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 Hydrogen fuel cells use hydrogen as a fuel in an electrochemical process that combines hydrogen and oxygen to produce electrical energy and water. The reverse process of electrolysis, which produces ‘green’ hydrogen and oxygen from water, can use a range of renewable energy resources (wind, wave, solar) to produce hydrogen as a fuel for renewable power generation. There is also growing interest in hydrogen power as a uniquely clean energy source that can produce heat and whose only by-products are water. Green hydrogen produced from electrolysis (a high energy process) and renewable energy sources is a high cost option, which only accounts for around 5% of total H2 production. Currently, the vast majority of global hydrogen production derives from fossil fuel sources (methane gas reforming) and will continue to do so for several decades. However, as manufacturing capacity for more efficient and cost-effective electrolysers grows, it is expected that costs of production will fall m...