Obstacle marking of wind turbines

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OBSTAFLASH obstacle lights with partly infrared LEDs for installation on wind turbines

With the expansion of wind energy in the course of the energy transition , both the dimensions and the number of wind turbines are growing . Therefore, adequate identification of obstacles in wind turbines is necessary in order to prevent collisions with aircraft or watercraft .

Identification as an obstacle to aviation

The labeling of wind turbines as obstacles to aviation is based on Annex 14 of the Agreement on International Civil Aviation . However, different regulations may be made through national regulations. In Germany, the marking of obstacles is regulated by the "General Administrative Regulation for the Marking of Aviation Obstacles" (AVV Marking).

In Germany, wind turbines are generally treated according to the guidelines for general aviation obstacles, so they must be marked from a total height of 100 m, in special cases even at a height of less than 100 m. Due to the special properties of wind turbines (rotating rotor blades, etc.), some labeling requirements have been specially adapted for the field of application of wind turbines.

Day marking

Harthäuser Wald wind farm with red markings

The daytime marking of wind turbines is usually done with colored markings, sometimes supplemented by white flashing fire.

A 6-meter-wide orange / red stripe is required on the tips of the rotor blades from a total height of 100 meters.

A second 6 meter wide orange / red stripe (between 6 m white / gray) is required both when the nacelle and the rotor blade tip are more than 65 meters away, as well as when the total height exceeds 100 m and there is no white flashing fire on the nacelle .

The mast is to be marked at a height of 40 ± 5 m above ground with an orange / red colored ring of 3 m (lattice mast: 6 m) wide, both if the total height exceeds 150 m and if the total height exceeds 100 m and due to a white flashing fire on the marking of the nacelle and the second orange / red stripe on the rotor blades.

The machine house must be provided with a 2 m wide orange / red stripe on both sides as soon as the total height exceeds 150 meters and there is no white flashing fire on the machine house.

The white flashing fire has 20,000 cd ± 25%, type A according to ICAO Annex 14.

Night marking

Neudorf wind farm at night

The night marking of the wind turbines is carried out from a total height of 100 m by hazard lights , fire W, red or blade tip obstacle lights (in connection with obstacle lights):

  • The hazard light is a red flashing omnidirectional light with a light intensity of 2,000 cd (medium-power light  type B according to ICAO Annex 14). They are usually used in duplicate to ensure that at least one fire is always visible from every direction, even if it is covered by a rotor blade. If hazard lights are used, the highest point of the rotor may not exceed it by a maximum of 50 m.
  • As an alternative to the hazard fire, the W, red fire, which is used exclusively in wind energy plants, can be used. It is an omnidirectional beacon with a special emission characteristic and a predetermined flashing sequence (1s on - 0.5s off - 1s on - 1.5s off). The fire W, red must be installed in duplicate on the nacelle and may be exceeded by a maximum of 65 m from the highest point of the rotor.
  • In the case of blade tip lighting, the tip of the rotor blades contains lights that have to achieve a light intensity of 10 cd in a defined radiation area. The topmost rotor blade must be fired (with a three-blade rotor in the range of ± 60 ° from the vertical). If the wind turbine is at a standstill or if the speed is below the lowest nominal speed, all peaks must be fired. When equipping wind turbines with blade tip obstruction lights, additional obstruction lights (= red omnidirectional fixed light with a light intensity of at least 10 cd in a radiation range of −2 ° to + 10 ° compared to the horizontal) are required on the nacelle.

Since May 2020, for system heights of more than 150 m and up to and including 315 m above ground or water, an additional lighting level, consisting of obstruction lights, must be installed halfway between the ground or water and the night marking. If necessary for technical reasons, the arrangement of the lighting levels can be deviated up or down by up to five meters. At least two obstruction lights per level must be visible from every direction. Previously, two additional lighting levels on the tower were required for wind turbines with a total height of approx. 200 m .

Demand-controlled night lighting

To the z. To be able to reduce night lights, which are sometimes perceived as annoying, to a minimum, various systems have been developed which only switch on the position lights when an aircraft is actually nearby. This is officially referred to as "demand-driven night identification" (BNK). Tests with a radar-based system developed jointly by Enertrag and Airbus began in 2012; In 2015 it was approved by German authorities. If radars with phased array antennas are used, a minimum of three to four radars must be installed. If the radars work according to the FMCW principle , a transmission power of 4 watts each is sufficient , about twice as much as that of a cell phone . A radar device is sufficient when using rotating antennas. If this is a classic pulse radar, then a pulse power in the kilowatt range can be expected.

