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Revolutions have a habit of taking their victims by surprise. This is true as much in technology as it is in politics. The fall of the Berlin Wall in 1989 was as unexpected by the regime that flourished behind it as was the threat of the personal computer to the complacent mainframe computer industry in the 1970s. In Power Surge, Christopher Flavin and Nicholas Lenssen argue convincingly that the world energy industry is on the verge of a revolution as profound as that which overtook the largely unsuspecting computing industry two decades ago.

They foresee major improvements in energy efficiency over the coming decades. Cost-effective energy conserving technologies should allow current standards of comfort, lighting and other energy-based services to be maintained, and in some cases improved, despite greatly reduced fuel inputs.

In the transport sector, Flavin and Lenssen foresee dramatic improvements in the fuel economy of road vehicles, through the use of new, strong but lightweight materials combined with highly efficient engines. These would initially be powered by natural gas but eventually by hydrogen, derived either by the electrolysis of water, using renewable energy sources such as photovoltaics or wind, or through the gasification of biomass.

But "technical fixes" like these, they stress, need to be implemented in tandem with social changes such as the revival of public transport and energy-efficient planning of human settlements.

On the supply side, they foresee a much more decentralised power system, with many small, efficient co-generation plants providing both electricity and heat to the buildings around them. These would be complemented by intermittent electricity from wind turbines and solar power systems, backed up by gas-fired combined cycle power plant (the gas for which would eventually come from biofuels), to provide electricity when the wind is not blowing and the sun not shining.

Sometime around the middle of the next century, if Flavin and Lenssen's vision of the future turns out to be broadly correct, about half of the world's energy could be coming from renewable sources. They are by no means alone in this expectation. A number of recent studies, carried out by bodies as diverse as the World Energy Council, the Shell International Petroleum Company, Greenpeace International and a team of United Nations specialists, have reached broadly similar conclusions.

The authors' study is a deliberately provocative one, and although I found their tone a little too relentlessly optimistic at times, and occasionally the text seemed to gloss over some important technical issues, it appears to be generally well researched.

Their analysis provides an interesting perspective from which to view recent changes in the UK energy system. In Britain, as in many other industrialised countries, privatisation and deregulation are removing the subsidies and monopoly status formerly enjoyed by the electricity, gas and coal industries and exposing them to the uncomfortable winds of competition.

Natural gas, already the most popular heating fuel, is replacing coal as the fuel of choice for electricity generation, burned in smaller, cleaner, more efficient gas-fired combined cycle power stations. The world's natural gas reserves have turned out to be much larger than many anticipated a decade or so ago: the ratio of proven reserves to annual global consumption is now 65 years for gas, compared with only 43 years for oil. Oil remains king of the transport fuels, but concerns about rising emissions of pollutants from the world's growing fleet of vehicles are stimulating a switch to cleaner fuels. Nuclear power, contrary to the expectations of many two decades ago, is proving increasingly unattractive economically.

Renewable energy sources, long dismissed as marginal and uneconomic, are, by contrast, beginning to be taken seriously. The cost of electricity from UK wind farms, for example, has dropped dramatically in less than five years, from over 10p per unit to around 4p per unit, cheaper than nuclear electricity but still a little dearer than electricity from gas. Other renewable sources of power, such as solar photovoltaics and electricity from biofuels, while not yet competitive with conventional sources, are also dropping in price as they follow the learning curve downwards.

These UK developments, parallelled in many other industrial countries, suggest that the world may indeed be beginning to move slowly in the direction anticipated by Flavin and Lenssen. But this initial momentum needs to be maintained if our energy systems are to progress successfully towards sustainability during the next century. And the fragile gains achieved so far could even be reversed. Energy companies, faced by increasing competitive pressures in the marketplace and by takeover battles in their boardrooms, are cutting back on their research and development efforts. At the same time, tax-cutting governments are reducing their energy research and development expenditure, threatening many valuable programmes. A balanced array of carrots and sticks will be needed to goad the world's energy systems towards sustainability during the next century.

Not everyone will agree with Flavin and Lenssen's analysis, and the energy path they advocate is not an easy one. But the other energy futures on offer are probably fraught with even greater costs and difficulties. This thoughtful but readable book deserves to be studied carefully by policymakers, industrialists and anyone else concerned with the future shape of the world's energy systems.

To judge by the title of their work, Robert Hill and his colleagues from Northumbria University might appear to be covering much the same territory as Lenssen and Flavin. But The Future of Energy Use devotes more space to describing current energy use than to exploring the future possibilities, and is much more academic in both style and content than Power Surge. The authors give a comprehensive overview of current energy sources and technologies, including "conventional" fossil and nuclear fuels as well as "alternative" sources such as wind or solar power. They examine energy planning issues and various ways of improving the very low efficiency with which energy is presently used. Commendably, they also tackle the difficult issue of energy costs, and in particular the problem of assessing the "external" social and environmental costs of energy generation. I thought the "Alternative energy resources" chapter could have been a little more extensive - especially since one of the authors is a leading UK authority on the subject. Another reservation is that many of the data cited in The Future of Energy Use are from the late 1980s and are now out of date.

But the book as a whole manages to cram an enormous amount of useful information into relatively few pages, with the help of a liberal sprinkling of simple but effective line drawings and tables. It represents extremely good value for money and will have wide appeal, not only to students of physics and engineering but also to planners and policymakers interested in the wider economic, social and environmental implications of current and future energy use.

While Power Surge might be described as journalistic and The Future of Energy Use as academic (without intending any pejorative connotations in these adjectives) Power from Wind can probably best be described as "scholarly".

Richard L. Hills is a historian of technology who, to judge by this volume as well as his earlier books on steam power and locomotives, is clearly in love with old machinery. It contains a wealth of detail on the history of windmills, from their origins in ancient Persia, Tibet and China to their more recent and widespread use in North America and Europe. Hills's descriptions of early windmills are exhaustive - and occasionally exhausting, where an extended verbal description of a complex mechanism becomes quite difficult to follow (at least for simple folk like myself) in the absence of an explanatory diagram. It must be said, though, that Power from Wind does have many excellent photographs and line drawings (though I would have liked to see more) and, as somehow befits an historical work, is attractively typeset, printed and bound. While his chapter on these "horizontal" (ie vertical axis) windmills is only claimed to be a brief treatment of the subject, it is nevertheless surprising that he does not even mention the French inventor Georges Darrieus, who in 1925 conceived the most efficient and successful of all vertical axis wind turbine designs. Darrieus-type turbines, with their characteristic "egg beater" shape, have in recent decades been installed in considerable numbers in wind farms in California and elsewhere.

In general, Hills's coverage of 20th-century wind power history is less satisfactory than his treatment of the more distant past. But this is understandable in a book that is clearly aimed at historians rather than scientists or engineers - fascinating though it will nevertheless be to the latter. I was particularly intrigued by some of the descriptions of the politics of early windmills. Hills describes the incandescent rage with which Abbot Sampson in 1191 greeted the news that Dean Herbert had built a windmill at nearby Bury St Edmunds. Fearing that this would take corn-grinding custom away from his own watermills, and despite the dean's protestations that "free benefit of the wind ought not to be denied any man", he ordered it to be pulled down.

We are fortunate that the modern-day operators of our competing privatised power utilities seek merely to demolish their rivals' arguments, not their installations.

Godfrey Boyle is director, energy and environment research unit, Open University.