Heat Pumps

Heat pumps provide heating, cooling and sanitary hot water for residential, commercial and industrial applications.

They convert ambient energy from air (aerothermal), ground (geothermal) and water (hydrothermal) but also excess heat from buildings and processes to useful heat. This conversion is done via the refrigerant cycle, which is also used in refrigerators and air conditioning systems. Heat pump technology is efficient and mature. Typical capacities range from 2-20kW for single family buildings, up to 100kW for multi-dwelling residential applications and even higher capacities for commercial applications. Industrial and district heating heat pumps reach capacities of several MW. Operating the unit when surplus electricity is available and storing that surplus energy in the form of heat provides significant demand response capacity to the electric system and enables the integration of a larger share of renewable electricity.

Heat pumps always provide heating and cooling at the same time. In the heating mode, outdoor ambient energy is the heat source and the building/process is the heat sink. In the cooling mode, the building/process is cooled down using the outside as heat sink. Highest efficiency is reached when heating and cooling is needed at the same time.

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A heat pump system consists of a heat source, the heat pump unit and a system to distribute heating and cooling. Among several possible concepts, the electric compression cycle is most common. The heat pump works as follows: (1) a transfer fluid (refrigerant) is exposed to the energy source, where it evaporates and thus cools the source. Using a compressor (2), the refrigerant vapour is compressed and its temperature increased. In the next step (3), the high temperature – high pressure vapour – is fed into a heat exchanger where the energy is transferred to a distribution system. The vapour cools down and condenses. After the pressure is released in an expansion valve (4), the liquid is exposed to the heat source again and the cycle is closed.