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AmerCable Incorporated

energy - fuel cells

There are five types of fuel cell technology determined by the composition of the electrolyte in the middle of the fuel cell.  UTC Power has experience in all five types.

Proton exchange membrane (PEM) fuel cells: PEM fuel cells, also known as polymer electrolyte fuel cells, are the type most fuel cell companies currently are developing . These fuel cell use a thin, solid membrane as an electrolyte. They deliver high-power density and offer the advantages of low weight and volume, compared with other fuel cells. They also operate at relatively low temperatures, around 175. Low-temperature operation allows them to start quickly (less warm-up time), which makes them particularly suited to transportation applications such as automobiles and fleet vehicles. UTC Fuel Cells is developing PEMs for cars and buses, as well as stationary applications.

Alkaline fuel cells (AFCs): One of the oldest fuel cell are the alkaline type. UTC Fuel Cells initially developed alkaline fuel cell power plants for the Apollo missions. The company produced an updated version that is still used today to provide electrical power in the space shuttle fleet. These power plants use potassium hydroxide. AFCs can reach efficiencies as high as 60 percent in space applications. However, they are susceptible to carbon contamination and therefore require pure hydrogen and oxygen. This pure-fuel requirement limits AFCs' terrestrial applications.

Phosphoric acid fuel cells (PAFCs): These fuel cells use liquid phosphoric acid as the electrolyte. UTC Fuel Cell's PC25, in production since 1991, is a PAFC power plant. These highly efficient fuel cells can achieve a total efficiency of 80 percent, when producing waste heat for co-generation. PAFC power plants are usually large, heavy and require warm-up time. For this reason, PAFCs are used mainly for stationary applications.

Solid oxide (SOFCs): Solid oxide fuel cells use a hard, non-porous ceramic compound as the electrolyte. SOFCs operate at very high temperatures -- around 1,800F. Heat can be recaptured for co-generation, making these fuel cells highly efficient--as much as 80 to 85 percent. Size, heat output and a long start-up time make these fuel cells more suitable for stationary applications. SOFCs are at a relatively early stage of development compared with the other fuel cell technologies. United Technologies Research Center currently is developing this technology.

Molten carbonate fuel cell (MCFC): Molten carbonate fuel cells use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide (LiAlO2) matrix. These systems are large and operate at very high temperatures, in the 1,200F range. MCFCs are very efficient when the heat produced is used for co-generation. However, because they use a corrosive electrolyte, their durability is limited. UTC Fuel Cells has worked with this technology in the past, but does not have current development programs for it.


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