They can be hit by bolts every three seconds for hours-long periods, even if thunderstorms are not nearby.
There are many surprising things about wind turbines: the way they can morph into immense fireballs, their ability to fly, the huge number of bats they kill. Perhaps it's not so astonishing, then, to learn that they can act like giant lightning-firing machine guns, too.
Turbines's hidden lives as lightning factories was investigated recently by Spanish and American researchers who monitored the massive structures with high-speed video and a "3-D Lightning Mapping Array." They found that in certain cases, the turbines would get hit as frequently as a bolt every three seconds, and that this crackling fusillade could last anywhere between a couple minutes to hours. Here's some of their footage:
So what's causing this barrage? One clue is that the lightning didn't strike when the turbines were not rotating. That led the scientists to speculate that the huge blades were gathering a friction-generated charge as they whirled through the air. That in turn made them so well primed for an electric discharge that they were sometimes hit by lightning even when the thunderstorms were "tens of kilometers away," they write in the Journal of Geophysical Research: Atmospheres.
The repeated zapping of turbines does not bode well for the health of these green machines. As Sandrine Ceurstemont at New Scientist reports:
The frequent lightning bolts could be damaging turbine blades, which are made of carbon-reinforced plastic. They are designed to resist occasional electrical discharges, but regular bolts could degrade them faster. "Wind turbines are exposed to a lot of electrical discharges and can easily be stressed," says [researcher Joan] Montanyà....
Another reason that lightning bolts pose a bigger problem for wind turbines is that they are hard to inspect and repair. Their blades sit on a tall structure, making them difficult to access. By contrast, when an aircraft is struck by lightning, it is checked and repaired the next time it lands.
Though this research might provide the best-yet documentation of this electrical interaction, people have known for a while that turbines are magnets for the blazing fury of Thor. Here's some footage of strikes floating around on YouTube: