[H.sub.2] $.

Your article on hydrogen fuel ["California Drives the Future of the Automobile," March/April] neglects one of the most important pieces of information: cost. On an equivalent energy value, industrial hydrogen costs about 10 times the price of gasoline. Of course, a gasoline engine only has a thermal efficiency of 25-30 percent, while a fuel cell operates at 50-60 percent efficiency, effectively dropping the cost of hydrogen derived energy to just five times that of gasoline.

I can just hear the protests from the Rocky Mountain Institute, which has a detailed plan for an ultralightweight 500-kilogram (kg) car whose 100-mile-per-gallon+ economy would compensate for the high cost of hydrogen. Who will be first to pilot such a vehicle on roads populated by 3,000-kg SUVs and pickups, not to mention 10,000-20,000-kg transport trucks?

I can hear others stating that technology will make hydrogen cheaper to produce. Your article states that hydrogen is now obtained by stripping it off methane, the cheapest source. Of course, that would make the hydrogen a "fossil fuel"! It can be a renewable resource if obtained from crop-derived ethanol, [but even] if you strip all six hydrogen atoms from ethanol you will capture 53 percent of the energy from the molecule. If you can only get four atoms, then you will get just 36 percent of the energy.

If you use electricity to generate hydrogen by hydrolyzing water, the hydrolyzer wastes around 40 percent of the energy input as heat. Then the gas must be compressed to at least 2,000 psi for transfer to a vehicle pressure tank. Compression generates more heat, which must be dissipated, wasting yet more energy. In the fuel cell, efficiency is roughly 55 percent. So the overall efficiency with which the original electricity powers the wheels is 0.55 X 0.60 = 33 percent. While slightly better than a gasoline car, this is considerably worse than either my diesel Mercedes "Smart" or my diesel VW, whose thermal efficiency is around 43 percent.

Satisfying our appetite for motor fuel with hydrogen will require new generating plants. If coal-fired, emissions of greenhouse gases and heavy metals will rise, even if gasoline consumption is displaced! I have not noticed any appetite for nuclear electricity in the U.S.A. and there is little in Canada. So it will have to be wind turbines and photovoltaics. Neither source of electricity is cheap.

PETER BURSZTYN

Barrie, Ontario, Canada

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