sim4dhs - Algorithm for the thermohydraulic simulation of district heating systems: Identification of optimal locations for additional heat sources

In 2023, renewables covered 22 % of Germany’s final energy use - 53 % in electricity but only 18 % in heat, even though heat makes up half of total consumption. In particular, district heating promises a high potential of reducing CO2 emissions. In order to unlock this potential, district heating systems must adapt to the technical requirements of renewable energies in order to keep or even improve the efficiency of the system. Lowering the grid temperatures is the key, but old building structures limit the reduction of the return temperature. This leads to increased mass flow and pressure losses and thus to local bottlenecks. But could decentral integrated renewable heat sources alone be enough to avoid thermal-hydraulic bottlenecks? This work presents sim4dhs, a non-convex MINLP model, that optimizes the locations of renewable heat sources so that as many extraction points as possible comply with the contractually required pressure differences. Results show additional heat sources can reduce bottlenecks effectively, and pressure boosting eliminates them entirely. Optimal locations are often at subtree entrances or midpoints of districts.