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'Soap' may make clean fuel-cell cars feasible

Volatile hydrogen can be stored safely in sodium borohydride

By Eric C. EvartsSpecial correspondent of The Christian Science Monitor / January 31, 2002


Space-age fuel cells that could eliminate auto emissions look as if they're just over the horizon.

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The key, if automaker DaimlerChrysler is right, is soap.

What's been holding back development of fuel-cell cars - which consume only clean, abundant hydrogen and emit only steam - is that the storage tanks such vehicles require are so big, there's hardly room for passengers, let alone cargo.

But DaimlerChrysler may be onto something with, in effect, a soap factory under the hood.

It involves simple borate - a chemical mined from the ground and used as laundry detergent.

The company showed a running prototype minivan at the North American International Auto Show in Detroit earlier this month that demonstrates the viability of the "borax fuel cell."

The fuel cell runs on hydrogen taken from sodium borohydride - a man-made chemical - in its "gas" tank. What's left is borax soap in the tank. The only emission from the tailpipe is steam.

If this works, it could have ramifications far beyond your driveway. Fuel cells - the power plants that provide heat and computing power to spacecraft - are seen as the power source of the future because they produce clean electricity from a virtually unlimited power source, hydrogen, and produce no pollution other than steam.

How fuel cells work

Fuel cells work by converting hydrogen and oxygen into water and electricity. While there are several varieties, the leading candidate for small consumer fuel cells are so-called proton exchange membrane or PEM fuel cells. This variety divides two chambers on opposite sides of a platinum-coated plastic membrane with microscopic holes just big enough for a hydrogen proton to jump through.

An electric circuit - in this case driving the van's motor - connects the two sides. Flip a switch - or step on the accelerator - and electrons leap off the hydrogen molecules and zip around the circuit. Meanwhile the positively charged hydrogen protons slip through the membrane, and with the help of their reunited electrons, bond with the oxygen on the other side to form water.

Since no combustion takes place, impurities in the air (the oxygen side of the fuel cell) are left alone and don't form smog.

Fuel cells are coming down enough in price to be competitive with electrical generators for midsize buildings. They are expected to be cheap enough to power cars in the near future.

Cars, badly in need of a new power source to replace the internal combustion engine, are likely to be the breakthrough application that could catapult fuel cells into daily life.

"Hydrogen fuel-cell vehicles would be a breakthrough on transportation as well as commercial and stationary [energy] efficiency." says Michael Brylawski, vice president of Hypercar Inc., in Snowmass, Colo., a company that hopes to commercialize a hydrogen fuel-cell car. He says they would usher in the renewable hydrogen economy, independent of fossil fuels.

He notes that a fuel-cell car could provide light and heat for houses when parked in the garage at night: The car's fuel cell could plug into the house to provide home electricity produced from hydrogen in the car's tank.

Since fuel cells run directly on hydrogen, they don't rely on fossil-fuel-burning power plants for energy, as battery-powered electric cars (ultimately) do.

For energy efficiency, the borax fuel cell could surpass all but gaseous hydrogen. Borate would have to be mined, hydrogen produced from water or some other chemical (possibly by solar energy), and sodium borohydride made in a factory.

All these processes use energy but promise to be more efficient than a fuel cell powered by liquid hydrogen, says Thomas Moore, vice president of future technology at DaimlerChrysler.

The bugaboo of automotive fuel cells so far has been storing hydrogen on board - and having any room left for people in the cars. In fact, the only commercially viable fuel-cell vehicles today are city buses that have enough space for large hydrogen tanks on the roof. Several are in use in Chicago and Vancouver, British Columbia.

Filling stations needed