Flexibility of Large-Scale Solar Heating Plant with Heat Pump and Thermal Energy Storage

In the future energy system, based wholly on renewable energy sources, biomass is likely to become a scarce resource because of high demand especially by the transport sector. The current paper investigates, what is the possibility of utilizing excess electrical energy from renewable generation to decrease biomass use in a district heating system. The paper focuses on the renewable energy-based district heating system in Marstal, Denmark, with heat produced in central solar heating plant, wood pellet boiler, heat pump and bio-oil boiler. The plant has been the object of research and developments since its construction in 1996 and its operation is well documented. In the first part of the paper, the background of the current study is explained and the system in question is presented. Subsequently, the methodology of the study is explained and the model used in the study is described. Due to lack of widely accepted definition of a metrics for comparing system flexibility the paper proposes such an indicator. It was concluded, that cheap electricity can partially replace scarce biomass for heat production for district heating system.