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 responsible Federal Ministry has stopped the continuous night-time flashing as of 31 December 2022.¹  

Since then, demand-driven night-time identification (DDNI) has been mandatory. ² As a result, since the beginning of the year, the flashing only starts when an aircraft falls below a certain distance from 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

Aircraft and helicopters are already equipped with transponder signals, which allow aircraft pilots to display the height and position of flying objects on the radar screen.³ The detection technology, which is now part of every wind turbine, is equipped with sensors that receive exactly those transponder signals. If an aircraft falls below a critical distance, the night-time obstacle marking is activated until the object leaves the radius of six kilometres again.⁴

The advantages of this technique were already apparent from a study in 2008.⁵ But there were resistances and concerns on the part of air traffic control. 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. 

Exceptions allowed

In four cases, plant operators can also be released from the obligation to BNK.⁸ 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 Wind-an-Land Act and other acceleration measures by the German Federal Government, the BNK obligation is likely to further increase acceptance and the pace of expansion.