of our Motherland.

Well or ground water used less frequently than other collectors. Such a system involves the construction of two wells, water is taken from one, which transfers its heat to the refrigerant in the heat pump, and cooled water is discharged into the second. Instead of a well, there may be a filtration well. In any case, the discharge well should be located at a distance of 15 - 20 m from the first one, and even downstream (groundwater also has its own flow). This system is quite difficult to operate, since the quality of the incoming water must be monitored - filtered, and protected from corrosion and contamination of the heat pump parts (evaporator).

Air

The simplest design is heating system with air source heat pump. No additional collector is needed. Air from the environment directly enters the evaporator, where it transfers its heat to the refrigerant, which in turn transfers heat to the coolant inside the house. This could be air for fan coil units or water for underfloor heating and radiators.

The installation costs of an air source heat pump are minimal, but the performance of the installation is highly dependent on the air temperature. In regions with warm winters (up to +5 - 0 °C) this is one of the most economical sources of heat. But if the air temperature drops below -15 °C, the performance drops so much that it makes no sense to use the pump, and it is more profitable to turn on a conventional electric heater or boiler.

Reviews on air source heat pumps for heating are very contradictory. It all depends on the region of their use. They are advantageous to use in regions with warm winters, for example, in Sochi, where there is no need for a backup heat source in case of severe frosts. It is also possible to install air source heat pumps in regions where the air is relatively dry and the temperature in winter is down to -15 °C. But in humid and cold climates, such installations suffer from icing and freezing. Icicles sticking to the fan prevent the entire system from working properly.

Heating with a heat pump: system cost and operating costs

The power of the heat pump is selected depending on the functions that will be assigned to it. If only heating, then calculations can be made in a special calculator that takes into account the heat losses of the building. By the way, the best performance of a heat pump is when the heat loss of the building is no more than 80 - 100 W/m2. For simplicity, we assume that to heat a house of 100 m2 with ceilings 3 m high and heat loss of 60 W/m2, a pump with a power of 10 kW is needed. To heat water, you will have to take a unit with a power reserve - 12 or 16 kW.

Heat pump cost depends not only on power, but also on reliability and the manufacturer’s requests. For example, a Russian-made 16 kW unit will cost $7,000, and a foreign pump RFM 17 with a power of 17 kW costs about $13,200. with all associated equipment except the manifold.

The next expense line will be reservoir arrangement. It also depends on the power of the installation. For example, for a house of 100 m2, in which heated floors (100 m2) or heating radiators of 80 m2 are installed everywhere, as well as to heat water to +40 °C with a volume of 150 l/hour, you will need to drill wells for collectors. Such a vertical collector will cost 13,000 USD.

A collector at the bottom of a reservoir will cost a little less. Under the same conditions, it will cost 11,000 USD. But it is better to check the cost of installing a geothermal system with specialized companies; it can vary greatly. For example, installing a horizontal collector for a 17 kW pump will cost only 2500 USD. And for an air source heat pump, a collector is not needed at all.

Total, the cost of the heat pump is 8000 USD. On average, the construction of a collector is 6000 USD. average.

The monthly cost of heating with a heat pump only includes electricity costs. They can be calculated as follows: the power consumption must be indicated on the pump. For example, for the above-mentioned 17 kW pump, the power consumption is 5.5 kW/h. In total, the heating system operates 225 days a year, i.e. 5400 hours. Taking into account the fact that the heat pump and compressor in it operate cyclically, the energy consumption must be halved. During the heating season, 5400h*5.5kW/h/2=14850 kW will be spent.

We multiply the number of kW spent by the cost of energy in your region. For example, 0.05 USD for 1 kW/hour. In total, 742.5 USD will be spent per year. For each month in which the heat pump worked for heating, it costs 100 USD. electricity costs. If you divide the expenses by 12 months, then you get 60 USD per month.

Please note that the lower the heat pump's power consumption, the lower the monthly costs. For example, there are 17 kW pumps that consume only 10,000 kW per year (costs 500 cu). It is also important that the performance of a heat pump is greater, the smaller the temperature difference between the heat source and the coolant in the heating system. That is why they say that it is more profitable to install warm floors and fan coil units. Although standard heating radiators with high-temperature coolant (+65 - +95 °C) can also be installed, but with an additional heat accumulator, for example, an indirect heating boiler. A boiler is also used to additionally heat the hot water.

Heat pumps are advantageous when used in bivalent systems. In addition to the pump, you can install a solar collector, which can fully supply the pump with electricity in the summer, when it works for cooling. For winter insurance, you can add a heat generator that will heat water for hot water supply and high-temperature radiators.

• Operating principle of heat pumps
• Heating circuit
• Advantages and disadvantages of heat pumps
• Homemade secrets

How it works

A heat or geothermal pump collects thermal energy from the environment, converts it using refrigerant, and supplies it to the home heating system.

The main components of the unit: compressor, heat exchanger, circulation pump, automation, supply circuit. The pump is capable of drawing heat from three sources.

• Air.
• Water.
• Priming.

Judging by the discussion threads, we have two options in demand - water and soil. This is due to temperature restrictions - the source must be positive. The location of the feeding circuit can be horizontal or vertical. In the first case, the main line is laid below the freezing level - from 1.5 meters deep. Or to the bottom of the reservoir, there even in severe frosts - up to + 4⁰С. The length of the circuit depends on the dimensions of the heated room and the power of the pump. In the second, wells are drilled for probes, the average depth is 50–70 meters. Piastrov A V, one of the forum members and the owner of a heat pump, described the vertical system this way.

Piastrov A V Member of FORUMHOUSE

The heat is collected by geothermal probes - a looped pipeline through which ethylene glycol circulates. They descend into wells 50–70 meters deep. This is an external circuit, and the number of wells depends on the power of the heat pump. For a house with a square area of ​​100 meters, you will need two probes - two wells.

Heating circuit

A heat pump, unlike gas, coal or electricity boilers, heats the medium to an average of 40⁰C. This is the optimal temperature at which both equipment wear and electricity consumption are minimal. For conventional radiators, such indicators are not enough. Therefore, with a heat pump, they usually use not pipes and radiators, but heated floors. It is more efficient when heating the coolant this way. Only the pitch between the pipes should be smaller. It is worth considering that heated floors create restrictions on the choice of furniture and dry out the air. Additional moisture will be required. In summer, floors can work for cooling.

Advantages and disadvantages

The main advantage of a heat pump is its high efficiency; for every kilowatt of electricity consumed, it produces about 5 kW of heat. Plus no physical effort during the work, no waste and carbon monoxide.

In addition, there is no dependence on gas workers and no going to authorities for approval. And the requirements for the boiler room are not so strict. After start-up, operating costs are minimal. Only electricity is paid; an average power pump consumes about 4 kW per hour. Modern models are pulsed, they do not operate continuously, but are switched on when necessary. This reduces the number of working hours per season and energy costs.

The main disadvantage of geothermal heating is the price; even a Chinese or domestic unit, not to mention European brands, costs several thousand euros. Together with the arrangement of the external circuit and installation, the pleasure will result in hundreds of thousands of rubles. According to calculations by experts and owners, the pump pays for itself in several years. It runs on a free source, compared to the cost of a ton of coal or a cubic meter of firewood, the savings are significant. But not everyone has an extra half a million for equipment and commissioning.

If there is a body of water close to the site, it turns out to be much cheaper, and there is no need to spend on expensive drilling.

Operating wells also optimize the process by becoming a source of heat. This is confirmed by a forum member det maros from Ust-Kamenogorsk. He works at a company that produces heat pumps and provides installation services. Therefore, he thoroughly understands the situation and answered the question of a thread participant whether he needs probes if there are wells on the site, and he answered exhaustively.

det maros FORUMHOUSE Member

Why bother with probes if there is enough water. You will drive from one well to another through the HP. We tinker with probes when there is no water in the area or the pole is small and does not cover the needs. A 10 kW pump requires a volume of 3 cubic meters.

Homemade secrets

But the biggest savings are obtained when you assemble the heat pump yourself. The leading unit, the compressor, is taken from powerful air conditioners and split systems; their technical parameters are similar. Heat exchangers are sold ready-made, but some craftsmen manage to solder them from copper pipes. Freon is used as a refrigerant; it is also sold in cylinders. Controllers, relays, stabilizers, all elements individually will cost half as much as in a ready-made kit.

Most often, homemade projects are organized over ponds or when there is already an existing well. Due to the fact that the lion's share of expenses falls on excavation work, and the maximum savings are on them.

