Solar District Heating in Europe: Supplying Renewable Zero-Emission Heat
Abstract
District heating is one major approach to increase the overall energy efficiency in urban areas and an important platform to increase the share of renewable energies in the heat supply. Solar thermal energy is emission-free, available everywhere and offers stable operating costs for decades. Together, they can play an important role in the energy transition of the heating sector in Europe and beyond. The integration of solar thermal systems into district heating offers different technical solutions, whereof some are applied since decades, some others, like decentral direct feed-in, are in evaluation. Generally, solar thermal systems are sensitive to the levels of the supply and return temperature and the detailed system integration, here especially regarding the hydraulics and the control strategy. In the case that the solar thermal system is applied to combined heat and power productions, the overall system can be designed to the best economics if the electricity market, the dynamics in the heat consumption and the solar thermal production etc. are considered. The integration of a large heat storage volume might be helpful to separate production and supply powers and therefore can lead to a system with lowest heat cost, although the investment cost can be quite high. At least such complex systems ask for dynamic system simulation during the design phase to ensure best economics and to enable a risk analysis for varying prerequisites.