Reducing shunt current in alkaline water electrolysis by decreasing the circulation flow rate

Renewable-powered alkaline water electrolysis frequently operates under low-load conditions because of intermittent power input, during which shunt-current losses can account for a substantial fraction of the total current and reduce Faradaic efficiency. Here, we investigate a 10-cell alkaline water electrolyzer and evaluate electrolyte circulation rate regulation as a practical strategy for mitigating shunt-current losses. Lowering the circulation flow rate promotes gas retention in the manifold, increases the effective electrical resistance of the electrolyte pathways, and suppresses shunt currents. In the low-current-density regime, this strategy improves Faradaic efficiency by 7–10 percentage points, while its benefit gradually diminishes at higher current densities. MATLAB-based equivalent-circuit simulations reproduce the experimental trends, supporting the proposed mechanism of bubble-induced changes in electrolyte resistance. These findings provide an operating strategy for improving the low-load efficiency of alkaline water electrolysis under fluctuating renewable-power input.