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05/01/2006 10:29 AM Fuel cells cannot store energy like a battery, but in some applications, such as stand-alone power plants based on discontinuous sources (solar, wind power), they are combined with electrolyzers and storage systems to form an energy storage system. The round-trip efficiency (electricity to hydrogen and back to electricity) of such plants is between 30 and 40%. In "combined heat and power" applications, a fuel cell is placed in a location where heat is also needed. A lower fuel-to-electricity conversion efficiency is tolerated (typically 15-20%), because most of the energy not converted into electricity is utilized as heat. Some heat is lost with the exhaust gas just as in a normal furnace, so the combined heat and power efficiency is still lower than 100%, typically around 80%. In terms of exergy however, the process is inefficient, and one could do better by maximizing the electricity generated and then using the electricity to drive a heat pump. Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, rural locations, and in certain military applications. A fuel cell system running on hydrogen can be compact, lightweight and has no major moving parts. A new application is combined heat and power (CHP) for family home, office buildings and factories. This type of system generates constant electric power (selling excess power back to the grid when it is not consumed), and at the same time produce hot air and water from the waste heat. Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 80% (45-50% electric + remainder as thermal). The largest manufacturer of PAFC fuel cells is UTC Power, a division of United Technologies Corporation. Molten-carbonate fuel cells have also been installed in these applications, and Solid-oxide fuel cell prototypes exist. However, since electrolyzer systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in large-scale energy storage, rural areas being one example. In this application, batteries would have to be largely oversized to meet the storage demand, but fuel cells only need a larger storage unit (typically cheaper than an electrochemical device). One such pilot program exists on Stuart Island off the State of Washington. There the Stuart Island Energy Initiative has built a complete system by which solar panels generate the current to run several electrolyzers whose hydrogen is stored in a 500 gallon tank at 150-200 PSI. The hydrogen is then used to run a 48V ReliOn hydrogen fuel cell that provides full electric back-up to the residential site on this off the grid island (see external link to SIEI.ORG). Protium, a rock band originating at Ponaganset High School in Glocester, RI was the world's first hydrogen fuel cell powered band. The band was powered by a 1kw Airgen Fuelcell from Ballard Power systems. The band has played at a number of fuel cell advocasy events inluding the Connecticut CEP, and the 2003 Fuel Cell Seminar in Miami beach, FL. Plug Power Inc. is a major player in the design, development and manufacture of PEM fuel cells for stationary applications, including products aimed at telecommunication, prime power, and combined heat and power (CHP) applications. Base load power plants Electric vehicles Auxiliary power Off-grid power supply For more details on this topic, see Hydrogen vehicle. and Hydrogen highway. Page 5 of 8 Fuel cell - Wikipedia, the free encyclopedia Fuel cell applications Suggested applications Hydrogen vehicles, boats and refuelling http://en.wikipedia.org/wiki/Fuel_cell