Let’s get real about cute little wind turbines
I used to write a lot about wind turbines on TreeHugger. I would go to the trade shows and listen to the spiels and come away impressed and write a post about them. Then the commenters would come along, often really knowledgeable people like wind expert Paul Gipe, and tell me that I don’t know what I am talking about. Of course, he was right; I am an architect, not an engineer and didn’t know what I was talking about.
After years of writing about turbines that never came on to the market, and some where the promoters went to jail, and a whole lot of reading, I decided that perhaps this is one of those green gizmo ideas that are more about looks and image than they are about actually doing good. Because every study of small urban wind turbines says they don’t work or they perform at a fraction of their promised output.
The biggest problem is turbulence. The wind near the ground is bouncing around, hitting everything and going in different directions. As the hilarious guys at Solacity write (and they actually sell wind turbines)
Wind turbines need wind. Not just any wind, but the nicely flowing, smooth, laminar kind. That cannot be found at 30 feet height. It can usually not be found at 60 feet. Sometimes you find it at 80 feet. More often than not it takes 100 feet of tower to get there.
© New Wind
Many of these small turbines are what is called a Savonius design, which looks like two halves or a barrel stuck together. They are cheap but not very efficient, since half the turbine is blocking the wind while the other half scoops it. It barely manages to get 40% efficiency compared to horizontal axis turbines and creates a huge amount of turbulence in its wake. As Mike Barnard of Clean Technica points out, "VAWT blades are in their optimal angle to the wind in only a small portion of their entire span, and their blades fly through air that they have made turbulent the majority of the time."
© Jérôme Michaud-Larivière
That’s what you see in the post on the very beautiful tree designed by Jérôme Michaud-Larivière; the ones facing the wind will generate a little bit of power and just block every other one behind it. It’s gorgeous but designed to fail.
Also, in the Windstream hybrid wind/solar system where the solar panels are going to disrupt the flow, the struts are going to cause turbulence, the panels should face south but prevailing winds are usually from the west, because that’s the way the world works. So they are just blocking and disrupting each other.
Philishave tower, London/ Lloyd Alter/CC BY 2.0
Then there are the turbines that are put on buildings for no other reason than to advertise “I am green!” The developer of the ugliest building in London that looks like a giant shaver actually wanted to put motors on the turbines so that would turn, because they sure don’t in the wind. Fortunately the architect refused so they just sit there.
And there is the wonderful parking garage with vertical axis turbines in the corners, without a hope of ever doing anything. Alex Wilson summed it all up in an article on building-integrated wind turbines:
Rooftop installations—even the best of them—are too small to be cost-effective, and the air flow too turbulent to be effectively harvested—whether vertical-axis or horizontal-axis. The truly integrated installations that are large enough to generate significant power will be too hard to permit or insure in North America to become a serious option, even if the vibration and noise concerns are successfully addressed.
I love wind power and I love design, and totally support TreeHugger writers showing gorgeous new turbine designs like these wild archimedes screws. We are a green design website, after all. They are lovely to look at and who knows, one of them might just really work.
But lets be realistic about it, acknowledge the problems and keep our eyes open.