What is on-demand night marking (BNK) for wind turbines?


Demand-driven night marking (BNK) for wind turbines is a crucial tool for increasing the acceptance of wind energy. By 1 January 2024, all wind turbines in Germany must be equipped with a BNK system. This obligation raises many questions in practice, and the conversion time for operators is short. Here is a brief summary of key points, challenges and recommendations for action for wind farm operators.

Key points of the BNK

1. Objective of the BNK: The BNK aims to reduce the flashing of wind turbines at night, which is a major point of criticism among the population. The lights should only be activated when a flying object is approaching at a critical height.

2. Technologies : There are three main technologies for BNK systems:

- Active radar: Detects objects in the airspace and covers multiple parks at the same time.

- Passive radar: Uses reflections of digital radio and television signals to locate flying objects.

- Transponder systems: Use signals from aircraft transponders.

3. Legal framework: The implementation of the BNK is required by law and is monitored by the Federal Network Agency. Failure to comply may result in loss of market premium.

Challenges and recommendations for action for operators

1. On-time implementation: The conversion can take up to a year. Operators should act promptly to meet the legal deadline.

2. Choice of system: Operators must select the appropriate system for their park, taking into account the type of infrastructure available, the size of the park and the local conditions.

3. Licensing issues: In particular, if external antennas are required, aspects of building law must be clarified. The onshore wind energy agency offers extensive information on this.

4. Economic considerations: An exemption can be applied for for existing installations where retrofitting is economically unreasonable. The Federal Network Agency provides application forms and information papers for this purpose.

5. Proactive planning: Operators should not wait for a possible extension of the deadline, but should proactively start the retrofit. This also includes a cost-benefit analysis.

6. Technological development: It is advisable to keep an eye on technological developments in the field of BNK systems, as new and more efficient solutions could emerge.


Demand-driven night-time marking is an important step towards reducing the visual impact of wind turbines and increasing public acceptance. For operators, there is a need to respond quickly and efficiently to these new requirements in order to comply with legal requirements and avoid financial disadvantages. Careful planning and selection of the right system are essential to both meet legal requirements and maintain operational efficiency.

How does on-demand night marking (BNK) work?

In the video, the BNK is briefly and simply explained by Light:Guard GmbH