Craftsman aparat2, from Riga, collected geothermal equipment himself and posted a photo report about it, with a detailed description of all operations.

aparat2 FORUMHOUSE Member

I assembled a HP from two single-phase compressors of 24,000 BTU each (7 kW h. in cold weather). The result was a cascade with a thermal power of 16-18 kilowatts, with an electricity consumption of about 4.5 kW per hour. I chose two compressors so that the currents would be lower; I will not start them at the same time. In the meantime, only the second floor is inhabited and one compressor is enough. And, having experimented on one, then I will improve the second design.

Also, the forum member decided not to spend money on ready-made plate-type heat exchangers. They are demanding in terms of water treatment, and they cost a lot. He combined a homemade exchanger with a battery to increase the output. The result was a working installation that was several times cheaper than a purchased one.

However, heat pumps are an alternative option when there is no gas and large heating areas. Even if you assemble the system yourself, the costs for components are substantial. You can study the topic more closely on the thread, there is a lot of useful advice there, forum users share their experiences and discuss various models. will help you understand the assembly. And the options for heating a large house without gas in the video are a clear example. For owners of wooden houses - video

Heat pump (HP) is a device that carries out the transfer, transformation and conversion of thermal energy. According to the principle of operation, it is similar to well-known devices and equipment, such as a refrigerator or air conditioner. The operation of any TN is based on the reverse Carnot cycle, named after the famous French physicist and mathematician Sidi Carnot.

Working principle of a heat pump

Let's study in more detail the physics of the operating processes of this equipment. The heat pump consists of four main elements:

1. Compressor
2. Heat exchanger (condenser)
3. Heat exchanger (evaporator)
4. Connecting fittings and automation elements.

Compressor necessary to compress and move refrigerant through the system. When freon is compressed, its temperature and pressure rise sharply (pressure develops up to 40 bar, temperature up to 140 C), and in the form of a gas with a high degree of compression it goes to the capacitor(adiabatic process, i.e. a process in which the system does not interact with external space), where it transfers energy to the consumer. The consumer can be either the immediate environment that needs to be heated (for example, indoor air) or the coolant (water, antifreeze, etc.), which then distributes energy through the heating system (radiators, heated floors, heated baseboards, convectors, fan coils, etc.). In this case, the temperature of the gas naturally decreases, and it changes its state of aggregation from gaseous to liquid (an isothermal process, i.e. a process occurring at a constant temperature).

Next, the refrigerant is in a liquid state enters the evaporator, passing through a thermostatic valve (TRV), which is necessary to reduce the pressure and dose the flow of freon into the evaporative heat exchanger. As a result of a decrease in pressure when passing through the evaporator channels, a phase transition occurs, and the state of aggregation of the refrigerant again changes to gaseous. In this case, the entropy of the gas decreases (based on the thermophysical properties of freons), which leads to a sharp drop in temperature, and heat is “removed” from an external source. The external source can be street air, the bowels of the earth, rivers, lakes. Next, the cooled gaseous freon is returned to the compressor, and the cycle repeats again.

In fact, it turns out that the heat engine itself does not produce heat, but is a device for moving, modifying and modifying energy from the environment into the room. However, this process requires electricity, the main consumer of which is the compressor unit. The ratio of the received thermal power to the expended electrical power is called the conversion factor (COR). It varies depending on the type of turbocharger, its manufacturer, and other factors and ranges from 2 to 6.

Currently, various types of ozone-friendly freons (R410A, R407C) are used as a refrigerant, which cause minimal damage to the environment.

Modern heat engines use scroll-type compressors that require no maintenance, have virtually no friction, and can operate continuously for 30-40 years. This ensures a long service life of the entire unit. For example, a German company Stiebel Eltron There are HPs that have operated without major repairs since the early 70s of the last century.

Types of Heat Pumps

Depending on the media used for the selection and redistribution of energy, as well as design features and methods of application, there are four main types of HP:

Air-to-air heat pump

This type of equipment uses street air as a low-potential energy source. Outwardly, it does not differ from a conventional split air conditioning system, but it has a number of functional features that allow it to operate at low temperatures (down to -30 C) and “remove” energy from the environment. The house is heated directly by warm air heated in the heat pump condenser.

Advantages of air-to-air HP:

• Low cost
• Short installation time and comparative ease of installation
• No possibility of coolant leakage

Flaws:

• Stable performance down to -20 C
• The need to install an indoor unit in each room or organize an air duct system to supply heated air to all rooms.
• Inability to obtain hot water (DHW)

In practice, such systems are used for seasonal housing and cannot act as the main source of heating.

Air-to-water heat pump

Their operating principle is similar to the previous type, however, they do not directly heat the air inside the room, but the coolant, which in turn is used to heat the house and prepare hot water.

Advantages of TN “Air – Water”:

• does not require the organization of an “external contour” (drilling)
• reliability and durability
• high efficiency indicators (COP) in the autumn and spring periods

Disadvantages of TN:

• Significant reduction in COP at low temperatures (up to 1.2)
• The need to defrost the external unit (reverse mode)
• Inability to operate at temperatures below -25 C - -30 C

Such pumps in our climate still cannot act as the only source of heating. Therefore, they are often installed (according to a bivalent scheme) in conjunction with additional heating equipment (electric, pellet, solid fuel, diesel boiler, fireplace with a water jacket). They are also suitable for the reconstruction and automation of old boiler houses using traditional fuels. This allows the system to be operated in automatic mode for most of the year (there is no need to load solid fuel or refuel diesel fuel), using only the power of the HP.

Brine-water heat pump

One of the most common in the Republic of Belarus. Using statistics from our organization, 90% of installed heat pumps are geothermal. In this case, the bowels of the earth are used as the “external contour”. Due to this, these heat pumps have the most important advantage over other types of heat pumps - a stable operating efficiency indicator (COP) regardless of the time of year.

According to established terminology, the external circuit is called geothermal.

There are two main types of geothermal circuit:

• Horizontal
• Vertical

Let's look at each of them in more detail.

Horizontal outline

Horizontal outline is a system of polyethylene pipes laid under the top layer of soil at a depth of about 1.5 - 2 m, below the freezing level. The temperature in this zone remains positive (from +3 to +15 C) throughout the calendar year, reaching a maximum in October and a minimum in May. The area occupied by the collector depends on the area of ​​the building, the degree of its insulation, and the size of the glazing. So, for example, for a two-story residential building with an area of ​​200 m2, which has good insulation that meets modern standards, about four acres of land (400 m2) will have to be allocated for a geothermal field. Of course, for a more accurate assessment of the diameter of the pipes used and the occupied area, a detailed thermal engineering calculation is required.

This is what the installation of a horizontal collector looks like at one of our facilities in Dzerzhinsk (Republic of Belarus):

Advantages of a horizontal collector:

• Lower cost compared to geothermal wells
• Possibility of carrying out work on its installation together with the laying of other communications (water supply, sewerage)

Disadvantages of a horizontal collector:

• Large occupied area (it is prohibited to erect permanent structures, pave asphalt, lay paving slabs, it is necessary to ensure natural access to light and precipitation)
• Lack of possibility of arrangement with ready-made landscape design of the site
• Less stability compared to a vertical collector.

The arrangement of this type of collector is usually carried out in two ways. In the first case over the entire laying area, remove the top layer of soil, 1.5-2m thick, the heat exchanger pipes are being laid out with a given step (from 0.6 to 1.5 m) and backfilling is carried out. To perform such work, powerful equipment is suitable, such as a front loader, bulldozer, excavators with a large reach and bucket volume.

In the second case laying the ground contour loops is carried out step by step in prepared trenches, width from 0.6 m to 1 m. Small excavators and backhoe loaders are suitable for this purpose.

Vertical outline

Vertical collector represents wells with depths from 50 to 200 m and more, into which special devices are lowered - geothermal probes. The temperature in this zone remains constant for many years and decades and increases with increasing depth. The increase occurs on average by 2-5 C for every 100 m. This characterizing value is called the temperature gradient.

The process of installing a vertical collector at our facility in the village of Kryzhovka, near Minsk:

Studying maps of temperature distribution at various depths on the territory of the Republic of Belarus and the city of Minsk in particular, one can notice that the temperature varies from region to region, and can differ significantly depending on location. So, for example, at a depth of 100 m in the area of ​​Svetlogorsk it can reach +13 C, and in some areas of the Vitebsk region at the same depth it does not exceed +8.5 C.

Of course, when calculating the drilling depth and designing the size, diameter and other characteristics of geothermal probes, it is necessary to take this factor into account. In addition, it is necessary to take into account the geological composition of the rocks being passed through. Only based on this data can you correctly design a geothermal circuit.

