Effect of pressure and thermal management on stray currents in alkaline water electrolyser stacks

Stray currents bypassing the active area through ports and manifolds decrease current efficiency in industrial alkaline water electrolysers (AWEs). The coupled electrical–thermal model for a 163-cell industrial stack quantifies how operating pressure and the inlet–outlet temperature difference ( Δ T ) affect stray-current losses, their inlet/outlet distribution, and current efficiency. Pressure influences conductivity through changes in void fraction and water-vapour formation. Thermal balance determines the inlet temperature and electrolyte flow rate to achieve a set Δ T . Increasing pressure compresses bubbles, reduces water-vapour mass flow, and increases outlet-side conductivity. This raises outlet-side stray-current losses, while the inlet-side share remains nearly constant. Raising Δ T lowers the inlet temperature and reduces the flow rate required to meet the outlet-temperature constraint, decreasing ionic conductivity at both the inlet and outlet. Thus, lowering pressure at fixed Δ T and raising Δ T at fixed pressure both reduce stray-current losses. Adjusting the electrolyte flow with input current can further suppress them. However, if the outlet void fraction saturates at 75 % (e.g., due to rapid gas removal), reducing pressure provides little additional benefit. In this case, the current-efficiency plateau occurs near 10 bar(a). This analysis highlights the need to manage both pressure and Δ T to design and control high-efficiency AWE stacks. • Industrial stack model links pressure and Δ T to stray-current losses. • Pressurisation increases outlet conductivity, leading to lower current efficiency. • Higher Δ T suppresses outlet conductivity by lowering inlet flow requirements. • Lye flow rate should be decreased with input current to reduce stray-current losses.