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Power Science

Windbreaks Could Help Wind Farms Boost Power Output (sciencenews.org) 62

Posted by BeauHD from the surprising-findings dept.
labloke11 shares a report from Science News: Windbreaks may sound like a counterintuitive idea for boosting the performance of a wind turbine. But physicists report that low walls that block wind could actually help wind farms produce more power. Scientists already knew that the output of a single wind turbine could be improved with a windbreak. While windbreaks slow wind speed close to the ground, above the height of the windbreak, wind speeds actually increase as air rushes over the top. But for large wind farms, there's a drawback. A windbreak's wake slows the flow of air as it travels farther through the rows of turbines. That could suggest that windbreaks would be a wash for wind farms with many turbines.

But by striking a balance between these competing effects, windbreaks placed in front of each turbine can increase power output, new computer simulations suggest. It comes down to the windbreaks' dimensions. Squat, wide barriers are the way to go, according to a simulated wind farm with six rows of turbines. To optimize performance, windbreaks should be a tenth the height of the turbine and at least five times the width of the blades, physicists report July 30 in Physical Review Fluids. Such an arrangement could increase the total power by about 10 percent, the researchers found. That's the equivalent of adding an additional turbine, on average, for every 10 in a wind farm. In the simulations, the wind always came from the same direction, suggesting the technique might be useful in locations where wind tends to blow one way, such as coastal regions. Future studies could investigate how this technique might apply in places where wind direction varies.
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Windbreaks Could Help Wind Farms Boost Power Output More

Windbreaks Could Help Wind Farms Boost Power Output

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  • Congrats to the people who sussed this out - 10% is a great improvement.

    • Re:Excellent! (Score:5, Interesting)

      by Smidge204 ( 605297 ) on Wednesday August 11, 2021 @07:22AM (#61679363) Journal

      Slight drawback, though?

      "A tenth the height of the turbine and at least five times the width of the blades" is about 85 feet (26 meters) high and 2100 feet (630 meters) long. That is a huge wall!

      Might be beneficial to include this consideration when evaluating natural terrain though; make use of the local landscape as natural windbreaks. I wonder if a row of trees would suffice? A lot of tree species are just about 100ft high on average...
      =Smidge=

      • Re: (Score:2)

        by AmiMoJo ( 196126 )

        I think it's only going to be of use where the terrain facilitates it or where someone is thinking about planting trees or building some new tall buildings.

        There is so much wind energy available, especially off-shore, it's just not going to be worth doing anything very disruptive or expensive to boost efficiency.

        • it's just not going to be worth doing anything very disruptive or expensive to boost efficiency.

          Indeed. Rather than trying to boost the efficiency of 10 turbines by 10% each, it will likely be more cost-effective to just install that 11th turbine.

          I once participated in an analysis to boost the efficiency of solar panels. We considered various mechanisms to clean off dust, cool the panels, or tilt the panels to face the sun. But it was always more cost-effective to just install 10% more panels.

          The easiest way to increase the output is to increase the input.

      • I wonder if a row of trees would suffice? A lot of tree species are just about 100ft high on average.../quote>

        Better yet, why wouldn't even more than a row of trees suffice? Like, a whole forest?

        • Ah whole forest would oy slow down the wind in front of the windmill.
          A row would push up the air that can not go through it.

          • Why would a row of trees do that (which it won't much, because wind can also go below the foliage) but a whole stand wouldn't?

            • A single barrier placed near the turbine will push the air up in a laminar flow.

              A series of barriers, starting much further in front of the turbine, will generate turbulence that will disrupt and slow the wind.

              You can get a (rough) estimate of the transition between laminar and turbulent flow by calculating the Reynold's Number [wikipedia.org] for the system.

              I have done CFD [wikipedia.org], and my educated guess is that a single sloping barrier would work better than a flat wall at maintaining laminar airflow, and a series of barriers wou

        • Well, by "Row of trees" I don't necessarily mean a single file row. Could be a few dozen trees thick, and would probably have to be to be a moderately effective wind barrier.

