MPC for collaborative heat transfer in a district heating network with distributed renewable energy generation and storage

District heating networks are ideally suited to include a high share of renewable energy sources into the heat production in urban areas with limited space. A powerful concept is the decentralized heat and electricity production where each household produces and stores heat, e.g., with solar thermal plants on the rooftops. To exploit the full potential, the households which have an excess of heat should be able to transfer heat to other households that have heat demand. We formulate the problem of a cooperative heat exchange and optimized district heating operation into a nonlinear MPC problem with binary decision variables that determine the heat exchange between the households and the central district heating plant. The resulting mixed-integer nonlinear problem is solved with a gradient-based optimization algorithm in combination with a suitable integer approximation scheme.