Gair Rhydd

The automotive industry seems an unlikely candidate to save the planet. On British roads alone, over 30 million cars belch around 85 million tonnes of carbon into the atmosphere every year.

Yet the Geneva Motor Show a fortnight ago featured row upon row of “Green Machines”, with different alternative fuels each vying to become the power source of choice for cleaner cars.

Hydrogen fuel cells are a particularly impressive candidate for “greening” the motor trade. By reacting hydrogen and oxygen in the presence of an electrolyte – a non-metallic conductor in which electrical flow is carried by the movement of ions – fuel cells can generate electricity without combustion, pumping out only water and making them exceptionally environmentally friendly as a source of energy for transportation.

Though they have been used by NASA for the space programme, the cost of materials has ruled out widespread commercial use – until now.

For the cells to run at a low temperature and be useable for transportation, they need to use a catalyst to get the reaction started. The Polymer Electrolyte Membrane (PEM) cells in development for use in vehicles employ platinum as a catalyst, but platinum tends to degrade with use – and it’s expensive. Energy produced by fuel cells using platinum as a catalyst costs around $1000 per kilowatt – around $100,000 per car.

Earlier this year, however, research at Lawrence Berkeley National Laboratory in the US, sponsored jointly by the Department of Energy and General Motors, uncovered a platinum-nickel alloy 90 times more efficient than the carbon ones currently used. “It’s far and away the most active oxygen-reducing catalyst ever reported,” says Lawrence Berkeley spokesperson Lynn Yarris.

Though using this new alloy could reduce the amount of platinum required by a factor of 20, it’s still too expensive for the production-lines, but has paved the way for the next stage of development.

Project scientist Vojislav Stamenkovic says that the target energy cost of around $30 per kilowatt ($3000 per car) can be achieved by engineering nanoparticle catalysts with the same properties as the larger platinum-nickel crystals.

“This will have an impact on the total amount of platinum in the fuel cell, making the system less expansive and more efficient,” he says.

Fuel cells’ potential is exciting industry and government alike, with £50 million from the UK’s public purse being invested in a hydrogen ‘demonstration scheme’ as part of a wider commitment to the research, development and promotion of green alternatives. “Our ability to bring new clean energy technologies to market is fundamental if we’re going to radically reduce emissions,” says Climate Change and Environment Minister Ian Pearson.

Yet not everyone is convinced. Former US Assistant Secretary of Energy Dr Joseph Romm outlined the difficulty of using fuel cells for transportation in his book, The Hype About Hydrogen. He remains sceptical despite Lawrence Berkeley Lab’s breakthrough.

“So many things have to go right,” he says. “And someone’s still going to have to build the hydrogen fuel stations. I don’t see that happening.”

The production and distribution of the hydrogen remains the biggest hurdle. Not only is it difficult to transport and store, as it’s so light, but it also doesn’t occur naturally and has to be produced from water – and uses more energy making it than can be extracted in fuel cells.

As the initial energy input often comes from coal-fired power stations, its green credentials are questionable – it would need to be manufactured using clean energy sources for there to be any environmental benefit.

That hasn’t stopped oil companies getting on board to maintain their fuel supply business when fuel cell technology comes into widespread use. The first forecourt to supply liquid hydrogen for fuel opened in Reykjavik in 2003, powering the city’s bus fleet. Its owners, Royal Dutch Shell, have a division devoted to the development of fuel cell technology, and expect a market by 2015.

But economics writer and precious-metal dealer Tim Worstall – who subsidised initial research into a different kind of fuel cell and is currently supplying materials for them (see “Are the best kind of fuel cell”, below) – has another idea. “As far as I can see it’s going to have to be distributed generation: home fuelling packs,” he says.

Worstall claims that the best way to produce the required fuel at home is to use titanium dioxide, in the presence of sunlight, to split water into hydrogen and oxygen. “Make roof tiles out of titanium dioxide slag, which is pretty cheap stuff – it’s the white in white paint – and generate the hydrogen from the rooftop of your house,” he suggests. “All this is at least another decade away, though.”

Even if full development of the technology is ten years away, there’s cause for enthusiasm already. The most advanced hydrogen-powered car to date is General Motors’ HydroGen3 prototype, approved for use on public roads in Japan. It has a range of 250 miles and a top speed of 100mph – and its fuel cells are small enough that they could potentially be manufactured in an existing plant. After another decade of development, hydrogen fuel cells might just achieve what was previously thought impossible: pleasing both petrolheads and environmentalists.

Are they the best kind of fuel cell?

