Wind and heat - a pilot project on district heating from wind turbines and heat pumps

This project has examined concrete and practical conditions for integration of heat pumps in the district heating system in Aarhus and should be seen in connection with the project Combination of wind power and heat pumps for Heating Plan Aarhus, which analyses how heat pumps can be used and interact with the electricity market. Heat pumps may for instance use heat in waste water to produce district heating. This technology has been used for many years for example in Sweden, which today has more than 35 heat pumps with a total heat capacity of 5,000 MW. Oslo and Helsinki have recently invested in two new large heat pumps of 18 and 90 MW respectively. In Frederikshavn (Jutland) a 900 kW heat pump has just been commissioned. These heat pumps often use waste water as their source of heat and produce district heating.

Various pump sizes examined

The project is based on a large heat pump with a heat production capacity of 150 MW, but a number of alternatives of varying plant size and connection to the electricity grid have also been examined. For example, heat pumps may be connected directly to wind turbines, which means that no indirect electricity taxes are paid for the electricity consumed. The location of wind turbines in Aarhus is therefore also part of the analyses.


Most configurations of heat pumps and wind turbines are smaller than originally outlined, primarily for economic reasons. The heat pumps in Aarhus may for instance be located at two large wastewater treatment plants: Marselisborg and Egå wastewater treatment plants, where the treated wastewater may be used. The temperature of the water is between 9 and 13°C in the winter and around 20°C in the summer. It is thus possible to obtain a higher coefficient of performance (COP) for the heat pumps than if the heat source was seawater. It is also possible to exploit industrial surplus heat by means of heat pumps. In that case, the COP would be 5-7.

Small heat pumps recommended

It is recommended that the possibilities of integrating a smaller heat pump of around 3-10 MW heat production capacity in Aarhus district heating system be further investigated as this seems to be most optimal economic and environmental solution, and it could be used to collect experiences with operation of the heat pump.


Last update 15-Sep-2011





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