          In practice I imagine it would basically be a forest with circular clearings around the turbine towers, minus access roads.
          =Smidge=

        • It is also really hard to plant trees or build walls in the sea.

      • Yeah a non-natural wall that size seems unwieldy, but natural barriers could easily work. I specifically like the idea of just putting them on the edge of forests, but I wonder if the "depth" of the wall matters. That is, if it is mounted on the edge of a forest, does the depth of the forest matter? Or does the wall need to be thin and wide? Would it need to be a few rows of trees and that's it?

        One other question would be if there are any drawbacks if the wind shifts. If it turns 180 deg is there any redu

      • Man, if Trump had just built wind turbines in the right place, us liberals would be so conflicted about building a wall...

      • Depending on what else you want to do on the land, you could use this information to design and layout buildings.

        (I didn't RTA, so I don't know if the thickness of the windbreak is limited)

      • I wonder if a row of trees would suffice?

        Traditional windbreaks [wikipedia.org] are rows of trees. I suspect the researchers used a wall because that was easier for their software to model.

        There is likely an unpublished paper on using a bunch of spheres to change the efficiency of wind turbines that's intended to model grazing cows. [wikipedia.org]

    • Congrats to the people who sussed this out - 10% is a great improvement.

      Yessirree, this would take wind from being 8% of the US power base to being 8.8%.

    • really.
      dirt farmers have been doing this for decades.
      dirt farmers use bushes and trees in high wind areas.
      but dirt farmers use bushes and trees for just the opposite reasons

  • We need a real bipartisan effort.. (Score:3)

    by h33t l4x0r ( 4107715 ) on Wednesday August 11, 2021 @06:55AM (#61679333)
    To all break wind together. That's the only way this can succeed, folks.
    • My Man... Methane is perhaps the worst greenhouse gas out there. All the cool kids have corked their assholes... DON'T YOU EVEN CARE ABOUT THE PLANET A LITTLE?

  • "could increase the total power by about 10 percent, the researchers found. That's the equivalent of adding an additional turbine, on average, for every 10 in a wind farm"

    Gee, I'm glad you explained what an increase of 10% is for your readership. I'm sure they were scratching their heads over that.

    • "Math is hard." - BeauZeau

    • Re:Science news for the innumerate? (Score:4, Funny)

      by Scarred Intellect ( 1648867 ) on Wednesday August 11, 2021 @08:39AM (#61679463) Homepage Journal

      "could increase the total power by about 10 percent, the researchers found. That's the equivalent of adding an additional turbine, on average, for every 10 in a wind farm"

      Gee, I'm glad you explained what an increase of 10% is for your readership. I'm sure they were scratching their heads over that.

      This was obviously for the Oregon graduates [slashdot.org] so they can understand. They don't need to math well.

    • A Percent or 1 out of 100, is often treated as a very small value. The actual scope of a percent is actually very situational.

      So if the Speed Limit is 50 MPH, and you go 10% faster (55 MPH) Chances are you are not going to get pulled over for speeding and you may still be the slowest person on the road. But in practical terms, you may not get to your destination much sooner than someone going 50MPH, for a short distance.

      However if you were to drive at 55 MPH for 10 hours, the person going 50 MPH will take 1

    • I think he Oregonsplained it: https://www.msn.com/en-us/news... [msn.com]

  • Really? (Score:1)

    by Anonymous Coward

    In the simulations, the wind always came from the same direction, suggesting the technique might be useful in locations where wind tends to blow one way, such as coastal regions.

    Don't know what coast you're on. On my coast the winds tend to blow one way in the mornings and the opposite way in the afternoons.

    • Along those lines, if the sea breeze turns into a land breeze, does efficiency go the other way and we get a reduction in output?

      • I gues you want to know if the wind is usually slower on land versus on sea.
        Yes it is.

