Simon Lennart Sahlin

Estimation of membrane hydration status for active proton exchange membrane fuel cell systems by impedance measurement: Start-up time measurements

Fuel cells are getting growing interest in industrial areas like backup systems for telecom applications or power source for electric vehicles. Although these systems are characterized by long periods of inactivity, they must be able to start at any instant in the shortest time. However, the membrane of which PEMFCs are made of tends to dry out when not in use. This increases the time interval required to start the system up and could lead to the destruction of the fuel cell. In this article a start-up time measurement setup is presented, which is part of a larger project, the membrane hydration status estimator for monitoring the humidity of a fuel cell stack during standby. The fuel cell has been placed in a climatic chamber, connected to hydrogen and the start-up time has been measured with different environmental conditions. Based on the previous results and the ones presented in this paper a correlation between the start-up time and relative humidity of the membrane can be derived.

High Temperature PEM Fuel Cell Systems, Control and Diagnostics

Various system topologies are available when it comes to designing high temperature PEM fuel cell systems. Very simple system designs are possible using pure hydrogen, and more complex system designs present themselves when alternative fuels are desired, using reformer systems. The use of reformed fuels utilizes one of the main advantages of the high temperature PEM fuel cell: robustness to fuel quality and impurities. In order for such systems to provide efficient, robust, and reliable energy, proper control strategies are needed. The complexity and nonlinearity of many of the components in such systems allow the development of both simple linear and also advanced fuzzy logic and neural network controllers able to adapt system performance to the ever changing conditions which the systems operate in over their entire lifetime.