Off the radar

The DTI has awarded turbine blade manufacturer NOI Scotland and Qinetiq £125,000 to develop wind turbine blades that will not interfere with radar.

Trade secretary Patricia Hewitt recently announced proposals for a new round of offshore wind turbines to be built, capable of producing up to 6GW of energy, in the Thames Estuary, Greater Wash and the North West.

But the interference to aircraft and weather radar screens caused by traditional turbine blades meant that last year more than 25% of all proposals faced objections from radar operators.

Now, in a move to solve the problem, the Department of Trade and Industry (DTI) has awarded turbine blade manufacturer NOI Scotland and Qinetiq £125,000 to develop wind turbine blades that will not interfere with radar.

The new blades will absorb radar signals and prevent ground-based radar stations from picking up spurious signals from nearby wind farms.

The two companies are also jointly investing a further £125,000 towards the cost of the project, which will involve modifying existing blade structures made from glass fibre-reinforced composites.

To make the composite blades better at absorbing the waves the team will remove some of the glass fibre layers and replace them with a material with electromagnetic properties.

‘This will allow us to keep the structural strength intact, but get a material with radar absorbing capability,’ said Steve Appleton, the technical leader of the project at Qinetiq.

By absorbing signals over the range of frequencies at which radar systems operate, the undisclosed material will reduce or prevent reflections from the blades, which can cause double imaging or spurious images to show up on radar screens.

The 18-month project will also include computer modelling work to demonstrate the effect of reducing the signature of the blade on radar screens, in an attempt to solve the problem without making the material too expensive, he said.

‘We will be doing simulations of what a typical radar would see if pointed at a low-signature turbine. That is quite involved, but it is very important. We want to find out the performance needed, as there is little point in putting in something which has the same level of sophistication as a stealth bomber if that is not what is needed.’

Despite this, the blades will be more expensive than existing blades, although not outrageously so, according to Dr. Colin Anderson, research and development manager at NOI Scotland. ‘But it will allow them to operate in areas where they would not otherwise be able to,’ he said.

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