Sorry about the length of this!
But I thought some here may find interesting...
(© Prospect Magazine, Feb 2002)
You can tell that something is going on in the motor industry when the sexiest and most futuristic car on show at this year?s Detroit motor show does not even have an engine. Instead, Autonomy, a prototype put on display by General Motors a few weeks ago, is powered by fuel cells.
A fuel cell is a device that combines oxygen and hydrogen to produce electrical energy, with heat and water vapour as byproducts. Combine a fuel cell with an electric motor, and the result is an engine that produces no noxious emissions or climate-changing carbon dioxide; and since oxygen is available from the air, a fuel cell powered car simply needs a steady supply of hydrogen to keep going. A further benefit, as the curvy Autonomy prototype demonstrated, is that fuel cells place fewer restrictions on the car?s shape. They do not all need to be concentrated in one place, as with a conventional engine. No more pollution, and the scope for radical new designs: little wonder that the motor industry has decided that fuel cells are the future.
There is no question that fuel cell vehicles are practical. Many prototypes are already running. Their technical viability has been demonstrated in trials, notably in California, where tough environmental legislation requires car makers to develop cleaner alternatives to petrol or diesel engines. Fuel cell-powered prototype buses are already running in some cities. DaimlerChrysler aims to be the first to the market with a fuel cell car based on the Mercedes-Benz A-Class, which is expected to go on sale in 2004. Other manufacturers also have fuel cell vehicles in the pipeline. Although a fuel cell now costs about 100 times more than a comparable conventional engine, the cost should fall as fuel cells enter mass production.
But there are still hurdles to overcome. The most obvious problem is how best to distribute and store the hydrogen fuel. Hydrogen is a gas at room temperature, and explosive when mixed with oxygen. Pressurised tanks are heavy and bulky. So various schemes have been devised to store hydrogen and enable quick, easy refuelling of hydrogen-powered cars. One promising approach relies on sponges made of carbon nanotubes. As its name suggests, a carbon nanotube is an extremely thin carbon tube, just a few nanometres (billionths of a metre) thick, and has the helpful property of being able to hold substantial numbers of molecules of other substances, including hydrogen, on its surface. So it might be possible to run cars on hydrogen ?bricks? made of nanotubes that could be swapped in and out at filling stations. Another approach involves storing the hydrogen as a liquid hydride. The hydrogen is extracted from the liquid to power the fuel cell, and the resulting liquid is stored in a second storage tank. Refuelling the car then involves pumping out the used liquid, and refuelling with fresh sodium borohydride.
Even when a sensible way to deliver and store hydrogen has been found, however, fuel cells are no silver bullet when it comes to eliminating pollution. For there will still be the problem of supplying hydrogen in the first place. Hydrogen does not grow on trees or emerge from wells. Despite being the most abundant element in the universe, on earth it is almost invariably combined with oxygen (in the form of water) or carbon (in the form of various hydrocarbons). Both water and hydrocarbons are plentiful. But extracting hydrogen from water requires lots of energy, which has to come from somewhere. Similarly, extracting hydrogen from hydrocarbons such as natural gas or coal also requires energy. Worse, it produces carbon dioxide, a greenhouse gas, as a byproduct. In short, while fuel-cell cars are likely to make the air easier to breathe in congested cities, they merely push the pollution problem ?upstream? to the hydrogen plants that will produce the fuel needed to run them.
That is not the car industry?s problem, of course. And there may be some virtue in moving pollution away from the automobile, which will often be in an urban location, to some remote place where humans are barely affected by it. But there is no escape from greenhouse gases, for they make an equal contribution to the atmosphere, and potentially to global warming, wherever they are emitted. The real problem, and one that car makers by definition have no interest in addressing, is western society?s addiction to the car.
Is there an alternative? One person who thinks so is Dean Kamen, an American inventor, who unveiled his much-hyped Segway Human Transporter, a fancy computerised scooter, in December. ?Cars are great for going long distances,? he told Time magazine, ?but it makes no sense at all for people in cities to use a 4,000-lb piece of metal to haul their 150-lb asses around town.? This is undeniable, with or without fuel cells. But Kamen?s vision of the future of transportation was greeted with smirks and laughter. Yet even if you do not agree with his answer, at least Kamen is asking the right question.
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