Fuel Cells - Green Power - Martin's Marine Engineering Page

Other Fuel Cell TechnologiesThe electrolyte defines the key properties, particularly operating temperature,of the fuel cell. For this reason, fuel cell technologies are named bytheir electrolyte. Four other distinct types of fuel cells have been developedin addition to the polymer electrolyte membrane fuel cell:• alkaline fuel cells• phosphoric acid fuel cells• molten carbonate fuel cells• solid oxide fuel cellsThese fuel cells operate at different temperatures and each is best suited toparticular applications. The main features of the five types of fuel cells aresummarized in chart form.Comparison of Five Fuel Cell TechnologiesFuel CellElectrolyteOperatingTemperature (°C)ElectrochemicalReactionsPolymer Electrolyte/Membrane (PEM)Solid organicpolymerpoly-perfluorosulfonicacid60 - 100Anode: H 2➔ 2H + + 2e -Cathode: 1/2 O 2+ 2H + + 2e - ➔ H 2OCell: H 2+ 1/2 O 2➔ H 2OAlkaline (AFC)Aqueous solution ofpotassium hydroxidesoaked in a matrix90 - 100Anode: H 2+ 2(OH) - ➔ 2H 2O + 2e -Cathode: 1/2 O 2+ H 2O + 2e - ➔ 2(OH) -Cell: H 2+ 1/2 O 2➔ H 2OPhosphoric Acid (PAFC)Liquid phosphoricacid soaked in amatrix175 - 200Anode: H 2➔ 2H + + 2e -Cathode: 1/2 O 2+ 2H + + 2e - ➔ H 2OCell: H 2+ 1/2 O 2➔ H 2OMolten Carbonate (MCFC)Liquid solution oflithium, sodium and/or potassium carbonates,soaked in amatrix600 - 1000Anode: H 2+ CO 32-➔ H 2O + CO 2+ 2e -Cathode: 1/2 O 2+ CO 2+ 2e - ➔ CO 32-Cell: H 2+ 1/2 O 2+ CO 2➔ H 2O + CO 2(CO 2is consumed at cathode and produced at anode)Solid Oxide (SOFC)Solid zirconium oxideto which a smallamount of ytrria isadded600 - 1000Anode: H 2+ O 2- ➔ H 2O + 2e -Cathode: 1/2 O 2+ 2e - ➔ O 2-Cell: H 2+ 1/2 O 2➔ H 2OThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net