ESM-Regio: simulation and optimization of regional energy systems in carbon-neutral scenarios

Abstract This work presents a high-resolution, sector-coupled energy system modeling framework developed within the research project ESM-Regio, designed to analyze regional energy transitions and the sector coupling potential in the context of Germany’s 2045 climate targets. In contrast to existing regional energy system models, our framework explicitly models medium-voltage distribution grids and incorporates asset aging into a sector-coupled techno-economic optimization. The framework operates on the medium-voltage level at a 15-minute temporal resolution and is designed to analyze regions ranging city to county (NUTS-3 level). The electricity, heat, transport, and gas sectors are integrated into the framework using a component-based simulation architecture. All sectors are represented with sectoral submodels which are iteratively coupled through alternating simulation and mixed-integer optimization stages to minimize operational system costs while accounting for technical grid constraints and asset aging. The methodology is applied to the distribution grid area of the regional utility Stadtwerke Bayreuth, for three representative weeks in each of the years 2019, 2030, and 2045. The results highlight the increasing importance of coordinated flexibility—such as building thermal inertia, battery storage, and electric vehicles—in mitigating grid stress under increased electrification. Across the investigated scenarios, coordinated flexibility usage reduces energy procurement costs by up to 22% and significantly lowers line and transformer loading. However, we find that while intelligent flexibility usage can reduce the need for grid expansion, it can not completely eliminate it in the carbon-neutral 2045 scenarios. The presented framework offers a scalable, data-driven approach to assess the impacts of sector coupling and to support infrastructure and regional energy transition planning aligned with national decarbonization goals.