The receiving stations of Deutsche Flugsicherung (DFS), the company in charge of air-traffic control for Germany, are an important part of the wireless communication infrastructure of the aviation industry. One of these radio navigation stations, close to the village of Löwenstedt in Germany’s northern state of Schleswig-Holstein, supports communications of pilots aloft.
At first, it did not appear feasible for a publicly-owned wind project to be erected close to this receiving station: To gain approval the wind turbines need to comply with highly stringent radio-shielding requirements.
Then the farm planners opted for Siemens Model SWT-3.0-113 wind turbines — direct-drive units that are the only wind turbines offering the required protection against electromagnetic emissions. Their remote-control capability ensure the wind turbines comply with the technical requirements governing the nearby radar installations operated by the Bundeswehr — the Federal Defense Forces of Germany.
Siemens is now set to deliver five Model SWT-3.0-113 units to the operator, Bürgerwindpark Löwenstedt GmbH & Co. KG. These units offer extremely low electromagnetic emissions of the permanent-magnet generator and the electrical systems. Because these units feature a closed cylindrical ring of conductive permanent magnets that rotate around the stator with the generator windings, the electrical energy does not have to be derived from moving components (e.g. slip rings).
Added to this is the shielded design of the generator’s power electronics and other electrical components, which are encapsulated in a metal housing as well as within the structure of the nacelle and the steel of the tower. Because of the position of the power converter in the bottom of the tower the range of electromagnetic emissions is very limited.
Faced with the stringent regulations, the offer from Siemens was the only solution developers WEB Andresen in the town Breklum and the engineers of Ingenieurbüro Henning Holst in nearby Husum would consider. The co-managing directors of the publicly-operated wind farm, Jan Peter Thoröe and Astrid Jensen, recognized that this solution offered the best chances for building the wind farm at this sensitive location.
Siemens’ Wind Power and Renewables Division submitted verifying proof of the turbines’ electromagnetic compatibility by measurement in the relevant frequency ranges, and the project was granted the required permit. All five Siemens wind turbines will be erected within a radius of two kilometers around the DFS receiver station.
“The conflicting interests of air traffic control and publicly-operated wind farms have presented problems for a number of wind power projects in the state of Schleswig-Holstein,” confirms Jan Peter Thoröe, chief technical officer of Bürgerwindpark Löwenstedt GmbH & Co. KG. “In Löwenstedt, Siemens’ advanced technology helps us comply with the regulations dictated by Deutsche Flugsicherung and the Bundeswehr, and simultaneously implement an important project in which more than 280 local citizens are stakeholders.”
“The design concept of our direct-drive D3-series wind turbines offers numerous advantages,” confirms Thomas Richterich, CEO of the Onshore Markets unit of Siemens Wind Power and Renewables Division. “For the Löwenstedt project, we are especially pleased that the unique electromagnetic compatibility of these units has contributed to ensuring project feasibility at this location.”