by December 5, 2002 0 comments

As we become increasingly mobile, we need more power to power our mobile devices, be them cellphones or notebooks or even the vehicles that carry us around. Traditional batteries are too bulky for comfort, and this is where fuel cells come in.

A fuel cell is an electrochemical device that produces electric power using hydrogen as fuel. This fuel may come from hydrogen gas itself, or hydrocarbons, such as methanol, propane, butane or natural gas. The hydrogen is oxidized using a suitable oxidant or even pure oxygen. The oxidation process releases large quantities of energy that can be converted into electricity. Fuel cells have an easily replaceable liquid fuel capsule, thereby, removing the need for messy recharging. 

A fuel cell works like a battery. It has an electrolyte sandwiched between the anode (the one with hydrogen) and the cathode (the one with oxygen) The hydrogen atom at the anode splits into a proton and an electron which take different paths. The proton passes through the electrolyte to the cathode, creating a current before it gets converted back to hydrogen, which now combines with oxygen to form a molecule of water. A fuel cell, thus, generates electricity, water and heat as byproducts of this reaction.

Hydrogen can be extracted from any hydrocarbon fuel like natural gas, methanol or propane.

Efforts are on to make fuel cells useable with laptops, cellphones, portable electronics, cars, buses, boats, trains and even planes. 

Fuel cell options
Direct Methanol Fuel Cell: It is targeted at cellphones, laptops and the like. This cell is similar to the PEM cells as it uses a polymer membrane as the electrolyte. 
Proton Exchange Membrane: Generating from 50 to 250 kW of power, it has a thin plastic sheet, the Proton Exchange Membrane, that allows hydrogen ions to pass through it.
Phosphoric Acid: Can use impure hydrogen as fuel, and is large size.
Molten Carbonate: This cell is for electric utilities and generates 10kW to 2MW. 
Solid Oxide: This cell is for large-scale generating stations and can give an output of 100kW and operates at 1000o C. 
Alkaline Fuel Cells: Can give an output of 300 watts to 5kW.

Fuel cells require oxygen and hydrogen to function. The oxygen comes from air, which is pumped into the cathode, but hydrogen is not so readily available. Since hydrogen is difficult to store, a device known as a reformer extracts hydrogen from hydrocarbon fuels. But reformers are not perfect, since they generate heat and do not produce pure hydrogen. This reduces the efficiency of a fuel cell.

Another concern with fuel cells is that since most of them contain flammable hydrocarbons, they would themselves be flammable. One big hurdle was crossed recently, when the US Department of Transportation approved laptops powered by fuel cells from PolyFuel to be carried aboard US aircraft.

Currently most fuel cells are quite big in size. That stands in the way of integrating them with cell phones and

Varun Sharma

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