The emergence of wind farms as an increasingly popular and respectable way of generating alternative energy has presented the Ministry of Defence with an acutely embarrassing technical challenge.

Much to the fury of the energy companies trying to tap into the wind turbine business, the MoD has been slapping objections on planning applications if the locations for prospective wind farms are within range of ground radar stations.

Radars, which play a vital part in ensuring safe flying for the RAF, particularly when the Tornado and Eurofighter/Typhoon pilots are operating as low as 250ft from the ground, already have problems distinguishing between the aircraft and all the “clutter” that spoils a perfectly clear picture.

Even weather-vane cocks on the top of church towers can send confusing images to radars which are being used to plot what is airborne.

Further difficulties could arise when ground radar equipment is being used to distinguish jets flying low at several hundred miles an hour when it is also picking up the rotating blades on 400ft-high wind turbines.

Despite all the technological breakthroughs in recent years, ground clutter — and sea clutter for jet fighters flying over water — create imperfections on the radar screen that have to be interpreted and eliminated by the experts.

They create a “mushiness” on the screen, according to Paul Jackson, editor of Jane’s All the World’s Aircraft. Low-level flying remains one of the most important elements of training for fast-jet pilots, but if wind farms proliferate around the coast they could have a lasting impact on the RAF’s capability in this area, unless a technological solution can be found.

There are about eight ground radar stations around Britain, and in Cumbria the Air Force has its special electronic tactics range at RAF Spadeadam where pilots fly as low as 100ft. The rotating action of wind turbine blades anywhere near this training site could seriously interfere with radars.

The problem for the MoD is that it does not want to be seen to be an obstacle in the way of progress on the renewable energy front.

The ministry has already been taken to task by the energy companies which have accused it of raising planning objections at the last minute after they had spent time and money putting forward their applications.

BAE Systems was awarded a contract by the MoD to try to find a way of mitigating the impact of wind turbines on military and civilian air traffic control radars. The answer will be to devise a software program which can filter out the rotating blades. Radars at sea already have to distinguish between an approaching wave-skimming missile and the turbulent surface of the sea or even a flock of seabirds.

At present, there seems to be an impasse, with the MoD’s heavy hand coming down on one side — although for good safety reasons — and the energy companies on the other, wanting to exploit Britain’s windy shores for the benefit of the nation’s energy supplies.

At least, for once, it’s not a Nimby issue.

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