London

Outmanoeuvred: radar stations struggle to tell the difference between low-flying jets and wind turbines. Credit: R. COOKE

Britain's bold plans to generate more electricity from wind energy may be shot down by the Royal Air Force (RAF), which says that wind farms confuse its air-defence radar system.

But wind-energy advocates are pressing the air force to ease up on rules that currently prohibit wind turbines from being located within a radius of 74 kilometres of any of its 13 air-defence radar stations.

Earlier this month, the Royal Society, Britain's science academy, intervened in the dispute. It wrote to both the Department of Trade and Industry (DTI) and the Ministry of Defence (MoD) to point out that the RAF's stipulation could derail government plans to generate 10% of electrical power from renewable sources by 2010.

David Wallace, the society's vice-president, wrote in the letter that nearly half of the wind farms proposed so far in Britain have been successfully opposed by the MoD because of their proximity to air-defence stations. Wallace said that the restrictions were a “significant obstacle on the prospects for developing the UK wind industry”.

On 1 March, the society gave written evidence to an inquiry by the House of Lords Science and Technology Committee on renewable energy. The society said that it was concerned about the number of applications for wind farms that had been turned down.

The MoD says that the 30- to 40-metre-long blades used on typical wind turbines can mask radar signals from low-flying aircraft or produce false alarms by reflecting radar beams. The wind-farm restriction is based on two RAF studies carried out in 1994 and 1997, the contents of which remain classified.

Other European countries do not impose such restrictions. Germany, for example, demands a distance of only 5 km between wind farms and radar stations. But MoD officials say that there are more low-flying aircraft in the United Kingdom.

A working group of representatives from the MoD, the DTI, the Civil Aviation Authority and the British Wind Energy Association was set up two years ago to address the problem. But it has so far failed to agree on whether the MoD rule is technically justified.

Instead, the group has discussed ways to avoid the problem, such as using radar systems that can distinguish between wind turbines and aircraft. The MoD may implement the more sophisticated radar in 2008, but the system is expensive and the ministry does not believe it will completely solve the problem. The Royal Society is urging government ministers to step in and resolve the dispute.