In the event of a defect in the radar system, the night lighting is switched back to continuous operation. This means that obstruction lights do not need to be used for approx. 98% of the time. First major projects to retrofit the system in existing wind farms are ongoing; For example, around 90% of all wind turbines in the Uckermark district are to be converted from permanent lighting to demand-controlled lighting in 2017 . At the beginning of February 2017, a project near the Holstein town of Marne was also announced in which around 200 wind turbines are to be converted to needs-based lighting. The company Airspex , a subsidiary of Enertrag is responsible. In addition to the company mentioned, Quantec Sensors should also be mentioned as a "big player" in the field of retrofitting wind turbines with BNK-capable fires. In May 2018, a system based on passive radar was also approved that does not require any own transmitter. Instead, the system uses deviations from existing television and cell phone waves to detect approaching flying objects.

Another technology is based on the use of on-board transponder signals from aircraft. With the Energy Collection Act of December 2018, this technology was proposed by law as a BNK solution. A ratification of the draft of a corresponding general administrative regulation for implementation by the Federal Council took place in February 2020. The advantage of using the transponder technology is the low cost of setting up the antennas on the nacelle of only a few wind turbines in one area, the high quality of the signal detection, as well the acquisition of all signals down to the ground in the prescribed effective area of ​​the BNK. A test system has been operating successfully since July 2019. In addition, the modern recording and evaluation of transponder signals, which have been tried and tested for many years in aviation, are widely accepted by night-time airspace users, for example because helicopter rescue services (HEMS providers) such as ADAC Air Rescue require detection from altitude zero for their flight operations.

Marked as an obstacle to shipping

Off the coast, wind turbines must not only be marked as an obstacle to aviation, but also as an obstacle to shipping. In Germany, in addition to visual identification, radio identification is also provided.

Visual identification

On the one hand, offshore wind energy plants must be marked with optical measures as an aviation obstacle according to the same specifications as plants on land. However, in order to be recognized by watercraft, additional identification is necessary.

Day marking

The day marking in the offshore area is carried out by a generally 15 m high yellow paint and black lettering attached to it. In the case of plants in the North Sea, the coating must be applied in a range from HAT (Highest Astronomical Tide = highest possible tidal water level) to HAT + 15 m, in the Baltic Sea in the range from 2 m to 17 m above mean water level. The lettering must be attached three to four times around the mast and be suitable for identifying the system. It includes an identification of the wind farm (up to three capital letters) as well as the plant number to be determined by the operator within the wind farm (up to four digits). The wind turbines can also be labeled with the word "EXIT" in conjunction with an arrow to show the shortest route to leave the wind farm.

Night marking

The night-time marking of offshore systems is carried out using 5 nautical miles and close-range marking . The 5 nautical mile lights must be attached to every wind turbine that is on the periphery of the park. The fire must be at a height of 10- 25  m are HAT. Either the light can be emitted in all directions or only in directions outside the wind farm. The lights must be switched on one hour before sunset and switched off one hour after sunrise. If visibility is poor, it must remain in operation during the day. All 5 nautical mile lights used must be equipped with automatic monitoring to detect a failure. The cycle of the 5 nautical mile lights is different at the corner points of a wind farm from the cycle of the lights along the peripheral line. The near-area marking can be done by illuminating the black lettering on the yellow paint. Alternatively, there is the inverse display, in which the lettering itself must light up yellow.

Radio identification

As part of the radio identification, every offshore wind farm must be equipped with AIS , VHF radio and certain VHF radio channels. Essential information for identifying the wind farm and its extent is transmitted via AIS. In order to guarantee a range of the AIS of 20  nm (around 37 km), an antenna height of at least 36 m above the highest tide must be maintained.

technology

Fire

While incandescent , halogen or fluorescent lamps were still used in older fires , more modern concepts are mainly based on long-lasting LED technology. In order to be recognized by pilots with night vision devices at night , some infrared LEDs should be installed in the fires / lights .
The white flashing medium -power light for marking the day is often also implemented with xenon lights .

Day / night switching

Switching between daytime and nighttime lighting is achieved using a twilight sensor that must respond to a switching threshold of 50 to 150  lux .

synchronization

In order to make the appearance of the lighting of wind turbines more harmonious for people, the lighting of a wind farm is often synchronized. This is done via a time signal that z. B. is received via GPS or DCF77 . This time signal from a master fire is often distributed to the other lights via the wind farm's internal network. Modern fires are each equipped with their own GPS sensor so that synchronization is guaranteed even if the master fire or the network fails.

