The wind of change

For centuries it's been fluttering willow trees, spinning weather- vanes and filling the sails of intrepid seafarers. But these days wind has a new role: producing "clean" electricity. Although the idea is more than a thousand years old, the growing appeal of wind power is now blowing in earnest across Europe and North America.

The Nineties have witnessed a world-wide growth in in the use of wind power. It is by far the world's fastest-growing energy source, with production quadrupling over the last 10 years. Global capacity now exceeds 8,000 megawatts (MW), though Britain still lags behind countries such as Denmark and Germany. There are currently 42 wind farms in the UK, providing 330MW of electricity - enough for 200,000 households. Denmark has more than six times as many turbines and Germany produces eight times as much electricity from wind power as Britain.

Britain is scheduled to increase the contribution that wind makes to its power sources as the nation tries to meet its renewable-energy commitment for the year 2010. The Government has pledged that by then 10 per cent of our energy needs will be met by renewable sources such as hydroelectric, solar, geothermal and wind power. Today, renewables account for just 2 per cent of Britain's energy use.

Advocates of renewable energy are applauding the 10 per cent goal, but many still feel that Britain is failing to live up to its potential. According to Nick Goodall, chief executive of the British Wind Energy Association, it is ironic that Britain has the richest wind resources in Europe, but still compares "quite pathetically" with much smaller countries on the Continent.

"It's almost embarrassing to meet my Danish, Dutch and Spanish colleagues," he says. "They say, `You've got all the wind; we've got all the turbines. What's the matter?'"

One problem is that wind farms are considered by many to be a blot on the landscape, despite the green kudos of being an environmentally friendly alternative to fossil fuels and nuclear power. Only recently has wind power become economically attractive. Falling costs and improvements in technology are making wind power more affordable and efficient: a modern 1MW turbine costs about pounds 400,000 and the cost of wind-generated electricity has fallen from about 10p per kilowatt hour to 3.5p since the first British turbines were installed in 1991.

At the same time, electricity companies are in the process of deregulating, which will allow consumers to choose their energy sources in an open market. This new degree of consumer control could mean a larger role for wind power and other renewable energy sources.

This is borne out, for example, in Alberta, Canada, which deregulated its energy companies in 1996. Growing numbers of people there are turning to companies such as Vision Quest Windelectric, which runs two 660kW facilities near Calgary. Vision Quest distributes its energy through the local utility and from there it is bought by a range of customers, including the giant Suncor Energy Inc. Vision Quest's customers also receive a document called an "emissions reduction credit", a certificate that acknowledges the offset of carbon dioxide emissions.

Despite its abundance of fossil fuels and hydroelectricity, Canada appears to be heading toward a wind-friendly future. In Quebec, a pair of giant wind-power generating stations are under construction; the $160m (pounds 100m) Le Nordais project will be able to produce 100MW of electricity.

Meanwhile, a Toronto co-operative is proposing a 660kW turbine on the city's waterfront - the first such station in an urban setting in North America. The co-op took the Danish "wind guilds" as its model. In Denmark, 100,000 people own shares in the small co-operatives that run the nation's wind turbines.

Bryan Young, general manager of the Toronto Renewable Energy Co-op, says that the best way to boost interest in wind power "is to have a high-profile wind turbine in an urban location, where everyone can see it". If the project goes ahead, the Toronto turbine will indeed be a highly visible landmark: its 80-metre tower will be one-seventh the height of the famous CN Tower.

The United States is showing a similar interest. California is the current wind-power leader in the US; the state's total wind-energy output could provide all of San Francisco's electricity needs. But central states such as Montana and Texas are quickly catching up. Wherever wind turbines go up, though, they tend to be manufactured in Europe. Not surprisingly, many of the biggest manufacturers - which include Vestas Wind Systems and NEG Micon - are based in Denmark.

Wind power is not new. The ancestors of today's sleek turbines once dotted the farms of medieval Europe and the Middle East, where the first windmills - probably a Persian invention - appeared in the seventh century. Today's most popular design is known as the horizontal axis wind turbine, in which a giant rotor - usually three-bladed and made of glass fibre - is mounted atop a steel tower. The design utilises the same aerodynamic forces that create "lift" in an aeroplane's wing.

When wind blows across the blades, a difference in air pressure forces them to spin. As the angled blades revolve, they turn a shaft connected to a gear-box. This in turn drives an electrical generator, which converts the rotational energy of the rotor blades into electricity. The result is "clean" power that does not pollute the atmosphere.

However, giant windmills are not to everyone's taste. While some may think of them as graceful symbols of civilisation, others find them aesthetically repulsive. One recent letter in the press complained that wind farms can be likened to "a cluster of gesticulating monsters".

Another, more tangible flaw is the threat that giant rotor blades pose to birds. According to one American. study, more than 500 birds of prey - including 78 golden eagles - were killed by the wind turbines at the Altamont Pass power station in California during a two-year period. To combat the problem, planners are trying to locate turbines away from avian flyways; designers have also turned to smooth, tubular towers that make it difficult for birds to find a perching-place.

On the engineering side, wind power suffers from not being "dispatchable". In other words, no one can predict how many kilowatt hours of energy a given turbine will produce on a given day. The output depends on the local wind speed: the slower the wind, the lower the output. And if the wind drops below a threshold value - generally between 15 and 20km per hour - the blades stop spinning entirely. However, modern turbines at gusty sites are usually in motion.

"Our experience is that we're generating 70 per cent of the time," says Jason Edworthy, director of Alberta's Vision Quest. "We can count on the energy that will be produced, but we can't tell you how much power at any exact moment will be there."

Britain, however, as the windiest outpost of western Europe, is better placed than most countries to take advantage of its plentiful supply of this renewable energy source.

The writer is a science journalist based in Toronto