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0000017a-15d9-d736-a57f-17ff90bb0000Ask Sam features Outside/In host Sam Evans-Brown answering listener questions about the mysteries and quirks of the natural world.Do you have a question you want Sam to answer on NHPR's Morning Edition? Call the Outside/In hotline at 1-844-GO-OTTER or email a voice memo to outsidein@nhpr.org.

Ask Sam: Why Do All Wind Turbines Look The Same?

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Every other Friday on Morning Edition, the Outside/In team tackles a question from a listener.

David from Mont Vernon asks: “How come all wind turbines — onshore and offshore — look the same? They all have three blades. And I’ve certainly seen designs for ones that look like egg-beaters and things that vibrate and all that kind of stuff and I just want to know why are they so boring and unimaginative in their design?” 

This question is extra pertinent because yesterday on Outside/In we launched a special 5-part series on offshore wind, because we are poised to see a boom in that industry. The Biden Administration wants 30GW to be built over the next 10 years

That’s enough that on a windy day it could more than power all of New England with offshore wind alone. So it behooves us to understand this technology. 

The wind turbine with the three blades at the top is known in the wind business as the Danish concept. And it was invented by Henrik Steisdal

“I started making wind turbines all the way back in 1976,” he told me in a zoom interview, “So it's about 45 years ago now and ended up building a wind turbine for my parents farm that could deliver the power that they used. And I got kind of hooked.”            

Henrik essentially invented that modern wind turbine out of stuff lying around his family's farm before he even entered college. 

As the caller points out, there are other designs: vertical axis wind turbines look like egg-beaters, and then there are bladeless turbines which look kinda like a pillar and generate electricity by just wiggling. 

But Henrik’s story actually tells us something about why those other designs have never taken off. Back when Henrik invented this turbine, there was this company that mostly made cranes, but was experimenting with the egg-beater turbines. But those vertical axis machines just weren’t making enough energy compared to the cost of building them. 

However, they bought Henrik’s design and were able to build a multi-billion dollar business out of it.

“And they are actually still the largest wind company in the world,” said Henrik, “And they started with a license of my technology back in 1979.”

That company is now called Vestas. But really this tells you it all comes down to dollars in, dollars out: a potential wind turbine design needs to generate more value in electricity than it costs to build it. The egg-beater turbines in particular have some big design disadvantages: like how one blade is always pushing into the wind as it comes back around. 

But there’s another part of the story, too. 

Once you get the initial design that seems promising, there’s something called path dependence. To make a technology genuinely cheap, you need to scale up, and start manufacturing at scale, which means you need giant factories. For practical purposes, this means companies need to go all-in on one design. Which means that once one design makes it out of the start-up phase, there’s enormous momentum and pressure to stick with it. 

Which is certainly the case with Danish-Concept-Style wind turbines. This also raises the barrier for a different design: because it’s competing against something that is already scaled up and we know how cheap it can be. 

And the three blade turbines are getting incredibly cost effective, because they just keep getting bigger and more powerful. That first one Henrik made was 30 kilowatts. The biggest offshore wind turbine today is 13 megawatts; more than 400 times more powerful!

A very interesting question is to ask how far can that go? How big can they get? 

Because we’re already reaching a point that the relationship between bigger turbines being more cost effective is starting to break down. They’re so big now, and accessing wind so powerful that they now need more steel and other materials because the forces acting on them are so extreme, which erodes their economics. 

So instead they’ve actually had to start making them smarter, so they react to the wind.

“If you have a really strong gust coming in you pitch it a little bit out of the wind,” Vincent Schellings, the Chief Technology officer with GE Wind told me, “From an energy capture perspective it's not really noticeable, but it leads to a significant reduction on the load on the turbine, which therefore allows us to use less material required for reinforcing the components.”

So, while, as David pointed out, they may all look the same, in fact, that three-blade design keeps getting craftier… and keeps getting cheaper, too. 

You can subscribe to NHPR’s Outside/In where-ever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to oustidein@nhpr.org, OR call the hotline, 1-844-GO-OTTER, OR submit it here.

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