As the practice and statistics of our organization show, 99% of problems during the operation of HP are associated with the functioning of the external circuit, and this problem does not appear immediately after commissioning of the equipment. And there is an explanation for this, because if the geocontour is incorrectly calculated (for example, in the territory of the Vitebsk region, where, as we remember, the geothermal gradient is one of the lowest in the Republic), its initial work is not satisfactory, but over time the thickness of the earth “cools” The thermodynamic balance is disrupted and troubles begin, and the problem can arise only in the second or third heating season. An oversized contour looks less problematic, but the customer is forced to pay for unnecessary meters of drilling due to the incompetence of the contractor, which inexorably leads to an increase in the cost of the entire project.

The study of the subsoil of the earth should be especially critical during the construction of large commercial facilities, where the number of wells is in the dozens, and the funds saved (or wasted) on their construction can be very significant.

Water-to-water heat pump

One type of geothermal heat source can be groundwater. They have a constant temperature (from +7 C and above), and occur in significant quantities at various depths in the territory of the Republic of Belarus. According to the technology, groundwater is lifted from a well by a centrifugal pump and enters a heat and mass transfer station, where it transfers energy to the antifreeze of the lower circuit of the heat pump. The operating efficiency of this system depends on the level of groundwater (depending on the depth of rise, a certain pump power is required), and the distance from the intake well to the exchange station. This technology has one of the highest COP values, but has a number of features that limit its use.

Among them:

• Lack of groundwater, or low level of its occurrence;
• Lack of constant well flow, decrease in static and dynamic levels;
• The need to take into account the salt composition and contamination (if the water quality is not adequate, the heat exchanger becomes clogged and performance indicators decrease)
• The need to install a drainage well to discharge significant volumes of waste water (from 2200 l/h or more)

As practice shows, the installation of such systems is advisable if there is a pond or river in the immediate vicinity. Waste water can also be used for economic and industrial purposes, for example, for irrigation, or for organizing artificial reservoirs.

As for the quality of intake water, for example, a German manufacturer of alternative heating systems Stiebel Eltron recommends the following settings: the total proportion of iron and magnesium is not more than 0.5 mg/l, the chloride content is less than 300 mg/l, the absence of precipitated substances. If these parameters are exceeded, it is necessary to install an additional purification system - a preparation and desalting station, which increases the material consumption of the project.

Drilling work for a heat pump.

Based on experience in the installation and operation of geothermal units, we recommend drilling wells of at least 100 m. Practice shows that better performance and stability of a heat engine will be observed, for example, for two wells of 150 m each than for three wells of 100 m each. Of course, the construction of such mines requires special equipment and a rotary drilling method. Small-sized auger installations are not able to provide the required length of wells.

Since the geothermal circuit is the most important component, and the correctness of its arrangement is the key to the successful functioning of the entire system, the drilling contractor must meet a number of criteria:

• It is necessary to have experience in producing this type of service;
• have a special tool for immersing probes;
• provide a guarantee that the probe will be immersed to the designed depth and guarantee its integrity and tightness during the work process;
• after immersion, carry out measures to plug the well to increase its heat transfer and productivity, caulk the shaft of the mine before backfilling.

In general, with proper design and qualified installation, geothermal probes are very reliable and can last up to 100 years.

The process of lowering a geothermal probe into a drilled well:

Geothermal probe on the frame, before performing a leak test (“pressure testing”):

conclusions

Based on our experience in the design of alternative energy systems, we can highlight the main facts that are fundamental when our Customers choose heat pumps:

• full safety and environmental friendliness(no combustion processes or moving parts)
• the opportunity to order the system “today” and enjoy using it in three weeks without any coordination with regulatory and licensing authorities.
• Full autonomy and minimal maintenance(there is no need to be a member of a gas cooperative, to depend on it; there is no need to throw firewood or carry out monthly cleaning of air ducts, organize the access of a fuel tanker, etc.)
• The cost of a plot for the construction of an individual house without gas supply is much lower and the delivery period does not depend on gas services
• Opportunity remote control via the Internet
• Advanced and innovative equipment of stylish design, which is not a shame to show to friends and acquaintances, which certainly emphasizes the status of the homeowner.

If we have not touched on any questions in this article and you want to ask them personally, you can come to our office at the address: Minsk, st. Odoevsky, 117, Nova Gros LLC and consult with our engineers.

We also have the opportunity to organize free visits to already completed operating facilities.

Contact telephone number: 044 765 29 58; 017 399 70 51

Any owner of a private home strives to minimize the cost of heating their home. In this regard, heat pumps are significantly more profitable than other heating options; they provide 2.5-4.5 kW of heat per kilowatt of electricity consumed. The other side of the coin: to obtain cheap energy, you will have to invest a lot of money in equipment; the most modest heating installation with a capacity of 10 kW will cost 3,500 USD. e. (starting price).

The only way to reduce costs by 2-3 times is to make a heat pump with your own hands (abbreviated as HP). Let's consider several real working options, collected and tested by enthusiastic craftsmen in practice. Since the manufacture of a complex unit requires basic knowledge about refrigeration machines, let's start with the theory.

Features and principle of operation of TN

How does a heat pump differ from other installations for heating private houses:

• unlike boilers and heaters, the unit does not produce heat on its own, but, like an air conditioner, moves it inside the building;
• The HP is called a pump because it “pumps out” energy from sources of low-grade heat - ambient air, water or soil;
• the installation is powered exclusively by the electricity consumed by the compressor, fans, circulation pumps and control board;
• The operation of the device is based on the Carnot cycle, used in all refrigeration machines, for example, air conditioners and split systems.

In heating mode, a traditional split system operates normally at temperatures above minus 5 degrees; in severe frost, the efficiency drops sharply

Reference. Heat is contained in any substance whose temperature is above absolute zero (minus 273 degrees). Modern technologies make it possible to extract this energy from air with temperatures down to -30 °C, land and water - up to +2 °C.

The Carnot heat exchange cycle involves a working fluid - freon gas, boiling at sub-zero temperatures. Alternately evaporating and condensing in two heat exchangers, the refrigerant absorbs energy from the environment and transfers it inside the building. In general, the principle of operation of a heat pump is the same as that turned on for heating:

1. While in the liquid phase, freon moves through the tubes of the external evaporator heat exchanger, as shown in the diagram. Receiving heat from air or water through metal walls, the refrigerant heats up, boils and evaporates.
2. Then the gas enters the compressor, which pumps up the pressure to the calculated value. Its task is to raise the boiling point of the substance so that freon condenses at a higher temperature.
3. Passing through the internal heat exchanger-condenser, the gas turns into liquid again and transfers the accumulated energy to the coolant (water) or room air directly.
4. At the last stage, the liquid refrigerant enters the receiver-moisture separator, then into the throttling device. The pressure of the substance drops again, freon is ready to go through a second cycle.

The operating principle of a heat pump is similar to the operating principle of a split system

Note. Conventional split systems and factory heat pumps have a common feature - the ability to transfer energy in both directions and operate in 2 modes - heating / cooling. The switching is realized using a four-way reversing valve, which changes the direction of gas flow along the circuit.

Domestic air conditioners and heat pumps use various types of thermostatic valves that reduce the refrigerant pressure in front of the evaporator. In household split systems, the role of a regulator is played by a simple capillary device, and an expensive thermostatic valve (TRV) is installed in the pumps.

Note that the above cycle occurs in all types of heat pumps. The difference lies in the methods of heat supply/removal, which we will list below.

Types of throttle valves: capillary tube (photo on the left) and thermostatic valve (TRV)

Types of installations

According to the generally accepted classification, heat pumps are divided into types according to the source of energy received and the type of coolant to which it is transferred:

Reference. Types of heat pumps are listed in order of increasing cost of equipment along with installation. Air plants are the cheapest, geothermal plants are expensive.

The main parameter characterizing a heat pump for heating a house is the efficiency coefficient COP, equal to the ratio between the energy received and the energy expended. For example, relatively inexpensive air heaters cannot boast of a high COP - 2.5...3.5. Let us explain: having spent 1 kW of electricity, the installation supplies 2.5-3.5 kW of heat to the home.

Methods for collecting heat from water sources: from a pond (left) and through wells (right)

Water and soil systems are more efficient, their real coefficient lies in the range of 3...4.5. Productivity is a variable value, depending on many factors: the design of the heat exchange circuit, immersion depth, temperature and water flow.

Important point. Water heat pumps are not capable of heating the coolant to 60-90 °C without additional circuits. The normal water temperature from the heat pump is 35...40 degrees, boilers clearly win here. Hence the manufacturers' recommendation: connect the equipment to low-temperature heating - water.

