IT WOULD take a wind farm the size of Saudi Arabia, and the electricity would cost twice as much as it does today, but there is more than enough wind to meet the world鈥檚 energy needs.
This upbeat assessment of wind power鈥檚 potential comes from the most comprehensive study yet of the world鈥檚 land-based wind resources, to be published in the journal Energy Economics. The bad news is that some of the regions possibly most in need of energy lack usable wind.
A team led by Wim Turkenburg of Utrecht University in the Netherlands divided the world鈥檚 land surface into 66,000 cells and calculated the potential for wind power in each one. The researchers excluded heavily built-up areas, nature reserves, lakes and mountains. They did not examine the potential of off-shore wind farms because not enough wind-speed data is available.
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The team assumed that wind power becomes economically viable when the average wind speed is more than 4 metres per second. Previous studies took 5.1 metres per second as the cut-off, but this was considered unreasonable as it excludes areas where wind turbines are already installed.
About 20 per cent of the world鈥檚 land surface has an average wind speed above the lower cut-off, and if harnessed, the wind would produce about 96 petawatt-hours per year, or six times the world鈥檚 electricity consumption in 2001. But the electricity would be expensive, at 25 times today鈥檚 prices. However, the global electricity demand in 2001 could be met by wind farms in an area of 2.4 million square kilometres, about the size of Saudi Arabia, and costing only about twice today鈥檚 prices.
The researchers assumed that one square kilometre could hold four wind turbines, each with a capacity of 1 megawatt. Some of today鈥檚 wind farms have four times this density. They also accounted for losses incurred when converting wind energy into electricity.
The analysis revealed that in most areas of the world the available wind energy is more than enough to meet today鈥檚 electricity needs. For instance, it is 300 times the demand in east Africa and twice that of western Europe (see Graphic).
Unfortunately, some densely populated regions, such as countries in south-east Asia, do not have usable wind. The areas with the greatest potential for cheap wind power are North and South America, western Europe and the countries of the former USSR.
Wind energy, however, cannot be the sole source of electricity as it is a fickle resource that can completely die off at times. 鈥淎s you exploit wind to a greater extent, matching supply and demand becomes an issue,鈥� says team member Bert de Vries of the National Institute of Public Health and the Environment in the Netherlands. And extending wind power may require expensive modifications to the grid system. 鈥淣o one knows the cost of these,鈥� de Vries says.
Some advances could help make wind energy viable. For example, it could soon be possible to predict wind speeds to within 15 per cent a day in advance, giving time for alternative power sources to be deployed if necessary. In Scandinavia excess energy from wind is stored by using it to pump water into reservoirs and using it to generate hydroelectricity when needed. 鈥淚t鈥檚 incredible how much development has been done in this area,鈥� de Vries says. 鈥淚f we don鈥檛 do anything apart from being pessimistic, there won鈥檛 be any changes.鈥�
John Twidell, editor of Wind Engineering, agrees. 鈥淭he limits are people鈥檚 perceptions and planning permission, not the technology,鈥� he says.