QinetiQ

In November 2009 UK company Vestas Wind Systems successfully trailed a radar mitigation technology for wind turbines.

This stealth technology is designed to reduce the radar signature of individual turbines, making them ‘invisible’ to air traffic control, military and other radar based systems, which could significantly increase the number of approved wind farm sites, that were previously blocked on the grounds of potential radar interference.

The technology was developed as part of a programme funded by DECC successor the Department of Trade and Industry (DTI). The stealth turbine uses a range of non-conventional radar absorbing materials (RAMs), which can be integrated into the current manufacturing processes for turbine components (nacelles, blades, towers etc.).

This is achieved by replacing one of the composite’s glass cloth layers with a specially modified alternative, which results in a thin composite (relevant to the wavelengths used) that can absorb more than 99% of incidental radar.

The technology however requires virtually no changes to manufacturing processes and incurs minimal mass and cost increases.

The radar absorbing materials can be designed to operate at aviation and maritime frequencies and include modified composites for nacelle and blades, and RAM coatings that can be sprayed onto the tower and other static surfaces.

A 44m prototype stealth blade was designed and fitted onto a Vestas V90 wind turbine on a wind farm in Norfolk, UK. Radar Cross Section (RSC) measurements were taken which showed significant RCS reductions.

QinetiQ is a leading international provider of technology-based service and solutions for the defence and related markets. They have been involved in various aspects of the wind industry, from accessing planning issues to increasing turbine reliability.