Engineering Development of a Capillary Fed Water Electrolyzer

This work considers the low-cost production of renewable (‘green’) hydrogen from water, using water electrolysis powered by renewable energy. Green hydrogen constitutes the major means of decarbonising hard-to-abate sectors of our economy, including heavy transport, shipping, aviation, chemicals, and steel, amongst others. Global adoption of green hydrogen would see it used as a carrier of renewable energy and a substitute for fossil fuels and chemicals. However, green hydrogen is presently not cost competitive with fossil-derived hydrogen. This work considered why that is and how it could be changed. The main reason for the high cost of producing green hydrogen is the poor efficiency of state-of-the-art commercial water electrolyzers. Modern-day electrolysis cells require ~47.5 kWh to produce 1 kg of hydrogen, with additional energy consumed by the supporting engineering plant (known as the balance-of-plant). The resulting total energy requirement of ~50-53.5 kWh per kg of hydrogen produced (vs. 39.4 kWh of total energy in 1 kg of hydrogen) indicated that ≥27% of the electricity supplied to such electrolyzers is wasted. The cost of this energy is the largest contributor to the cost of producing green hydrogen.