Applications
Using planar SOFCs, stationary power generation systems of from 1 kW to 25 kW size have been fabricated and tested by several organizations. Several hundred 1kW size combined heat and power (CHP) units for residential application were field tested by Sulzer Hexis; however, their cost and performance degradation was high and stack lifetime too short. With improved sealing materials and sealing concepts, planar SOFC prototype systems in the 1 to 5 kW sizes have recently been developed and are being tested by various organizations with greater success. Using tubular (cylindrical) SOFCs, Siemens/ Westinghouse fabri-cated a 100 kW atmospheric power generation system.10 The system was successfully operated for two years in the Netherlands on desulfurized natural gas without any detectable performance degradation. It provided up to 108 kW of ac electricity at an efficiency of 46% to the Dutch grid and approximately 85 kW of hot water for the local district heating system. At the conclusion of the operation in The Netherlands, the system was moved to a German utility site in Essen, Germany, where it operated successfully for another 4,000 hours. After replacing some cells, the system was then installed and operated in Italy, for over two years, again with very stable performance. Siemens/Westinghouse tubular cells have also been used to fabricate and field test over a dozen 5 kW size CHP units, each about the size of a refrigerator. These units gave excellent performance and performance stability on a variety of hydrocarbon fuels. However, at present, their cost is high; future such units are expected to use higher power density alternate tubular geometry cells to drive down the cost.