What a heat pump is and the principle of its work

What is a heat pump? This is equipment that allows you to efficiently convert electrical energy into heat or cooling. The main feature of a heat pump is that it is able to generate high potential energy in exchange for minimally expended resources.

In doing so, it can perform three functions:

Read below about existing types of heat pumps and how they work.

Classic heat pump design

The design of the heat pump consists of two blocks - outdoor and indoor. In a geothermal heat pump or a water-to-water pump, the function of the outdoor unit is performed by soil and water, respectively.    

Heat pumps operate according to the Carnot cycle: 

Thanks to this principle of heat transfer, the energy conversion efficiency is much higher than the energy spent. At the same time, the savings are obvious – the average energy conversion efficiency for air thermal is 3.5, and for geothermal – 5.

Types of heat pumps

We discussed what a heat pump is. Let’s look at their types, which differ in the source of energy. 

Air-to-air heat pump

Any air conditioner, in fact, is an air-to-air heat pump. What is the difference? On the other hand, the air-to-air heat pump operates at low temperatures, down to -25 °C.

In these heat pumps, you need to consider:

Pump tipe	Advantages	Disadvantages
Air-to-air heat pump	✓  works at a temperature of -25°C, ✓ нdoes not require the design of a heating system, ✓ easy installation, ✓ low cost.	✓ does not provide DHW (hot water supply), only air heating and cooling, ✓ noise from the engine is heard, ✓ does not accumulate warm air.

Pump tipe

• Air-to-air heat pump
  Air-to-air heat pump

Advantages

• Air-to-air heat pump
  ✓  works at a temperature of -25°C,
  ✓ нdoes not require the design of a heating system,
  ✓ easy installation,
  ✓ low cost.

Disadvantages

• Air-to-air heat pump
  ✓ does not provide DHW (hot water supply), only air heating and cooling,
  ✓ noise from the engine is heard,
  ✓ does not accumulate warm air.

Air-to-water heat pump

It is common in Europe, where compact and high-tech houses are built. Such a heat pump uses the heat of external air, heats it by compressing Freon in the compressor and transfers it to water through the condenser. It can cool and heat air, as well as heat water.

When installing an air-to-water heat pump, it is necessary to provide a low-temperature heating system, which implies the maximum coverage area with a water-heated floor and the presence of auxiliary elements - floor convectors, fan coil units and radiators.

For the high efficiency of such a system, it is important to take into account the following factors:

Pump type	Advantages	Disadvantages
Air-to-water heat pump	✓ provides air cooling and heating, as well as water heating, ✓ energy efficiency - energy conversion efficiency is 3.5, ✓ affordable price.	✓ must be used with a backup heat source if the area of the room is more than 190 m2

Pump type

• Air-to-water heat pump
  Air-to-water heat pump

Advantages

• Air-to-water heat pump
  ✓ provides air cooling and heating, as well as water heating,
  ✓ energy efficiency - energy conversion efficiency is 3.5,
  ✓ affordable price.

Disadvantages

• Air-to-water heat pump
  ✓ must be used with a backup heat source if the area of the room is more than 190 m2
  
  
  

Ground-to-water heat pump (geothermal)

The source of energy for a geothermal heat pump is the heat of the earth. The temperature of the soil, regardless of the season, is +14-15 °C at a depth of 70 m; therefore the energy conversion efficiency here is 5 (energy conversion efficiency of the air pump is 3.5). This self-sufficient and highly efficient equipment contributes to a stable and constant heat exchange. In winter, the house is heated by taking cold into the ground, and in summer, the accumulated cold is used for cooling.

Pump type	Advantages	Disadvantages
Ground-to-water	✓ provides air cooling and heating, as well as water heating, ✓ high and stable energy conversion efficiency	✓ high cost ✓ large area required.

Pump type

• Ground-to-water
  Ground-to-water

Advantages

• Ground-to-water
  ✓ provides air cooling and heating, as well as water heating,
  ✓ high and stable energy conversion efficiency

Disadvantages

• Ground-to-water
  ✓ high cost
  ✓ large area required.

In household use, the difference between an air-to-water pump and a geothermal one is in two factors: the energy conversion efficiency and the area of ​​​​application, since an air pump is used up to 250 m2, and a geothermal pump is 250 m2 and above. However, in any type of pump, the weather dependence factor is always taken into account when the heat pump is optimized for certain climatic conditions in a particular area.

