Angelica Liponi

Water electrolysis is a potential contributor to global decarbonization, enhancing the flexibility and resilience of the electricity system and enabling integration with different sectors, such as industry and transportation, by acting as an energy vector and storage, as well as chemical feedstock. This study investigates the potential of hydrogen production by electrolysis in future national electric grid scenarios for Italy as a case study. It examines the impact of increasing photovoltaic and wind capacities up to five times the 2019 levels, considering an electricity storage capacity of up to 200 GWh. The feasibility of fully meeting current national hydrogen consumption through electrolysis in these scenarios is assessed by considering different overall electrolysis capacities. Specific CO₂ emissions associated with hydrogen production are evaluated as an indicator of environmental feasibility and compared with the conventional steam methane reforming. In addition, the levelized cost of hydrogen production is evaluated as an indicator of economic feasibility. Some limitations of electrolysis emerge when it is considered the sole way to decarbonize hydrogen production. Very high renewable shares are required to make electrolysis alone a feasible solution. Aiming to maximize the use of renewable curtailment for electrolysis conflicts with maximizing the electrolyzers’ utilization factor, thus, negatively affecting hydrogen production costs. Furthermore, since priority is given to the use of renewable and stored electricity to meet electricity demand, the remaining electricity is insufficient to produce the entire hydrogen demand in most of the considered scenarios, particularly when substantial storage supports the grid, as this reduces the curtailment available for electrolysis.

Mitigating the effects of global warming by reducing greenhouse gas emissions requires the adoption of sustainable practices and the promotion of renewable energies. However, in an energy scenario strongly dominated by intermittent energy sources, storage systems are becoming increasingly important. In this context, the conversion of renewable energy peaks into green hydrogen can be considered an interesting possibility. Furthermore, the use of power-to-gas systems solves, at least in a transition phase, the problems associated with the lack of infrastructure dedicated to hydrogen. In this study, a power-to-gas system producing synthetic methane from wind energy was modelled. Three management strategies were implemented and compared to assess the flexibility and versatility of the system. Results showed the importance of using an intermediate hydrogen storage tank to reduce the amount of surplus hydrogen. However, the choice of a management strategy depends on the purpose for which the power-to-methane system is designed.

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