Es wird das nächtliche Blinken von Windkrafträdern in einem Windpark dargestellt.

New law on night-time identification Mandatory for DDNI: flashing only when needed at night

16.02.2023 6 Reading Time

klimaVest: Redakteurin Annemarie Fountoukas
Annemarie Fountoukas

If wind energy is to have a future in Germany, it needs to be accepted by a broad majority. However, with their night-time flashing, wind turbines have not only led to some citizens losing sleep, but also turned them into opponents of wind power. After some back and forth, the Federal Network Agency had to end the continuous night-time flashing on 31 December 2022.

Since then, demand-driven night-time identification (DDNI) has been mandatory. Consequently, since the beginning of the year, the flashing only starts when an aircraft comes within a certain distance of the wind turbine. This means that, especially in rural areas, where there is little air traffic, only the stars are likely to twinkle at night. 

Not rocket science, but an uphill battle

Aeroplanes and helicopters are already equipped with transponder signals that show the altitude and position of flying objects on the radar screen to air traffic controllers. This detection technology, that is now part of every wind turbine, is equipped with sensors that receive precisely those transponder signals. If an aircraft flies too close to a wind turbine, the night-time obstacle identification is activated until the craft leaves the designated six kilometre radius again.

The advantages of this technique were already apparent in a study in 2008,  but was met with resistance and concerns from the German air traffic control authorities. While the DDNI systems have been extensively tested and inspected over the years, more and taller wind turbines were built, and the nationwide flashing scenario has become increasingly intense. 

DDNI technology stands for tested safety

Twelve years after the publication of the aforementioned study, any concerns have been resolved and the technical requirements for the implementation of DDNI was set out in Annex 6 of the AVV (German General Administrative Regulation on the Identification of Aviation Obstacles). 

Technical acceptance of DDNI is carried out by the state aviation authorities by means of a declaration from the system operator on the installation of the DDNI system, the positive result of the type examination, the amended Federal Immission Control Act (BImSchG) approval and the commissioning protocol of the DDNI system.

Exceptions allowed

In four cases, system operators could also be released from the obligation to provide DDNI. Firstly: in the case of economic unreasonableness; this may be the case for small wind farms with a relatively short remuneration period and must be applied for accordingly. Secondly: wind turbines with a location close to an airport; in this case, air traffic law has a higher priority and DDNI is not permitted. 

Thirdly: systems that are under 100 metres in height; they are already exempt from night-time marking, and therefore also exempt from DDNI. Fourthly: end of the EEG subsidy; if systems lose their entitlement to payment in accordance with the EEG within three years of the start of the DDNI obligation, the DDNI obligation also lapses. 

In addition to the German Onshore Wind Energy Act, the DDNI obligation should increase acceptance and the pace of expansion.

¹ HiWUS study: Development of an obstacle lighting concept to minimise light emissions at onshore and offshore wind farms and plants, with particular attention paid to the compatibility of environmental impact and safety of air and sea transport;