Cleaning Up the World's Exhaust Pipes: They're Quiet, Efficient, Run on Renewable Energy Sources and Their Exhaust Is Just a Cloud of Water Vapour. Could the Rise of Fuel-Cell Vehicles Spell the End of the Internal Combustion Engine? (Renewable-Energy Special)

Article excerpt

When global car giant Daimler-Benz (now DaimlerChrysler) announced in 1997 that it was investing US$500million (300million [pounds sterling]) in a small Canadian fuel-cell manufacturer called Ballard Power Systems, the statement sent shock waves through the industry. The impact was immediate: fuel cells suddenly appeared on agenda in corporate boardrooms the world over. Up to that point, the entire global investment had been about US$ 1billion, much of it through NASA. Now, it seemed that the major car manufacturers were announcing new initiatives on a monthly basis. The head of Ford even predicted the end of the internal combustion engine.

Hydrogen-based fuel cells aren't the only renewable-energy alternative for the transport sector. Liquid bio fuels such as biodiesel and ethanol may also have a role. However, many analysts and car and oil companies believe that fuel cells are probably the key long-term option for transforming the global fleet of some 650 million vehicles that is literally choking the planet. The transport sector consumes 25 per cent of the energy we produce and its carbon emissions are rising faster than those of any other sector, so these developments can't come soon enough. But how credible are the alternatives to the oil-based internal combustion engine? And is it practical to shift the US$2trillion-a-year energy economy over to hydrogen?

Fuel for thought

It was the English natural scientist Sir William Grove who, in 1839, first discovered the principle behind the fuel cell. However, high production costs and low power output limited its use until 1988, when high-output fuel cells arrived on the scene and the race to develop a fuel-cell car began.

Fuel cells are a dream come true for air quality and the global climate. They run on renewable fuels and produce negligible amounts of pollutants or greenhouse gases. They are also extremely efficient, converting more than 60 per cent of the available chemical energy into electrical energy--about two to three times the efficiency of a conventional petrol engine.

Fuel cells effectively reverse the electrolysis process, combining hydrogen fuel with oxygen from the air to produce water, electricity and heat (see the graphic on page 90). They are typically combined in stacks and can be used as anything from tiny batteries to enormous power plants.

At present, hydrogen is produced on a relatively small scale for industrial use. Of course, water provides us with an abundant source of hydrogen, and liberating the hydrogen is relatively easy--simply passing electricity through the water will do it. However, much of our current electricity comes from polluting and/or non-renewable fuel sources. The hydrogen could be obtained from natural gas, but this again is a non-renewable fossil fuel.

Hydrogen is also highly flammable, potentially explosive and hence difficult to store and to distribute. It must be kept at -253[degrees]C to stay liquid, which requires lots of energy. And although there are tens of thousands of petrol stations around the world, there are only a handful of hydrogen stations. Turning the trickle of hydrogen produced at present into a supply and distribution network capable of serving whole nations of fuel-cell cars would take years, even decades, and cost billions.

For this reason, car and fuel-cell manufacturers are also working on systems that use methanol for fuel. Indeed, DaimlerChrysler's recent Necar 5, runs on methanol. Methanol and petrol are alike in many ways--in particular, methanol is a liquid at room temperature--so it wouldn't be very difficult to adapt the petrol stations and tankers of the existing distribution network to take methanol. Although methanol is currently produced primarily from natural gas, a non-renewable fossil fuel, it could be obtained in the long term from renewable sources such as organic waste. …