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High hurdles for hydrogen

High costs, technological hurdles and challenges from increasingly viable alternatives are clouding the prospects for hydrogen fuel cells, writes Ian Lewis

THE ATTRACTIONS of an on-board fuel that produces only water as a by-product and which can be produced from renewable sources are self-evident. However, the optimism of a couple of years ago – partly engendered by the US government's enthusiasm for hydrogen power – is fading.

"The technology is certainly better than it was a few years ago, but there are still a lot of difficulties in meeting cost targets, with the requirement for a new fuelling infrastructure and with the need for some level of government support, because the benefits are primarily public and the costs are primarily private," says David Hart, principal research fellow in the Centre for Environmental Policy, at London's Imperial College.

The most common technology uses hydrogen gas stored in a tank in a vehicle to produce electricity from a stack of fuel cells, which then drives an electric motor. This concept has been around since the 1960s, but has only been put to the test in anything other than basic-concept vehicles in the last few years. And the recent development spurt has thrown up some unexpected reliability issues, according to those working in the sector.

"After you've run something for 5,000 hours, you suddenly realise there are problems you didn't know about before and that is where the efforts are concentrated at the moment," Hart says.

Another problem has been the expense of safely compressing hydrogen to a level where it occupies an acceptably small space in a vehicle, while still giving the vehicle a decent range – a requirement for it to be adopted as a mass-market transport solution. Efforts have been made to introduce 700-bar hydrogen compression to supersede more commonly used the 350-bar compression standard, in order to reduce the size of on-board tanks. However, many in the sector are now resigning themselves to using 350-bar compression for the moment to avoid the higher cost and technical problems arising from containing the hydrogen at a higher pressure.

Overcoming public worries

The industry is well aware that it must also overcome public worries over the safety of hydrogen, a volatile gas that still conjures up visions of the Hindenburg airship disaster of 1937. Manufacturers also remember only too well the fate of diesel engines in the US, which, on their introduction in the 1970s, malfunctioned sufficiently that they remain unpopular in that country still. In Europe, where diesel engines were introduced later, they make up a much higher proportion of vehicles on the road.

As a result, there has been an unwillingness to rush hydrogen technology to the market before it has been rigorously – and expensively – tested to levels well beyond those likely to be experienced in everyday use.

However, despite hydrogen power's difficult evolution, new vehicles continue to be introduced gradually. Experimental hydrogen-powered buses and van fleets long visible in cities across Europe, the US and elsewhere are being joined by prototype hydrogen-fuelled cars from manufacturers such as Daimler Chrysler, BMW, GM, Mazda and Honda.

One of the latest, Honda's FCX Clarity, is set to be the first fuel-cell car to be given a production run – albeit a limited and, so far, undisclosed one – later in 2008, with sales envisaged in the Los Angeles region, where refuelling facilities exist. It can travel up to 270 miles on one tank and reach a speed of 100 miles an hour.

Honda says fuel economy is 20% better than its previous prototype and has a combined fuel-economy equivalent to around 68 miles a gallon. It notes this is more than double that of gasoline-powered cars and 1.5 times that of a gasoline-electric hybrid vehicle of comparable size and performance. Some of this improvement can be attributed to improvements in fuel-cell and battery technology that, among other things, have made the car significantly lighter than its predecessors.

While its high cost – mainly through leasing at around $600 a month – and restricted refuelling options mean this car does not mark the start of mass production of hydrogen-powered vehicles, the Clarity's launch is still a milestone for the sector. The data compiled by watching how it behaves in every-day use will be invaluable to engineers. "It's a very serious first step," says Hart.

Meanwhile, Iceland continues to make progress with plans to achieve by 2050 an economy run only on local, renewable energy sources, where hydrogen will be an important component, especially in the transport sector. Hire cars with batteries topped up by hydrogen power can already be rented in Reykjavik, the capital. By 2035, the government hopes, most cars will run on hydrogen in one form or another. In April 2008, the launch of a whale-watching vessel with a fuel-cell-powered auxiliary engine marked the first step towards an ambitious goal of powering the country's fishing fleet – one of the world's largest – with hydrogen.

Rivals gain strength

However, question marks remain over an industry that has a long lead time for development, could be years away from mass market commercialisation and is not alone in offering potentially plentiful, clean fuel. Japanese manufacturers have repeatedly cited 2015 as a date when they could foresee larger-scale production line runs of hydrogen-powered vehicles. GM and Daimler Chrysler have suggested the industry could take off as early as 2012.

But some analysts remain doubtful about the potential of fuel cells in transportation. "If everything goes well, you might see the start of some sort of mass production in 20 years' time, but if another technology develops faster then it may not happen at all," says Dolf Gielen, an analyst in the Energy Technology Policy Division of the International Energy Agency. "My impression is that enthusiasm [for hydrogen] is somewhat lower than a couple of years ago, not so much because of lack of progress in hydrogen, but because of the alternatives that have emerged."

In the short-term, biofuels provide the main competition, being relatively cheap and requiring comparatively little modification to existing tried-and-tested engine technology. While the environmental friendliness and effect on food production of present biofuels technology and production are matters of heated debate, second-generation biofuels may prove less controversial. If they deliver more efficient use of feedstock vegetation and put less pressure on arable land, then there may be little incentive to push ahead with costly alternatives.

In the longer-term, improvements in electric car-battery technology, providing greater battery lifespan and longer vehicle range, could prove to be the undoing of the hydrogen sector. Although such improvements may also benefit vehicles using hydrogen to charge batteries, it would also galvanise other technologies, not least the mains powered, or plug-in electric cars.

With the battery concept already well established in relatively reliable hybrid cars, such as the Toyota Prius, the idea of refuelling a car merely by plugging it into the electricity grid through a socket at home could prove a more attractive option for consumers than seeking out hydrogen from a limited filling-station network.

But the adoption of plug-in cars may create more problems than just those relating to reliability and range. An entire nation recharging its vehicles overnight is likely to test the capacity of any grid, raising the possibility of costly and difficult grid expansion.

It is also not impossible to produce hydrogen on a small-scale at home or at a workplace, as Honda has been eager to point out. The company says it is in the process of developing a home-based, solar-powered hydrogen generation system, though this is an expensive technique at present, and Honda has no immediate plans to commercialise it.

Developing sources

Developing solar power and other renewable energy sources to produce hydrogen is another important part of the equation, because most hydrogen today is produced by reforming natural gas – a process that adds to atmospheric emissions of carbon dioxide (CO2), unless carbon capture and storage technology is employed.

In addition, says Hart, it is likely that the automotive sector will be powered by a number of technologies, rather than just one single winner. The pace of change may ultimately be determined by the incentives offered by governments – especially those of the world's big vehicle-manufacturing countries – to cut down CO2 emissions from vehicles.

 

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