The British say, the proof of the pudding is the eating. In the fuel cell world this means that it is finally in the application and not in the laboratory where the systems need to demonstrate their durability. The 2010/1015 U.S. DOE lifetime target for automotive applications is 5,000 h, which is equivalent to 150,000 driven miles, and the Japanese NEDO's lifetime targets for stationary applications are 40,000 and 90,000 h at 2010 and 2015, respectively.
Therefore testing under real the world conditions of the most important applications of the automotive and stationary CHP areas is of high importance. Real world operating conditions include start/stop cycles, dynamics operation and load cycling as well as the use of ambient air for the cathode supply including all of it's impurities, or hydrogen obtained from reformation of hydrocarbons where again a number of side products of the reforming reactions pose challenges for the durability of the fuel cell system. In addition to harsh operating conditions, in many applications, the system cannot be tailored to provide favourable operating conditions for durability, such as i.e. fully humidified feeds, slow dynamics or inert-gas purging upon start/ stop cycles, due to economic, space or weight boundary conditions. One further important and sometimes under-estimated challenge is the interplay of the different sub-systemes (e.g., reformer, humidifier, stack, tailgas burner, a.s.f.) forming an functioning fuel cell system. On the system level therefore, the control algorithms and feedback loops of the system need also need detailed elaboration to allow for durable system operation.
In Part III, degradation phenomena and mitigation strategies for the systems used in stationary CHP and automotive applications are discussed by some of the most prominent industrial developers in the respective field.