Phosphoric acid fuel cells (PAFCs) consist of an anode and a cathode made of a finely dispersed platinum catalyst on carbon and a silicon carbide structure that holds the phosphoric acid electrolyte. They are quite resistant to poisoning by carbon monoxide but tend to have lower efficiency than other fuel cell types in producing electricity. However, these cells operate at moderately high temperatures of around 180ºC and overall efficiency can be over 80% if this process heat is harnessed for cogeneration.
This type of fuel cell is used in stationary power generators with output in the 100 kW to 400 kW range to power many commercial premises around the world, and they are also finding application in large vehicles such as buses. Most fuel cell units sold before 2001 used PAFC technology.
Other types of fuel cell technologies available:
The proton exchange membrane fuel cell (PEMFC) uses a water-based, acidic polymer membrane as its electrolyte, with platinum-based electrodes.
The direct methanol fuel cell (DMFC) is a relatively recent addition to the suite of fuel cell technologies.
Phosphoric acid fuel cells (PAFCs) consist of an anode and a cathode made of a finely dispersed platinum catalyst on carbon and a silicon carbide structure that holds the phosphoric acid electrolyte.
Alkaline fuel cells (AFCs) were one of the first fuel cell technologies to be developed and were originally used by NASA in the space programme to produce both electricity and water aboard spacecraft.
Molten carbonate fuel cells (MCFCs) use a molten carbonate salt suspended in a porous ceramic matrix as the electrolyte.
Solid oxide fuel cells work at very high temperatures, the highest of all the fuel cell types at around 800ºC to 1,000°C.