Green Machine: Giant wind turbines to catch a breeze

Helen Knight, technology reporter

When it comes to building new wind turbines, the prevailing view is that bigger is definitely better. Larger turbines are seen as particularly attractive for offshore wind energy generation, where building underwater foundations make up a huge fraction of the cost of construction. Bigger turbines mean you can generate more energy from each device, reducing the number of foundations you need, and so giving you more bang for your buck.

To this end wind turbine maker Vestas, based in Randers, Denmark, announced this week that it has designed a 7-megawatt offshore wind turbine. The turbine, dubbed the V164, will have three 80-metre-long blades, and will reach a tip height of 187 metres. The turbine will have a swept area of 21,124 square metres, around three times the size of the football pitch at Wembley Stadium.

The turbine will be able to produce 30 per cent more energy per tonne than previous devices, says Vestas' Finn Strom Madsen. That is because a turbine's power output is proportional to the square of the length of its blades.

"The energy needed to produce the turbines themselves will be paid back in around 10 months," he says.

The company plans to begin building a prototype next year, providing it receives sufficient interest from customers.

Vestas is not alone in believing size matters. US company Clipper, based in California, is developing a 10 MW turbine, the Britannia, while a consortium of European researchers has been investigating similar-sized devices.

However, there may be a limit to how much energy we can generate from the wind, irrespective of how large or efficient turbines become. Axel Kleidon at the Max Planck Institute for Biogeochemistry in Jena, Germany, believes the laws of thermodynamics mean building too many wind farms could cause us to seriously deplete the energy available in the atmosphere.