Wind turbines often get a bad press; unsightly, expensive and, of course, they do not work when there is little wind. Yet there may be a surprising solution to these problems.
Many companies around the world are developing kites that generate electricity. They use wing shapes similar to aircraft wings and are flown on long cables that can reach 400m (1,300ft); the hubs of conventional wind turbines can only reach around 100m (300ft). At a higher altitude, kites can tap into stronger and more consistent winds, meaning power generation is more productive. It is a simple equation: more height means more wind and more power.
They have other benefits too. They are cheaper to build than wind turbines. They are also easier to install and maintain, and are much less obtrusive on the landscape.
Kites are also more efficient, as 60 per cent of the energy generated by wind turbines comes from near the tips of the blades because they spin fastest, while the rest of the blades are slower and much less efficient. Yet energy produced by kites is so efficient that it is about as cheap as coal-generated power.
Kites are used to generate power using small propellers like miniature wind turbines, although they spin much faster and so are far more efficient. The power generated is then sent back down to the ground through the metal cable that tethers the kite.
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Additionally, the pulling power of the tethering cable can be used — as the kite goes up it pulls the cable and spins a generator on the ground. By using various flying patterns, the tension in the cable can be kept taut; and when the tension slackens, the kite dives down and starts the cycle over again.
Kite-generated power is not a pipe dream. Google has invested heavily in a US kite firm, and a UK company, Kite Power Solutions, has received substantial funding from the government and from Shell.