Fuel Cell Types

The fuel cell is in principle very simple, however the chemical reactions do not readily take place, and unless special materials are used for the electrodes and the electrolyte, the current produced per cm2 is extremely small and the electrical power losses in the electrolyte are very large. To overcome these problems different types of fuel cell have been developed, The different varieties are distinguished by the electrolyte used, though the construction of the electrodes is also different in each case. However, in all types there are separate reactions at the anode and the cathode, and charged ions move through the electrolyte, while electrons move round an external circuit. Another common feature is that the electrodes must be porous, because the gasses must be in contact with the electrode and the electrolyte at the same time.

The types of five types of fuel cell that are in current use, or show that most promise are:-

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  TYPE	 OPERATING TEMP.      PRESENT OR POTENTIAL APPLICATIONS
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ALKALI	  50 - 250 oC	Used in space vehicles (Apollo, Shuttle)
			Possible uses in land vehicles and submarines
------------------------------------------------------------------------ 
SOLID	  50 - 100 oC	Great potential for cars and buses, but also
POLYMER			a host of other applications.
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PHOSPHORIC   ~220 oC	Medium scale CHP systems. 200kW units in
   ACID			commercial production by IFC Corp., USA
------------------------------------------------------------------------
MOLTEN	     ~600 oC	Medium to large scale CHP systems. 1-2 MW
CARBONATE		trial systems being built now.
------------------------------------------------------------------------
SOLID	500 - 1000 oC	All sizes of CHP systems, 2kW to multi MW
OXIDE			Least developed, but potentially very widely useful
------------------------------------------------------------------------
For further details about all these fuel cells, you are referred to an excellent new book, "FUEL SYSTEMS EXPLAINED", by J.Larminie and A.Dicks, published by J.Wiley & Sons, ISBN 0471 49026 1. It is available from April 2000 in the UK, and from June in the USA/Canada.

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