01 June 2012
Heat pumps represent an important technology for district heating and cooling systems, since they utilize renewable heat sources/sinks and so reduce primary energy consumption and greenhouse gas emissions in comparison with boiler systems. Current state-of-the-art technology has a maximum outlet water temperature of 90 °C, which means that heat pumps are applicable even in high-temperature systems. The most promising and environmentally benign
working fluids for the future are ammonia (R717) and HFO1234ze, which will replace R134a. Carbon dioxide (CO2) is also an interesting option in district heating systems with low return temperature.