Experimental Investigation into the Dynamic Performance of Start–Stop Operations and Trapezoidal Step Current in Proton Exchange Membrane Electrolyzers

The frequent fluctuations in renewable energy supply can cause proton exchange membrane water electrolysis hydrogen production to deviate from stable operation at the optimal operating point, potentially leading to local overheating and hot spots. To investigate this issue, an experimental bench was designed and constructed to analyze the dynamic response of the inlet water temperature and flow rate on the voltage and temperature of the electrolytic cell during start–stop processes and step current conditions. The results indicate that under operating conditions of 40 °C, 9 A, and 100 mL/min, the voltage can surge to a maximum of 11.12 V, which poses a risk of damaging the proton exchange membrane. Upon power cessation, the voltage drops instantaneously to 4.3 V (±0.05 V). When maintaining the same water flow, a type III step current can effectively mitigate voltage surges, reducing the peak by up to 4.68 V. This study provides fundamental data support for optimizing low-load operations in fluctuating photovoltaic hydrogen production systems.