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Fuel cells hold the promise of a new low to zero polluting energy conversion technology. These electro-chemical energy conversion devices convert fuel and oxygen directly into electricity. They are clean, quiet, highly efficient, and when run with hydrogen as the fuel, their only by-product is water. Fuel cells can be implemented as part of an economy that is less environmentally damaging, and less dependent on fossil fuels. The solid oxide fuel cell (SOFC) is very close to commercialization and has several advantages over other fuel cell paradigms. The main advantage of the SOFC is the capability to run on existing fossil fuels such as natural gas. Every other type of fuel cell, such as the proton exchange membrane (PEM) fuel cell or the molten carbonate fuel cell (MCFC) requires sufficiently pure hydrogen to operate. SOFCs have the capability to operate on a wide range of fuels. The SOFC is also tolerant of carbon monoxide, which will poison other types of fuel cells. Carbon monoxide can even be used as a fuel.
SOFCs have a very high efficiency when compared to current energy generation technologies. Normal operating SOFC systems can achieve an efficiency of 40-60% whereas state-of-the-art thermal power plants such as steam turbines and combustion engines can achieve a maximum of 30-40% efficiency. The solid oxide fuel cell is poised to penetrate the stationary power generation market. In this market, fuel cells could gain more widespread acceptance as commercial energy conversion devices. One of the limiting factors in the widespread use of SOFCs, and fuel cells in general, is the high initial investment necessary. The commercial manufacture of SOFCs will reduce prices through economies of scale, making them more competitive in the market. Working PrinciplesSOFC’s have operating principles similar to those of batteries, in that they are solid-state devices that convert chemical energy into electrical energy. This chemical energy is obtained from the incoming hydrogen and oxygen gas flows and their reaction with the anode and cathode. This reaction only takes place at elevated temperatures (above 800°C), which necessitates the use of a high-temperature heating device. The three main parts of the fuel cell electrode/electrolyte assembly are the anode, cathode, and electrolyte (See figure below). On the cathode side of the cell, incoming air reacts to form oxygen ions. These ions are conducted through the electrolyte, to the anode. The fuel (in our case hydrogen) enters on the anode surface of the fuel cell and reacts with oxygen ions to produce water, in the form of steam, and free electrons. Free electrons flow from the anode to the cathode in an external circuit. The electrons sustain the reduction reaction at the cathode, and the cycle repeats itself.
For more information on Fuel Cells, please visit the following links: LINKS Siemens Westinghouse Fuel Cells National Fuel Cell Research Center
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