Water Management Concepts in PEMFC With Biomimetic and TRIZ Design Methods

Excessive water accumulation at the cathode can cause cathode flooding in a fuel cell. Two design methodologies, TRIZ (Theory of Inventive Problem Solving) and biomimetic design, were applied to address the problem. A concept generated from TRIZ involves reversing the direction of cathode flow periodically to introduce dryer gas to the previous outlet, where it is previously saturated, with the humidified gas exiting the previous inlet. The concept is intended to reduce the potential for a channel to flood. A prototype apparatus was created to evaluate the concept. It consisted of a cell with a bare Nafion™ membrane pressurized by water on one side and with air flowing on the other side. The prototype apparatus demonstrated a potential loss of overall water removal efficiency in air. Therefore, the flow direction reversal concept may not benefit an actual fuel cell. A second concept generated from the biomimetic design method involves gathering liquid water with cavities and directing the liquid water out of the flow channels. Cavities for water collection in the flow channels of a bipolar plate are created in two configurations. In the first configuration the cavity is created by extending a straight channel from the u-bend in the channel. In the second configuration, the cavity is created by a hole perpendicular to the channel into the bipolar plate. Once the liquid water is collected at cavities, the water is directed out of the cell with wicking materials. A prototype with injected liquid water demonstrated the potential benefits for a fuel cell.