Dispatch optimization of high-temperature heat pump technologies for district heating
To achieve international climate targets, it is crucial to decarbonise the heating sector. In Germany, heating and cooling account for over 50% of final energy consumption. Significant reductions in greenhouse gas emissions can be realised through electrification via power-to-heat (PtH) technologies. High-temperature heat pumps are a promising PtH solution, potentially providing CO2-free heat supply by utilizing surplus renewable electricity. Numerous studies in the literature analyze the operational planning of heat pumps using mathematical optimization. Often, a generation portfolio is dimensioned for a specific application, such as supplying a district heating network, and the cost-optimal operation of this portfolio is determined while considering electricity market participation. The novelty of the present study lies in the comparison of different high-temperature heat pump technologies (i.e., transcritical/subcritical) and determination of the techno-economically optimal design of the corresponding heat supply system consisting of the heat pump, an electric boiler, and a heat storage. The analysis includes the technology-dependent coefficient of performance, the ratio of heat provided by heat pump and the electric boiler, and the capacity of the thermal storage system. For the dispatch optimization, a mixed-integer linear programming (MILP) model is formulated. Electricity procurement from the day-ahead and intraday electricity market is considered to meet the representative thermal demand profiles. In addition, technology-dependent partial load operation and dynamic operational characteristics are modeled. The heat supply system designs, the impacts of dynamic operation (i.e., starts, stops, and load changes) as well as electricity procurement are evaluated using the levelized cost of heat (LCOH) metric. The results show that part load performance and transient penalties do not have to be considered during dispatch optimization as their impact on the results is comparatively low (<10 %). Moreover, it is shown that COP advantages of 10 % can be outperformed by lower CAPEX.