A 'stealth' blade is fitted onto a wind turbine in Norfolk

Conflict between wind farms and radar moves closer to solution

Two recent developments address the difficulty of siting wind farms near radar installations.

A leading turbine manufacturer has successfully tested a full-scale ‘stealth’ rotor in the UK, and a Scottish airport has said it will deploy a groundbreaking holographic radar mitigation system to counteract interference.

Vestas conducted its stealth turbine test at a UK customer site with technology partner QinetiQ, as part of an ongoing research collaboration. Preliminary results, announced at the International Wind and Radar Forum in Ottawa, Canada, showed that a Vestas V90 turbine with stealth rotor achieved a reduction in radar cross-section of approximately 99 per cent, or 20 decibels, compared with standard turbines.

Full-scale testing of the three-blade stealth turbine early in 2011 followed initial site tests of a single, 44m blade in 2009. Additional design optimisation led to process cost reductions and quality improvements that were verified by the new test.

The stealth effect is achieved by using a portfolio of radar absorbing materials that can be designed to operate at aviation and maritime frequencies, without affecting the turbines’ performance or appearance.

“Our testing has demonstrated that we have adapted military stealth technology to make wind turbines viable for many locations that have been restricted by radar concerns,” said Vestas Technology R&D president Finn Strøm Madsen. “This is a critical step toward the commercialisation of stealth turbines.”

A different approach is being adopted by Glasgow Prestwick Airport, which has selected Cambridge Consultants to provide the first stage in a turbine radar mitigation system and Part 1 Safety Case based on its holographic radar technology.

The region surrounding the airport is important to the growth of the UK wind industry, with the potential for hundreds of turbines if the problem of radar interference can be overcome.

GPA opted for holographic radar over competing technical solutions because it suits the airport’s operational requirement and, as a modular system, can be deployed more flexibly than current alternatives.

Holographic radar is a non-scanning, continuously tracking 3D radar that can discriminate between turbines and aircraft based on behaviour. It can operate at low level without loss of cover, and its 3D plots make seamless integration into radar displays easier.

Craig Webster, commercial director at Cambridge Consultants said: “The most exciting thing about this programme is the level of collaboration. Prestwick have gone to considerable lengths to bring all parties together, including competing wind farm developers, to work up a solution that meets the needs of air traffic controllers and allows wind farms to be built in their region.”

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