Thermal energy demand represents about 50% of the energy demand of buildings in Europe. Solar thermal systems can provide heat directly, decarbonizing heat while avoiding electricity-to-heat conversion steps. Solar thermal collectors collect heat by absorbing sunlight and can either be small and distributed at the building scale or much larger, centralized and combined with district heating networks; heat storage facilities can help level out the intermittency of the solar resource. Now, Kristina Orehounig and colleagues from ETH Zurich and the Swiss Federal Laboratories for Materials Science and Technology (EMPA) report a modelling case study of a group of 11 buildings in Switzerland and compare various solar thermal system configurations to identify the best option in terms of solar heat penetration and levelized costs.
The researchers use quasi-steady-state simulations to model the heat demand of each building in a year-long weekly breakdown for space heating and domestic water heating. Various solar thermal system configurations, including distributed and centralized solar thermal systems, with long- and short-term storage complemented with auxiliary electric heat, are compared by evaluating the fraction of heat obtained from solar energy and the levelized energy costs. The researchers show that, for this group of buildings, the best configuration is based on building-scale collectors and storage tanks with separate short- and long-term storage capabilities. This configuration could provide about 50% of heating demand. A sensitivity analysis also shows that it could be competitive with electric-based heating if electricity prices rise as projected.