Stirring up trouble?

Ill founded? Well intentioned? Just a storm in a scientific teacup? Roger East seeks some perspective on a row about the alleged risks of hydrogen leakage.

The hydrogen industry is so sensitive to safety scares that the mere mention of Hindenburg can trigger its 66-year-old posttraumatic stress syndrome. It was 1937 when the airship of that name went dramatically up in flames, taking with it the high hopes invested in dirigibles as a form of transport. The horror of that incident casts a long shadow - even though recent research has shown that the conflagration had little to do with all the hydrogen that provided the airship’s buoyancy.

We now know it was down to the flammability of the airship’s skin coating, set alight by static electricity. But the damage is done. Small wonder, then, that the defenders of hydrogen got their guns out fast this summer, when a paper published in Science raised a different kind of safety issue - on the global environmental level.

In this controversial paper, Tracey Tromp et al. wrote up what a team led by Yak Yung had been calculating at the California Institute of Technology. This turned not on the carbon-cutting emissions benefits of a much-hyped future energy solution, but on a potential link - horror of horrors - with damage to the ozone layer. Hydrogen leakage, said the Californian researchers, scaled up to the proportions that might characterise a wholly hydrogen-based fuel economy, could raise the water content of the stratosphere. The cooling effect of this could affect the chemistry in such a way as to exacerbate the problem of those ozone holes at the poles, about which we’ve rightly become so concerned.

Among those who cried ‘foul’ was the German Hydrogen Association (DWV), decrying the paper’s assumption of 10- 20% hydrogen leakages as a figure “plucked from thin air”. Helpfully reminding us that making, moving and using hydrogen is not a new development - it is long established on a substantial scale in the chemicals industry, where the volumes required will continue to outstrip ‘energetic use’ for some years - the DVW also points out that there’s no sign so far of the dire effects of leakage predicted in the Science paper.

“If hydrogen is shown to be environmentally friendly in every respect, then designers could potentially save billions in needless safeguards.”

The DVW position remains that hydrogen is clean and safe, and that the obstacles on the way to hydrogen energy are mainly economic and political in nature, not scientific or technical. The high efficiency of the hydrogen fuel cell offers a realistic way forward in the rational use of resources. But this will sit alongside, not replace, the generation of energy by other (and, increasingly, renewable) means. Hydrogen can be a good ‘vector’, a means to store and transport energy wherever there are obstacles to the final delivery of electricity. And electricity will remain our most important energy for the foreseeable future.

The Rocky Mountain Institute’s hydrogen hero Amory Lovins also entered the lists to criticise, or rather to condemn, the Science paper. Its assumption of 10- 20% hydrogen leakage, he says, is a simple misreading of its own references, which really state that the German hydrogen system loses 0.1% of its throughput to leakage, and that a completely hydrogen based global economy leaking even as much as 2-3% (and using no direct renewable energy) would emit about as much hydrogen as the fossil-fuel system emits now.

For all the alarm bells rung by their claims, Yak Yung’s team would surely say they are being no more than prudent about possible hydrogen leakage problems. It may be, they admit explicitly, that excess hydrogen will simply be absorbed in the soil rather than the atmosphere. But what no-one should dispute is the importance of a better understanding of the whole hydrogen cycle. “We have an unprecedented opportunity this time to understand what we’re getting into before we even switch to the new technology,” says Tracey Tromp, the lead author, making a telling comparison with “the case with the internal-combustion engine, when we started learning the effects of carbon dioxide decades later”. As another colleague, John Eiler, elaborates: “If we had had perfect foreknowledge of the effects of carbon dioxide a hundred years ago, would we have abandoned the internal combustion engine? Probably not. But we might have begun the process of controlling CO2 emissions earlier.”

“Understanding the effects of hydrogen on the environment now”, says Tromp, “should help direct the technologies that will be the basis of a hydrogen economy. If hydrogen emissions present an environmental hazard, then recognising that hazard now can help guide investments in technologies to favour designs that minimise leakage. On the other hand, if hydrogen is shown to be environmentally friendly in every respect, then designers could pursue the most cost-effective technologies and potentially save billions in needless safeguards.”

Scientists, in their nature, are apt to stress the need for more research, though none would want to be suspected of scaremongering. Yet the status quo is unsustainable, and our need for solutions is pressing. The balance between precaution and prevarication is becoming familiar territory, if not common ground, in some of the biggest debates around science and sustainability. When it comes to playing up the possible downsides of hydrogen, perhaps it pays to pose the cynic’s question: who benefits?

DEMYTHTIFYING

The ‘ozone myth’ isn’t the only dragon that Amory Lovins sets out to slay in his advocacy of hydrogen as the fuel of the future. No fewer than 19 others are targeted in his typically coruscating essay ‘Twenty hydrogen myths’. Among these are:

Won’t it actually increase carbon emissions?

In the short run, hydrogen will indeed be made mainly by ‘reforming’ natural gas, as it is now, rather than by electrolysis. But by using that hydrogen in fuel cells, vehicles should still halve total carbon emissions per mile - and offer over 80% cuts in quintupled-efficiency vehicles. That’s a lot better than likely reductions without hydrogen, and is a sound interim step while zero-carbon hydrogen sources are being deployed.

Isn’t hydrogen likely to squeeze out renewables?

Both many renewables and many hydrogen programmes are worthwhile and important for national prosperity and security. We should do both, not sacrifice one for the other. Fortunately, hydrogen creates important new economic opportunities and advantages for many renewable energy sources, so a well designed hydrogen economy should speed up the wide adoption of renewables.

Doesn’t making hydrogen use more energy than it yields?

Yes - that’s a law of physics that applies to any form of energy conversion. But that’s only part of the equation. The pay back is getting a form of energy that’s both portable and highly efficient to use. Using oil is typically 88% efficient from wellhead to car tank, but only 16% efficient from car tank to wheels. That’s 14% from well to wheels. Hydrogen in an advanced fuel-cell car does three times better - its (lower) 70% efficiency from natural gas well to hydrogen in the tank, and (much higher) 60% efficiency from tank to wheels, works out at 42% overall.

Isn’t fuel cell technology both unproven and prohibitively expensive?

Invented in 1839, fuel cells have been widely used for decades in aerospace and military applications. Breakthroughs since the early 1990s mean that, even in this decade, they’ll start becoming affordable. As for most other manufactured goods, real cost should fall by about 15-30% for each doubling of cumulative production.

Aren’t the financing requirements unfeasible?

The total cost of a hydrogen transition is probably a lot more than the $1.7 billion proposed by US President Bush over the next five years, but probably far less than $100 billion. It may not be much bigger than the billions of dollars that the private sector has already committed to pieces of the puzzle - if the money is intelligently spent on an integrated buildings-and-vehicles transition that bootstraps its investment from its own revenue and earns an attractive return at each stage. And evidence is emerging that this future will be more profitable, not only for customers and the earth, but even for oil companies.

The full text of Lovins’s essay (from which Chris Littlecott selected and summarised these five points) can be downloaded from www.rmi.org

30 July 2003

Roger East