As you know, I've been fascinated with wind turbines since my visit to the Allegheny Ridge Wind Farm in 2007. Here on my blog I've talked about Wind Turbines vs. Tornadoes and Hurricanes. I've talked about Wind Power Myths and Wind Farms on Radar Causing Tornado Warnings. Today, I'd like to talk about lightning.
Caryn Hill is a photographer from Tornado Alley and wife of Roger Hill, veteran storm chaser and co-owner of Silver Lining Tours. The couple was recently featured in Outdoor Photography magazine. Last week, Caryn posted a photo on Facebook (shown above / used with permission) showing a wind turbine getting struck by lightning in Limon, Colo., on July 30. Ironically, on Aug. 2, South Dakota Meteorologist Aaron White posted this picture from a viewer of a wind turbine on fire, presumably after a lightning strike:
Wind turbines (like all tall structures that frequently are struck by lightning) are "grounded" by a standard metal cable (we have one of these on the AccuWeather roof, as do my mom's and grandmother's houses). When properly grounded, the lightning goes down the cable and into the ground (clearly something that didn't happen above). When I toured the (under construction) Allegheny Ridge Wind Farm in 2007, I took some pictures up close of the lightning cabling inside the blades. Here we see the inside of a turbine blade waiting to be installed, with the lightning rod running down the blade on the left:
The cable is glued to the blade and below is what the end of it looks like. This cable will be connected to one that goes deep into the ground, so that the lightning is able to take a direct path which doesn't damage the turbine. Connected to this end is a small white box the size of a credit card:
The cable running inside the blades transmits the lightning through a "Peak Current Sensor" inside the white box before channeling it to the ground. The PCS is a credit-card device that records the amperage of the strike and can be scanned by a mobile computer/phone. This data (I presume) is collected by maintenance workers when they perform maintenance on the inside of the blades and stored for research or insurance purposes.
By the way, these blades are BIG. In the photo below, I was lucky enough to view, up close, a blade that had not yet been installed. The blades are over 100 feet long and were hauled in from the plant nearby on trucks pulling several tractor trailer flatbeds.
The Allegheny Ridge Wind Farm, at the time, consisted of 30 newly-installed wind turbines - with 30 more to come - on top of the Allegheny Mountain ridges southwest of Altoona, Pa., developed by GAMESA Energy. The turbines have grown north since... the total number of turbines in this local area is as high as 90 when the newer North Allegheny Wind Farm (run by Duke Energy) is included.
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