Which way ahead for hydrogen cars?
Box 1 | Plenty of power from fuel cells
The fuel cells in the Opel wagon that stole some of the limelight at the marathons at the 2000 Sydney Olympics took up no more space than a normal car engine. A few years ago the stack of fuel cells needed to run such a car would have taken up the whole boot and back seat area. And the hydrogen-powered Opel has good performance credentials – it can accelerate from 0 to 100 kilometres per hour in 16 seconds and has a top speed of 140 kilometres per hour.
Fuel cells have been around for a long time – Sir William Grove, a Welsh physicist, invented one that ran on hydrogen way back in 1839 – but their potential as a commercial power source is only now beginning to be realised. With different applications in mind (from large-scale power generation to electricity for portable electronic devices), researchers are working on many types of cells – alkaline, phosphoric acid, molten carbonate and proton exchange membrane (PEM). In Australia, CSIRO and industry researchers are collaborating in developing a solid oxide fuel cell.
A fuel cell for vehicles
For vehicles, attention has focused on the PEM fuel cell. Its key component, the membrane, is a sheet of rubbery plastic coated with a platinum catalyst. The catalyst splits hydrogen gas into protons and electrons (a hydrogen atom comprises just one proton and one electron). The protons pass through the membrane and the electrons leave the cell along wires; this is the electric current generated by the cell. When the protons and electrons meet again on the other side of the membrane, they combine with oxygen to form water. As long as hydrogen is supplied the cycle continues, with hydrogen and oxygen being turned into water while generating electricity. A great advantage of this type of fuel cell is that it operates at 60-90ºC whereas other types require temperatures of 500-1000ºC.
The breakthroughs that turned stacks of PEM cells into suitable power packs for cars came in the 1990s. Ballard Power Systems of Canada, whose two largest shareholders are DaimlerChrysler and Ford, discovered a way to multiply a stack’s power output per litre of cell space from less than 200 to more than 1300 watts. With such a stack under the bonnet, an electric car can match the performance of petrol-powered models.
Trials of PEM fuel cell buses in Perth
Trials of Mercedes-Benz buses powered by Ballard’s PEM fuel cells have been conducted successfully over the past few years in Chicago and Vancouver, and Perth is one of eleven cities around the world to host a bigger series of trials. Beginning in 2002, these trials involve a total of 33 fuel cell powered buses. The three buses in Perth slot into the regular commuter fleet and are fuelled by hydrogen produced at the BP petroleum refinery at Kwinana.
Box
Box 2. Alternative hydrogen storage systems
Related sites
Fuel cell descriptions (US Department of Defense Fuel Cell Demonstration Program)
How the PEM fuel cell works (Schatz Energy Research Centre, Humbolt State University, USA)
Posted May 2001.