A Novel Method for Analyzing Highly Renewable and Sector-Coupled Subnational Energy Systems—Case Study of Schleswig-Holstein

The energy transition requires an integration of different energy carriers, including electricity, heat, and transport sectors. Energy modeling methods and tools are essential to provide a clear insight into the energy transition. However, the methodologies often overlook the details of small-scale energy systems. The study states an innovative approach to facilitate subnational energy systems with 100% renewable penetration and sectoral integration. An optimization model, the “Open Sector-coupled Energy Model for Subnational Energy Systems” (OSeEM–SN), was developed under the Open Energy Modeling Framework (Oemof). The model is validated using the case study of Schleswig-Holstein. The study assumes three scenarios representing 25%, 50%, and 100% of the total available biomass potentials. OSeEM–SN reaches feasible solutions without additional offshore wind investment, indicating that it can be reserved for supplying other states’ energy demand. The annual investment cost varies between 1.02 and 1.44 bn €/year for the three scenarios. The electricity generation decreases by 17%, indicating that, with high biomass-based combined heat and power plants, the curtailment from other renewable plants can be decreased. Ground source heat pumps dominate the heat mix; however, their installation decreases by 28% as the biomass penetrates fully into the energy mix. The validation confirms OSeEM–SN as a beneficial tool to examine different scenarios for subnational energy systems.