Sustainable heat supply for cities BigSolar makes a significant contribution to the heat transition. High solar fractions up to 50 % for cities with a dis-trict heating grid. BigSolar is a smart combination of large-scale solar thermal collectors, a seasonal thermal energy storage and absorption heat pumps. An intelligent control engineering of these advanced hybrid generation technologies reflects SOLID’s knowledge and expertise. A holistic approach, economically competitive for a long-term substitution of fossil fuel, saving GHG emissions, peak load management and waste heat integration.