The aim of the project was to find the economic feasibility of using solar thermal energy as a complementing energy source in small scale (0.5-2 MWth) DH plants in north european conditions. Considered fuels saved are wood pellets or light heating oil. Also, the feasibility of moving the solar thermal plant was to be estimated, if possible.

Only short term thermal energy storage and ground mounted collector arrays were considered. Thermal load profiles for domestic hot water (DHW) and space heating (SH) on an hourly basis were created based on measured data from several sites. For the simulation studies the number of cases had to be limited; a “bad case” and a “good case” scenarios for solar were studied, assuming that most of other cases fall in between. Yearly energy balances and system sizings were obtained by simulations.

The feasibilities of the studied sizings were calculated with the Net Present Value (NPV) method. As sensitivity analysis different scenarios in fuel price increase and interest rates were considered.