Self-Optimization Control for Alkaline Water Electrolyzers Considering Electrolyzer Temperature Variations

Hydrogen production by alkaline water electrolysis is an effective way to consume excess power from renewable energy sources (RESs). Nevertheless, it is hard for alkaline water electrolyzers (AWEs) to consume the power from RESs totally because its power flexibility is limited. The low-load efficiency of AWEs is poor so it can only operate in 40%–100% power range. In addition, the hydrogen production efficiency is influenced by the operating temperature. When the electrolyzer temperature varies under the input power fluctuation, the efficiency cannot maintain at a higher level. To address these problems, a self-optimization control strategy is proposed to improve the efficiency of AWEs. First, an equivalent circuit model of AWEs is developed and the efficiency-power map under different temperature is depicted. Based on this, the self-optimization control strategy is proposed. By tracking the optimal efficiency point adaptively, the electrolyzer operates in different modes according to the input power and the temperature. The proposed control strategy is verified on a 10 kW commercial AWE. The results show that the efficiency of AWEs can be raised greatly under different temperatures by the proposed control. Especially, at 80 °C the hydrogen production efficiency can be raised from 19.12% to 42.33% at 15% rated power.