Thursday, September 07, 2006

What Should I Know About Fuel Cell Cars?

Fuel Cell Cars
By Marius Ciobanu

Fuel Cell cars are the cars of the future. A lot of research has been done with electric cars, but until the battery costs go down, the driving range goes up and the weight of the batteries goes down, this will not be an option for the general public, unlike the popular hybrid cars. A hybrid car has a gas engine and an electric engine. The gas can continually recharge the electric batteries.

In a fuel cell car, the fuel used is compressed or liquid hydrogen. A fuel cell converts hydrogen and oxygen to water, and produces electricity. Due to ongoing problems with storing liquid or compressed hydrogen, currently, mostly buses are using fuel cell technology. They can hold large tanks of compressed hydrogen on their roofs. The type of hydrogen fuel cell currently used for buses and cars is the Proton Exchange Membrane Fuel Cell (PEMFC).

The fuel cell uses a catalyst, which is a platinum powder or compound, to facilitate the reaction of hydrogen with oxygen. The catalyst is spread as a thin coat on a large surface for maximum effect.

Why are there problems using hydrogen as a fuel? Except at high compression, and/or low temperatures, hydrogen is a gas. It is the lightest gas, and would tend to have high leakage through pipelines. Due to its high energy content, it is also very explosive. There was the explosion of the Hindenburg in 1937 in New Jersey. That was a hydrogen lifted dirigible which went on fire. Due to the use of heavy safety equipment to compress hydrogen, this is why fuel cell technology is first being used in buses.

Another option being developed is to use hydrocarbons that are hydrogen rich as the basis for hydrogen fuel cell technology. Hydrocarbons are compounds of hydrogen and carbon. The leading candidates are CH4, which is methane gas, a pure form of natural gas, and methanol, a liquid alcohol compound, CH4OH. Both methanol and methane can be converted to hydrogen gas using a chemical reformer. Reformers have a drawback in that they lower fuel efficiency by as much as half. There is increased miniaturization of chemical reformers for automobiles.

However, other compounds are being experimented with that are easier to catalytically convert to hydrogen for a fuel cell and can be more easily stored in a vehicle’s fuel tank. An example of the type of system that could work is being experimented on at Daimler-Chrysler. It involves simple borate, borax, a compound chemical that is produced and used for soap. A running prototype minivan was displayed at the North American Auto Show in 2002. The hydrogen fuel cell can run on hydrogen that is liberated in a simple chemical reaction from sodium borohydride. This chemical can be made in refineries from a combination of borax soap and Hydrogen gas. The vehicle could run on sodium borohydride, which would be processed in the car to yield hydrogen gas for the fuel cell. The only exhaust product would be water (H20). The other waste product would be borax (a form of soap), which would then have to be reprocessed to sodium borohydride, to refuel the car again. Infrastructure to produce hydrogen from methane or ammonia and then produce sodium borohydride would be necessary at your local refueling station.

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