hardware internet tech

Wind Farms In The Night: On-Demand Warning Lights Are Coming

There appears to be no shortage of reasons to hate on wind farms. That’s especially the case if you live close by one, and as studies have shown, their general acceptance indeed grows with their distance. Whatever your favorite flavor of renewable energy might be, that’s at least something it has in common with nuclear or fossil power plants: not in my back yard. The difference is of course that it requires a lot more wind turbines to achieve the same output, therefore affecting a lot more back yards in total — in constantly increasing numbers globally.

Personally, as someone who encounters them occasionally from the distance, I find wind turbines mostly to be an eyesore, particularly in scenic mountainous landscapes. They can add a futuristic vibe to some otherwise boring flatlands. In other words, I can not judge the claims actual residents have on their impact on humans or the environment. So let’s leave opinions and emotions out of it and look at the facts and tech of one issue in particular: light pollution.

This might not be the first issue that comes to mind when thinking about wind farms. But wind turbines are tall enough to require warning lights for air traffic safety, and can be seen for miles, blinking away in the night sky. From a pure efficiency standpoint, this doesn’t seem reasonable, considering how often an aircraft is actually passing by on average. Most of the time, those lights simply blink for nothing, lighting up the countryside. Can we change this?

Light On Demand

Map of wind farm locations in Europe with heavy concentration visible in GermanyWind farms locations across Europe as reported in the Wind Power database (Source: SETIS)

Improving warning lights to light up only when there’s an actual aircraft to warn in its vicinity isn’t a new idea, and individual tests to achieve this have been successfully carried out in the past. Looking at the map of wind farms in Europe, it’s not too surprising that Germany is especially interested in this subject, and is now implementing new regulations to enforce an on-demand warning light system as requirement for wind farms, expected to come into affect this summer.

Generally speaking, there are two options to know about an object in the sky within a wind turbine’s surroundings:

  1. the turbine is looking for an aircraft in the sky
  2. the aircraft reports its presence to the turbine

Established technologies exist for both options in form of radar and transponder signals respectively.


To simplify the basic concept of radar: radio waves are emitted into the wild, and if there is anything in their way, they bounce back to be received again, making it possible to determine the presence and distance of an object. Repeat it in a constant manner, and that object’s angle and velocity can be determined as well.

Like anything else in technology, radar systems have vastly improved and changed over time, and using Active Electronically Scanned Array (AESA) antennas nowadays, they can not only track multiple objects at once, but also look a lot more subtle than they used to. Instead of huge antennas rotating around, causing potentially new problems with the public, the radio wave angles are directed electronically, allowing the whole system to be fully stationary and placed into an inconspicuous looking box. Paint it like a cow, and no one might even notice it at all.

Transponder Signals

It would be even less conspicuous if we moved the responsibility to the aircraft itself, namely using ADS-B signals. ADS-B is often considered as a replacement for radar itself in air traffic control, and essentially consists of a transponder located within the aircraft that is periodically sending the aircraft’s identity, position, and altitude as radio signals for everyone to receive.

Of course, if a Raspberry Pi or ESP32 at home can receive the signals and make sense of the data, so can a wind farm.

The Catch

So far so good in theory, but as usual, in practice it isn’t that straightforward. A sophisticated system like an active phased array radar has a price tag, and the whole point here was to encourage more wind power adoption. Costs aside, if there is any disturbance with the radar signal causing it to become unreliable, the whole system would have to be bypassed, turning the lights fully back on anyway.

ADS-B would have significantly lower costs, however there are other concerns and issues with that approach, aside from possible satellite navigation reliability concerns. While large commercial airplanes are mostly regulated to require ADS-B transponders, it’s not necessarily the case for the smaller ones. And of course, not everything that flies has to be an airplane to begin with, and neither would it necessarily be of civil use. As ADS-B allows the tracking of an aircraft, some of them might not want to have that option, and others maybe shouldn’t have that option. In worst case, the system won’t be able to detect the very object that would actually need the warning lights.

Ignoring the details of which technology would be used, another aspect to consider is the interoperability with the wind turbines themselves, and the grown complexity of such a system as well as the security implications following it. Once the lights are triggered by an external event, and that event needs to be distributed to multiple turbines, things can go wrong in a lot of places, and the general reliability of such a system would be questionable. Plus, it wouldn’t take a take a hardcore conspiracy theorist to think about the consequences of such a system maliciously malfunctioning one day.

The Bigger Issue

But let’s take a step back and look at the initial problem itself: warnings lights are brightening up the night sky in order to inform pilots that a tall construction is present. To me, it sparks the question “why?”. Why do we fully rely on humans to handle air traffic safety here?

This isn’t even a question about your stance on renewable energy or light pollution, but why is there a necessity to shine a light at all as warning — regardless if it’s continually or on-demand, or whether we are talking about wind turbines, radio towers or just any tall enough construction. Installing on-demand warning light systems surely makes sense from an efficiency point of view, and I guess you have to start in some place, so why not wind turbines, but shouldn’t we rather focus on a whole new warning system altogether?

Take ship navigation for comparison: for centuries the lighthouse was the essential system to aid ships to safe harbor and avoid collisions on rocks and cliffs. And yes, they are still around today, with a surprising percentage of them even shining into the sea, but for the most part, newer navigation systems have replaced them for most of the parts. Yet, provocatively stated, air safety regulations are one step short of hiring plane spotters to manually turn the warning lights on. Ships have detailed maps of the ocean floor. Why don’t airplanes have the same for the ground?

We will see what the future brings, maybe our grandchildren will shake their heads in disbelief how we used to place all this responsibility in a few human hands without any concerns. Until then, we can look forward to a slightly darker night sky in the countryside again, at least in some parts of the world. Whether all this is really happening in the name of promoting renewable energy sources remains to be seen.

(Banner image by Jeswin Thomas)