Early detection of malfunctions and control systems with In situ sensors in technical fuel cells

Recent development progress of fuel cell systems has generated significant interest in the potential application for on-board electricity generation, e.g. in aircrafts and other applications with a high demand on safety and reliability. To satisfy the required high operational reliability, stable and safe operation of the fuel cell stack must be guaranteed. Therefore an intelligent diagnostic system is needed to detect first indications of a potential malfunction, well ahead of the occurrence of a failure or severe problem. To implement such a diagnostic system, sensors in the stack are needed to provide accurate information about the status of the cells. Furthermore for a highly efficient fuel cell a homogeneous utilization of the whole active area is needed. In addition, a homogeneous current and temperature distribution enables longer lifetime of the cell. During operation of large commercial fuel cells the local conditions can vary (e.g. reactivity, efficiency and power density are not homogeneous) due to non-uniform water content in the membrane, inhomogeneous temperature distribution, or reactant gradients in the cell. To determine inhomogeneous activity, a locally resolved measurement technique is desired. The implementation of the concept and the range of application of locally resolved measurements are the focus of this paper