Comparative experimental study of alkaline and proton exchange membrane water electrolysis for green hydrogen production

Alkaline electrolysis (ALK) and polymer electrolyte membrane electrolysis (PEM) are two pivotal technologies supporting the advancement of green hydrogen production. Understanding their distinct characteristics is essential for optimizing production systems, with potential implications for future hybrid electrolysis strategies. However, experimental studies on green hydrogen electrolysis are limited, particularly comparative investigations between these two systems. This study conducts a comprehensive comparative experimental analysis of ALK and PEM systems with an identical hydrogen production rate of 1400 ml/min. It focuses on electro-heat-mass coupled dynamics across steady-state, cold-start, controlled dynamic processes, and solar power integration. Results reveal that PEM consumes less energy for hydrogen production, ranging from 4.1 to 4.3 kWh/Nm3, compared to 4.6–4.8 kWh/Nm3 for ALK. This study proposes that cold start time be characterized by two specific time points: reaching rated electrical parameters and achieving operational conditions. The second time point is typically longer and represents the primary limiting factor in the cold start process. Dynamic responses during ramp-up and ramp-down processes are notably asymmetric, with longer durations observed during ramp-down. Heat and gas purity responses to electrical changes also follow distinct patterns, with hydrogen to oxygen (HTO) stabilizing slower than temperature and oxygen to hydrogen (OTH). This facilitates the potential that the lower load limit can be reduced under dynamic conditions compared to steady states, as demonstrated by ALK and PEM adjusting from 50 % to 30 % and from 40 % to 10 % respectively in solar integration. Both systems exhibit agile ramp rate, with ALK adjusting its current by 70 %/s and PEM by 90 %/s. Both systems show viability for solar power integration, with PEM being more immediately suitable, while ALK requires further investigation to effectively manage rising HTO levels. This study provides an experimental data foundation and insights for advancing green hydrogen production. •A comprehensive comparative experimental study of ALK and PEM electrolysis is conducted.•Dynamic response durations for ramp-down are longer than for ramp-up.•Cold start time should be characterized by reaching rated current and operational conditions.•The lower load range limit can be reduced of dynamic processes compared to steady states.•Both ALK and PEM systems exhibit agile ramp