Types of Fuel Cells: Let’s Get Familiar
October 19th, 2010
There are five primary types of fuel cells based on their unique electrolyte use, and each has specific characteristics that make it better in certain applications over others.
- Polymer Electrolyte Fuel Cell (PEFC) or Proton Exchange Membrane Fuel Cell (PEMFC) The electrolyte in this type of fuel cell is an ion exchange membrane made of some type of polymer that is a good conductor of protons. This type of fuel cell runs at low temperatures with electrical efficiencies of about 45, and is the primary candidate for automotive, small stationary, and portable power applications. PEMFCs require very pure hydrogen as the fuel.
- Phosphoric Acid Fuel Cell (PAFC) The electrolyte in this type of fuel cell is phosphoric acid, concentrated to 100. PAFCs have a high operating temperature and achieve an electrical efficiency of about 37-42. Buses and stationary applications currently use PAFCs.
- Molten Carbonate Fuel Cell (MCFC) The electrolyte in this type of fuel cell is usually a combination of alkali carbonates, retained in a ceramic matrix. The MCFC operates at very high temperatures which enables the end user to utilize both the electricity and the thermal energy generated by the fuel cell, resulting in electrical efficiencies of more than 70 percent. MCFCs are well-suited to large-scale stationary applications, and are currently being demonstrated for powering buildings.
- Solid Oxide Fuel Cell (SOFC) The electrolyte in the SOFC is a solid, nonporous metal oxide. At temperatures over 650 degrees Celsius, the SOFC can utilize a hydrocarbon fuel directly, without reforming, similar to the MCFC. Also similar to the MCFC, the SOFC generates both electricity and usable thermal energy. High-temperature SOFCs are being demonstrated for stationary power applications, while low-temperature SOFCs are also being looked at for automotive applications.
- Alkaline Fuel Cell (AFC) This was one of the first modern fuel cells to be developed and was used to provide on-board electric power for the Apollo space vehicle. The electrolyte in this fuel cell is Alkaline (KOH). AFCs require pure hydrogen and pure oxygen as the reactants. The operating temperature for this type of fuel cell is around 200 degrees Celsius.
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