Validation of a mosaik-based Python simulation framework for smart district energy plants with a large heat pump share
Integrating heat pumps into smart district energy plants (DEP) is a key strategy for decarbonizing residential heating systems, but it introduces substantial modeling and operational challenges, particularly when combined with 4th generation district heating networks and multi-source heat pump configurations. To address these challenges, we developed DES.sim, a modular, object-oriented, and open-source simulation framework based on the mosaik co-simulation framework. The framework provides parameter-driven longterm simulations of heat pump (HP) centered district energy systems (DES) and includes low-complexity component and controller models, support for multiple DHN topologies, and flexible integration of custom components. We validated DES.sim using one year of measurement data from an operational DES in Karlsruhe-Durlach, Germany, that contains a hybrid HP and gas boiler system. The system-wide energy balance shows very good agreement between simulation and measurement: the simulated shares of HP and gas boiler generation closely match the measured shares (72.0 % simulated vs. 71.7 % measured HP share). The thermal outputs to domestic hot water and space heating are reproduced almost exactly. Only slight deviations occur in the HP performance indicators, with the simulated seasonal performance factor (SPF) 1.2 % lower than measured. This difference results from model simplifications, including the representation of two parallel heat pumps as a single aggregated unit. Overall, the validation confirms that DES.sim reliably reproduces the system-level behavior of the real DEP and is suitable for strategic design studies and operational analyses. Its parameter-based setup and modular structure make it well suited for future work on multi-parameter optimization and sensitivity analyses under varying technological and scenario assumptions.