Radar issues are hampering 5.9GW of wind project development. That is about to change, with turbine manufacturers and radar operators tackling the issue from both ends.

By Emma Clarke in London

If aesthetic concerns and logistical challenges weren’t enough of a barrier, around half of UK wind farm developments are being held back in the planning system on the grounds that they could interfere with radars and low flights.

The British Wind Energy Association (BWEA) has estimated that aviation objections are holding back 5.9GW of wind projects in the planning system, plus a potential 5.8GW in the pre-planning system.

The issue is that turbines are massive structures that are highly reflective to radar signals and have fast-moving blades. As a result they show up on radar displays, which is of concern to both military and civil radar operators.

Some large wind farms - such as the 140-turbine Whitelee Windfarm in Scotland - have overcome aviation objections though the development of technical solutions such as data fusion or gap infill radar, where data is collected from multiple radars.

“Unfortunately the costs associated with these [technologies] is quite high, which means that unless you’ve got the megawatts behind you, you couldn’t look at such a project,” says Nicola Vaughan, head of aviation at BWEA.

In an effort to find a common solution, the wind energy industry joined forces in April this year to invest in a central industry fund. The Aviation Investment Fund Company (AIFC), bringing together eighteen developers including energy giants E.ON, EDF, RWE and Vattenfall, has already raised £3.2 million (US$5.3mn; €3.5mn), which will be invested in advanced technologies to solve wind turbine interference with radars.

“To get competitors to come together to address the issue was a key milestone,” says Vaughan. “Now we have stakeholders around the table, we can identify solutions, implement them, and get the show on the road.”

Intelligent radars

The first programme, co-supported by AIFC, the UK Department of Energy and Climate Change (DECC), The Crown Estate and NATS En Route (NERL), is to find a solution that will eliminate wind turbine interference of en route radar displays.

There are 17 en route radars across the UK, operated by NERL and supplied by Raytheon Canada. The proposed Raytheon solution is a hardware and software fix to enable the 2D radars to discriminate between turbines and aircraft.

With NERL currently objecting to 5.4GW of projects both in the planning and pre-planning stage, the programme has great potential, says Simon Christian, project director at ScottishPower Renewables and chair of the AIFC. “This would be a big prize for the wind industry,” he says, adding that the impact on wind energy costs would be “marginal” since the investment would be spread across such a large volume of new wind energy capacity.

Funding still required

The 19-month R&D contract, signed in October, brings together £5.15 million, including £1.6m from wind companies, £2m from the Crown Estate and £1.55m from DECC. One issue still to be resolved, however, is who will fund the rollout of the technology. “Nobody wants to fund this right now, but we have 18 months until the technology is ready to thrash this out,” says Christian.

While the Raytheon solution has the potential to fix the en route radar problem, issues still remain with MoD radar. To address these, the AIFC has also committed to fund a MoD and IBM study for expanding the UK Air Defence and Ground Environment Command and Control System (UCCS) to accept air traffic control radar feeds.

And there is scope for additional research, says Christian. “The more funding we get in, the more technologies we can invest in,” he says, adding that the fund is still open to other developers.

Removing turbines from the picture

While the AIFC tackles radar solutions, wind turbine manufacturer Vestas and technology provider QinetiQ are also working on technology that would make turbines and blades partly invisible to radar.

Inspired by technology used in stealth warplanes and ships, this ‘Stealth Turbine’ technology reduces the size of the radar signature of turbines to the point where they can be ‘factored out’ of air traffic control and air defence systems.

A composite technology was recently tested (as part of a programme part-funded by UK Government department for Business Innovation and Skills) in a single prototype stealth blade on a Vestas V90 turbine in Norfolk, UK. “It performed pretty well,” says Steve Appleton, research specialist at Vestas, with tests showing that the blade’s radar cross section had been significantly reduced. “But there are still improvements to be made,” he adds.

Next year Vestas and QinetiQ will fund a full-scale trial to test the radar-absorbing materials as a modified composite in the blades and nacelle of a bespoke turbine, and as a coating applied to its tower.

Appleton couldn’t give precise details, but assures developers that costs will be manageable. “This isn’t black magic; we’re not building [something like] a stealth bomber that costs millions of euros. If it works, it will be an affordable and low-maintenance solution,” he says.

He adds that the technology should work alongside, rather than against, the radar fixes being developed by NERL. “It is difficult to see how a low signature turbine wouldn’t make a radar fix work even better,” he says. 

It is expected that these technology fixes will have application beyond Great Britain. While many issues are unique to the UK, as a result of its large network of radars, other countries including the USA, Germany and France are also facing increasing aviation objections.

In Germany, for example, up to 1,000MW of wind energy capacity is being held back as a result of (mostly military) radar objections, according to Ulf Gerder, spokesperson at the German WindEnergy Association. Work to overcome these issues, as elsewhere in Europe and USA, is still in the earliest stages.

“If we want to protect the climate and reach our renewable energy targets, we need to find a solution,” says Gerder. And with efforts now underway to tackle this problem from both the radar and turbine ends, achieving these targets might just be possible.

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Emma Clarke at: emma.jane.clarke@gmail.com

Or write to the Editor, Rikki Stancich: rstancich@gmail.com