While most current fuel cell research and development concentrates on PEM cells such as those being developed by Lawrence Berkeley Lab, the Solid-state Energy Conversion Alliance, part of the US Department of Energy, is funding research into solid oxide fuel cells (SOFCs), with a parallel programme in the EU.

Rather than taking in air, SOFCs use an oxide electrolyte to provide the system with oxygen. Although they use less expensive materials than PEM cells, they need to run at a high temperature (around 900ºC) and are, at present, better suited to use in combined heat and power plants for the home or businesses.

Though the technology is five to ten years behind PEM cells, they could be used at a lower temperature – and for vehicles – in the future, with the addition of the rare earth metal scandium. Tests on an electrolyte made of scandium, yttrium and zirconium oxides as part of the EU’s SOFC programme have shown that the required temperature comes down. They are currently experimenting with the proportions of each element to get the lowest possible starting temperature.

Alternative Alternatives

Biofuels

Fuel made from living organisms or their byproducts, usually refers to biologically produced diesel and ethanol (“biodiesel” and “bioethanol”). Biofuels are carbon neutral – since the carbon released has been recently captured by plants, they don’t affect the net amount of carbon in the atmosphere. The energy released per amount of carbon emitted is lower than for fossil fuels, however.

While biologically derived fuels have EU support under their Biofuels Directive, with a target of 5.75% of energy generation to come from biofuels by the end of 2010, they’re plagued by politics in the US, where the government is subsidising production of biofuels from corn rather than using more efficient imported sugarcane – the amount of corn required to produce enough fuel to fill an SUV could feed an average person for a year. Increased demand has also raised the price of food, with the cost of British wheat increasing by over 50% in the last year.

An advantage of biofuels is that they can be some can be used in existing engines – many diesel engines will run on biodiesel, and fuel composed of 100% biodiesel is available across Europe, though it is more common to use a blend of up to 20% bi-diesel and 80% hydrocarbons.

Solar

Powered by an array of solar panels attached to the car’s body. Although they’re about as environmentally friendly as it gets, solar-powered vehicles are inefficient except in the case of golf buggies, which spend most of their lives parked and recharging. While they are useable in sunny climes such as Australia, where the Wold Solar Challenge sees sun-powered vehicles racing over 3000km every two years, for much of the UK (and elsewhere) it would be more useful to employ rain-power than solar. They aren’t great performers either – even specially built racing cars which minimise friction and drag, such as the Dutch-built Nuna 3 (pictured), are currently limited to under 90mph, and unlikely to get any quicker.

Although their poor performance and adverse climate all but rules out their use in much of the developed world, they may be a useful technology in warmer developing countries where the other green alternatives may find it hard to penetrate.

Electric

Although the Sinclair C4 may have ruined their image forever in the UK, battery-powered vehicles have much more support than hydrogen-based technologies in the US, where they’re under production by almost every major car company. They share many issues with hydrogen: their lack of emissions is only truly green if the electricity used to charge the batteries comes from a clean source, but at the same time a devoted home solution – solar panels or a miniature wind turbine – could be employed.

While lengthy recharge times have previously been a problem, Phoenix Motor Cars recently launched a 250 mile range battery pack rechargeable in just ten minutes.

Later this year, Tesla Motors are due to release a roadster developed in partnership with Lotus, with a sale price of around $100,000 (£50,000). Their prototypes were capable of travelling 250 miles before needing to recharge, ran at an energy cost equivalent to 135 miles per gallon of petrol and achieved a top speed of 130 miles per hour – only 20mph slower than Lotus’s Elise.

The current, slower models of electric car are useful for stop-start city driving where speed isn’t too important. However, the wear caused by frequent short trips can damage the battery – and they can cost up to $20,000 to replace.

Hydrogen combustion

BMW are currently pioneering hydrogen internal combustion rather than fuel cells – essentially the same as a normal internal combustion engine but burning liquid hydrogen rather than petrol.

Yet while this avoids the need for an expensive catalyst as with PEM cells or high temperatures as with SOFCs, the inherent inefficiency of combustion combined with the cost of producing hydrogen in the first place means it’s unlikely that this would be any cheaper than using fuel cells. Joseph Romm, sceptical as ever, described it as a “particularly pointless thing to do”.

Like biofuels, however, they do have the advantage of being able to provide transportation with zero carbon emissions at the point of use without the need for significant technological development – existing engines can be converted to run on hydrogen.

As is the case with many of the other alternatives mentioned, while this hydrogen would, in the short term, be produced in coal-fired power stations, it would be beneficial to produce emissions only in a limited number of locations, where they can be easily managed.