Storage batteries in photovoltaic-electrochemical device for solar hydrogen production

Hydrogen produced by water electrolysis, and electrochemical batteries are widely considered as primary routes for the long- and short-term storage of photovoltaic (PV) energy. At the same time fast power ramps and idle periods in PV power generation may cause degradation of water splitting electrochemical (EC) cells. Implementation of batteries in PV-EC systems is a viable option for smoothening out intermittence of PV power. Notably, the spreading of PV energy over the diurnal cycle reduces power of the EC cell and thus its overpotential loss. We study these potential advantages theoretically and experimentally for a simple parallel connected combination of PV, EC, and battery cells (PV-EC-B) operated without power management electronics. We show feasibility of the unaided operation of PV-EC-B device in a relevant duty cycle and explore how PV-EC-B system can operate at higher solar-to-hydrogen efficiency than the equivalent reference PV-EC system despite the losses caused by the battery.