måndag 26 november 2007

What will cars be like when the oil runs out?

aptera 230 mpg electric 3-wheeled car
Originally uploaded by mod*mom.

The oil will not run out. It will just become more and more expensive. And will people kick the car habit when that happens? Not if they can help it.

What are the alternatives? Hydrocarbons are the perfect transport fuel. They come in convenient liquid form and have a high energy density.

One possible substitute is hydrogen. It can be converted into electricity using a fuel cell, with the cars driven by electric motors or it can be used in an ordinary internal combustion engine, suitably adapted. But fuel cells are likely to be expensive, since they use rare metals such as platinum. And hydrogen is difficult to store and handle, as it does not liquify except at very low temperatures, which makes it awkward and potentially dangerous to deal with. The biggest objection, however, is that energy is needed to manufacture hydrogen. As it does not occur naturally, it is not an energy source but simply a means of storing energy obtained from somewhere else.

What about biofuels? They are fine if they do not have to be grown specially, for example if they are made from waste materials, such as biogas from sewage and landfill sites.. Otherwise, the production of biofuels takes up land, water and other resources needed to grow food. Ethanol, another biofuel, can be made from waste products, though it tends to be made from crops specially grown. And ethanol-powered vehicles emit toxic and irritant gases.

How about electricity? As long as there are only a few electric vehicles, they can be powered by low-cost off-peak electricity which is usually available because nuclear power stations cannot easily be switched off. If there was any substantial number of electric cars all being charged at night, then the demand would quickly grow to the point that there would no longer be an off-peak period.

There is also the issue of batteries. These contain either lead or lithium. The former is toxic and the latter is a fire hazard. The production of both is energy intensive and they have a limited life; fortunately, the metals in them can be recycled quite efficiency. But they are heavy.

There are no easy answers but with the days of cheap portable energy coming to an end, the future of personal transport must be ultra-lightweight vehicles running at speeds where air resistance is not significant, which means around 30kph. And being too flimsy to share the roads with today's heavy vehicles, they will need a suitable infrastructure of their own.

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