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Objections from radar operators are blocking nearly 12 GW of potential British wind projects. "We believe that stealth turbine technology could be a genuine game-changer for the renewable energy industry by removing a major barrier to its development," says Mark Roberts, strategic business director for energy and environment at technology consultant QinetiQ, the company behind the technology.

The firm has worked with Danish turbine manufacturer Vestas on the Norfolk test to demonstrate its radar absorbing material (RAM) technology. Originally developed for use on ships and aircraft, QinetiQ has been working on using the technology for turbines for the past five years. For the trial, a 44-metre prototype blade incorporating the stealth materials was fitted on to a Vestas V90 turbine at North Pickenham wind farm, owned by developer Enertrag UK. Radar cross-section (RCS) measurements were taken on QinetiQ's portable radar system, and the results showed significant RCS reductions in line with expectations, it says.

The next step is to build a full stealth machine. "That means three blades, nacelle, nose cone and tower," says Dave Moore, head of business development for materials at QinetiQ. RAM materials will be integrated as part of the manufacturing process for composite components, such as the blades, while the tower and any other static metal structures will be sprayed with a RAM coating.

Integrating RAM materials makes little difference to the composite manufacturing process, says Moore: "That was one of the criteria Vestas gave us from the start."

Another was minimal cost increase. While the UK government provided 40% of the funding for the £1.04 million stealth turbine project, Vestas and QinetiQ financed the remaining 60% - this means that this specific technology will only be available on Vestas machines. "We have other stealth technologies to solve other problems and we will work with other manufacturers on other technologies," says Moore.

QinetiQ and Vestas hope to have their technology in the market-place sooner than the Raytheon radar (see news report, p50), says Moore. But he adds: "There are manufacturing and production issues to be addressed, supply chain issues to be finalised - the usual practicalities of getting from a prototype to full-scale production." Meantime, the stealth technology they have developed does not represent the overall solution to radar problems for the wind industry. Indeed, Moore points out that all of the bodies working to solve the problem agree there is no magic cure. "What will be available to the market-place is a small portfolio of potential mitigation solutions," Moore says.