What types of heat pumps are there?
This question is probably asked by all heat pump newcomers who are switching their heating and hot water preparation to environmentally friendly energy. In this comparison, you will find out what types of heat pumps there are, which heat source they each use and what special advantages they offer you in terms of criteria such as efficiency, investment costs, space, payback period and efficiency.
What heat source does a heat pump use?
Every heat pump – we will limit ourselves to compression heat pumps in this article – works according to the same functional principle. It extracts heat energy from its environment, “pumps” it to a higher temperature level and then transfers it to the heating system. A rule of thumb says that the heat pump requires 75 percent ambient heat and 25 percent electricity to generate heat energy.
The main difference lies in the heat medium. Nature stores the free energy of the sun in the air, in the ground and in water – and it is precisely from these regenerative heat sources that the three most common types of air/water heat pump, water/water heat pump and brine/water heat pump are fed. For the sake of completeness, it should be mentioned that other heat sources such as waste water, exhaust air and solar ice storage are used in practice.
The air/water heat pump

How an air/water heat pump works
This heat pump uses the thermal energy stored in the ambient air to operate your heating system. The air is sucked in by a fan, pulled or pushed and blown past the evaporator pipe system in which the refrigerant circulates. The refrigerant cycle begins. By reversing the process, i.e. your heat pump emits the warm room air outside, you can also use a high-quality, reversible heat pump for cooling. In this way, the indoor temperature can be lowered to pleasant values of around 20 degrees Celsius and below, saving you expensive purchase and operating costs for an air conditioning system. The only downside is that you need a panel heating system, such as underfloor heating, to distribute large quantities of cool air throughout the house. By using/replacing fan convectors, cooling (temperature control) is also possible with conventional ones.
Depending on the installation location, a distinction is made between two models: monobloc appliances, in which the refrigerant circuit is located in one unit – either for indoor or outdoor installation - and split heat pumps with two separate units. The unit with the fan, evaporator, compressor and expansion valve is located outside. The unit with the condenser, which transfers the energy to the heating circuit or the buffer cylinder, and the heat pump control unit are located indoors in the boiler room or utility room. Each variant has its advantages:
Advantages of indoor installation: no pipes required for electricity, refrigerant, water and data transfer, no heat loss due to transport of heating water from outside to inside
Advantages of outdoor installation: less space required in the house, always sufficient air flow, no wall openings required for the air ducts
Advantages of split heat pumps: High flexibility in installation, heat is transferred to the heating system internally, so no insulated pipes are required to transport the heating water from the outside to the inside
Good air/water heat pumps should have an annual coefficient of performance of at least 3 and therefore an efficiency of more than 300 percent. (Explanation: The seasonal performance factor of a heat pump indicates the ratio between the amount of heat generated and the amount of electricity required per year).
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The brine/water heat pump

A brine/water heat pump extracts thermal energy from the ground using ground collectors or geothermal probes
A brine/water heat pump, also known as a geothermal heat pump, uses geothermal energy to operate your heating system and can even be used for passive cooling on hot days. The thermal energy is transported to the evaporator via the brine, a mixture of water, salt and antifreeze. The brine circulates either in coiled pipes of ground or ring collectors laid close to the surface or in u-tubes within vertical geothermal probes laid up to 100 m deep.
As the geothermal heat remains almost constant throughout the year, meaning that the heat pump does not have to compensate for major temperature differences even in freezing cold weather, brine/water heat pumps score highly in terms of efficiency compared to air/water heat pumps.
This means you need less electricity and can make considerable savings on running costs. The higher investment costs are a disadvantage. This is because complex earthworks or drilling are required to lay a geothermal probe and ground collectors require a lot of unsealed surface area.
Our tip: Are you planning an energy-efficient renovation of your old or existing building and want to retrofit a heat pump? Let us advise you on ring trench collectors! The pipes in which the brine circulates are laid horizontally or vertically in a trench around your property. This means that less land needs to be dug up and in certain cases you can do the work yourself.
Brine/water heat pumps with ring trench collectors are cheaper than you think and the investment costs for the appliance alone are in the range of high-quality air/water heat pumps. If you consider the costs over the entire service life of your heat pump, you can even save a lot of money on the bottom line due to the lower electricity requirements! Of course, these ground collectors are also a smart idea for new buildings.
The water/water heat pump

The water/water heat pump works with two wells to utilize the heat of the groundwater for heating and cooling. Groundwater is pumped upwards via an extraction well and passes through the heat exchanger, after which the cooled water is fed back into the groundwater via the return well.
Groundwater temperatures in our latitudes are between 5 and 15 °C. As they practically no longer fluctuate from depths of 10 to 15 meters, a water/water heat pump is extremely efficient. However, a few things have to come together before installation. For example, you need a hydrological report, your house must be located in the immediate vicinity of usable surface water and the water temperature must not fall below 7 °C.
Our conclusion
A heat pump is THE environmentally friendly, efficient heating system of the future, as it uses the free heat sources of ambient air, geothermal energy or groundwater. If you generate the electricity to run your heat pump with your own photovoltaic system, you are well on the way to climate-neutral heating. Whether in a detached house, new build, old building, existing building or apartment building, you are sure to find the right heat pump for you from the various types available!