FUEL CELLS - Desktop Study

3. FUEL CELL TYPES

Fuel cells are categorised by the electrolyte employed, and include the following types-

- SPFC; Solid Polymer Fuel Cell (or Proton Exchange Membrane)
- AFC; Alkaline Fuel Cell
- PAFC; Phosphoric Acid Fuel cell
- MCFC; Molten Carbonate Fuel Cell
- SOFC; Solid Oxide Fuel Cell

These types operate at a variety of temperatures ranging from less than 100 degrees C to around 1000 degrees C. Each has a slightly different chemical reaction and ion transportation mechanism, as well as an impurity tolerance and electrical performance. 

Proton Exchange Membrane
Proton Exchange Membrane fuel cells operate at relatively low temperature of about 80 degrees C and have an efficiency of about 40%. They use hydrogen as a fuel and have a great future for automotive applications and to replace small batteries.

Alkaline fuel cell
Alkaline fuel cells use very pure hydrogen as a fuel and use alkaline potassium hydroxide as the electrolyte. They can achieve very high efficiencies (up to 70%) and operate under low temperature, about 70 degrees C. Alkaline fuel cells have been used in space missions by NASA, but until recently they were too expensive for commercial applications. Nevertheless companies like Zevco (Belgium) and Ballard (Canada) have reduced the capital costs and approached (and in some cases started) commercialisation.

Phosphoric Acid Fuel cell
Phosphoric acid fuel cell operate at 200 degrees C and can use different fuels such as natural gas and methane. They need an external reformer to use fuels other than hydrogen. Their efficiency is about 45%. They are used for applications such as CHP plant from 200 kW to 20 MW

Molten carbonate fuel cell
Molten carbonate fuel cells promise to convert coal-based fuel with a high efficiency of 50-60%. This cell operates at 600 deg. C and is used in huge power plant (1 to 2 MW).

Solid oxide fuel cell
Solid oxide fuel cells have high efficiency (near 60%) and operate at high temperatures - about 1000 deg. C. They are used in CHP power plant of size ranging from 2KW to 20 MW.

Back to top                  Next section