What are the lights on top of a wind turbine?

Flashing warning lights on turbine nacelles are mostly for the benefit of aircraft flying at night. The lights have progressed from incandescent to Led-based units. The details of several recent lights show advanced lighting systems.

One model of obstruction light comes in a one-piece mount. An internal enclosure houses the flash circuitry and GPS synchronization circuitry, so it can synch up with other lights of the same model in the vicinity. A bird spike on the dome discourages its use as a resting pad. The light’s beam projects 360° with a 3° divergence at 50% peak vertical.

The 33-lb light comes with a regulated power supply with built-in over voltage protection, and contacts for monitoring and alarms. An internal photocell eliminates need for an external one, and it runs on 100 to 240 Vac.

Another light features a compact flash head to reduce wind load on fixed obstructions such as wind turbines, towers, and bridges. Operating at just 20W, the series of lights is said to offer the lowest power consumption of any L-864 product (FAA designation for a flashing red obstruction light, 20 to 40 flashes per minute) to help save energy and reduce operating costs.

With less than an 8.5-in. height, the shock and vibration- resistant lights offer a low profile to reduce the impact of wind sheer on the mounting structure, making it well suited for high- altitude applications and improved performance in inclement weather.

Another version of obstruction light can be set to a steady burn or outfitted with a controller to signal 20 to 40 flash-per-minute. This Led-based light features optics to minimize ground scatter and nearly eliminate community-light pollution. in addition, sharp beam cutoff provides a lower level of scatter—below 0.1 millifootcandles—over a mile, while delivering an FAA required 2,000 candelas to passing aircraft.

Intended to easily retrofit existing incandescent fixtures, the lights offers up to 10 or more years of life expectancy to reduce maintenance costs and frequency of risky tower climbs associated with outdated beacon equipment.

Environmental scientists familiar with bird migration patterns say that when obstruction lights on wind farms flash out of sequence with each other, migrating birds know enough to fly around the grouping. When held steady, birds seem to think that they are seeing something large on which to land.

Readers interested in more information on obstruction marking and lighting can refer to FAA Advisory Circular AC 70/7460-1Kof.