What is the function of a heat pump and how do you choose the proper one?


1. how does a heat pump work?
A heat pump is a heating system that uses thermal energy stored in the environment to heat buildings. However, unlike oil, wood or gas heating systems, heating does not work through combustion, but through a vapor process – as in a refrigerator, the key is to raise thermal energy to a higher level with low temperatures. While in the refrigerator this results in the interior remaining comfortably cool, the process in the heat pump allows environmental heat to be used in the heating system. In the heat pump, a vapor process takes place – thermal energy from air, earth or water is transferred to a coolant via a heat exchanger (the evaporator). The coolant, which is usually gas, evaporates at a lower pressure and temperature as it absorbs heat from the environment. In the second step of the heat pump process, a compressor increases the pressure of the vaporous coolant until its temperature is higher than that of the heating system. Only in this way can the heat also be transferred to the heating medium, usually water or air, via another heat exchanger (the condenser). In the process, the coolant cools down, its pressure drops and the medium condenses. Fully regenerated, the coolant flows back to the evaporator through the expansion valve, which returns the pressure to its initial state, and the heat pump process can begin again.

The heat pump draws in the heat stored in the air, in the water or in the ground and transfers it to the heating system

The heat for heating can be drawn from the groundwater, the soil from the garden through a ground collector, from a geoprobe or from the air. An important ratio in the heat pump is the heating coefficient, which is the ratio of input to output. A higher number here represents a higher efficiency of the heat pump.

2. types of heat pumps
The energy for the heat pump can be obtained from different sources. It depends on where the building is located. The choice is the use of thermal energy from the air, the earth or groundwater.

What advantages of heat pumps would you highlight? When should you choose a heat pump?

The most important advantage is the now very high energy efficiency of modern heat pumps. Continuous development in recent years has led to an incredible increase in COP values and thus to a drastic reduction in operating costs. Further advantages are the flexible installation of the devices, the uncomplicated operation, the fact that no separate technical room is necessary and last but not least, the fact that heat pumps can also be used for cooling! Basically I recommend to everyone who needs a new heating system to include a heat pump in his consideration! Since meanwhile systems were developed, which function also with reorganization building projects with e.g. radiators very well and cost-efficiently! In the new building sector meanwhile no way leads past a heat pump.

How do you know which heat pump is best for your home? Are there any limitations to be aware of?

Due to the abundance of different concepts and construction types of heat pumps, it will probably be best to contact a professional for advice and to find the best and most suitable system. Basically, heat pumps are uncomplicated and easy to install. Only the sound emissions that a heat pump emits are a criterion to which special attention must be paid, as certain sound values must be complied with at the respective location!

2.1 Air-to-water heat pump
The easiest way to obtain environmental energy for the heat pump is from the air. All that is needed is a device for drawing in and blowing out the outside air. If the air-to-water heat pump is installed inside the building, for example, this works via ducts connecting the heater to ventilation grilles in the exterior wall. With a device for outdoor installation, even these ducts are not necessary and the thermal energy of the air can be obtained directly from the environment. The air-to-water heat pump extracts heat from the air and transfers it to the water in the heating system.

One disadvantage of air as an energy source, however, is that it is often only available at temperatures below freezing in winter – the time when heating is most needed. As a result, the heat exchangers through which the cold outside air is passed must always be kept frost-free, and the efficiency of the heat pump decreases. The heating coefficient (efficiency) of the air-water heat pump is 3.4 – 4.

Air-to-water heat pumps

2.2 Brine-water heat pump or ground source heat pump
As in the air, thermal energy is also stored in the earth, which you can use for heating with brine-water heat pumps. This is made possible by pipes inserted into the ground, through which a mixture of water and antifreeze circulates. This liquid extracts heat from the earth and transports it to the heat pump. The pipes can be inserted, for example, in the form of deep boreholes or surface collectors. In the case of probe drilling, the plastic pipes (geoprobes) are installed in boreholes up to 100 meters deep. While each meter can extract a thermal energy of about 50 watts from the ground, to heat a modern building you need about 150 meters of depth, which can be divided among several boreholes.

If probe drilling is not possible for technical or legal reasons, the thermal energy of the earth can also be extracted directly below the surface in the garden. In this case, the pipes are laid at a depth of about 1.50 meters. Each square meter extracts about 25 watts from the ground, so to heat a modern family house you need a total area of about 350 square meters.

Compared to the air, thermal energy from the ground can be obtained at higher temperatures throughout the year. This increases the efficiency of the heat pump and reduces the heating costs incurred. The heating coefficient (efficiency) of the brine-water heat pump is between 4.4 – 5.

Ground collectors -as a rule, about twice as much space is needed for the surface collectors as living space is to be heated.

2.3 Water-to-water heat pump
Thermal energy is also stored in groundwater. Groundwater is the ideal energy source for the heat pump because it has a temperature between 8 and 12 degrees Celsius throughout the year, so there are almost no seasonal energy fluctuations. For the operation of a water-water heat pump, two groundwater wells are required, a production well, which is also called a suction well, and an absorption well.

Groundwater is pumped up through the production well, and thermal energy is extracted from the water in the heat pump. The heating coefficient (efficiency) of the water-water heat pump is between 5.2 and 6.2. The cooled water is then returned to the same groundwater layer through the absorption well. The depth of the production well as well as the absorption well can vary between 4 and 15 meters depending on the level of the groundwater.

Whether a heat pump heating system can be used without further ado with groundwater is decided after a test of the water quality. This is because various chemical ingredients can put a lot of stress on the heat exchanger and limit its function.

The heat pump takes energy for heating from groundwater or surface water

3. save heating costs with a heat pump
The heat pump works on electricity, but consumes three to five times less energy than it produces and uses this surplus for heating. If we compare a heating system with a heat pump with an ordinary oil heating system, the savings are about 2.5 – 4 times higher.

The lower the temperature you heat with, the higher the savings. Heat pumps are particularly suitable for low-temperature heating over large areas such as walls, ceilings or conventional floor heating.

4. which heat pump is best?
If the heat pump operates at a lower capacity than it was originally designed for, the efficiency of the heat pump will also be lower. Therefore, before buying and installing the heat pump, it is essential to determine the energy requirements of the house, the heating system (e.g. radiators or underfloor heating) and the available media (water, earth or air).

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