Operation Range Enhancement for Alkaline Electrolysers Driven by Renewable Energy Sources

Abstract Low-cost and mature alkaline water electrolysis is suitable for large-scale hydrogen production from renewable energy sources (RESs). However, the poor low-load performance of alkaline water electrolysers (AWEs) makes it difficult to follow fluctuant RESs in full range. For low-load AWEs, existing researches only pay attention to the impurity problem and its solutions, but here, we find other two urgent problems to be solved, namely inefficiency and inconsistency. Through the detailed operation process analysis of AWEs and the established equivalent electrical model, the inefficiency and inconsistency mechanisms of low-load AWEs are revealed. Furthermore, an overcurrent pulse-width modulation method is proposed to enhance the efficiency and consistency of AWEs. Especially, compared to the conventional dc power supply, 1) the maximum efficiency improvement can exceed two times, 2) the operation range can be extended to 10% of rated load. The proposed method just changes the power supply, it can be easily generalized and can facilitate the hydrogen production from RESs.