Off-grid solar-hydrogen generation by passive electrolysis

A novel embodiment of a polymer electrolyte membrane (PEM) electrolyser is presented as a means for producing hydrogen off-grid by the efficient absorption of the time-varying power output of a solar photovoltaic (PV) panel or array. The balance-of-plant power load was minimised using passive design principles to ensure efficient operation under cloudy, sunset and wintry conditions. Heat generated during the electrolysis process is stored when appropriate to significantly enhance the efficiency of hydrogen production after a period of darkness. A prototype field trial demonstrated the electrolyser's ability to track closely the highly variable output of the PV year-round under a wide range of operating conditions. Hydrogen yields for various geographical locations were estimated to vary from 25 to 65 kg p.a. for a 1.6 kW electrolyser with fixed-tilt PV panels depending on local levels of solar insolation. This could be increased to over 100 kg p.a. by employing a PV panel of greater capacity and a battery for absorbing the peak generation and then discharging it overnight to the electrolyser.