River Wissey Lovell Fuller

Electric Cars

June 2001

They Are Coming (One Day)

Looking at the feasibility of electric cars with rechargeable batteries last month I concluded that they are never likely to be viable for any purpose other than short journeys or urban work. This conclusion was reached simply on the basis of the practical difficulty of recharging at a sufficiently high rate to enable enough energy to be stored for use on longer and faster journeys.

Electric cars in which the electricity is generated within the vehicle do remain a strong possibility, however, and the most promising method of generation is the fuel cell. Fuel cells are devices in which the potential energy released from a chemical reaction is converted directly into electricity.

The conventional way of harnessing the energy release from a chemical reaction is to allow that reaction to produce heat through a combustion process and then to use some form of engine to convert the heat into work. Unfortunately the second law of thermodynamics restricts the efficiency with which heat can be converted into work so that the overall efficiency of the conversion of chemical energy into work is strictly limited. In a fuel cell the chemical energy is converted directly into electricity without the intermediate step of combustion with a resulting major improvement in efficiency.

A fuel cell was successfully demonstrated by a man named Bacon around 60years ago or more, he fed hydrogen and oxygen into the cell and produced electricity. Since then there has been significant development of the hydrogen-oxygen cell which has found wide application in the space programme where the presence of the two substances as fuel and oxidant for the main rocket motors made them particularly suitable. For some years there was extensive research endeavouring to produce a fuel cell for road vehicles that would burn hydrocarbon fuels. This work met with some success after pre-treating the hydrocarbon fuel to generate hydrogen and carbon monoxide but does not appear to have achieved a point where it could be practically and economically applied.

With the growing concern over global warming, which most believe to be attributable to the burning of hydrocarbon fuels, and concern over the limited nature of world oil reserves, there has been increased attention given to the possibility of hydogen-air fuel cells for automotive applications. This attention has been encouraged because it represents an environmentalist's dream as the only exhaust product, after combining the hydrogen with the oxygen.

Ron Watts

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