The video above was taken at the National Wind Technology Center, a research facility run by the Department of Energy outside Boulder, Colorado. In it, DOE’s Simon Edelman scales the inside of a 270-foot GE wind turbine, pointing out various features of the turbine and safety procedures for moving around inside it. Eventually, he pops out on top, making my stomach flip.
Wind turbines have become a familiar feature of the landscape in some parts of the country, but many people don’t understand how they work and why they keep getting better and cheaper.
Watching the video brings home what giant industrial machines these things are. There’s some digital IT stuff going on — lasers and other sensors detect wind speed and calculate the right angle for the blade; control software monitors performance — but for the most part, a wind turbine is just a big, clever mechanical machine.
Here’s one quick example of how they work and how they’re improving.
Turbines start up at wind speeds of around 8 to 16 mph (they shut off at wind speeds of 55 mph or over — any higher and they risk damage). The wind pushes the giant blades, which can be over 160 feet long, around slowly, at around 30 to 60 revolutions per minute.
So there’s an engineering problem: The main shaft, attached to the blades, is spinning at 30 to 60 RPM, but to generate power, a generator needs to spin a coil around a magnet at around 1000 to 1800 RPM. How do you make slow rotation into fast rotation?
Gears! The slow-rotating main shaft is connected to a fast-rotating shaft by a gearbox, which uses a series of gears to accelerate rotation.
The gearbox is a big, heavy, expensive, and failure-prone part of a wind turbine — that’s why researchers are focusing so much attention on it.
One of the coolest areas of development is in “direct drive” turbines, which don’t need a gearbox at all — they just use the main shaft as the generator shaft. They can do this because they use bigger (and still more expensive) generators that don’t require such fast rotation and can generate power at varying rotation speeds.
As this piece in Power Engineering describes, costs of direct-drive turbines are falling quickly and they are approaching cost parity with geared turbines. Though it will likely take a decade or two, the industry seems to be steadily shifting to direct drive, which will further reduce maintenance costs and increase reliability.
If you haven’t had your fill of nerdy turbine videos, here’s one that walks through a Lagerwey direct-drive turbine:
This one has an elevator instead of a giant ladder. Seems better!
Anyway, more efficiently transforming the wind’s motion into electrical power is just one more way these big machines are getting better.
So endeth your wind turbine lesson for the day.