Wind News

Wednesday 14 October 2009

The 45m ‘Stealth‘ blade was tested at North Pickering

A 'stealth' turbine blade has been tested in Norfolk over the last week to see if it is invisible to radar, writes Will Nichols.

The 45m blade, which was manufactured by Vestas, was installed last Tuesday for a week-long test by defence company QinetiQ at a wind farm owned by energy company Enertrag UK at North Pickering, near Swaffham.

MOD facilities have raised objections to wind farms in the past, as when moving quickly the blades intermittently show up on radar screens, giving a similar impression to a small plane. While the radar objection alone has not seen any applications rejected, it can form part of what David Linley, manager of projects at wind energy company Enertrag UK, called a "montage of complaints" against wind farm developments.

Speaking to NewEnergyFocus yesterday (October 13), Mr Linley said: "If they were a solid object they would appear permanently on radar screens, but when the blades are moving they appear intermittently. Apparently, if this occurs quickly, the controllers may believe it's a light aircraft."

To combat this, QinetiQ said it has developed a Radar-Absorbing Material (RAM) which can be incorporated into the turbine blade structure. Replacing one of the composite's glass cloth layers with a specially modified version enables thin composites to absorb more than 99% of incidental radar.

A spokesman for Vestas told NewEnergyFocus that the company was exploring the idea and hoped to present its findings, along with QinetiQ, at the BWEA annual conference next week.

"We are testing this right now and we've been looking into it for quite a while. It's something that the wind industry would like to see and we hope to share the results within a couple of weeks," he said.

Mr Linley said that if the trial proved successful Enertrag would consider adopting the new technology in future projects, adding it could represent "quite a step forward" for new wind farm applications.

An MOD spokeswoman said that the ministry was fully supportive of the Government's renewable energy policies and targets, but had to protect Britain's assets and activities against anything that may "adversely affect operations".

"We have a responsibility to provide adequate air defence radar coverage to help maintain national security and to ensure the safety of aircraft and of people on the ground. Where wind turbines are at risk of interfering with radar systems we do what is practicable to work with developers to try to find effective mitigation. We assess each proposal on a case by case basis and only raise planning objections where it is absolutely necessary to do so," she said

Following the trial, the blade was being taken by road to Southampton yesterday, amid warnings of severe traffic delays in the Swaffham area.