Simply explained: How does a heat pump work?
How does a heat pump work and how does it heat?
The functionality of a heat pump can be explained quite simply: it makes the energy from the environment usable for indoor use. It therefore does not consume any fossil energy and is therefore absolutely climate-friendly compared to oil or gas heating systems. In addition, the operating costs for a heat pump heating system are between 30 and 50 percent lower than those of an oil or gas heating system.
The technology behind it is essentially based on the reverse principle of refrigerators. These draw the warm air from its interior and direct it to the outside so that it is nice and cool inside. Heat pumps conduct energy outside the building to the inside. Depending on the model, they make use of the free energy from the outside air, groundwater or the ground.
Regardless of the heat source, a technical principle consisting of four steps runs continuously inside every heat pump system. In this process, a liquid refrigerant is repeatedly evaporated, compressed, liquefied and relaxed. Before that, it absorbs the thermal energy from the environment and makes it usable for the heating system. And this is how the process works in detail:
Vaporize: After the heat from the outside air, the earth or the groundwater has been absorbed into the heat pump circuit, it is transferred to a refrigerant. The agent is responsible for transporting the thermal energy and absorbing it in its liquid state, causing it to evaporate and become gaseous.
Condense: The gaseous refrigerant is compressed to a higher pressure level in the compressor. As a result, the temperature of the gas rises to 60 to 100 degrees.
Liquefy: The compressed, hot refrigerant transfers its energy to the heating system or to the in-house heat storage tank. As a result, it condenses and becomes liquid again.
Relax: The previously built up pressure is reduced again via a valve. As a result, the refrigerant continues to cool down until it reaches its initial temperature. In this state, it flows back into the evaporator, and the process begins again.
Still not vivid enough? In the following video, we have explained again in a very simple way how a heat pump works.
What heat pumps are there and how do they differ?
Brine-to-water heat pump
The so-called geothermal heat pump or brine-water heat pump uses the earth's environmental energy for heating. To do this, the heat pump must be connected to geothermal collectors or geothermal probes, which are buried one to two metres (geothermal collector) or up to 100 metres deep (geothermal probe) in the ground and equipped with supply lines to the heat pump. A geothermal collector thus uses the near-surface heat, while a geothermal probe taps into the deep heat. Which type of development is right for you is decided, among other things, by the available space. For example, a geothermal collector cannot be built over. Since there is a constant temperature below the earth's surface all year round, brine-water heat pumps work particularly efficiently.
Air-to-Water Heat Pump
This model can be installed indoors with a connection to the outside or outdoors directly on the wall of the house. The effort for structural measures can be minimized accordingly. With an air source heat pump, the outside air is sucked in by a fan and passed on to a heat exchanger. However, the air temperature is subject to strong fluctuations. The resulting temperature differences must be compensated for by the heat pump system. This means that the colder the air sucked in, the more the refrigerant has to be heated by electricity. Air source heat pumps therefore work less efficiently than geothermal heat pumps.
Water-to-Water Heat Pump
In this model, the heat contained in the groundwater is used to heat. The advantage is that there are consistently high temperatures in the groundwater all year round. This is why a water heat pump works as efficiently as a geothermal heat pump. On the other hand, the installation of the system is somewhat more complex. For this purpose, two wells with a drilling depth of at least five metres and a distance of at least 15 metres must be built – a suction well that extracts the groundwater and a swallow well that releases the water used.
Did you know? Under certain conditions, heat pumps can even be used as climate-friendly and cost-effective alternatives to air conditioning systems. You can read exactly how this works in our article "Cold instead of hot: Cooling with heat pumps.“
How does a heat pump work in winter?
Heat pumps are adapted to individual heating requirements and heat reliably even at extreme sub-zero temperatures down to -35 degrees. This is because air, water or soil are always warmer than the refrigerants used. If the heat pump cannot cover the heating demand, a heating element automatically kicks in. This is installed in all modern heat pumps and serves as an additional heat generator in an emergency if the heat pump cannot provide the necessary heating power. In view of increasingly mild winters, however, this rarely happens.
However, it can happen that the electricity consumption of air source heat pumps in particular increases slightly in winter. This is because heat pumps require more energy the greater the temperature difference between the energy source and the heating temperature. The ground temperature is also about ten to 13 degrees at -20 degrees air temperature at a depth of two to three meters. In winter, the geothermal heat pump therefore has to use much less energy than an air source heat pump to bring the absorbed heat to room temperature. The same applies to water heat pumps, because the temperature of the groundwater is between eight and twelve degrees all year round.
How to calculate the electricity consumption of a heat pump
Despite their slightly increased electricity consumption in winter, heat pumps still heat very efficiently and economically, because they have a High Efficiency have.
In order to estimate its actual electricity consumption, the individual annual performance factor (COP) of the heat pump is required. This varies depending on the model and design of the pump. In addition, the individual heating requirement of the house plays a role. You can find this on your heating bill, for example.
You can use this formula to determine the electricity consumption of a heat pump:
Example:
Modern heat pumps have an annual performance factor of between 3 and 5, whereby 5 is more efficient than 3. Suppose a heat pump has a COP of 4, the heating capacity is 10 kW, and it is heated for 2000 hours per year.
This results in an energy consumption of 13.7 kWh per day. With an electricity price of 0.40 euros/kWh, this is about 5.50 euros per day. By comparison, an oil heating system consumes an average of 25 litres of heating oil per day. This costs - with a heating oil price of 0.80 euros/litre - about 20 euros per day.
Are there government subsidies for the installation of heat pumps?
The federal government subsidizes the installation of heat pumps. The new Heating Act, officially: Building Energy Act (GEG), regulates that applicants can receive a subsidy of up to 70 percent of the costs from January 2024. Our guide shows all the Funding programmes for energy-efficient renovation at a glance. More details on the Building Energy Act can be found in the article "All about the Heating Act".
source : So funktioniert klimafreundliches Heizen mit einer Wärmepumpe - enercity Magazin