The production of hydrogen as both chemical feed and energy carrier using low-carbon technologies is one of the solutions to reach net-zero emissions. This paper, firstly, reviews the publications on the life-cycle assessment of photovoltaic (PV)-based hydrogen production focused on the carbon footprint. Secondly, it updates the global warming potential (GWP) values of this H₂ production process considering the state-of-the-art PV panels for installation in Italy. In the literature, H₂ produced in Europe and the rest of the world results in a mean GWP equal to 4.83 and 3.82 kg CO₂ eq./kg H₂, respectively, in which PV systems contribute the highest share. The average efficiency of PV panels assumed in the literature is lower than the current PV modules. Updating the supply chain, efficiency, and manufacturing energy and material flows of PV modules can decrease the GWP value of the H₂ produced by nearly 60% (1.75 kg CO₂ eq./kg H₂, with use of alkaline electrolyzer) in the Italian context, which can be further reduced with advancements in PV panels or electrolysis efficiency. The study proves that advancement in the PV industry and additional savings in the electrolyzer’s electrical demand can further decrease the carbon footprint of PV-based H₂.

The application of hydrogen in heavy-duty vehicles or trains has been suggested as a promising solution to decarbonize the transportation sector. In this study, a one-dimensional engine modeling is employed to evaluate the potential of hydrogen as a fuel for railway applications. A turbocharged diesel engine is simulated as the baseline unit, and the results are validated with experimental data. The same engine is converted to become compatible with hydrogen through some modifications in the turbocharger group and the injection and ignition systems to preserve the performance of the baseline configuration. The findings show that the engine traction power is reduced from 600 to 400 kW, indicating an inferior performance for the hydrogen-fueled engine. The energy consumption of the hydrogen-fueled engine on a real train mission profile is almost two times the diesel version. However, our Life Cycle Assessment analysis with a Well-to-Wheel system boundary shows a 56% reduction in equivalent CO₂ emissions for the engine fueled with photovoltaic-based green hydrogen. Substituting diesel with low-carbon hydrogen can decrease the train’s carbon footprint from 4.27 to even less than 2 kg CO₂ eq./km, suggesting that moderately modified engines are a promising solution for decarbonizing non-feasibly electrified railway sections.