In technical jargon, the technical use of these three heat sources is called geothermal energy (from the Greek word for earth), aerothermal energy (from the Greek word for air) and hydrothermal energy (from the Greek word for water).

In most cases, the ingenious operating principle of the heat pump comes into action. It raises the temperature of the heat source to the temperatures required for heating and hot water preparation. Just like your fridge at home, it uses a refrigerant that evaporates at sub-zero temperatures. In the heat pump's refrigeration circuit, the vaporous refrigerant is compressed further and heats up in the process. Once it has released its heat energy to your heating system, it is expanded again and the cycle begins anew. The refrigerant propane, which we use in our state-of-the-art Hybrox air/water heat pumps, evaporates at minus 42 degrees Celsius, for example, and liquefies again at 70 degrees Celsius and 26 bar. This makes it ideal for renovating heating systems in old buildings, where higher flow temperatures are usually required. We have described exactly how the heat pump works in more detail in another article.

The heat pump obtains the majority of the required heat energy from the environment. Under ideal conditions, modern heat pumps achieve a ratio of four-fifths environmental energy to one-fifth electrical energy, which is required to operate the compressor. The fact that they work with varying degrees of efficiency is also due to the temperatures of the heat source – we will now leave aside the structural condition of the property, the existing radiators and individual user behavior.

The smaller the temperature difference between the heat source and the flow temperature of your heating system, the less electrical energy the heat pump requires.

Air/water heat pumps and air/air heat pumps are the most common heat pumps. There is a simple reason for this: the energy from the air as a heat source can be tapped without great expense and you do not have to drill or dig on your property. A powerful fan is all you need to direct the outside air to the heat pump. In the commercial sector, larger heat pumps are often also fed with process heat from industrial plants and heat from exhaust air, waste water or room air.

By the way, cold winters with temperatures of minus 20 degrees Celsius are no problem for powerful heat pumps like our Hybrox. They heat your rooms reliably even without switching on the electric immersion heater. It is in the nature of physics that the efficiency of the air/water heat pump deteriorates at extremely low outside temperatures. What about geothermal heat pumps instead?

Scientists estimate that the Earth's core has a temperature of more than 6000 degrees Celsius. And although the earth has been cooling down since its formation, it is still producing heat through the decay of radioactive substances in its interior. By human standards, this heat source is infinite. Good for you if you're thinking of getting a geothermal heat pump.

The further inwards you go, the warmer our planet is. As the uppermost soil is largely heated by the sun, seasonal fluctuations still influence its temperature. From a depth of 15 meters to around 100 meters, the ground temperature in our latitudes is a constant 10 degrees Celsius and then rises by an average of around 3 degrees Celsius per 100 meters depth due to the heat inside the earth.

What do the ground temperatures now mean for the efficiency of your geothermal heat pump? That depends on whether you opt for a horizontal solution with ground collectors or a vertical solution with geothermal probes. Ground collectors are laid close to the surface at a depth of up to one and a half meters. Since, as explained above, the ground temperature fluctuates down to a depth of 15 meters, the temperature of the frost-proof brine that circulates in the collector tubes and transports the heat to the heat pump also drops in winter. This slightly increases the temperature difference and electricity consumption, albeit to a lesser extent than with an air/water heat pump. Ideally, you should use the ground source heat pump in summer to passively cool your rooms, as this allows the ground around the collectors to regenerate.

Geothermal probes, on the other hand, are installed at depths of up to 100 meters in the private sector. No temperature fluctuations and higher ground temperatures mean that your geothermal heat pump works with high efficiency and achieves excellent annual coefficients of performance.

Ground collectors and geothermal probes are the most common heat exchangers for the earth as a heat source. However, there is a whole range of other solutions such as geothermal baskets, spiral probes and trench collectors. Ice storage heaters are becoming increasingly popular. What at first sounds like a contradiction in terms is actually particularly efficient. These heating systems work with a brine/water heat pump and not only use the earth as a heat source, but also the thermal energy from the air and sun via a solar air absorber.

Two wells must be installed to use the heat from the groundwater. The groundwater is pumped up via the extraction well, passes through the heat exchanger of the water/water heat pump and is fed back into the groundwater via the return well.

In our latitudes, the temperature of the groundwater ranges between 5 and 15 degrees Celsius. From a depth of 10 to 15 meters, they hardly fluctuate any more, so a water-to-water heat pump is just as efficient as a geothermal heat pump with geothermal probes. However, you will need a hydrological report and there must be usable surface water near your house.

In addition to groundwater, river water or seawater is also used to operate heat pumps. As a rule, these solutions supply neighborhoods and districts with thermal energy.

The best way to find out which of these heat sources you want to use for your heat pump project, which heat pump is worthwhile for you and whether your property is suitable for ground collectors or geothermal probes is to discuss this with one of our trained specialist partner companies.