11/30/2018

Conflict Is Blowin’ In The Wind

4:38 minutes

four wind turbines in a row on a ridge overlooking the ocean and a blue sky
Wind turbines. Credit: Kahunapule Michael Johnson/flickr/CC BY-NC-SA 2.0

Wind energy development is spreading around the nation. Installed generating capacity has tripled in the last decade, according to the American Wind Energy Association, with over 90,000 megawatts of combined capacity in the U.S.  As developers move to identify promising locations for wind farms, however, they may need to consider more than just logistics, wind speeds, and distribution lines.

[We nearly missed one of the largest volcanic eruptions in history.]

Writing in the journal Nature Energy, researchers report that “wake effects” from one wind farm can sap the energy of a downwind generating facility as far as 50 km away. While the exact amount of the loss depends on factors including wind direction and the stratification of the atmosphere, downwind locations can see losses of around 5 percent—which can stack up to economic losses of millions of dollars over a few years time.  But Julie Lundquist, one of the authors of the report, says the wake effects aren’t likely to dampen the growth of wind power, as the effects are very predictable and can be planned around. She joins Ira to talk about the wake effect and the challenges of planning wind farm locations in a competitive market.

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Segment Guests

Julie Lundquist

Julie Lundquist is an Associate Professor in the Department of Atmospheric and Oceanic Sciences and a Fellow in the Renewable and Sustainable Energy Institute at the
University of Colorado Boulder in Boulder, Colorado.

Segment Transcript

IRA FLATOW: And now it’s time to play Good Thing, Bad Thing. 

[MUSIC PLAYING] 

Because every story has a flip side. 

Wind energy development is spreading around the nation. Installed generating capacity has tripled in the last decade, according to the American Wind Energy Association, with over 90,000 megawatts of combined capacity in the US. 

But as developers jockey for position in wind reach areas, there may be unexpected consequences. 

Julie Lundquist is associate professor in the Department of Atmospheric and Oceanic Sciences at the University of Colorado in Boulder and lead author of a report on wind farm positioning, published this week in the journal Nature Energy. She joins me from Germany. Welcome to Science Friday. 

JULIE LUNDQUIST: It’s great to be here, Ira. Thank you. 

IRA FLATOW: Yeah. Thanks for staying up late. So the good news is wind energy is booming in the US, right? 

JULIE LUNDQUIST: Right. Now we’re building a lot more wind farms. And that’s providing more renewably generated electricity. 

IRA FLATOW: But there’s also, your team found, a possible downside to packing too many wind farms too close together. 

JULIE LUNDQUIST: Yeah, just like people, wind farms aren’t always good neighbors to each other. There are some circumstances where wind farms can cause adverse consequences to their neighboring wind farms. 

IRA FLATOW: How do they do that? 

JULIE LUNDQUIST: Well, you have to understand this phenomenon called the wind turbine wake. And I think that we’re all probably familiar with wakes, if we think about water flowing past a rock and stream, for example. You know how the water downstream is generally slower and a lot more turbulent than the water upstream? And air is another geophysical fluid, just like water. And so the air downstream or downwind from a wind turbine is also a lot slower and more turbulent. 

And that air makes it more difficult for the downwind turbines to generate as much electricity as they would normally like to. And that’s just for one wind turbine. And if you combine in groups of 10 or 20 or 100 wind turbines together, then those individual wind turbine wakes can form a larger wind farm wake. 

IRA FLATOW: And that’s when the effect happens. 

JULIE LUNDQUIST: Yeah, yeah. 

IRA FLATOW: So you have a problem if you put too many wind farms together. One starts interfering wake-wise with the other ones. 

JULIE LUNDQUIST: Yeah, but we’ve noticed that these wind farm wakes. And actually, wind turbine wakes, are really only a problem in certain circumstances. So if you think about how the air that you fly in if you’re in an airplane, that changes on a daily basis. So during the day, it’s very bumpy and very turbulent. And that turbulence, just like it would diffuse out a smoke plume from a smokestack or something like that, that would diffuse out during the day. 

A wind turbine wake and a wind farm wake is normally not an issue for concern during daytime circumstances. We are able to talk about how in nighttime circumstances, that’s when these wind farm wakes can spread for very long distances downstream and then cause adverse consequences to downwind wind farms. 

IRA FLATOW: So how big an effect is this, then? 

JULIE LUNDQUIST: Well, if you want to think about the spatial extents of the wake, for the complex of wind farms that we were simulating in Texas, we found wakes that extended at least 45 kilometers downstream. 

IRA FLATOW: Wow. 

JULIE LUNDQUIST: Yeah, and that’s pretty significant. 

IRA FLATOW: And how much has it reduced the output of the wind farms? 

JULIE LUNDQUIST: Well, that depends a lot on the details of the construction and the orientation of the turbines. But if you want to think about how often the wake happens, that’s kind of an important consideration, as well. So we have these possibilities of these very large wakes extending downstream. But for the month that we simulated these wind farm wakes, we noticed that it was only 4% of the time did we find a wake that occurred such that it would impact the downwind production by 20%. 

IRA FLATOW: So that’s not really a deal breaker, then. You’re just being careful where you put your wind farms. 

JULIE LUNDQUIST: Yeah, it’s not a deal breaker at all. And one of the exciting things that we found was that the wake effects can be very well predicted. And so if you can predict a phenomenon, then you can manage it. And so it’s not going to be a surprise if a wind farm is built close to another neighbor. If both parties are aware that this could happen in certain circumstances, then they can make the financial arrangements or the legal arrangements to make sure that lots of renewably generated electricity can still be produced. And the wake effect can be accounted for. 

IRA FLATOW: All right, Julie Lundquist, thank you for taking time to be with us today. 

JULIE LUNDQUIST: My pleasure. 

IRA FLATOW: Dr. Lundquist, associate professor at the University of Colorado in Boulder.

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