Which TN is better to collect

Let us formulate the problem: you need to build a homemade heat pump at the lowest cost. A number of logical conclusions follow from this:

1. The installation will have to use a minimum of expensive parts, so it will not be possible to achieve a high COP value. In terms of performance coefficient, our device will lose to factory models.
2. Accordingly, it makes no sense to make a purely air HP; it is easier to use it in heating mode.
3. To get real benefits, you need to manufacture an air-to-water, water-to-water heat pump, or build a geothermal installation. In the first case, you can achieve a COP of about 2-2.2, in the rest you can achieve 3-3.5.
4. It will not be possible to do without underfloor heating circuits. Coolant heated to 30-35 degrees is incompatible with the radiator network, except in the southern regions.

Laying the external circuit of the HP to the reservoir

Comment. Manufacturers claim: the inverter split system operates at street temperatures of minus 15-30 °C. In reality, heating efficiency is significantly reduced. According to homeowners' reviews, on frosty days the indoor unit supplies a barely warm air stream.

To implement the water version of the HP, certain conditions are required (optional):

• a pond 25-50 m from the home; at a greater distance, electricity consumption will increase significantly due to a powerful circulation pump;
• a well or well with a sufficient supply (debit) of water and a place for drainage (pit, second well, drainage ditch, sewer);
• prefabricated sewer (if they let you crash into it).

Groundwater flow is easy to calculate. In the process of heat extraction, a homemade heat pump will lower their temperature by 4-5 °C, from here the volume of the flow is determined through the heat capacity of the water. To obtain 1 kW of heat (we take the water temperature delta to be 5 degrees), you need to drive about 170 liters through the heat pump within an hour.

Heating a house with an area of ​​100 m² will require a power of 10 kW and a water consumption of 1.7 tons per hour - an impressive volume. A similar heat water pump is suitable for a small country house of 30-40 m², preferably insulated.

Methods for selecting heat from geothermal heat pumps

Assembling a geothermal system is more feasible, although the process is quite labor-intensive. We immediately reject the option of laying the pipe horizontally over an area at a depth of 1.5 m - you will have to shovel the entire area or pay money for the services of earth-moving equipment. The method of drilling wells is much simpler and cheaper to implement, with virtually no disturbance to the landscape.

The simplest heat pump from a window air conditioner

As you might guess, to manufacture a water-to-air heat pump you will need a window cooler in working condition. It is very advisable to buy a model equipped with a reversing valve and capable of heating, otherwise you will have to redo the freon circuit.

Advice. When buying a used air conditioner, pay attention to the nameplate, which displays the technical characteristics of the household appliance. The parameter you are interested in is (indicated in kilowatts or British thermal units - BTU).

The heating capacity of the device is greater than the refrigeration capacity and is equal to the sum of two parameters - performance plus the heat generated by the compressor

With some luck, you won't even have to release the freon and resolder the pipes. How to convert an air conditioner into a heat pump:

Recommendation. If the heat exchanger cannot be placed in the tank without damaging the freon lines, try to evacuate the gas and cut the tubes at the required points (away from the evaporator). After assembling the water heat exchange unit, the circuit will have to be soldered and filled with freon. The amount of refrigerant is also indicated on the label.

Now all that remains is to launch a homemade HP and adjust the water flow, achieving maximum efficiency. Please note: the improvised heater uses a completely factory “filling”; you just moved the radiator from air to liquid. How the system works live, watch the video of the master craftsman:

Making a geothermal installation

If the previous option allows you to achieve approximately double savings, then even a homemade earthen circuit will give a COP in the region of 3 (three kilowatts of heat per 1 kW of electricity consumed). True, financial and labor costs will also increase significantly.

Although a lot of examples of assembling such devices have been published on the Internet, there are no universal instructions with drawings. We will offer a working version, assembled and tested by a real home craftsman, although many things will have to be thought out and completed independently - it is difficult to put all the information about heat pumps in one publication.

Calculation of the soil circuit and pump heat exchangers

Following our own recommendations, we begin to calculate a geothermal pump with vertical U-shaped probes placed in wells. It is necessary to find out the total length of the external contour, and then the depth and number of vertical shafts.

Initial data for the example: you need to heat a private insulated house with an area of ​​80 m² and a ceiling height of 2.8 m, located in the middle zone. We will not spend on heating; we will determine the need for heat by area, taking into account thermal insulation - 7 kW.

If desired, you can arrange a horizontal collector, but then you will have to allocate a large area for excavation work

Important clarification. Engineering calculations of heat pumps are quite complex and require highly qualified performers; entire books are devoted to this topic. The article provides simplified calculations taken from the practical experience of builders and craftsmen who love homemade products.

The intensity of heat exchange between the ground and the non-freezing liquid circulating along the circuit depends on the type of soil:

• 1 linear meter of a vertical probe immersed in underground water will receive about 80 W of heat;
• in rocky soils, the heat removal will be about 70 W/m;
• clayey soils saturated with moisture will deliver approximately 50 W per 1 m of collector;
• dry rocks – 20 W/m.

Reference. The vertical probe consists of 2 loops of pipes lowered to the bottom of the well and filled with concrete.

An example of calculating the length of a pipe. To extract the required 7 kW of thermal energy from raw clay rock, you will need 7000 W divided by 50 W/m, we get a total probe depth of 140 m. Now the pipeline is distributed into wells 20 m deep, which you can drill with your own hands. A total of 7 drillings for 2 heat exchange loops, the total length of the pipe is 7 x 20 x 4 = 560 m.

The next step is to calculate the heat exchange area of ​​the evaporator and condenser. Various Internet resources and forums offer certain calculation formulas, which in most cases are incorrect. We will not take the liberty of recommending such methods and misleading you, but we will offer a cunning option:

1. Contact any well-known manufacturer of plate heat exchangers, for example, Alfa Laval, Kaori, Anvitek and so on. You can go to the official website of the brand.
2. Fill out the heat exchanger selection form or call the manager and order the selection of the unit, listing the parameters of the media (antifreeze, freon) - inlet and outlet temperatures, heat load.
3. The company’s specialist will make the necessary calculations and offer a suitable heat exchanger model. Among its characteristics you will find the main one - the exchange surface area.

Plate units are very effective, but expensive (200-500 euros). It is cheaper to assemble a shell-and-tube heat exchanger from a copper tube with an outer diameter of 9.5 or 12.7 mm. Multiply the figure given by the manufacturer by a safety factor of 1.1 and divide by the circumference of the pipe to obtain the footage.

A stainless steel plate heat exchanger is an ideal evaporator option, it is efficient and takes up little space. The problem is the high price of the product

Example. The heat exchange area of ​​the proposed unit was 0.9 m². Having selected a ½” copper tube with a diameter of 12.7 mm, we calculate the circumference in meters: 12.7 x 3.14 / 1000 ≈ 0.04 m. Determine the total footage: 0.9 x 1.1 / 0.04 ≈ 25 m.

Equipment and materials

It is proposed to build the future heat pump on the basis of an outdoor unit of a split system of suitable power (indicated on the plate). Why is it better to use a used air conditioner:

• the device is already equipped with all components - compressor, throttle, receiver and starting electrics;
• homemade heat exchangers can be placed in the body of the refrigeration machine;
• There are convenient service ports for refilling freon.

Note. Users who are knowledgeable about the topic select equipment separately - compressor, expansion valve, controller, and so on. If you have experience and knowledge, such an approach is only welcome.

It is impractical to assemble a HP on the basis of an old refrigerator - the power of the unit is too low. In the best case, it will be possible to “squeeze” up to 1 kW of heat, which is enough to heat one small room.

In addition to the external split unit, you will need the following materials:

• HDPE pipe Ø20 mm - to the earthen circuit;
• polyethylene fittings for assembling collectors and connecting to heat exchangers;
• circulation pumps – 2 pcs.;
• pressure gauges, thermometers;
• high-quality water hose or HDPE pipe with a diameter of 25-32 mm for the shell of the evaporator and condenser;
• copper tube Ø9.5-12.7 mm with a wall thickness of at least 1 mm;
• insulation for pipelines and freon lines;
• kit for sealing heating cables laid inside the water supply (needed to seal the ends of copper pipes).

Set of bushings for hermetic entry of copper tube

A saline solution of water or antifreeze for heating – ethylene glycol – is used as an external coolant. You will also need a supply of freon, the brand of which is indicated on the nameplate of the split system.

Assembling the heat exchange block

Before starting installation work, the outdoor module must be disassembled - remove all covers, remove the fan and the large standard radiator. Disconnect the solenoid that controls the reversing valve if you do not plan to use the pump as a coolant. Temperature and pressure sensors must be preserved.

