have designed a piezoelectric microvalve for integration in PEM fuel cells. Using micro-electromechanical systems (MEMS) technology, the fully integrated valve will optimize air and hydrogen flow to help eliminate problems including poor fuel conversion efficiency, hot spots, decreased cell life and reduced cell voltage.
Based on a flow and energy management concept developed within the NETL Gas Energy Systems Dynamics Focus Area, the system controls cell-to-cell flow distribution inside a stack. The University of Pittsburgh is manufacturing the first prototype for testing.
Currently, fuel cell designers manage reactant concentrations by imposing relatively large pressure drops across the flow channels throughout the cell, to ensure adequate flow in each individual channel within the cell. A new design is necessary because commercial microvalves do not meet fuel cell application requirements such as hydrogen tolerance, thermally insensitive activation, and geometric constraints. In the MEMS solution, small microvalves are integrated into the stack to provide improved flow distribution and higher efficiency, at reasonable cost.
Characteristics of the design include scalable geometry (height and width), axial flow, relatively simple and reliable operation, non-thermally activated, low-voltage operation, and a linear actuator response. Because the design employs MEMS technology, the fabrication techniques are borrowed from the semiconductor industry, promising high volume, low-cost production. An entire valve is only 20 mm long × 4 mm wide × 290 µm thick. The researchers, who claim the valve is also applicable to SOFCs, will test and evaluate the new design at NETL's fuel cell testing facility in Morgantown, West Virginia.