Suitable areas for onshore wind farms are becoming increasingly scarce. In some areas, mainly in Lower Saxony and Schleswig-Holstein, one technology is literally interfering with the other. Wherever air traffic control, meteorological services or the armed forces operate their transmitting and receiving equipment, they are disturbed by electromagnetic fields generated by wind turbines. Some wind farms already fail in their planning phase due to this conflict of interest. The German Wind Energy Association estimates the nationwide output of these prevented projects at over 4 gigawatts. In Löwenstedt in the district of North Frisia, Siemens are now showing that approval is merely a question of the right wind turbines.
Initially, it appeared that Bürgerwindpark (a citizens’ wind farm) Löwenstedt would fail approval because the German Air Traffic Control places the highest demands on its receiving location in terms of electromagnetic compatibility of wind turbines. The project planners then opted for type SWT-3.0-113 turbines from Siemens. Only the direct driven wind turbines from this manufacturer offer the required protection against electromagnetic emissions. The technical requirements of the Federal Armed Forces, who operate radar stations in the area, are also met by the turbines due to their control options.
Since a closed ring of permanent magnets revolves around the stator with the coils of the generator in case of the direct-drive systems from Siemens, the electrical energy does not have to be discharged with slip rings, for example. The shielded design of the generator and of the electrical components also contribute to its radio compatibility: both a metal case as well as the design of the nacelle and the steel tower shield electromagnetic fields. Siemens submitted metrological proof of the electromagnetic compatibility of the turbines in the frequency range relevant to air traffic control, and the project then received the necessary stamp of approval.
“The conflicting interests of air traffic control and community wind farms are the cause of many problems that wind projects face in Schleswig-Holstein,” said the technical director Jan Peter Thoröe from Bürgerwindpark Löwenstedt GmbH & Co. KG. “In Löwenstedt, advanced Siemens technology helps us meet the requirements stipulated by DFS (German Air Traffic Control) and the Federal Armed Forces, and realise an important project in which more than 280 citizens are involved.”