Prosumers in district heating networks – A Swedish case study

A prosumer is a customer that both uses and supplies energy, such as electricity or district heat. These are already a part of the electricity system. Lately, prosumers have also been discussed as a part of the district heating systems. This calls for more knowledge in this area. The present study seeks to evaluate the potential for district heating contribution from small scale prosumers, based on excess heat, and their environmental impact in an area with diverse building types. The results were mainly developed through a case study performed on Hyllie, an area under construction in Malmo, Sweden. Data from property developers and some measured data were used to evaluate the annual prosumer potential of buildings. Environmental calculations were performed by simulations in the commercial simulation programme NetSim and data from Swedish literature. Four cases were investigated, based on whether the prosumers were allowed to deliver heat beyond the Hyllie borders or not and on two different ways of managing the supply temperature. The temperature of the excess heat was either raised with a heat pump, or directly utilised in the district heating network. In the latter case, the temperature of the domestic hot water was raised with electricity. The results showed that the potential for excess heat prosumers is fairly big, in Hyllie around 50–120% of the annual heat demand. Most of the excess heat is however produced during the summer months. The environmental results showed that the environmental output of the electricity applied in the prosumer solution decided whether or not the prosumer solution was better than the conventional district heating solution.