Assembly procedure for the main VT block:

1. Make a condenser and evaporator by inserting a copper tube inside a hose of the estimated length. At the ends, install tees to connect the ground and heating circuits; seal the protruding copper tubes using a special kit for the heating cable.
   
2. Using a piece of plastic pipe Ø150-250 mm as a core, wind homemade two-pipe circuits and bring the ends in the right directions, as is done below in the video.
3. Place and secure both shell-and-tube heat exchangers in place of the standard radiator, solder the copper tubes to the corresponding terminals. It is better to connect a “hot” heat exchanger-condenser to the service ports.
   
4. Install factory sensors that measure coolant temperature. Insulate the bare sections of the tubes and the heat exchange devices themselves.
5. Place thermometers and pressure gauges on the water lines.

Advice. If you plan to install the main unit outdoors, you need to take measures to prevent the oil from solidifying in the compressor. Purchase and install a winter kit for electric oil sump heating.

On thematic forums there is another way to make an evaporator - a copper tube is wound in a spiral, then inserted inside a closed container (tank or barrel). The option is quite reasonable with a large number of turns, when the calculated heat exchanger simply does not fit in the air conditioner housing.

Construction of the soil contour

At this stage, simple but labor-intensive excavation work and placement of probes in wells are performed. The latter can be done manually or by inviting a drilling machine. The distance between adjacent wells is at least 5 m. Further work order:

1. Dig a shallow trench between the drillings to lay the supply pipes.
2. Place 2 loops of polyethylene pipes into each hole and fill the holes with concrete.
3. Bring the lines to the connection point and mount a common manifold using HDPE fittings.
4. Insulate pipelines laid in the ground and fill them with soil.

On the left in the photo is lowering the probe into a plastic casing pipe, on the right is laying connections in the trench

Important point. Before concreting and backfilling, be sure to check the tightness of the circuit. For example, connect an air compressor to the manifold, pump up a pressure of 3-4 bar and leave for several hours.

When connecting highways, follow the diagram presented below. Bends with taps will be needed when filling the system with brine or ethylene glycol. Lead the two main pipes from the collector to the heat pump and connect to the “cold” evaporator heat exchanger.

Air vents must be installed at the highest points of both water circuits; they are not shown in the diagram.

Do not forget to install a pump unit responsible for the circulation of the liquid, the direction of flow is towards the freon in the evaporator. The media passing through the condenser and evaporator must move towards each other. How to properly fill the cold side lines, watch the video:

In a similar way, the condenser is connected to the house floor heating system. A mixing unit with a three-way valve does not need to be installed due to the low supply temperature. If you need to combine the transformer with other heat sources (solar collectors, boilers), use multiple terminals.

Refueling and starting the system

After installing and connecting the unit to the electrical network, an important stage begins - filling the system with refrigerant. A pitfall awaits here: you don’t know how much freon you need to charge, because the volume of the main circuit has increased significantly due to the installation of a homemade condenser with an evaporator.

The issue is solved by the filling method based on the pressure and overheating temperature of the refrigerant, measured at the compressor inlet (freon is supplied there in a gaseous state). Detailed instructions for filling out the temperature measurement method are set out in.

The second part of the video describes how to fill the system with R22 freon based on the pressure and superheat temperature of the refrigerant:

Upon completion of refueling, turn on both circulation pumps to first speed and start the compressor. Monitor the temperature of the brine and internal coolant using thermometers. During the warm-up stage, the lines with the refrigerant may freeze, and subsequently the frost should melt.

Conclusion

Making and running a geothermal heat pump with your own hands is very difficult. It will probably require repeated improvements, bug fixes, and tweaks. As a rule, most problems with homemade heat pumps occur due to improper assembly or filling of the main heat exchange circuit. If the unit immediately fails (the automatic safety system has tripped) or does not heat the coolant, it is worth calling a refrigeration equipment technician - he will carry out diagnostics and point out any mistakes made.

By the end of the 19th century, powerful refrigeration units appeared that could pump at least twice as much heat as the energy required to operate them. It was a shock, because formally it turned out that a thermal perpetual motion machine was possible! However, upon closer examination, it turned out that perpetual motion is still far away, and low-grade heat produced using a heat pump and high-grade heat obtained, for example, by burning fuel are two big differences. True, the corresponding formulation of the second principle was somewhat modified. So what are heat pumps? In a nutshell, a heat pump is a modern and high-tech appliance for heating and air conditioning. Heat pump collects heat from the street or from the ground and directs it into the house.

Working principle of a heat pump

Working principle of a heat pump is simple: due to mechanical work or other types of energy, it ensures the concentration of heat, previously evenly distributed over a certain volume, in one part of this volume. In the other part, accordingly, a heat deficit is formed, that is, cold.

Historically, heat pumps first began to be widely used as refrigerators - in essence, any refrigerator is a heat pump that pumps heat from the refrigeration chamber to the outside (into the room or outside). There is still no alternative to these devices, and with all the variety of modern refrigeration technology, the basic principle remains the same: pumping out heat from the refrigeration chamber using additional external energy.

Naturally, almost immediately they noticed that the noticeable heating of the condenser heat exchanger (in a household refrigerator it is usually made in the form of a black panel or grille on the back wall of the cabinet) could also be used for heating. This was already the idea of ​​a heater based on a heat pump in its modern form - a refrigerator in reverse, when heat is pumped into a closed volume (room) from an unlimited external volume (from the street). However, in this area, the heat pump has plenty of competitors - from traditional wood stoves and fireplaces to all sorts of modern heating systems. Therefore, for many years, while fuel was relatively cheap, this idea was viewed as nothing more than a curiosity - in most cases it was absolutely unprofitable economically, and only extremely rarely was such use justified - usually to recover heat pumped out by powerful refrigeration units in countries with not too cold climate. And only with the rapid rise in energy prices, the complication and rise in price of heating equipment and the relative reduction in the cost of production of heat pumps against this background, does such an idea become economically profitable in itself - after all, having paid once for a rather complex and expensive installation, then it will be possible to constantly save at reduced fuel consumption. Heat pumps are the basis of the increasingly popular ideas of cogeneration - the simultaneous production of heat and cold - and trigeneration - the production of heat, cold and electricity at once.

Since the heat pump is the essence of any refrigeration unit, we can say that the concept of “refrigeration machine” is its pseudonym. However, it should be borne in mind that despite the universality of the operating principles used, the designs of refrigeration machines are still focused specifically on producing cold, not heat - for example, the generated cold is concentrated in one place, and the resulting heat can be dissipated in several different parts of the installation , because in a regular refrigerator the task is not to utilize this heat, but simply to get rid of it.

Heat pump classes

Currently, two classes of heat pumps are most widely used. One class includes thermoelectric ones using the Peltier effect, and the other includes evaporative ones, which in turn are divided into mechanical compressor (piston or turbine) and absorption (diffusion) ones. In addition, interest in the use of vortex tubes, in which the Ranque effect operates, as heat pumps is gradually increasing.

Heat pumps based on the Peltier effect

Peltier element

The Peltier effect is that when a small constant voltage is applied to two sides of a specially prepared semiconductor wafer, one side of this wafer heats up and the other cools. So, basically, the thermoelectric heat pump is ready!

The physical essence of the effect is as follows. A Peltier element plate (also known as a “thermoelectric element”, English Thermoelectric Cooler, TEC) consists of two layers of semiconductor with different electron energy levels in the conduction band. When an electron moves under the influence of an external voltage to a higher-energy conduction band of another semiconductor, it must acquire energy. When it receives this energy, the contact point between the semiconductors cools (when current flows in the opposite direction, the opposite effect occurs - the contact point between the layers heats up in addition to the usual ohmic heating).

Advantages of Peltier elements

The advantage of Peltier elements is the maximum simplicity of their design (what could be simpler than a plate to which two wires are soldered?) and the complete absence of any moving parts, as well as internal flows of liquids or gases. The consequence of this is absolute silent operation, compactness, complete indifference to spatial orientation (provided sufficient heat dissipation is ensured) and very high resistance to vibration and shock loads. And the operating voltage is only a few volts, so a few batteries or a car battery are enough for operation.

Disadvantages of Peltier elements

The main disadvantage of thermoelectric elements is their relatively low efficiency - approximately we can assume that per unit of pumped heat they will require twice as much external energy supplied. That is, by supplying 1 J of electrical energy, we can remove only 0.5 J of heat from the cooled area. It is clear that all the total 1.5 J will be released on the “warm” side of the Peltier element and will need to be diverted to the external environment. This is many times lower than the efficiency of compression evaporative heat pumps.

