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Air source and Geothermal Heat Pumps: What are they?


The industry is rapidly changing towards greener and cleaner energy sources for both residential and commercial properties. There is a great understanding that heat pump technology is the way forward and they are right. Here I explain a a little on the two main types which people question the most. Air-source heat pumps and Geothermal heat pumps.


Air source heat pump

One way to use the suns energy is to use air heat pumps. The energy of the sun is stored not only in the ground, but also in the ambient air. In the case of air heat pumps, the outside air is therefore sucked in by means of a fan and processed by means of a heat pump for heating purposes or for hot water. 

The major advantage of air heat pumps is that they can be installed independently of mining and water licensing procedures. In addition, air is a freely available medium of energy and an air source heat pump can be installed practically anywhere outdoors and sometimes even indoors. The simple installation also makes air-heat pumps the most cost-effective option among heat pumps. In addition, the space requirement is low. Only about 1 cubic meter of space is needed for the technology, which can be set up in the open air in the absence of space.

Different types of air-to-air 

There are two different types of air heat pumps available. Both versions of the air heat pump work on the same principle. Both the air-to-air heat pump and the air-to-water heat pump extract heat from the surrounding air. In contrast to the air-water heat pump, the air-to-air heat pump has a refrigerant circuit inside the house which the heated air is delivered via a ventilation system or wall unit. Air-to-air heat pumps therefore are most efficient in airtight buildings and certified passive house.

Efficiency and conclusion

As a rule, an air heat pump covers the heat demand even in frosty outside temperatures. In order to achieve the greatest possible economic efficiency, the annual outdoor temperatures at the place of use should be taken into account in the system design.


Geothermal Heat Pump

The operation of a geothermal heat pump is easily explained. The soil stores the energy that hits the earth from the sun. This can be direct sunlight or the heat absorbed by air or rain. Below the ground past 4 metres, temperatures are relatively constant between 7 and 12 degrees throughout the year. Depending on location, soil type and water content,. This geothermal heat is sufficient to make them usable by evaporation and condensation for heating.

Function of the geothermal heat pump

A geothermal heat pump works the other way around like a fridge. The refrigerator is cooled inside and heated outside, in the geothermal heat pump, the condenser is therefore not used for cooling, but for heating. The geothermal heat pump is operated via supplied electrical energy and brings the "pre-warmed" working medium in the ground to a higher, usable temperature for heating purposes. The working medium is usually an environmentally friendly agent such as propane or ammonia. To bring the gaseous medium to a higher temperature level, it is compressed by means of a compressor so that it heats up and can deliver this heat to the heating circuit. Subsequently, the working fluid is liquefied by condensation again. In the evaporator, the energy of the heat source then ensures that


For the use of a geothermal heat pump two different variants come into question. One way is the heat can be taken from the soil required by geothermal collectors or by geothermal probes . Each system has its advantages and disadvantages, which must be carefully weighed according to circumstances and claims. Geothermal probes are much more expensive to purchase than geothermal collectors, but due to the 40 to 99 meter deep holes, they achieve constant output all year round. In addition, the use of land is not affected. In the case of ground collectors, heating coils are laid about 20 cm below the frost limit in the ground around 1.5m, whereby the size of the installed collectors depends significantly on the storage capacity of the soil and the heat requirement of the house.


Ground Water Heat Pump

A ground source heat pump or water-to-water heat pump uses the heat contained in the ground or a water source to heat it. Since the ground and water has a consistent temperature over the course of the year, it is ideally suited as both a heat source and a cooling source.


In a water-to-water heat pump, a so-called production well is first drilled. The depth of the hole depends on the height of the groundwater level and the heating capacity required. From this well, the groundwater is pumped up and through pipes to the actual heat pump directed. Here, the groundwater is extracted from the heat via a refrigerant, which has a very low boiling point. The refrigerant is compressed and passed in gaseous form to a heat exchanger. In the heat exchanger, the heat is in turn passed on to the heating water. The groundwater is on average by the heat extraction by about five degrees colder. The cold groundwater is then returned via pipes to the second well. Water protection regulations normally require that it be pumped to the same depth from which it was taken. Significantly, the second well is called the Swallow Well and takes in the chilled water.

Requirements and planning

When using the groundwater as a heat source, the legal regulations of the water protection must be strictly observed. A permit must always be obtained. When planning the system, a minimum distance between the two wells of approximately ten to fifteen meters must be planned. The wells should not be drilled much deeper than fifteen feet. Otherwise, the pumps need too much energy. In addition, the groundwater must have a certain quality. If the groundwater at the planned location contains too much manganese or iron, the heat pump can not be operated. It would come to the so-called oozing, in which deposit oxides in the two wells. Also, the heat exchanger could not work properly due to the deposits.

Advantages and disadvantages

The cost of a water-water heat pump is relatively large. The two well bores cause comparatively high costs. In addition, an additional pump for the groundwater is necessary. The power consumption of this pump can degrade the efficiency of the entire system. On the other hand, water-water heat pumps need comparatively little space on the property. Also, the economy is high at a high groundwater temperature. Furthermore, water-water heat pumps can be well designed and accurately calculated due to the constant temperature of the groundwater. Another big advantage is the possibility to use the heat pump for cooling in the summer. In addition, heat pump systems that use groundwater are ideal for so-called passive operation.

Conclusion of water to water

Water-water heat pumps use groundwater as a heat source. The conditions for installation and operation are relatively complex. In addition to the permission of the authorities, the groundwater level and water quality must be right. Due to the constant groundwater temperature, they achieve excellent efficiencies year-round. Another advantage is the year-round usability, so also for cooling in the summer


Hopefully you enjoyed reading and have a more understanding of the different types of heat pumps available to you.

If you wish to learn more or get some friendly expert advice please get in touch now



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