Electrolytic hydrogenfuture technology for energy storage

This paper reviews water electrolysis technolo-gies for hydrogen production and also surveys the state of the art of water electrolysis integration with renewable energies. First, attention is paid to the thermodynamic and electrochem-ical processes to better understand how electrolysis cells work and how they can be combined to build big electrolysis mod-ules. The electrolysis process and the characteristics, advan-tages, drawbacks, and challenges of the three main existing electrolysis technologies, namely alkaline, polymer electrolyte membrane, and solid oxide electrolyte, are then discussed. Current manufacturers and the main features of commercially available electrolyzers are extensively reviewed. Finally, the possible configurations allowing the integration of water elec-trolysis units with renewable energy sources in both autono-mous and grid-connected systems are presented and some relevant demonstration projects are commented.