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Large Wind Turbines

March 16, 2015
Paul Gipe

DLP Wind Turbine Blades Another Idea that Won’t See the Light of Day

Michael Bender posted a message on an Electric Vehicle forum about an idea of modifying wind turbine blades to use a principle commercialized by Texas Instruments for early digital projectors: Digital Light Processing or DLP. If I understood his question correctly, the idea would be to use the DLP equivalent micro electronics to control portions of a wind turbine blade to instantaneously optimize their position relative to the wind. He concluded that probably this idea would never work, but was curious what I thought.

I get email—and the occasional phone call—from inventors with some idea or another that’s going to revolutionize wind energy. Normally, I don’t write a response, instead I suggest they go to the library and do some more research.

Bender’s question was on a public forum that I benefited from so I thought I’d sketch out some ideas.

Yes, folks like me who work in the industry typically dismiss these ideas out of hand. We internalize a lot of processes and out comes, “nope, not going to happen.”

Here’s why.

My sense is that engineering is all about compromise. (I am not an engineer, though I’ve studied engineering.) It’s not about maximum efficiency, or maximum (or minimum) anything. It’s more about what works best given all the constraints.

So, an idea could maximize aerodynamic performance, but could you build it, could you build it cheap enough, could you build it so it would work for a long time?

I’ve argued for three decades that one of the great failures of American wind turbine design was the desire for maximum aerodynamic efficiency—or performance. This is a very long story and I am not going to repeat it here. You can see my 1995 book Wind Energy Comes of Age for a blow by blow account. American designers may have won the battle for efficiency but they lost the war for what works reliably in the field.

Wind turbines are not aircraft. They are power plants. They must operate thousands of hours per year (more than 6,000 hours per year) with little or no maintenance—actually little or no physical supervision. They are automatons and must take care of themselves. So their systems must be as simple as possible and as rugged and reliable as possible. Complexity can be added only when it’s absolutely necessary, for example, to keep the turbine from destroying itself.

And unlike solar panels, which are static, wind turbines are huge mechanical devices. The biggest, most dynamic parts of a wind turbine are the blades. This is the part that all wind turbine designers must get right or they don’t have a wind turbine—or they have a wind turbine on the ground in pieces.

The Danes succeeded where we failed in wind turbine design because they built relatively unsophisticated wind turbines. They were crude by American engineering standards of the day, but as a result they were rugged—and reliable. And the most unsophisticated part of the Danish wind turbine was the rotor. Even then the blades looked funky compared to the sleek blades we were fielding. I’ve written that it was enough to bring a tear to an engineer’s eye, looking at the crude airfoils on the early Danish wind turbines.

Nevertheless, the Danish wind turbines worked more reliably than the American turbines and the business of power plants is generating electricity day in day out, year after year. So we all ended up with Danish wind turbines, or their derivatives.

So to sum up, adding a micro-electronic system to instantaneously modify the surface of a massive physical structure like a wind turbine blade may gain a few points in efficiency at the cost of increasing complexity and increasing the risk of catastrophic failure. In other words, it's not going to happen.

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