The heat pump extracts heat from sea water by raising the temperature of an ammonia refrigerant via a heat exchanger. The now gaseous ammonia is then compressed by a motor driven compressor, raising the temperature of the ammonia to around 90˚C.

The heat from the ammonia is then transferred via another heat exchanger to the hot water supply system. Six ABB 11kV motors were selected to drive the ammonia compressors, three of 660kW and three of 1250kW.