Novel concept for evaporative cooling of fuel cells: an experimental study based on neutron imaging

Polymer electrolyte fuel cells (PEFC), although a promising technology for carbon free production of electricity, are penalized by system complexity, partly due to cooling and humidifying systems. These systems are necessary to avoid the heating up and drying of the membrane, which stop the electrochemical reaction. Here, we present an evaporative cooling concept for PEFC developed at Paul Scherrer Institute (PSI). Unlike other concepts, our approach does not require any additional layer in the cell structure. Water flows through dedicated anode flowfield channels, parallel to the gas channels, and is distributed over the cell area thanks to a modified gas diffusion layer (GDL). A synthesis method developed at Paul Scherrer Institut (PSI) transforms some portions of the GDL into hydrophilic patterns, which wick the water from the supply channels at low capillary pressure. These hydrophilic areas, parallel and equally spaced, define pathways for liquid water separated from the gases, which avoids flooding. A test cell was built to investigate both water transport with the help of neutron radiography and heat transport thanks to integrated heat flux sensors. Here, we will present how the evaporation can be controlled by the mass flow rates, temperatures, pressures of gases, and the geometry of the hydrophilic lines.