Against the background of such a low efficiency, the remaining disadvantages are usually not so important - and this is a low specific productivity combined with a high specific cost.

Use of Peltier elements

In accordance with their characteristics, the main area of ​​application of Peltier elements is currently usually limited to cases where it is necessary to cool something not very powerful, especially in conditions of strong shaking and vibration and with strict restrictions on weight and dimensions, - for example, various components and parts of electronic equipment, primarily military, aviation and space equipment. Perhaps the most widespread use of Peltier elements in everyday life is in low-power (5..30 W) portable car refrigerators.

Evaporative compression heat pumps

Diagram of the operating cycle of an evaporative compression heat pump

The operating principle of this class of heat pumps is as follows. The gaseous (wholly or partially) refrigerant is compressed by a compressor to a pressure at which it can turn into a liquid. Naturally, this heats up. The heated compressed refrigerant is supplied to the condenser radiator, where it is cooled to ambient temperature, releasing excess heat to it. This is the heating zone (the back wall of the kitchen refrigerator). If at the condenser inlet a significant part of the compressed hot refrigerant still remained in the form of vapor, then when the temperature decreases during heat exchange, it also condenses and turns into a liquid state. The relatively cooled liquid refrigerant is supplied to the expansion chamber, where, passing through a throttle or expander, it loses pressure, expands and evaporates, at least partially transforming into gaseous form, and, accordingly, is cooled - significantly below the ambient temperature and even below the temperature in cooling zone of the heat pump. Passing through the channels of the evaporator panel, the cold mixture of liquid and vapor coolant removes heat from the cooling zone. Due to this heat, the remaining liquid part of the refrigerant continues to evaporate, maintaining a consistently low evaporator temperature and ensuring efficient heat removal. After this, the refrigerant in the form of vapor reaches the inlet of the compressor, which pumps it out and compresses it again. Then everything repeats all over again.

Thus, in the “hot” section of the compressor-condenser-throttle, the refrigerant is under high pressure and mainly in a liquid state, and in the “cold” section of the throttle-evaporator-compressor, the pressure is low, and the refrigerant is mainly in a vapor state. Both compression and vacuum are created by the same compressor. On the side of the duct opposite from the compressor, the high and low pressure zones are separated by a throttle that limits the flow of refrigerant.

Powerful industrial refrigerators use toxic but effective ammonia as a refrigerant, powerful turbochargers and sometimes expanders. In household refrigerators and air conditioners, the refrigerant is usually safer freons, and instead of turbo units, piston compressors and “capillary tubes” (chokes) are used.

In the general case, a change in the state of aggregation of the refrigerant is not necessary - the principle will work for a constantly gaseous refrigerant - however, the large heat of change in the state of aggregation greatly increases the efficiency of the operating cycle. But if the refrigerant is in liquid form all the time, there will be no effect fundamentally - after all, the liquid is practically incompressible, and therefore neither increasing nor removing the pressure will change its temperature..

Chokes and expanders

The terms “throttle” and “expander” that are repeatedly used on this page usually mean little to people who are far from refrigeration technology. Therefore, a few words should be said about these devices and the main difference between them.

In technology, a throttle is a device designed to normalize flow by forcefully limiting it. In electrical engineering, this name is assigned to coils designed to limit the rate of current rise and usually used to protect electrical circuits from impulse noise. In hydraulics, throttles are usually called flow limiters, which are specially created narrowings of the channel with a precisely calculated (calibrated) clearance that provides the desired flow or the required flow resistance. A classic example of such chokes are jets, which were widely used in carburetor engines to ensure the calculated flow of gasoline during the preparation of the fuel mixture. The throttle valve in the same carburetors normalized the flow of air - the second necessary ingredient of this mixture.

In refrigeration engineering, a throttle is used to restrict the flow of refrigerant into the expansion chamber and maintain there the conditions necessary for efficient evaporation and adiabatic expansion. Too much flow can generally lead to the expansion chamber being filled with refrigerant (the compressor simply will not have time to pump it out) or, at least, to the loss of the necessary vacuum there. But it is the evaporation of the liquid refrigerant and the adiabatic expansion of its vapor that ensures the drop in the refrigerant temperature below the ambient temperature necessary for the operation of the refrigerator.

Operating principles of a throttle (left), piston expander (center) and turboexpander (left).

In the expander, the expansion chamber is somewhat modernized. In it, the evaporating and expanding refrigerant additionally performs mechanical work, moving the piston located there or rotating the turbine. In this case, the refrigerant flow can be limited due to the resistance of the piston or turbine wheel, although in reality this usually requires very careful selection and coordination of all system parameters. Therefore, when using expanders, the main flow rationing can be carried out by a throttle (calibrated narrowing of the liquid refrigerant supply channel).

A turboexpander is effective only at high flows of the working fluid; at low flows its efficiency is close to conventional throttling. A piston expander can operate effectively with a much lower flow rate of the working fluid, but its design is an order of magnitude more complex than a turbine: in addition to the piston itself with all the necessary guides, seals and return system, inlet and outlet valves with appropriate control are required.

The advantage of an expander over a throttle is more efficient cooling due to the fact that part of the thermal energy of the refrigerant is converted into mechanical work and in this form is removed from the thermal cycle. Moreover, this work can then be put to good use, say, to drive pumps and compressors, as is done in the Zysin refrigerator. But a simple throttle has an absolutely primitive design and does not contain a single moving part, and therefore in terms of reliability, durability, as well as simplicity and cost of production, it leaves the expander far behind. It is these reasons that usually limit the scope of use of expanders to powerful cryogenic equipment, and in household refrigerators less efficient, but practically eternal chokes are used, called “capillary tubes” there and representing a simple copper tube of sufficiently long length with a clearance of small diameter (usually from 0.6 to 2 mm), which provides the necessary hydraulic resistance for the calculated refrigerant flow.

Advantages of compression heat pumps

The main advantage of this type of heat pump is its high efficiency, the highest among modern heat pumps. The ratio of externally supplied and pumped energy can reach 1:3 - that is, for every joule of energy supplied, 3 J of heat will be pumped out from the cooling zone - compare with 0.5 J for Pelte elements! In this case, the compressor can stand separately, and the heat it generates (1 J) does not have to be removed to the external environment in the same place where 3 J of heat is released, pumped out from the cooling zone.

By the way, there is a theory of thermodynamic phenomena that differs from the generally accepted one, but is very interesting and convincing. So, one of its conclusions is that the work of compressing a gas, in principle, can only account for about 30% of its total energy. This means that the ratio of supplied and pumped energy of 1:3 corresponds to the theoretical limit and cannot be improved in principle using thermodynamic methods of heat pumping. However, some manufacturers are already claiming to achieve a ratio of 1:5 and even 1:6, and this is true - after all, in real refrigeration cycles, not only compression of the gaseous refrigerant is used, but also a change in its state of aggregation, and it is the latter process that is the main one.. .

Disadvantages of compression heat pumps

The disadvantages of these heat pumps include, firstly, the very presence of a compressor, which inevitably creates noise and is subject to wear, and secondly, the need to use a special refrigerant and maintain absolute tightness along its entire operating path. However, household compression refrigerators that operate continuously for 20 years or more without any repairs are not at all uncommon. Another feature is a fairly high sensitivity to position in space. On its side or upside down, both the refrigerator and the air conditioner are unlikely to work. But this is due to the characteristics of specific designs, and not to the general principle of operation.

As a rule, compression heat pumps and refrigeration units are designed with the expectation that all refrigerant at the compressor inlet is in a vapor state. Therefore, if a large amount of unevaporated liquid refrigerant enters the compressor inlet, it can cause hydraulic shock and, as a result, serious damage to the unit. The reason for this situation may be either equipment wear or too low a condenser temperature - the refrigerant entering the evaporator is too cold and evaporates too sluggishly. For a regular refrigerator, this situation can arise if you try to turn it on in a very cold room (for example, at a temperature of about 0°C and below) or if it has just been brought into a normal room from the cold. For a compression heat pump operating for heating, this can happen if you try to warm up a frozen room with it, even though it is also cold outside. Not very complex technical solutions eliminate this danger, but they increase the cost of the design, and during the normal operation of mass-produced household appliances there is no need for them - such situations do not arise.

Using compression heat pumps

Due to its high efficiency, this particular type of heat pump has become almost universally widespread, displacing all others into various exotic applications. And even the relative complexity of the design and its sensitivity to damage cannot limit their widespread use - almost every kitchen has a compression refrigerator or freezer, or even more than one!

