Investigation of water management for residential PEM fuel cells under ultra-low inlet pressure

Integrating hydrogen energy into residential power sectors globally holds pivotal importance in advancing the adoption of green energy. Safety-compliant ultra-low fuel cell inlet pressure (3 kPa) is critical in this regard. Under such conditions, water management capability becomes the primary limiting factor for household fuel cell performance. This study employed synchronized visualization and water velocity measurements on both the cathode and anode sides using two high-resolution cameras and a high-speed camera. The findings indicate that under ultra-low pressure, water removal challenges predominantly result in a tendency to form slug flow with a slow-paced movement, hindering reverse diffusion and proton drag water transport processes. We propose a method to modify the flow channel surface contact angle to approximately 110 degrees, promoting a transition from slug flow to liquid film flow in over 70 % of anode channels and 50 % of cathode channels. With this modified surface, the formative two-phase interface shape can promote the fragmentation of the liquid phase obtained by simulation, thereby enhancing mass transfer and increasing the maximum output power by 10.3 %. Guided by a three-dimensional transport analysis of liquid water within the channels of Proton Exchange Membrane Fuel Cells, this study verifies the performance and stability of a 1.4 kW fuel cell stack. Achieving the results that the stack under ultra-low inlet pressure can be operated stably for over 200 h, maintaining a standard deviation of the output voltage among individual cells within 5 %.