Aalborg CSP was selected as turnkey supplier of a 2.5MW electrical wastewater heat pump system for E.ON Denmark. With the new heat pump, E.ON Denmark will be able to further optimize their green district heating supply in Frederikssund by utilizing the energy from wastewater for more climate-friendly district heating with a high efficiency.


Client:       E.ON Denmark
Location:    Frederikssund
Status:    Under construction
Technology:    Heat pump system
Capacity:    2.5MW
Contract type:    EPC

Custom made heat pump with high COP

The heat pump, which applies the natural refrigerant ammonia, will have a maximum output of approx. 2,500 KW. It is custom made for E.ON Frederikssund to ensure a high COP (Coefficient Of Performance). This, in order to guarantee that the consumers obtain as high an amount of kWh district heating as possible from the kWh of electricity supplied to the heat pump.

The heat pump is to extract approx. 7 °C from the wastewater. By means of the heat pump, the temperature is increased to approx. 70 °C depending on the season in question, after which it is supplied directly through the district heating pipes in Frederikssund. 

Sustainable and flexible system

The relatively high temperature of wastewater ensures a more stable and sustainable energy supply. The solution is furthermore designed flexibly in a manner which allows for changes in the heat source, thereby giving certainty to the bankability of the long-term investment. A possible switch of heat source can allow the plant to utilize the outdoor air as an energy source if the treatment plant were to be closed down in connection with potential future changes in the wastewater plan.


  • Design and delivery of heat pump system
  • Design and delivery of pipping (valves, drain, headers etc.) 
  • Design and delivery of civil works
  • Mechanical and electrical installation
  • P&I diagrams and control system
  • 3D model
  • Strength and flex calculations
  • Documentation
  • Supervision of installation and commissioning
  • Legalization of the plant


Andreas Zourellis
VP Sales - International
District heating / industrial solar technologies
Phone: +45 50 30 00 25 
E-mail: azo@aalborgcsp.com