Two case studies for renewable district heating with solar fraction ≥ 70 %
Abstract
Two case studies of renewable district heating in rural areas with high solar fraction are presented. The first solar district heating system is currently under construction. Here, an approximately 8 km heating network will supply heat to 180 households. The main heat supply components are a large collector field (11,700 m²), a seasonal pit storage tank with 26,600 m³, two internal heat pumps (combined 1.5 MW thermal) to discharge the storage tank and raise the temperature for district heating, and a biomass boiler. The total energy demand of 3.6 GWh/a is supplied by solar thermal (67%) and biomass (26%). The rest is supplied by the internal heat pump (electricity 6%). The second district is smaller, with a total energy demand of 2.3 GWh/a for 100 buildings and a 5 km heating network. The demand is covered exclusively by solar thermal energy (87%) and an internal heat pump (electricity 13%). The main components of the second case study are 5,700 m² of collectors (flat plate and evacuated tube), one 15,000 m³ storage tank and the large heat pump (1 MW thermal). Both systems were modeled in TRNSYS and optimized by using numerical algorithms to achieve the lowest levelized cost of heat (LCoH).