How heat pumps work

Efficient heating is that simple

As an environmentally friendly heating and cooling solution, heat pumps help to reduce heating costs and climate-damaging CO2 emissions - and thus minimise the ecological footprint. The principle behind the heating technology is as simple as it is efficient: it is "environmental heat becomes heating heat". But how exactly does a heat pump work?

At a glance

Heat pumps as an environmentally friendly heating and cooling solution: they reduce CO₂ emissions and heating costs by utilising energy from the environment.
Operating principle: Environmental energy (air, earth, water) + small quantity of electricity = heat. With 20 % electrical energy and 80 % environmental energy, 100 % heating capacity is generated.
COP value as a measure of efficiency: Indicates the ratio of electrical power input to heat output. The higher, the more efficient.
How the heat pump works: heat absorption (air, earth, water), compression by compressing the refrigerant and heat dissipation to the heating system.
Refrigerant circuit: Refrigerant evaporates, is compressed and releases heat, then liquefies again.
Flexible use: Provides sufficient heat on cold days and can also cool in summer; operating modes such as monovalent, bivalent, monoenergetic and modulating are possible.

The principle of the heat pump: energy from the environment + electricity = heat

Free energy sources are available right on our doorstep: Heat is stored in the ground, in the air or in groundwater. The principle of the heat pump is based on this, as it utilises this environmental energy for heating your own four walls or for hot water production.

The heat pump uses electricity to convert this energy into heating energy - but only a very small quantity, as a simplified calculation shows: With 20 per cent electrical "auxiliary energy" and 80 per cent free energy from the environment, efficient heat pumps, such as the new x-change dynamic pro models, generate 100 per cent heating energy.

The COP value tells you more about the ratio of electrical power consumed to heat output. The higher the value, the more efficient the heat pump.

How does a heat pump work?

The way a heat pump works is easy to explain: Figuratively speaking, a heat pump works like a household appliance that has been around for a lengthy time, the refrigerator - only in reverse:

A refrigerator extracts heat from its contents and releases it to the outside at the back of the appliance.
A heat pump absorbs energy from the outside and releases it into the rooms.

How the heat pump works in three steps

Step 1: Heat absorption

Air heat pump function: It uses an integrated fan to draw in ambient air in order to extract heat from it. Air-to-water heat pumps can be installed outdoors or in the boiler room.
Ground source heat pump function: This extracts heat from the ground. To do this, a heat transfer fluid, known as brine, circulates in geothermal probes or geothermal collectors laid over a large area in the ground and absorbs the geothermal heat.
Groundwater heat pump function: It pumps groundwater with a suction well, extracts energy from it and returns it via an absorption well.

Step 2: Heat compression

In the heat pump unit, the energy generated is transferred to an environmentally friendly refrigerant such as propane (R290) in a separate circuit. This vaporises. The subsequent compression of the vapour raises the temperature of the refrigerant to a level that can be used for the heating system.

Step 3: Heat distribution

The energy of the refrigerant is transferred to the heating system via a heat exchanger.
There, the heat can either be stored temporarily in a heat storage unit until it is needed. Or the heat is manifolded directly into the rooms. This is done via heated water that flows through radiators or underfloor heating.

Refrigerant circuit: What happens in the heat pump?

The actual functioning of heat pumps is based on a refrigerant cycle that takes place within the heat pump. What happens in detail?

The thermal energy meets an environmentally friendly refrigerant. The heating causes it to vaporise and expand.
The vaporised refrigerant is then compressed under pressure in the compressor. This increases the temperature.
The hot vapour transfers its heat to the heating system via a heat exchanger. The refrigerant cools down and liquefies again.
Finally, the liquid refrigerant flows through an expansion valve, which lowers the pressure and cools it down further.

Now the process can start all over again.

Extra tip: Cooling with a heat pump

Incidentally, the principle of the heat pump can also be reversed. In this case, operation is reversed - and the heat pump works like a refrigerator. Instead of bringing heat into the rooms, it extracts heat from them to keep the inside of the house pleasantly cool.

Thanks to this active cooling function - integrated as standard in the x-change dynamic pro heat pumps - you benefit from cosy temperatures at any time of year and can save yourself the additional investment in an air conditioning system.

Does the heat pump principle also work in winter?

Relatively constant temperatures prevail in the soil and groundwater. Depending on the depth, they are around 10 degrees Celsius in both winter and summer. When utilising these energy sources, the heat pump works efficiently at any time of year.

Air source heat pumps, on the other hand, are dependent on the outside temperature. However, the heat pump principle also works when temperatures are below zero. The vaporised refrigerant then only needs to be compressed more in order to reach the required temperature level.

Different operating modes

Technical terms of the heat pump function simply explained

Monovalent heat pump: The heat pump acts as the only heat source. This is easiest to realise in low energy houses or in new buildings that have very good thermal insulation.
Bivalent operation: The heat pump is supported by another heat generator. For example, the heat pump heating system can be relieved by combining it with a solar thermal system to generate hot water.
Monoenergetic operation: On very cold days, the electric heat pump is supported by an additional electric heater - usually a heating rod.
Modulating heat pump: The heat pump only runs at full speed when it is absolutely necessary - and this is usually only a few days a year. This means it works particularly efficiently.

FAQ

How does a heat pump work, simply explained?

A heat pump absorbs free environmental energy from the surroundings. In a refrigerant circuit, the temperature is increased by compression and then transferred to the heating system.

How well does a heat pump work in cold winters?

The heat pump principle consisting of heat absorption, heat compression, heat transfer and expansion also works in cold winters and provides sufficient heat in the rooms. However, the more the absorbed environmental energy has to be increased, the more the refrigerant in the heat pump has to be compressed. This increases electricity consumption somewhat. However, this is usually only the case on a few days a year when temperatures fall well below 0 degrees.

Does a heat pump work as air conditioning and heating?

A heat pump is first and foremost an environmentally friendly heating solution. But it can also be used to cool the building comfortably in summer. It extracts heat from the rooms and dissipates it to the outside. This effectively lowers the temperature inside the house. Compared to an air conditioning system, there is no draught.

At what temperature does an air source heat pump work?

Air source heat pumps generally work at all temperatures, but their efficiency decreases as the outside air temperature falls. The outdoor temperatures at which a heat pump works efficiently can be recognised by the addition of the COP value: COP 4.96 (A2/W35) means, for example, that at an outside temperature of 2 degrees and a flow temperature of 35 degrees, a very high coefficient of performance of 4.96 is achieved. This means that 4.96 kW of heating energy is generated with one kW of electricity

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