Fuel for future debate

Hydrogen has been heralded as the fuel of the future for more than a century. Science fiction writers, as usual, were among the first to see the shape of things to come. As Peter Hoffman reminds us, Jules Verne's 1874 novel, The Mysterious Island , predicted that "water will one day be used as a fuel, that hydrogen and oxygen, which constitute it, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable". The low costs of fossil fuels during the 19th and 20th centuries postponed the dawn of the hydrogen age but, if Hoffman is right, the 21st century could be when this fuel comes into its own.

Verne, of course, was not strictly correct. Water is not a fuel, and even the hydrogen of which it is partly composed is not like the familiar fossil fuels that can be extracted from the ground and burnt. To be used as a fuel, hydrogen needs to be separated from the elements to which it is normally bonded - most commonly to oxygen in water. That separation requires energy to drive processes such as electrolysis. So hydrogen is best seen as an energy carrier that can be generated from intermittent sources such as wind or solar power and stored until needed. It can then be converted to electricity or heat, ideally via a fuel cell in which it re-combines with atmospheric oxygen to form water, with no polluting emissions. Hoffman's account makes it clear that, with growing recognition of the need to reduce global carbon emissions, hydrogen is once again attracting a lot of interest and funding because it is a zero-carbon fuel - provided the energy used to separate it comes from carbon-free sources.

As editor of the Hydrogen and Fuel Cell Letter , Hoffman has been a well-informed observer of the hydrogen scene for decades. He takes us on a guided tour of the hydrogen energy world, from the paper presented in 1820 by the Revd W. Cecil to the Cambridge Philosophical Society on the "Application of hydrogen gas to produce moving power in machinery", to Iceland's establishment in 1999 of a consortium, including Shell, Daimler-Chrysler and Norsk Hydro, that aims to convert the country's fishing fleet and road vehicles to run on hydrogen generated from hydroelectric and geothermal sources.

Hoffman covers the generation of hydrogen from fossil, nuclear and renewable sources; its use in vehicles, using conventional engines and fuel cells; its potential as a climate-friendly fuel for aircraft; and as a fuel for utilities, to provide power and heat in stationary applications. He also tackles the crucial issue of safety. Hydrogen is still associated with the 1937 fire on the airship Hindenburg. But, as Hoffman explains, hydrogen was not the cause of that disaster and it can be at least as safe as other fuels if handled correctly.

Tomorrow's Energy is interesting and informative, and includes fascinating pictures of past and future hydrogen developments. Its journalistic style perhaps includes too many numbers (and parenthetical asides) to hold the attention of the general reader, while lacking the more rigorous structure, with diagrams, graphs, tables and referencing, sought by academics or professionals. Nevertheless, it is worth reading as a general overview of this increasingly important subject.

Godfrey Boyle is co-director, Energy and Environment Research Unit, Open University.