The potential for combined biomass and solar heating systems for domestic hot water preparation and room heating is large. The energetic performance of these systems is largely influenced by hydraulic setup and control. The effect of these interactions has been evaluated with dynamic system tests in the laboratory. Simulations were performed with a measurement-validated model to assess the annual performance of different system-setups. Based on results obtained from pellet boiler measurements a new model for the boiler was elaborated, taking into account reduced efficiency under part load operation and increased electricity use in on/off cycling operation. System tests and simulation results have shown that the use of solar thermal energy in combination with a pellet heating system reduces burner starts, fuel use and electricity consumption considerably. The combined system was synergetic because solar gains reduced inefficient boiler operation during spring, summer and autumn.

SPF Institute for Solar Technology