Fuel cells can continuously convert the chemical energy of a fuel (hydrogen, methanol, methane, etc.) and an oxidant into electrical energy at up to 83% e¥ciency with very low pollutant emissions. Depending on the type of electrolyte used in a fuel cell, one can distinguish the following six main types:

1. Alkaline fuel cell (AFC) 2. Proton exchange membrane fuel cell (PEMFC)—also called polymer electrolyte fuel cell (PEFC)

or solid polymer fuel cell (SPFC) 3. Direct methanol fuel cell (DMFC) 4. Phosphoric acid fuel cell (PAFC) 5. Molten carbonate fuel cell (MCFC) 6. Solid oxide fuel cell (SOFC)

še œrst four types of fuel cells operate at temperatures below 200°C, MCFC and SOFC operate at temperatures higher than 650°C.