Functionality of the heat pump simply explained
What is a heat pump? The heat pump is an environmentally friendly heating system that uses efficient technology to harness energy from our environment. If you're looking for an easy-to-understand explanation of heat pump technology, you've come to the right place with our Bosch guide. We'll give you a brief and clear explanation of how a heat pump works and is constructed, the schematic principle of operation that heat pump heating makes use of, and how the different types of heat pumps work.
Table of content
- How does a heat pump heating system work?
- Structure and principle of the heat pump simply explained
- Function of an air-to-water heat pump
- How does a geothermal heat pump work?
- Function of a water-water heat pump
- How does a heat pump work in winter?
- Can a heat pump also cool?
- FAQ on how a heat pump works
How does a heat pump heating system work?
The environment offers inexhaustible sources of energy, which can tap the heating heat pump. Simply explained, heat pumps draw energy from the surrounding air, soil or groundwater and harness the extracted heat for heating and hot water, transporting it to the living spaces. With the help of free environmental energy, the heat pump can easily and efficiently achieve a high level of thermal comfort in the house. Heat pump technology is schematically based on the same principle, although the type of energy source tapped differs.
The operation of a heat pump can be compared to the principle of a refrigerator - with the difference that heat is generated rather than cold. While a refrigerator extracts heat from its interior and dissipates it outside to cool the food, the heat pump conversely extracts heat from the environment outside the house and uses it to heat your living spaces.
Structure and principle of the heat pump simply explained
The structure of a heat pump is composed of three components with which the heat pump system works:
- The heat source (air, earth, groundwater), from which the energy is extracted from the environment.
- The heat pump, which utilizes the extracted environmental heat by means of heat pump technology.
- The heat distribution and storage system, which distributes or stores the heat in the living spaces.
But what exactly does a heat pump do to convert the environmental heat into usable heating energy? Inside the heat pump, a technical principle consisting of four steps runs continuously in a closed loop process. In the repeating heat pump cycle, the evaporation, compression, liquefaction and expansion of a refrigerant takes place to generate heating energy. The liquid refrigerant absorbs thermal energy from the environment and must be raised to a temperature level that is usable by the heating system. This is done using some electricity. The higher the temperature difference between the energy source and the required useful heat, the more electrical drive power must be applied.
Let's take a closer look at the heat pump principle:
- evaporation: at the so-called evaporator, the heat from the environment is transferred to the heat pump circuit. A refrigerant is responsible for absorbing and transporting the heat energy. It absorbs the environmental heat in a liquid state, causing it to evaporate and become gaseous.
- compression: In a current-driven compressor, called a compressor, the gaseous refrigerant is compressed, greatly increasing pressure and temperature. You can also observe this part of the operating principle of a heat pump in a bicycle air pump, which heats up when you pump up air. Hence the term "pumping" in connection with a heat pump.
- liquefy: In the third step, the compressed, heated refrigerant transfers its heat to the heating circuit, thereby cooling and becoming liquid again. This happens at the so-called condenser or condenser with the help of a heat exchanger. The heat is then stored in the heat pump's hot water and buffer tank.
- depressurization: In the final step, the pressure of the liquid refrigerant is reduced again in an expansion or flash valve, causing it to cool further until it reaches its initial temperature. The heat pump cycle can begin again. You may have noticed that liquids cool when they are pressurized and the pressure is reduced in the case of spray cans. The can becomes noticeably cold when you spray for a longer period of time.
In the following, we consider the function of the types of heat pumps, which differ by the tapped heat source.
Function of an air-to-water heat pump
In an air-to-water heat pump, the thermal energy of the outside air serves as a heat source. It can be easily tapped by simply setting up the device and thus requires little construction effort. The operation of the air-to-water heat pump follows the same scheme as all types of heat pumps, in that a refrigerant absorbs the environmental heat. In an air-to-water heat pump, the ambient air is drawn in by a fan, passed on to a heat exchanger and converted into heating energy in the heat pump circuit via the evaporation, compression, condensation and expansion of a refrigerant. A decisive factor in this process is the temperature of the energy source. The air temperature is not constant, but changes with the season. This creates temperature differences that the heat pump system must compensate for. The colder the outside air drawn in, the more the temperature in the refrigerant circuit must be raised so that the energy can be used for heating and hot water production.