Evaporative absorption (diffusion) heat pumps

Duty cycle of evaporator absorption heat pumps is very similar to the operating cycle of evaporative compression units discussed just above. The main difference is that if in the previous case the vacuum necessary for evaporation of the refrigerant is created by mechanical suction of vapors by a compressor, then in absorption units the evaporated refrigerant flows from the evaporator into the absorber block, where it is absorbed (absorbed) by another substance - the absorbent. Thus, steam is removed from the volume of the evaporator and the vacuum is restored there, ensuring the evaporation of new portions of the refrigerant. A necessary condition is such an “affinity” between the refrigerant and the absorbent so that their binding forces during absorption can create a significant vacuum in the volume of the evaporator. Historically, the first and still widely used pair of substances is ammonia NH3 (refrigerant) and water (absorbent). When absorbed, ammonia vapor dissolves in water, penetrating (diffusing) into its thickness. From this process came the alternative names of such heat pumps - diffusion or absorption-diffusion.
In order to re-separate the refrigerant (ammonia) and the absorbent (water), the spent ammonia-rich water-ammonia mixture is heated in the desorber by an external source of thermal energy until boiling, then cooled somewhat. Water condenses first, but at high temperatures immediately after condensation, it can hold very little ammonia, so most of the ammonia remains in the form of vapor. Here, the pressurized liquid fraction (water) and gaseous fraction (ammonia) are separated and separately cooled to ambient temperature. Cooled water with a low ammonia content is sent to the absorber, and when cooled in the condenser, the ammonia becomes liquid and enters the evaporator. There, the pressure drops and the ammonia evaporates, again cooling the evaporator and taking heat from outside. Then the ammonia vapor is recombined with water, removing excess ammonia vapor from the evaporator and maintaining a low pressure there. The ammonia-enriched solution is again sent to the desorber for separation. In principle, to desorption of ammonia it is not necessary to boil the solution; it is enough to simply heat it close to the boiling point, and the “excess” ammonia will evaporate from the water. But boiling allows the separation to be carried out most quickly and efficiently. The quality of such separation is the main condition that determines the vacuum in the evaporator, and therefore the efficiency of the absorption unit, and many tricks in the design are aimed precisely at this. As a result, in terms of organization and number of stages of the operating cycle, absorption-diffusion heat pumps are perhaps the most complex of all common types of similar equipment.

The “highlight” of the operating principle is that it uses heating of the working fluid (up to its boiling) to produce cold. In this case, the type of heating source is not important - it can even be an open fire (burner flame), so the use of electricity is not necessary. To create the necessary pressure difference that causes the movement of the working fluid, mechanical pumps can sometimes be used (usually in powerful installations with large volumes of working fluid), and sometimes, in particular in household refrigerators, elements without moving parts (thermosiphons).

Absorption-diffusion refrigeration unit (ADHA) of the Morozko-ZM refrigerator. 1 - heat exchanger; 2 - solution collection; 3 - hydrogen battery; 4 - absorber; 5 - regenerative gas heat exchanger; 6 - reflux condenser (“dehydrator”); 7 - capacitor; 8 - evaporator; 9 - generator; 10 - thermosyphon; 11 - regenerator; 12 - weak solution tubes; 13 - steam pipe; 14 - electric heater; 15 - thermal insulation.

The first absorption refrigeration machines (ABRM) using an ammonia-water mixture appeared in the second half of the 19th century. They were not widely used in everyday life due to the toxicity of ammonia, but were very widely used in industry, providing cooling down to –45°C. In single-stage ABCMs, theoretically, the maximum cooling capacity is equal to the amount of heat spent on heating (in reality, of course, it is noticeably less). It was this fact that reinforced the confidence of the defenders of the very formulation of the second law of thermodynamics, which was discussed at the beginning of this page. However, absorption heat pumps have now overcome this limitation. In the 1950s, more efficient two-stage (two condensers or two absorbers) lithium bromide ABHMs (refrigerant - water, absorbent - lithium bromide LiBr) appeared. Three-stage ABHM variants were patented in 1985-1993. Their prototypes are 30–50% more efficient than two-stage ones and are closer to mass-produced models of compression units.

Advantages of absorption heat pumps

The main advantage of absorption heat pumps is the ability to use not only expensive electricity for their operation, but also any heat source of sufficient temperature and power - superheated or waste steam, the flame of gas, gasoline and any other burners - even exhaust gases and free solar energy.

The second advantage of these units, especially valuable in domestic applications, is the ability to create structures that do not contain moving parts, and therefore are practically silent (in Soviet models of this type, you could sometimes hear a quiet gurgle or a slight hiss, but, of course, this does not suit any How does it compare to the noise of a running compressor?

Finally, in household models, the working fluid (usually a water-ammonia mixture with the addition of hydrogen or helium) in the volumes used does not pose a great danger to others, even in the event of an emergency depressurization of the working part (this is accompanied by a very unpleasant stench, so it is impossible to notice a strong leak is impossible, and the room with the emergency unit will have to be left and ventilated “automatically”; ultra-low concentrations of ammonia are natural and absolutely harmless). In industrial installations, the volume of ammonia is large and the concentration of ammonia during leaks can be lethal, but in any case, ammonia is considered environmentally friendly - it is believed that, unlike freons, it does not destroy the ozone layer and does not cause a greenhouse effect.

Disadvantages of absorption heat pumps

The main disadvantage of this type of heat pumps- lower efficiency compared to compression ones.

The second disadvantage is the complexity of the design of the unit itself and the rather high corrosion load from the working fluid, either requiring the use of expensive and difficult to process corrosion-resistant materials, or reducing the service life of the unit to 5..7 years. As a result, the cost of hardware is noticeably higher than that of compression units of the same performance (primarily this applies to powerful industrial units).

Thirdly, many designs are very critical to placement during installation - in particular, some models of household refrigerators required installation strictly horizontally, and refused to work even if they deviated by a few degrees. The use of forced movement of the working fluid using pumps largely alleviates the severity of this problem, but lifting with a silent thermosiphon and draining by gravity requires very careful alignment of the unit.

Unlike compression machines, absorption machines are not so afraid of too low temperatures - their efficiency is simply reduced. But it’s not for nothing that I placed this paragraph in the disadvantages section, because this does not mean that they can work in severe cold - in the cold, an aqueous solution of ammonia will simply freeze, unlike freons used in compression machines, the freezing point of which is usually below –100°C. True, if the ice does not break anything, then after thawing the absorption unit will continue to operate, even if it has not been disconnected from the network all this time - after all, it does not have mechanical pumps and compressors, and the heating power in household models is low enough for boiling in the area the heater did not become too intense. However, all this depends on the specific design features...

Using absorption heat pumps

Despite the somewhat lower efficiency and relatively higher cost compared to compression units, the use of absorption heat engines is absolutely justified where there is no electricity or where there are large volumes of waste heat (waste steam, hot exhaust or flue gases, etc. - up to presolar heating). In particular, special models of refrigerators powered by gas burners are produced, intended for motorists and yachtsmen.

Currently, in Europe, gas boilers are sometimes replaced by absorption heat pumps heated by a gas burner or diesel fuel - they allow not only to utilize the heat of combustion of fuel, but also to “pump up” additional heat from the street or from the depths of the earth!

As experience shows, options with electric heating are also quite competitive in everyday life, primarily in the low power range - somewhere from 20 to 100 W. Lower powers are the domain of thermoelectric elements, but at higher powers the advantages of compression systems are still undeniable. In particular, among the Soviet and post-Soviet brands of refrigerators of this type, “Morozko”, “Sever”, “Kristall”, “Kiev” were popular with a typical volume of the refrigerating chamber from 30 to 140 liters, although there are also models with 260 liters (“ Crystal-12"). By the way, when assessing energy consumption, it is worth considering the fact that compression refrigerators almost always operate in short-term mode, while absorption refrigerators are usually turned on for a much longer period or generally operate continuously. Therefore, even if the rated power of the heater is much less than the power of the compressor, the ratio of average daily energy consumption may be completely different.

Vortex heat pumps

Vortex heat pumps The Ranque effect is used to separate warm and cold air. The essence of the effect is that gas, tangentially supplied into a pipe at high speed, swirls and separates inside this pipe: cooled gas can be taken from the center of the pipe, and heated gas from the periphery. The same effect, although to a much lesser extent, also applies to liquids.

Advantages of vortex heat pumps

The main advantage of this type of heat pump is its simplicity of design and high performance. The vortex tube does not contain moving parts, and this ensures its high reliability and long service life. Vibration and position in space have virtually no effect on its operation.

