The MoD had vetoed the offshore projects in the Greater Wash off the east coast of England, objecting to the clutter effect that the turbines' rotating blades would produce on its air defence radar screens.
Under the deal, the first of its kind in the UK, a Lockheed Martin TPS-77 radar will be installed at the MoD's remote radar head at Trimingham in Norfolk. The Department of Energy and Climate Change will contribute around £4 million, with the rest provided by the developers of the five projects that are in line of sight of the radar: Sheringham Shoal, Race Bank, Docking Shoal, Dudgeon and Triton Knoll. Serco, Lockheed Martin's partner in the UK, will provide logistics support.
The breakthrough came after aircraft trials in 2008 at Horns Rev offshore wind farm in Denmark, followed by an extensive modelling exercise. These showed that the Lockheed Martin radar is able to filter the movement of wind turbines with other air and seaborne activity.
Horns Rev wind farm is representative of the 317MW Sheringham Shoal wind farm, which is under construction and is the most advanced project, explains Nicola Vaughan, head of aviation at British trade association Renewable UK. It pushed for the report of the Danish trials to be unclassified so that it could be shared with the rest of the industry.
The Lockheed Martin radar, which is already installed in over 160 locations worldwide, will be operational by November 2011 to coincide with the completion of Sheringham Shoal wind farm. Its 88 wind turbines will be sited between 17 and 23km off the coast of north Norfolk. As a condition of consent for the wind farm, its developer Scira Offshore was required to put in place a technical fix before operation to mitigate the turbines' interference with the MoD's Trimingham radar.
The alternative to the current solution would have been gap infill radars for each of the four wind farms, to be funded at the developers' expense.
Nearly 13GW of potential wind capacity is blocked by aviation objections from MoD, National Air Traffic Services (Nats), or airports. The MoD is currently objecting to over 7GW of wind: 5GW due to its impact on air defence radar and 1.6GW on the MoD's air traffic control radar.
Although the Greater Wash wind farms represent the biggest chunk of capacity that is blocked by radar objections, the industry is now turning its attention to finding solutions for projects that are in line of the MoD's two other air defence radar on the east coast of England. These are at Brizlee Wood in Northumberland, which is affecting onshore wind projects, and Saxton Wold in Yorkshire, which is holding up Westernmost Rough and Humber Gateway offshore projects, as well as a number of onshore wind farms.
Vaughan says that the industry would like the MoD to test the performance of its recently installed BAE Systems 102 radar at those two sites against the effect of wind turbines. Results from modelling conducted to date have been necessarily conservative, she says. "It is possible the radar will perform better than the modelling suggests. There is more we need to do, not just with the MoD but also with Nats. There are a lot of opportunities to address radar issues holistically for a large region rather than just on a project-by-project basis," she says.
Vaughan hopes to be able to repeat the model of working with the MoD. "The level of engagement and co-operation was brilliant," she says. "They had no other agenda; just a will to resolve the issue while maintaining air defence security."