Europe: Radar holds up repowering

Around 1 GW of German wind development, mainly in windy northern Germany, is being prevented from proceeding due to military radar problems, says Germany's wind energy association Bundesverband Windenergie (BWE).

Britain is facing similar issues but on a bigger scale, with 4.7 GW of projects blocked (Windpower Monthly, May 2009). BWE is particularly frustrated because many of the blocked projects in Germany are repowering developments, in which large numbers of old turbines are replaced with fewer, state-of-the-art, larger ones.

Military radar systems are usually located in open landscapes that are also favoured for wind developments. By their nature, radar systems are highly sensitive to moving objects, including those some distance away. The disturbing reflections and deflections of radar waves by wind turbines vary with the number of turbines in a station and their spatial arrangement. These problems can be reduced by the military's modernisation of its radar equipment, replacing analogue with digital, but progress is slow.

In early autumn a prominent report in national newspaper Suddeutsche Zeitung carried speculation that the military wants the wind industry to pay for digital upgrades to radar systems. "This is not our job," Hermann Albers, BWE chairman, responded. BWE spokesman Ulf Gerders acknowledges that "radar is a sensitive issue and Germany's defence cannot be compromised". But he adds: "We would be happy if the German military authorities were prepared to treat each wind project case by case and not issue blanket rejections."

Gerders believes that technical solutions can be found in bilateral talks. Marco Jentsch, spokesman for the German military administration's north division, agrees. "We have to strike a balance," he says, stressing that the military is keen to support alternative energy. "Wherever possible, we will see whether small adjustments, moving turbines a bit to the left or to the right, can alleviate the problems."

A partial solution

Work is required on both radar technology and turbine blade reflectivity, he says, citing a report on improving their compatibility for national defence and flight security. The report, produced in July by radar equipment supplier EADS Defence and Security on behalf of the federal environment ministry, says that modern equipment with digital processing of signals would be more compatible with wind turbines than the existing ASR 910 radar equipment used for military air security, but will not solve the problem completely.

Digital systems will be introduced from 2011. Turbine manufacturers, in particular blade makers, should be closely involved in optimising systems, the report adds. "Blade companies are already competing to lead the field in reducing radar problems," says Gerder. "Research in this area is very important but is kept strictly under wraps for patent reasons."

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