Esbjerg, Denmark
The utility company DinForsyning in Esbjerg, Denmark is currently building the largest seawater heat pump in Denmark and the largest CO2 heat pump worldwide (status February 2023). It has a nominal capacity of 70 MW heat and can deliver district heating at forward temperatures of 60 °C to 90 °C at return temperatures of around 35 °C. The plant consists of two identical CO2 heat pumps in parallel. The heat pumps use a single-stage, transcritical cycle. The compressor is a turbo compressor including an expansion unit and is equipped with a variable speed drive. The evaporator is a shell-and-plate heat exchanger. The heat pump further includes a low-pressure receiver. The heat source is seawater from the North Sea that is taken in from 600 m off the coast and reinjected at 1.5 km off the coast. The nominal seawater intake is 14000 m3/h.
The heat pump is designed to operate flexibly, i.e. it is expected to be able to ramp from minimum load to maximum load and from (hot) stand-by to full load in less than 30 seconds. The heat pump is part of the project “Fremtidens fjernvarme” (District heating of the future) of DinForsyning that further includes biomass-fired boilers, electric boilers, a large-scale battery and natural gas boilers. It will be possible to deliver frequency regulation (including primary reserve) from the heat pump alone or in combination with the other assets in the system.