Coelho, AntónioSoares, FilipeIria, José2025-05-232025-05-239789531842976http://www.scopus.com/inward/record.url?scp=86000015295&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733751599As the global community transitions towards decarbonization and sustainable energy, green hydrogen is emerging as a key clean energy carrier. This paper addresses the role of hydrogen in transportation, emphasizing the European Union's additionality principle for renewable energy sources in green hydrogen production. It introduces a model for optimally designing hydrogen fueling stations, considering electrolyzers, hydrogen storage, fuel cells, PV systems, and batteries. This model also considers the participation in electricity (energy and secondary reserve), hydrogen, and oxygen markets, and it is evaluated under different additionality policy scenarios. Results indicate that stricter additionality policies reduce the internal rate of return. However, participation in secondary reserve markets significantly boosts operational revenues and compensates for higher investment costs.This paper is co-financed by Component 5 - Capitalization and Business Innovation, integrated in the Resilience Dimension of the Recovery and Resilience Plan within the scope of the Recovery and Resilience Mechanism (MRR) of the European Union (EU), framed in the Next Generation EU, for the period 2021 - 2026, within project ATE, with reference 56.enPublisher Copyright: © 2024 IEEE.additionalityenergy marketsgreen hydrogenhydrogen fueling stationsmulti-energy systemssecondary reserve202410.1109/ISGTEUROPE62998.2024.1086340686000015295