Updating the MULTINODE add-on for EnergyPLAN to model energy systems with high spatial resolution: A case study of the mainland Portugal electrical system

The increasing complexity of energy systems transitioning toward decarbonization requires advances in planning tools, particularly in terms of spatial and temporal resolution. This study applies EnergyPLAN, together with its MULTINODE add-on, to model energy systems at high spatial resolution. We revise the original MULTINODE equations to better represent cross–border flows and introduce a post–processing procedure that improves the dispatch of thermal generation, hydro reservoirs and pumped storage. We also use PyPSA to cluster the national transmission grid and estimate representative internal inter-regional transfer capacities. The approach is applied to mainland Portugal’s 2023 electrical system, comparing results at the national, 2-region, and 5-region (NUTS 2) scales and performing sensitivity analyses on the most critical methodological assumptions. Results show that the NUTS 2 configuration significantly improves model accuracy by more faithfully reproducing the dispatch of all technologies, reducing deviations from real-world data to below 16%. Higher spatial resolution also reveals important regional dynamics, such as Lisbon’s structural import dependency and Alentejo’s suitability for developing green-hydrogen hubs. However, challenges remain regarding the availability of granular data and the estimation of internal transmission limits.