What a water-water heat pump is

It is used in the industrial sector, as access to large bodies of water is needed. These heat pumps convert energy by pumping water (rivers, lakes), where the temperature at the bottom of the reservoir is stable all year round. The heat pump device is laid on the bottom of the reservoir and the longer its length, the more powerful the pump. As an example, such a pump can operate in a system with hydroelectric power plants. When the hydroelectric power plant dumps the generated heat into the water, it can be used by distributing it to nearby cities.

Pump type	Advantages	Disadvantages
Water-to-water	✓ provides air cooling and heating, as well as water heating, ✓ high energy conversion efficiency all year round.	✓ costly installation,, ✓ difficult to maintain.

Pump type

• Water-to-water
  Water-to-water

Advantages

• Water-to-water
  ✓ provides air cooling and heating, as well as water heating,
  ✓ high energy conversion efficiency all year round.

Disadvantages

• Water-to-water
  ✓ costly installation,,
  ✓ difficult to maintain.

Spiral collector

Also receives energy from water, suitable for those who have their own reservoir. The heat exchanger is immersed in water and held on special floats. It is important that the collector do not silt up, and the area of the reservoir is sufficient so that it does not freeze in winter.

Pump type	Advantages	Disadvantages
Spiral collector	✓ provides air heating and cooling, as well as water heating ✓ high-energy conversion efficiency.	✓ complexity of installation and maintenance.

Pump type

• Spiral collector
  Spiral collector

Advantages 

• Spiral collector
  ✓ provides air heating and cooling, as well as water heating
  ✓ high-energy conversion efficiency.

Disadvantages

• Spiral collector
  ✓ complexity of installation and maintenance.

Requirements for energy sources

Each alternative energy source has its own characteristics. 

Heat pump air conditioning

Air source heat pumps always operate in active mode, while ground source heat pumps can cool the air in passive mode.

What a heat pump with active cooling is

Active cooling of any heat pump means its actual operation – when the compressor starts and consumes electricity to cool the liquid inside the system to a temperature of + 7 °C. Then, depending on the type of pump, the cooled heat carrier is supplied to the premises through fan coil units or floors and walls. 

Passive cooling

Passive cooling can be implemented with the help of a geothermal heat pump. This is due to the cold that enters the ground under the house in winter. In spring, cold water rises and cools the rooms directly through the fan coils. When the ground temperature begins to rise and reaches above +10°C, then active cooling will begin thanks to a compressor.

How the efficiency of a heat pump for heating is calculated

When calculating efficiency, several factors must be taken into account.

Two main coefficients are also calculated:

According to the Construction Norms & Regulations, in Kyiv and the Kyiv region, heating should be calculated for temperatures up to -22 °C. An air source heat pump can operate independently at temperatures down to -7-10 °C, but it is important to consider the square area and the quality of the building insulation. If the temperature is lower, auxiliary devices are used. Geothermal heat pumps can operate independently at a given temperature and do not require additional energy sources.

Pluses and minuses of heat pumps

Heat pumps do not have significant disadvantages. The efficiency of their use depends on the type of pump that is selected for a particular room. 

The main advantages of heat pumps:

Features of operation of air-to-air and air-to-water heat pumps:

Features of operation of ground-to-water heat pumps:

Features of operation of water-to-water heat pumps:

When to use a heat pump in ukraine

For the last two years, Ukraine has been catching up with Europe in terms of technology. Europeans have been working for decades to abandon expensive gas and switch to new highly efficient equipment. In addition, Europeans receive a 40% subsidy when they switch from a convection boiler to a heat pump. 

Ukrainians have long used cheap gas from Russia as their main source of heat. At the moment, there is no subsidy system, although until 2020, 3000 kilowatt-hours were allocated to the house with a 50% discount and another 50% discount for the night tariff. Perhaps such a system will appear again in the future.

Therefore, heat pumps are important and should always be used in Ukraine. In 2014, there was a push to promote the transition to alternative energy sources. In terms of energy resources, Ukraine is a self-sufficient country, which is now in the phase of abandoning dependence on natural resources and switching to more efficient ways of generating energy - electric boilers or heat pumps..