A powerful air flow prevents freezing well, and the efficiency of vortex tubes depends little on the temperature of the inlet flow. The practical absence of fundamental temperature restrictions associated with hypothermia, overheating or freezing of the working fluid is also very important.

In some cases, the ability to achieve a record high temperature separation in one stage plays a role: in the literature, cooling figures of 200° or more are given. Typically one stage cools the air by 50..80°C.

Disadvantages of vortex heat pumps

Unfortunately, the efficiency of these devices is currently noticeably inferior to that of evaporative compression units. In addition, for efficient operation they require a high flow rate of the working fluid. Maximum efficiency is observed at an input flow rate equal to 40..50% of the speed of sound - such a flow itself creates a lot of noise, and in addition, requires a productive and powerful compressor - the device is also by no means quiet and rather capricious.

The lack of a generally accepted theory of this phenomenon, suitable for practical engineering use, makes the design of such units a largely empirical exercise, where the result depends heavily on luck: “right or wrong.” More or less reliable results are obtained only by reproducing already created successful samples, and the results of attempts to significantly change certain parameters are not always predictable and sometimes look paradoxical.

Using vortex heat pumps

However, the use of such devices is currently expanding. They are justified primarily where there is already gas under pressure, as well as in various fire and explosion hazardous industries - after all, supplying a flow of air under pressure into a dangerous area is often much safer and cheaper than pulling protected electrical wiring there and installing electric motors in a special design .

Heat pump efficiency limits

Why are heat pumps still not widely used for heating (perhaps the only relatively common class of such devices are air conditioners with inverters)? There are several reasons for this, and in addition to the subjective ones associated with the lack of heating traditions using this technique, there are also objective ones, the main ones being freezing of the heat sink and a relatively narrow temperature range for effective operation.

In vortex (primarily gas) installations, there are usually no problems of overcooling and freezing. They do not use a change in the aggregate state of the working fluid, and a powerful air flow performs the functions of the “No Frost” system. However, their efficiency is much less than that of evaporative heat pumps.

Hypothermia

In evaporative heat pumps, high efficiency is ensured by changing the state of aggregation of the working fluid - the transition from liquid to gas and back. Accordingly, this process is possible in a relatively narrow temperature range. At too high temperatures, the working fluid will always remain gaseous, and at too low temperatures, it will evaporate with great difficulty or even freeze. As a result, when the temperature goes beyond the optimal range, the most energy-efficient phase transition becomes difficult or is completely excluded from the operating cycle, and the efficiency of the compression unit drops significantly, and if the refrigerant remains constantly liquid, it will not work at all.

Freezing

Heat extraction from air

Even if the temperatures of all heat pump units remain within the required range, during operation the heat extraction unit - the evaporator - is always covered with drops of moisture condensing from the surrounding air. But liquid water drains from it on its own, without particularly interfering with heat exchange. When the evaporator temperature becomes too low, the condensate drops freeze, and the newly condensed moisture immediately turns into frost, which remains on the evaporator, gradually forming a thick snow “coat” - this is exactly what happens in the freezer of a regular refrigerator. As a result, the efficiency of heat exchange is significantly reduced, and then it is necessary to stop operation and defrost the evaporator. As a rule, in the refrigerator evaporator the temperature drops by 25..50°C, and in air conditioners, due to their specifics, the temperature difference is smaller - 10..15°C. Knowing this, it becomes clear why most air conditioners cannot be adjusted to a lower temperature +13..+17°С - this threshold is set by their designers to avoid icing of the evaporator, because its defrosting mode is usually not provided. This is also one of the reasons why almost all air conditioners with inverter mode do not work even at not very high negative temperatures - only recently have models began to appear that are designed to operate in temperatures down to -25°C. In most cases, already at –5..–10°C, energy costs for defrosting become comparable to the amount of heat pumped from the street, and pumping heat from the street turns out to be ineffective, especially if the humidity of the outside air is close to 100% - then the external heat sink becomes covered with ice especially fast.

Heat extraction from soil and water

In this regard, heat from the depths of the earth has recently been increasingly considered as a non-freezing source of “cold heat” for heat pumps. This does not mean heated layers of the earth’s crust located many kilometers deep, or even geothermal water sources (although, if you are lucky and they are nearby, it would be foolish to neglect such a gift of fate). This refers to the “ordinary” heat of soil layers located at a depth of 5 to 50 meters. As is known, in the middle zone the soil at such depths has a temperature of about +5°C, which changes very little throughout the year. In more southern areas, this temperature can reach +10°C and higher. Thus, the temperature difference between a comfortable +25°C and the ground around the heat sink is very stable and does not exceed 20°C, regardless of the frost outside (it should be noted that usually the temperature at the outlet of the heat pump is +50..+60°C, but and a temperature difference of 50°C is quite feasible for heat pumps, including modern household refrigerators, which can easily provide –18°C in the freezer at room temperatures above +30°C).

However, if you bury one compact but powerful heat exchanger, it is unlikely that you will be able to achieve the desired effect. Essentially, the heat extractor in this case acts as the evaporator of the freezer, and if there is no powerful heat influx in the place where it is located (geothermal source or underground river), it will quickly freeze the surrounding soil, which will end all heat pumping. The solution may be to extract heat not from one point, but evenly from a large underground volume, however, the cost of building a heat extractor covering thousands of cubic meters of soil at a considerable depth will most likely make this solution absolutely unprofitable economically. A less expensive option is to drill several wells at intervals of several meters from each other, as was done in the experimental “active house” near Moscow, but this is not cheap either - anyone who has made a well for water can independently estimate the costs of creating a geothermal fields of at least a dozen 30-meter wells. In addition, constant heat extraction, although less strong than in the case of a compact heat exchanger, will still reduce the temperature of the soil around the heat extractors compared to the original one. This will lead to a decrease in the efficiency of the heat pump during its long-term operation, and the period of temperature stabilization at a new level may take several years, during which the conditions for heat extraction will deteriorate. However, you can try to partially compensate for winter heat loss by increasing its injection to depth in the summer heat. But even without taking into account the additional energy costs for this procedure, the benefit from it will not be too great - the heat capacity of a ground heat accumulator of reasonable size is quite limited, and it clearly will not be enough for the entire Russian winter, although such a supply of heat is still better than nothing. In addition, the level, volume and flow rate of groundwater are of great importance here - abundantly moistened soil with a sufficiently high water flow rate will not allow making “reserves for the winter” - flowing water will take the pumped heat with it (even a tiny movement of groundwater by 1 meter per day in just a week will carry the stored heat to the side by 7 meters, and it will be outside the working area of ​​the heat exchanger). True, the same flow of groundwater will reduce the degree of cooling of the soil in winter - new portions of water will bring new heat received away from the heat exchanger. Therefore, if there is a deep lake, large pond or river nearby that never freezes to the bottom, then it is better not to dig the soil, but to place a relatively compact heat exchanger in the reservoir - unlike stationary soil, even in a stagnant pond or lake, convection of free water can provide much more efficient heat supply to the heat extractor from a significant volume of the reservoir. But here it is necessary to make sure that the heat exchanger under no circumstances overcools to the freezing point of water and does not begin to freeze ice, since the difference between convection heat transfer in water and the heat transfer of an ice coat is enormous (at the same time, the thermal conductivity of frozen and unfrozen soil is often not so different strongly, and an attempt to use the enormous heat of crystallization of water in ground heat removal under certain conditions can be justified).

Operating principle of a geothermal heat pump is based on collecting heat from soil or water and transferring it to the building’s heating system. To collect heat, an antifreeze liquid flows through a pipe located in the soil or body of water near the building to the heat pump. A heat pump, like a refrigerator, cools a liquid (removes heat), and the liquid is cooled by approximately 5 °C. The liquid again flows through the pipe in the external soil or water, restores its temperature, and again enters the heat pump. The heat collected by the heat pump is transferred to the heating system and/or to heat hot water.

It is possible to extract heat from underground water - underground water with a temperature of about 10 °C is supplied from a well to a heat pump, which cools the water to +1...+2 °C, and returns the water underground. Any object with a temperature above minus two hundred and seventy-three degrees Celsius has thermal energy - the so-called “absolute zero”.

That is, a heat pump can take heat from any object - earth, reservoir, ice, rock, etc. If, for example, in the summer, a building needs to be cooled (conditioned), then the reverse process occurs - heat is taken from the building and dumped into the ground (reservoir). The same heat pump can work for heating in winter and for cooling the building in summer. Obviously, a heat pump can heat water for domestic hot water supply, air condition through fan coil units, heat a swimming pool, cool, for example, an ice skating rink, heat roofs and ice paths...
One piece of equipment can perform all the functions of heating and cooling a building.