Home News Aalborg CSP gets new order for a wastewater heat pump.

Aalborg CSP gets new order for a wastewater heat pump.

by Linda Bertelsen

The North Jutland specialist in renewable energy, Aalborg CSP, received before the summer holidays an order for the turnkey contract of a 2.5 MW heat pump for wastewater from E.ON for their heat production in Frederikssund.

With the establishment of the new heat pump at the Novafos wastewater plant, E.ON will be able to optimize its green district heating supply in Frederikssund. With the utilization of energy from the wastewater, the citizens of Frederikssund will already be able to boast even more climate-friendly district heating from 2023.

Heat pumps are gaining ground in the Danish district heating plants. They are now considered to be an essential piece in the ongoing green transition. The order to E.ON consists of an entire engineering company for a heat pump with an associated exchanger, pipes, and purification system. It intends to take the energy out of the purified soil water before it is discharged into Roskilde Fjord.

Specially designed heat pump with high COP

With the establishment of the wastewater heat pump, E.ON joins an increasing number of Danish utility companies that integrate heat pumps into their district heating production. The heat pump, which uses ammonia as a coolant, will have a maximum performance of approx—2,500 kW. The heat pump is specially designed for E.ON Frederikssund to ensure a high COP (Coefficient Of Performance). The tailormade design guarantees that the consumers get the most kWh of district heating possible from the power supplied to the heat pump.

The wastewater temperature varies throughout the year, and the plan with the heat pump in Frederikssund is to extract approx. 7° C from the wastewater. The heat pump raises the temperature to around 70° C, depending on the current season. It is subsequently sent directly into the district heating pipes in Frederikssund.

Sustainable but complex and flexible technology

As a starting point, recycling the energy in wastewater must be considered a pure “win/win” situation. In part, it is good for the aquatic environment to lower the outlet temperature of the treated wastewater. This way, it is closer to the temperature of the aquatic environment into which it is discharged. It is also favorable for district heating consumers, as the relatively high temperature in wastewater ensures a more stable energy supply. In addition to the climatic advantages that the new heat pump solution provides, the solution is also future-proof and designed flexibly. This means it will be possible to use outside air as an energy source should the treatment plant be shut down in the future in connection with changes in the wastewater plan.

Well-thought-out flexible quality solution

Using wastewater as an energy source is not a new technology. Still, it is also not a problem-free technology either. Aalborg CSP has therefore prepared thorough studies of the area so that all known challenges have been considered in the final facility for E.ON Frederikssund. The used wastewater filters, automatic cleaning of exchangers and special exchangers, and more are all of very high quality so that they can withstand the wastewater. This well-thought-out flexible quality solution was one of the main reasons Aalborg CSP was awarded the order.


  • Customer: E.ON
  • The capacity of the heat pump system: 2.5 MW
  • System supplier: Aalborg CSP A/S in collaboration with Nature and Frontmatec
  • Scope of delivery: Complete engineering contract for the heat pump
  • Location: Frederikssund
  • Max. temperature: 75º C
  • Heat pump type: Specially designed heat pump from Sabro
  • The expected lifetime of the heat pump: 25 years

Press release from Aalborg CSP