Aalborg CSP delivers yet another wastewater heat pump

Date: 29/12/2022


Danish renewable energy specialist Aalborg CSP has secured yet another order for a wastewater heat pump.

Example of compressor rack from Advansor high res Aalborg CSP

The order is awarded by the Danish district heating plant Egedal Fjernvarme and is a turnkey contract for a 1.5 MW heat pump with associated heat exchanger, piping, purification system and building optimizations. The new heat pump will enable Egedal Fjernvarme to utilize the energy from wastewater for green district heating production. The order is the second wastewater heat pump order secured in the last months for Aalborg CSP.

The renewable energy interest has increased simultaneously with the higher price of fossil fuels as e.g., natural gas. An increasing number of Danish district heating plants has turned their attention towards alternative solutions such as heat pumps. Heat pumps can assist district heating plants in reducing their gas dependency, help stabilizing energy prices and at the same time strengthening the security of supply.

Best price per MWhth heat delivered

Egedal Fjernvarme is experiencing an increased demand following the expansion of the district heating network. With the new heat pump Egedal Fjernvarme is able to exploit the excess energy from a local wastewater treatment plant to supply green district heating. The heat pump contributes to ensuring sufficient heating capacity to supply both current and future district heating customers.

The heat pump for Egedal Fjernvarme applies the natural refrigerant CO2 and will have a maximum output of approx. 1,500 kW. The plant consists of two units – also referred to as racks – and is custom made 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.

Green, sustainable, and low-cost district heating for wastewater and river water

The wastewater temperature varies throughout the year. It is, however, typically warmer than both sea water and air, making it an ideal choice of heat source for a heat pump system to produce district heating in a green, sustainable, and low-cost way.

Aalborg CSP’s system design concept applies for both wastewater and river water heat pumps. The heat pump configuration is designed and selected specifically to give the optimal performance in the customer’s operating temperatures.
The heat pump extracts the energy from the purified wastewater and uses the energy for heating the district heating water. The low-temperature energy is compressed into remote energy at a normal flow temperature of up to 75°C by means of the electric heat pump. The wastewater is cooled as the energy is extracted. The process of cooling the wastewater is controlled in a way that prevents the lowest outlet temperature to fall below 2 °C. Afterwards, the purified and cooled wastewater is discharged into a nearby river.

There are several advantages of using wastewater and river water as a renewable energy source for heat pumps. On the one hand, it is positive for district heating consumers, as the relatively high temperature of wastewater ensures a more stable and sustainable energy supply. Likewise, it is positive for the aquatic environment that the outlet temperature of the treated wastewater is decreased and is hence closer to the temperature of the aquatic environment into which it is discharged.


Client: Egedal Fjernvarme
Capacity of the heat pump: 1.5 MW
System supplier: Aalborg CSP A/S in collaboration with Frontmatec, Advansor and NatRef Engineering
Scope: Turnkey EPC contract
Location: Stenløse
Temperature: Up to 75º C
Type of heat pump: CO2 wastewater heat pump
Life expectancy: 25 years