On-Demand Night-Time Marking (ADLS) for Wind Turbines with Deutsche Windtechnik Control and WAGO

Deutsche Windtechnik Steuerung, headquartered in Husum-Ostenfeld, has taken the leadership in wind farm maintenance. The company has maintenance contracts in Germany for around 2,400 turbines, with more worldwide. In addition to standard maintenance of land-based and offshore wind turbines, the team from Deutschen Windtechnik Steuerung conducts research into developing and expanding their services. In 2018, when a draft law for on-demand night-time marking (ADLS) of wind turbines was proposed, Deutschen Windtechnik Steuerung’s technicians and engineers began developing a solution to switch on the red flashing lights at the top of wind turbines, but only when they were needed. At that time, no finished industrial product could satisfy the legislators’ lofty safety requirements.

Merely switching the lights off is simply not a solution here, as the lights fulfill a necessary safety function: they warn any approaching aircraft about the wind turbines. Therefore, the solution must monitor the air space and emit a signal that allows the night-time marking to illuminate as soon as helicopters, airplanes, etc., approach within a radius of four kilometers. Wind turbine operators must legally implement ADLS on land by 31 December 2022 and at sea by 31 December 2023. The law applies to wind turbines starting at a height of 100 meters, meaning that most wind turbines in Germany are affected.

There are currently a mere handful of solutions to implement ADLS. Three vendors rely on WAGO – Deutsche Windtechnik Steuerung is among them. They have developed a so-called ADLS Box that operators can retrofit on their wind turbines.

“During the development of our ADLS Box, we had to overcome several obstacles. It wasn’t a sure-fire success,” recalls Karl Keusgen, CEO at Deutschen Windtechnik Steuerung. “ADLS represents an intervention in air traffic safety. We had to provide a lot of supporting evidence. This included, for example, that the lights must illuminate within a specific time – something that had to be guaranteed. Another obstacle was the variety of wind energy systems as well as geographic challenges, like mountains and valleys,” continues Keusgen.

The solution from Deutschen Windtechnik Steuerung provides an independent, transponder-based system that can be integrated into existing wind farms. There are three different configuration levels. The complete solution equips the entire wind farm. A transponder receiver functions as the master box, which is centrally located in the wind farm and operated by Deutschen Windtechnik Steuerung. Each individual wind turbine receives an ADSL Box – a slave box that can control the night-time marking system. That box is installed in the turbine’s nacelle.


Starting in January 2023, wind turbines are legally obligated to feature a system for on-demand night-time marking in order to reduce light pollution.
Photo: Udo Hallstein/vor-ort-foto.de

The WAGO Relay (Item No. 857-304) with Push-in CAGE CLAMP® plays an important role in transmitting the signals. Deutsche Windtechnik Steuerung installs three WAGO relays in the slave boxes and four in the master box. One relay in each box switches the light on and off. The second relay fulfills a test function, and the third provides feedback about whether the box is functioning correctly or if a fault has occurred. The fourth relay in the master box is necessary for externally activating the light signal, as not all aircraft transmit a signal that can be detected by monitoring the air space. These include German Armed Forces aircraft, among others, which can then independently actuate the night-time marking for the wind farm by using the fourth relay.

“We could also have solved that with software. However, a relay simplifies the process and ensures a higher level of safety,” shares Ragnar Duborg (Sales Office in Hamburg) in explaining the background for using a fourth relay. After about a year of conceptual work and subsequent development, Deutsche Windtechnik Steuerung received approval for its ADLS solution in 2020. “It was important for the approval that our ADLS Box detected every type of aircraft,” according to Ploog. “We developed multi-faceted software to account for every condition,” adds Keusgen.


Deutsche Windtechnik Steuerung decided to use WAGO relays in order to reliably transmit signals.
Photo: Tim Riediger/vor-ort-foto.de