Integrated Planning of Multi-Energy Systems: A Graph-Theoretical Framework

Abstract:
The increasing complexity of energy systems due to sector coupling and decarbonization is further complicated by regional planning constraints from social, economic, and infrastructural factors. This paper presents a graph-based modeling framework for multi-energy systems (MES), where each energy carrier network is represented as a layer within a multilayer graph, interconnected through a dedicated coupling layer. Network expansion planning is formulated using a Steiner tree problem solution to account for street topography and solved iteratively with a mixed-integer linear program (MILP). The resulting planning solution is validated using a steady-state solver based on a block-structured Newton-Raphson (NR) method, which computes flows and state variables across all carriers simultaneously. Flow results are iteratively fed back into the MILP to represent realistic operational conditions. The proposed model is tested and validated on a realistic case study based on a German distribution network. The results demonstrate reduced costs in the MES system planning compared to the single system solution, and demonstrate the method’s potential in future optimizations of integrated energy systems.