Heat Pump based on treated wastewater delivering green district heating in Odense

Greener district heating and a better water environment are the results of Fjernvarme Fyns newest heat pump system utilizing heat from treated wastewater at Ejby Moelle Renseanlæg in Odense.

The large electric heat pumps are now capable of covering the annual heat demand from 5.000 households or approximately 5 % of Fjernvarme Fyns annual heat production. It is the largest electric heat pump system based on treated wastewater in Denmark.

The customers won’t feel that the heat is coming from wastewater as everything is delivered in an enclosed system, where district heating and wastewater are kept completely separate. Only the heat is transferred.

Climate benefit
In Denmark, there are vast amounts of renewable energy distributed in the national grid and this electricity runs the large-scale heat pumps. When the heat pumps further utilize excess heat it becomes a major benefit to the climate. The active heat pump system at Ejby Mølle reduces CO2 by 30.000 tons a year.

Technological leap
The project is built on thorough analysis and planning conducted in cooperation between Fjernvarne Fyn and VandCenter Syd. The project utilizes the ability of heat pumps to extract heat from a material that does not necessarily have a high temperature. Treated wastewater acts as a stable heat source that’s typically warmer than both air and seawater.

An important step
The project is an important step for the green transition of the district heating company Fjernvarme Fyn. Alongside a long list of other projects, the new large-scale heat pump system plays an active role in phasing out coal and other fossil fuels.

Director of Development, Kim Winther says:

“We need innovation in the fight against climate change, and the cooperation between Fjernvarme Fyn and VandCenter Syd is a good example. As new climate-friendly and future-proof solutions take over we will reduce the use of fossil fuels while increasing the integration of renewable energy. It’s great for the climate and future generations”

Great for the environment

The project is also beneficial for the animals and microorganisms living in the small local river. That’s a result of the treated wastewater giving up its excess heat to the district heating supply on its way through the heat pump before it is led back into the small local river.


  • Max heat output: 19 MW
    Max electricity output: 4.9 MW
  • Coefficient of Performance (COP): 390 %
    Excess heat temperature: 7-21 °C
    District heating flow temperature: 60-69 °C
  • Expected annual district heat production: 59 GWh
    Capacity: 5,000 households annual heat consumption

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Sector: District energy

Country / Region: Denmark

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