        However 'efficiency' means something different ;)

        • Re: (Score:2)

          by JoeRobe ( 207552 )

          No, that's not what I was wondering, but I do agree. I want to know if that +10% gain in output with the wind in one direction turns into a -10% "loss" (all other things like wind speed being equal) when the wind comes from the other direction. i.e. when there is a wall just behind the turbine. It comes down to how the total wind field is modified by the presence of the wall.

          I guess I was thinking about efficiency improvement as an increase in power output relative to what you would expect for a given wi

  • I wonder what a venturi would yield for performance. Could help on slow days.

  • Birds (Score:2)

    by suss ( 158993 )

    How many more birds will this suck up and kill?

    https://en.wikipedia.org/wiki/... [wikipedia.org]

    • Re: (Score:2)

      by nagora ( 177841 )

      How many more birds will this suck up and kill?

      3

    • According to your own source, at leas about 2000-20000 times LESS than living in a building with windows.
      Hundreds to thousands of time less than growing food.
      And the less is said about cats the better.

      • Re: (Score:2)

        by suss ( 158993 )

        So basically you're saying: "Other things are killing birds, let's not interfere with things that will kill even more"...

        • Think of all the chickens. Us humans are deadly. Maybe we need to go back and live in caves.

        • Re: (Score:2)

          by epine ( 68316 )

          You're doing it wrong. Wind power kills birds. It's some substantial number of birds per GW/hour no matter how you slice it.

          But there's a simple solution: more nuclear, less wind.

          Nuclear dumps a lot of waste heat into the local environment (river, atmosphere). I'm sure this has many effects on wildlife, but we barely know what they are.

          Fewer marked bird graves. And we all lived happily ever after.

          • > But there's a simple solution: more nuclear, less wind.

            Apparently wind and nuclear are on par in terms of bird deaths per GWh or power produced.

            https://www.desmog.com/2018/02... [desmog.com]

            So more nuclear plants in lieu of more wind farms will not help the situation. At least with wind you have substantially less toxic waste to deal with (both from mining operations and as waste)
            =Smidge=

      • "living in a building with windows" - Why are you dragging MS into this?

  • Finally one explained it to me!
    Now I know what 10 percent means.

    I wonder: does that work for potatoes and apples, too?

  • ... most of the wind farms I've seen are located in farmers' fields. How keen are they to devote more of their farmland to a wind break? How much would they decide to charge the wind farm owners for this? Would the increased power generation offset the increase in what the farm owners would charge? (Maybe they'd decide to give up farming altogether and just rent out their entire acreage for wind farm use.) Would any of this result in lower power costs for consumers? (Silly me... of course it wouldn't.)

    • I suppose it would depend on how close the windbreak needs to be. If it can be at the edge of the field, no farmer is going to care. In fact, they might welcome it because it would also help with runoff from neighbors and random trash blowing onto the field that might damage field implements.

      If it has to be up close to each turbine, yeah that might annoy them by losing further acreage.

  • Such an arrangement could increase the total power by about 10 percent, the researchers found. That's the equivalent of adding an additional turbine, on average, for every 10 in a wind farm.

    Thanks for explaining how percentages work. Seriously?

  • Squat, wide barriers are the way to go, according to a simulated wind farm with six rows of turbines.

    The summary just describes these as walls, and the best configuration as a squat, wide wall...

    But wouldn't a better configuration be a wedge instead of a wall? That is to say, a slope that led from the top of the wall outward away from the windmills....

    That would seem to amplify the effect of compressing the air moving over the wall and toward the windmills, while eliminating some turbulence created by the

  • So is this acting more like a weir or a hydraulic jump? Air is a fluid after all, so most of the classical engineering problems that water engineers have already solved could probably benefit wind farm engineers too.

  • Much of this is common knowledge for people that sail. There is more wind at the top of the mast than at the bottom. Boats in front of you affect the wind you see in different ways. Sailing towards a land feature will change the wind direction and speed. In the simplest case building a wall in front of a windmill that is 90 degrees to the wind will increase wind speed at the bottom of the windmill. That's a win. Curved wall maybe buys you some velocity increase from slightly changing wind directions. But if

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