Alkaline water electrolysis powered by renewable energy sources is one of the most promising strategies for environmentally friendly hydrogen production. However, wind and solar energy sources are highly dependent on weather conditions. As a result, power fluctuations affect the electrolyzer and cause several negative effects. Considering these limiting effects which reduce the water electrolysis efficiency, a novel operation strategy is proposed in this study. It is based on pumping the electrolyte according to the current density supplied by a solar PV module, in order to achieve the suitable fluid dynamics conditions in an electrolysis cell. To this aim, a mathematical model including the influence of electrode-membrane distance, temperature and electrolyte flow rate has been developed and used as optimization tool. The obtained results confirm the convenience of the selected strategy, especially when the electrolyzer is powered by renewable energies.

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Combination of alkaline water electrolysis with renewable energy sources can be one of the most sustainable strategies for H 2 production. However, solar and wind energy sources are strongly dependent on weather conditions, which can cause fluctuations of power supplied to the electrolyzer. This variability usually involves some problems related with increments of the void fraction, generation of explosive mixtures or reduction in the efficiency. In order to limit these effects and to reduce the required voltage in the electrolysis, an optimized operation strategy is proposed in this study based on pumping flow according to the current supplied to the electrolysis cell. To this aim, a mathematical model including influence of different operation variables as electrodes distance, temperature and electrolyte flow rate has been developed and used as optimization tool. The obtained results confirm the convenience of the selected strategy, especially when the electrolyzer is powered by RREE.