Good to know: Domestic hot water heat pumps also use the air as a heat source, but not the outside air, but the warm room air already present in the building. With the waste heat from technical systems, it is possible to provide hot water in the house. This is why it is also called a hot water heat pump. Heating with a domestic hot water heat pump does not work. The same applies to air-to-air heat pumps, which use the exhaust air from indoor spaces to recover heat for ventilation systems in high-efficiency new buildings.
How does a geothermal heat pump work?
The functioning of a geothermal heat pump is based on the principle of geothermal energy. This refers to the thermal energy stored in the ground. The brine-to-water heat pump uses thermal energy from the ground as a heat source. The function of a brine-to-water heat pump is made possible by ground probes or ground collectors, which extract heat from the subsoil and convert it in the heat pump cycle into usable energy for heating and hot water preparation. To tap the geothermal energy, earthworks or deep drilling are necessary. Depending on how deep the borehole is, near-surface heat or deep heat can be tapped. The temperature of the heat source is crucial for the efficiency and function of a heat pump. In the ground, there is a relatively constant ground temperature throughout the year. As a result, the geothermal heat pump works particularly efficiently.
Function of a water-water heat pump
A water-water heat pump uses thermal energy from groundwater as a heat source. To function, the so-called groundwater heat pump requires two wells: A suction well, which extracts the groundwater, and an absorption well, which releases the used water back into the ground. The operation of the water-to-water heat pump, as in all types of heat pumps, is based on a closed refrigerant circuit. In this case, the refrigerant absorbs the thermal energy of the groundwater and makes it usable for space heating in the heat pump cycle. Groundwater has constantly high temperatures. Therefore, the water-to-water heat pump is considered the most efficient heat pump.
How does a heat pump work in winter?
Despite lower outdoor temperatures, a heat pump works reliably even in winter, because constant temperatures prevail in the ground and groundwater, regardless of the season. Even with outdoor temperatures in the air below 0 °C, the function of the heat pump in winter is possible and economical due to its high efficiency. If extreme sub-zero temperatures of up to -20 °C occur, an electric heater is temporarily switched on as a backup. In this way, the heat pump can still supply sufficient heat even at very low outside temperatures without losing efficiency. Alternatively, a heat pump can also be operated as a hybrid system in combination with a gas boiler, which takes over the peak load in winter.
Are you basically looking for tips on how to reduce your heating costs? Whether you live in a rented apartment or in your own home, our guide to economical heating will tell you how you can easily reduce your heating costs and save additional energy.
Can a heat pump also cool?
The genius of a heat pump is that it is the only heating system that can both heat and cool in its function. In this way, you can make good use of your heat pump all year round and eliminate the need for additional air conditioning in your home. You can cool your rooms in the summer with a heat pump if the unit has a reversible heat pump function and is planned accordingly from the beginning. With many models, a cooling function can also be retrofitted. The important thing here is that the heating system must be optimally matched to the heat pump air conditioner. Wall or floor heating systems are best suited for cooling with a heat pump.
Cooling with a heat pump works in the same way as heat generation, only via a reverse refrigerant circuit. In this process, the heat from the heating system is dissipated to the outside, which cools the heating system. However, the cooling effect of a reversible heat pump is not as strong as that of an air conditioner.
Infobox
Good to know: Does a heat pump also work with normal radiators? Find out more in our guide to heat pump radiators.
FAQ on how a heat pump works
What is a heat pump?
How does a heat pump work simply explained?
What does a heat pump look like?
How does a heat pump for the house work?
How does an air source heat pump work in winter?