Measures to increase acceptance

With the increasing height of wind turbines, the number of systems for which there is an obligation to mark obstacles also increases. This is often perceived as annoying by people in their environment and also makes a certain contribution to light pollution . Since light counts as immission within the meaning of the Federal Immission Control Act (BImSchG), the immission control report can even stipulate requirements for reducing light emission. There are a number of measures to increase acceptance in order to keep light emissions as low as possible, but still as high as necessary.

  1. The first starting point in this sense is the fire itself. The hazard fire and fire W, red, may be shielded from below. Furthermore, the fire W, red ES ("ES" stands for "extended specification") has been approved since 2009, which, in addition to the lower technical lighting limits to be observed, also specifies an upper limit for the luminous intensity.
  2. The second starting point is dimming the fire when visibility is good. If with the help of a certified visibility measuring device a visibility of more than 5 km is determined, the power of the fire (applies to white flashing fire, hazard lights and fire W, red) may be reduced to 30% of the nominal light intensity, with a visibility of more than 10 km to 10 %.
  3. Need-based lighting (also: needs-based night-time labeling, needs-based night-time labeling): The aim of needs-based lighting is to keep light emissions as low as possible by keeping the lighting switched off when there is no flying object in the surrounding airspace. It is imperative that all objects in flight are recorded in the relevant airspace and that fail -safe technology is used. Three different systems are currently under discussion: transponders (secondary radar), primary radar and passive radar .
    • Transponder (secondary radar): A radar sensor installed in the wind farm receives the transponder signals that can be sent out by airplanes and helicopters to identify them. If a flying object is located in the warning-relevant area, the lights are switched on. This technology is comparatively inexpensive, but requires a transponder requirement or a transponder activation requirement at night.
    • Primary radar: With this technology, antennas in the wind farm generate electromagnetic pulses that are reflected on objects in flight and recorded by sensors. The flight route is calculated from the echoes received and the lights are switched on in the event of a critical approach. Due to the more complex technology, this system is more expensive than the transponder method. In addition, there are systems that are not permitted in Germany due to frequency overlaps with military applications. However, it is advantageous that a flight object is recognized even if it does not transmit any signals itself. Since, in contrast to the transponder solution, all relevant components are arranged on the floor, the system detects any malfunctions and switches on the lights.
    • Passive radar: The properties of the emitted electromagnetic signals are known from nearby transmitters (e.g. from the radio or mobile radio sector). If there is a flying object in the airspace, the changes in the signal are recorded and the flight path can be deduced with a complicated calculation . This system has had its official recognition since May 2018.

swell

Individual evidence

  1. ↑ General administrative regulation for the marking of aviation obstacles. Federal Ministry of Transport and Digital Infrastructure , April 20, 2020, accessed on June 2, 2020 .
  2. ↑ Collection of radar devices on the radar tutorial : special radar Spexer 500 AC for demand-controlled lighting
  3. ↑ Terma's SCANTER 5202 radar as wind farm obstruction light control project
  4. ↑ Earning ends nightly continuous flashing on wind turbines . In: IWR , April 1, 2015, accessed January 2, 2017.
  5. ↑ Uckermark is switched off . In: Märkische Oderzeitung , December 16, 2016. Accessed January 2, 2017.
  6. ↑ Enertrag supplies lighting systems for up to 200 wind turbines . In: IWR , February 1, 2017. Retrieved February 1, 2017.
  7. ↑ WEA night marking: The new development receives recognition under aviation law . In: IWR , May 30, 2018. Retrieved June 18, 2018.
  8. ↑ Demand-controlled lighting on wind turbines . Press release from the Fraunhofer Institute for High Frequency Physics and Radar Technology . Retrieved June 18, 2018.
  9. ↑ Energy Collection Act of December 17, 2018
  10. ↑ Andreas Wilkens: Wind turbines will soon only flash when necessary. Heise Medien, February 14, 2020, accessed on February 14, 2020 .
  11. ^ Press release from Lanthan GmbH & Co. KG . In: IWR , September 5, 2019. Retrieved October 10, 2019.
  12. ↑ Statement on the BNK transponder .
  13. ↑ For example dozens of wind turbines northeast of the Neusiedlersee , which can be seen from the church Donnerskirchen (west of the lake). As of October 2017.
  14. ↑ FSAV of November 26, 2004, amended by Article 13 of the law of December 17, 2018 (Federal Law Gazette I p. 2549) .
  15. ↑ Announcement in NfL I-1687-19 . in Luftverkehr.de, accessed on October 10, 2019