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Why SOFC Technology?

Why SOFC Technology?

Like most fuel cell technologies, SOFCs are modular, scalable, and efficient. They are not subject to Carnot cycle limitations because they are not heat engines. Also, they benefit the public by minimizing emissions, such as oxides of nitrogen (NOx) <0.5 PPM compared to earlier combustion-based electrical power generation technologies due to lower operating temperatures. There are more reasons why SOFCs are the fuel cell technology of choice in the Office of Fossil Energy.

First, relative to other fuel cell types, SOFCs are fuel-flexible – they can reform methane internally, use carbon monoxide as a fuel, and tolerate some degree of common fossil fuel impurities, such as ammonia and chlorides. Sulfur-bearing contaminants, such as hydrogen sulfide, are tolerated less but can be dealt with using available commercial desulfurization methods. With internal reforming, this reaction is heat-absorbing and will tend to cool the cell and the module. This advantage can reduce the need for cooling air consequently reducing the parasitic power needed to supply that air.

Second, experimental data and analyses suggest that advanced SOFCs have an economic entitlement relative to prior established commercial technologies and the National Energy Technology Laboratory evaluated fuel cell types. Planar SOFCs using a thin ceramic (yttria-stabilized zirconia, or YSZ) electrolyte could operate at lower temperatures (<800°C) than predecessor SOFC topologies, allowing the use of lower-cost stainless steel interconnects, rather than a costly and difficult-to-process ceramic interconnects required of higher-temperature SOFCs. Furthermore, the short conduction path from the anode of one cell to the cathode of the next results in lower ohmic losses and, therefore, higher stack efficiency and lower cost than many of its predecessors.

Third, SOFC is a high-temperature technology, thus its exhaust streams will tend to have high temperatures. High grade exhaust heat can enable high-efficiency combined cycle combinations such as SOFC/gas turbine/steam turbine.

Lastly, SOFCs are ideal for carbon capture in that the fuel and oxidant (air) streams can be kept separate by design, thereby facilitating high levels of carbon capture without substantial additional cost.