The high-temperature fuel cells, MCFC and SOFC, are especially suitable where both heat and power are needed, or where the excess heat can be exploited in some form. With operating temperatures up to 1000ºC, heat can be converted to electric power in turbines, thus increasing the overall efficiency of fuel cell systems even more. Stationary systems range from small combined heat and power (CHP) plants for households or auxiliary power units (APU) of some kilowatts to large power plants with a capacity of several megawatts. Field tests are already running in hospitals, military bases, office buildings and at industrial sites. Remote installations with no grid connection, back-up power for hospitals, other large buildings and premium power applications (high reliability) are some examples where fuel cells are already operating.

MTU Friedrichshafen MCFC

For stationary power, the most important properties are high efficiency, reliability and long lifetime. High-temperature fuel cells have the advantage that, when combined with heat turbines, they can achieve very high efficiency (up to 80%), and they can use most kinds of available fuels (reformed fossil fuels or also internal reforming). Due to the nature of high-temperature fuel cells and the complexity of the complete systems, they are mostly suited for continuous operation. Several hours are needed to shut down a large SOFC. An average of 40000 hours operating time is required, which is not yet reached by many prototype systems. The main problem is material degradation due to the high temperature and corrosive environments.

For power generators below the megawatt range, both PEMFC and PAFC may be more suitable than the high-temperature fuel cells.Several systems with an output power around 200-250 kW have shown reliable long-term operation. Another stationary application is small distributed household systems (CHP) supplying up to 10 kW of heat and power.  

Several international companies are involved in the development of stationary fuel cell systems. Siemens Westinghouse and Sulzer-Hexis are working on SOFC, while MTU-Friedrichshafen and Fuel Cell Energy are pursuing MCFC technology. Ballard and UTC Fuel Cells have already partially commercialised some PEMFC and PAFC systems, respectively. In the lower household power range, an increasing number of companies is entering the fuel cell business.

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