The wind turbine war

During the last year there has been a debate in Sweden regarding wind turbines and their effect on doppler radars. The Swedish Air Force does not approve the power industry to build wind turbines within 40 kilometer radius from military and civilian airbases.

The Swedish Government has requested the Defence Research Agency, FOI to together with the Armed Forces, the Defence Material Administration, the Bureau of Energy and the Transport Authority to investigate how other countries are handling wind turbines.

The investigation has been completed and presented to the Government (part 1, part 2). The comparison has been between Sweden, Denmark, Finland, Norway and Germany.

In Finland and Norway the wind industry has not been fully established, so there are no conflicts. In Germany and Denmark the Air Forces has always been very restricted to perform low level flying due to very dense populated countries. Denmark is a small country and there are not many alternate solutions. But, in Germany no wind turbines are allowed within 50x30 ("Nichtbebauungszonen") from the airports.

The power industry focus their analysis of the FOI report on low level flying and forgets about the affect on radar stations and communication. Anyway, the Chicaco Convention states that within 55 kilometer radius of an airfield the clearance must be 300 m between an aircraft and any obstacle. Since most airfields use 600 meters as instrumental approach height this would require that no wind turbine (including whatever hill they are located on) is no higher than 300 meter. But there must also be a possibility to perform a low level circling procedure if the wind is not in the right direction. Circling is normally done at 150 meters, with visual contact of the ground.

The report points out three specific conditions for Sweden:

- Sweden is still neutral and must therefore keep a national capability.

- All basic flying training and basic tactical training of pilots are done in Sweden. Even if the basic training should in the future be moved to another country, the Gripen tactical training will still be performed in Sweden. This, not only for Swedish pilots, but also for Hungarian and Czech Republic pilots.

- Low level flying is an essential part of the Swedish tactics. During the last years the Swedish Air Force has changed focus to NATO tactics and medium altitude flying. But since many Swedish politicians are starting to understand that there are a need to be able to defend Sweden, there will also be a need to return to the old tactics that has served Sweden well. Not only is Swedish pilots interested in this training. Many other countries use the RFN test range in Vidsel to perform low level flying, since it is difficult to do so in most parts of Europe.

Unfortunately the debate has been a bit one-sided with the public making fun of Gripens inability to handle the effect on the radar. Even some Swedish politicians have been duped. This is however not a problem specific to the Gripen, but to all doppler radars, both airborne and stationary.

The civilian radars are mostly not affected since most of them uses SSR - Second Surveillance Radar techniques. This requires all aircraft to have a transponder and to use it. In case of smuggling, broken transponders or a military attack the civilian radars will see nothing at all.

Sweden is not the only country where the armed forces object to wind turbines. In the UK there are talks about letting the power industry replace radar equipment that is affected by wind turbines.

One of the problems with wind farms is the effect of their turbine blades on air traffic control and defense radars. Wind turbine blades have extremely large radar signatures, especially when grouped in a farm, and their movement creates doppler effects. The net effect is to create massive amounts of radar “noise”, and a “shadow” region behind the wind turbines. “2D” radars that don’t use multiple vertical beams are especially prone; unfortunately, many air traffic control radars fit that profile.

Britain is especially interested in wind farm power, and this drawback posed a significant problem. They’re beginning to respond by buying new long-range radars from Lockheed Martin, for emplacement near wind farms. These moves follow a 2005 report [PDF] that concluded:

“Flying over or in close proximity to a wind turbine can significantly hamper the ability of an ATC (Air Traffic Control) operator to maintain the identity of his own aircraft and is also unacceptable in the context of the safe provision of ATS...”

Some air defense radars were also affected, and until recently, the UK Ministry of Defence has objected to wind farms located near Air Defence Radars. After some research, however, they concluded that Lockheed Martin’s widely-0used AN/TPS-77 long-range air defense radar was likely to be “wind farm friendly.” A contract was issued to Serco, who installed a TPS-77 radar near Cromer, on the Norfolk coast. UK MOD Defence Equipment and Support (DE&S), and the Department of Energy and Climate Change were also involved, and following tests, the UK MoD has dropped its objections to 5 proposed wind farms in the area.

With their concept proven, a follow-on agreement was signed with wind farm developers, who will be funding the emplacement of another 2 AN/TPS-77 radars in Northumberland and Yorkshire, as part of their project’s installation cost.

The TPS-77 is a transportable version of the L-Band FPS-117. Like its counterpart, it offers secondary air traffic control capabilities, and can be stationed at fixed sites within radomes. It can also be moved, however, using trucks or even a C-130 Hercules aircraft, if redeployment becomes necessary. The antenna array and electronics shelter are both standard ISO packages. When set up, the TPS-77 works at ranges out to 280 miles and at elevations up to 100,000 feet, providing 360 degree azimuth coverage for 24 hours a day, through weather and clutter, even with no on-site personnel.

I wonder why the power industry is focusing on the 10% of Swedish territory that the Armed Forces does not want them to build wind turbines. What about the other 90%? What is also forgotten in the debate is that the Armed Forces have always been an approving authority when it comes to building masts in Sweden due to the effect they can have on low level flying. But in these cases the power industry has forgotten to get this approval before building (knowingly or not). The Armed Forces have approved building 21.300 wind turbines. So far only 1.655 of these have been built. According to the Government there is a need for 3.400 turbines.

The argument that the Swedish Air Force has been operating unaffected out of Sicily, where there are plenty of wind turbines, during the Libya operation is not a very good one. There were no tactical flying over Sicily. The enemy were in Libya, a 1000 mile away.

But maybe the solution would be, as is suggested in the UK, that the power industry at their own cost replaces radar stations that are affected by the wind turbines? If this would be the case, then the power industry can choose to build at almost any location, but take the cost for it.

SVT, Ny Teknik