The quest to make hydrogen the fuel of the future

Box 2 | Hydrogen – too hot to handle?

Hydrogen might be the most abundant element in the Universe, but as an energy store there are gaps in our knowledge – and a few misconceptions.

For instance, some people believe that hydrogen is not a safe fuel. This attitude was probably formed over many years by incidents such as the Hindenburg disaster in the 1930s, when a hydrogen-filled airship burst into flames in the USA and killed more than 30 people. The incident is memorable because it was filmed and has been shown in countless newsreels, newspapers and television programs. But hydrogen wasn't the culprit. It's now believed that the flammability of a coating on the airship's fabric was the main cause of the inferno.

Likewise, some people wrongly blamed hydrogen fuel for the 1986 Challenger space shuttle disaster, rather than the faulty o-rings later identified by investigators.

Like other fuels, such as petrol and gas, hydrogen is very flammable. But refineries and industrial sites have been producing, storing and using hydrogen safely for a long time. In fact, a hydrogen pipeline has been operating in Germany's Ruhr Valley since 1938 with no apparent problems.

But like any fuel, hydrogen has to be treated with respect, with appropriate storage and handling guidelines. What's different is that because hydrogen is not widely used, people are unfamiliar with how to handle it. But that's changing as more countries draw up appropriate safety frameworks.

Surprisingly, you might actually be better off in the vicinity of a hydrogen spill rather than a petrol or gas accident. Hydrogen is the lightest known element. Gaseous hydrogen has 1/14th the density of air, so when released it disperses quickly and has a strong tendency to rise up. If there's a leak, it doesn't hang around for long so the risk of fire is brief. Even liquid hydrogen, if spilled, evaporates almost instantaneously on account of its low boiling point and diffuses rapidly away.

When it burns, the pale flames tend to shoot upwards (rather than outwards) and there is less radiant heat to burn bystanders, damage property or cause secondary fires. BMW, which has produced a car with an internal combustion engine that uses liquid hydrogen or petrol, has not found safety concerns to be an overwhelming issue. Other factors in hydrogen's favour are that it's non-toxic to the environment, non-corrosive, has no disadvantageous physiological effects, and won't pollute waterways if there is a leak.

But it's not all good news. Hydrogen is colourless, odourless and tasteless. If there's a leak, you won't notice it unless there is a sensor or safety system to alert you. In addition, when hydrogen burns the flames are less obvious than flames of other fuels, posing a further safety risk.

Research at the University of Sheffield in the United Kingdom indicates that hydrogen cars could be a problem if they were involved in an accident in a tunnel, where any fire could reach up to the roof in a 'jet flame' and possibly damage ceilings, sensors and sprinkler systems.

Despite the bad image it might have developed over the years, there seems to be a general consensus that hydrogen is as safe as other fuels such as petrol – if you understand its properties and follow appropriate handling and storage guidelines. Development of such frameworks is underway as researchers pursue the quest to develop a universal hydrogen economy.

Box
Box 1. Storing and distributing hydrogen

Related sites
Hydrogen safety (US Department of Energy )
Fuel cell engine safety (US Department of Energy )
Australian fuel cells and safety (National Hydrogen Institute of Australia)
Hydrogen cars pose tunnel fire risk (New Scientist, 14 November 2007)

External sites are not endorsed by the Australian Academy of Science.
Posted September 2008.