Steam turbine/SOFC hybrid systems

Unlike molten carbonates, solid oxides use a hard ceramic electrolyte instead of a liquid. That means the fuel cell can be cast into a variety of useful shapes, such as tubes. With higher temperatures, sofcs may be able to cogenerate steam at temperatures as high as i,ooo°f. The Siemens Westinghouse Power Corporation has built the first advanced hybrid system, which combines a gas turbine with a tubular sofc. As of 2003, the 220 kW hybrid system has operated in California for more than 2,000 hours with a respectable 53 percent efficiency, comparable to current combined cycle gas turbines. The ultimate goal is an efficiency of 70 percent or more. 

In the SOFC systems, fuel and air enter the SOFC stack, and electricity, exhaust gas and possibly hot water or steam exit the system. Such systems Include atmospheric SOFC CHP systems pressurised SOFC/turbine hybrid systems atmospheric SOFC residential and auxiliary power systems and oxygen separating systems. The difference between an SOFC stack and an SOFC system is generally referred to as the balance-of-plant (BOP). BOP equipment may differ for each application, depending on the size of the system, the operating pressure, and the fuel used. 

A typical SOFC system takes fuel and air as the input and electricity hot water or steam is the main output. Major commercial organisations have shown interest and made large investments in this technology. They have come up with their own designs for different applications. Different SOFC systems include residential and auxiliary power systems, oxygen separating systems, pressurised SOFC or turbine hybrid systems, and atmospheric SOFC combined heat and power (CHP) systems. 

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