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Earth Power Technology

Wind Farms Can Interfere With Doppler Radar 179

Posted by timothy
from the whiteout-on-the-right-parts-of-the-screen dept.
T Murphy writes "Wind farms can appear like storms or tornadoes on Doppler radar when placed too close to the radar. Tornado alley is a good area for wind farms, and good terrain for the turbines is also ideal for Doppler radar. With many new farms being constructed, the problem is growing. A false tornado warning was issued in Kansas by a computer, although canceled by a meteorologist aware of the problem — there are fears that false positives will grow. Worse would be a tornado ignored as a wind turbine. While meteorologists are trying to work with wind farm owners to shut off the turbines during bad weather, they have no control over the placement or operation of the turbines. Efforts are being made to improve detection technology to avoid further problems."
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Wind Farms Can Interfere With Doppler Radar

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  • Simple fix? (Score:3, Interesting)

    by B5_geek (638928) on Sunday August 30, 2009 @03:13PM (#29253647)

    Of course the turbulence will look like tornadoes, but can't they adjust the sensitivity to "if vortex 3m ignore" Or set them to scan Higher then 100m Or whatever the tallest turbine is in that region?

  • by Anonymous Coward on Sunday August 30, 2009 @03:14PM (#29253655)

    Any weather researcher that knows what he is doing has moved off of Doppler years ago.

    It's all dynamic phased radar arrays now. These have no trouble with wind farms.

  • by get quad (917331) on Sunday August 30, 2009 @03:20PM (#29253701)
    Simple solution - pan/tilt/zoom IP-based cameras placed within each wind farm where we can actually SEE if there's an oncoming tornado, etc. Very small investment considering the cost of the actual wind farm itself. Welcome to the new millenium.
  • by WGFCrafty (1062506) on Sunday August 30, 2009 @03:30PM (#29253797)
    Because it's sometimes really scary to have hundred foot turbine blades flying many many thousands of feet really really fast.

    http://www.youtube.com/watch?v=c3FZtmlHwcA [youtube.com]
    Same one as above in slow motion:
    http://www.youtube.com/watch?v=lvvRHhsQhi8 [youtube.com]
  • Re:Maps? (Score:5, Interesting)

    by negRo_slim (636783) <mils_oRgen@hotmail.com> on Sunday August 30, 2009 @03:34PM (#29253827)

    If only the wind turbines were on stationary towers, then they might be able to map them, and use such a map to inform their interpretation of the radar data.

    Exactly and then ignore the Doppler readings of that area, and instead take notice when a bunch of turbines suddenly go offline.

  • by Anonymous Coward on Sunday August 30, 2009 @03:38PM (#29253851)

    All electricity-generating windmills have adjustable-pitch blades.

    Power stations can't just produce as much power as they feel like, since electricity can't practically be stored. It has to be used up within about one second of hitting the grid, and if the demand is not there, you need to be shutting down generators.

    To deal with this, windmills have adjustable blades so they can extract a variable amount of energy from the wind.

    In severe weather, modern windmills are set up to constantly adjust the pitch in response to varying winds just to minimize the excess load on the blades and spine. This is no different that a pilot flying through turbulent air constantly steering the aircraft to minimized the shaking and stress on the airframe.

  • Re:Simple fix? (Score:2, Interesting)

    by the_other_chewey (1119125) on Sunday August 30, 2009 @03:52PM (#29253927)
    Eaven easier: Wind turbines don't move around - in other words: Their location is known and doesn't change.
    It should be trivial to filter those out. What a non-story.
  • Re:Simple fix? (Score:1, Interesting)

    by Anonymous Coward on Sunday August 30, 2009 @03:57PM (#29253953)

    Three meter resolution? Try 1km during the best situations.

    And derived products, which weather warnings are based off of, have even lower resolutions than 1km.

  • Military issues. (Score:4, Interesting)

    by Demonantis (1340557) on Sunday August 30, 2009 @03:58PM (#29253965)
    The United Kingdom military has had to stop the development of some wind farms because it would leave a blind spot to their early warning systems. Their government has doled out a fair bit of cash to find a solution to the issue.
  • If.. Then (Score:3, Interesting)

    by DynaSoar (714234) on Sunday August 30, 2009 @04:16PM (#29254093) Journal

    If the tornado is occurring where the wind farm is, it's the turbines.

    If the tornado is occurring where the wind farm is, and the electricity goes out, it's not the turbines.

    It'd be a damn shame with all this great technology and great problems to solve if they had to rely on a phone call to a guy at the wind farm who had to look out the window for them in order to know whether there was a tornado or not.

  • by doninwny (1628081) on Sunday August 30, 2009 @04:34PM (#29254211)
    http://radar.weather.gov/radar.php?rid=buf&product=N0R&overlay=11101111&loop=no [weather.gov] Perfect example, if you look at the National Weather Service radar for Buffalo, southeast of the "o" in Buffalo you'll see an orange strip, there are about 100 windmills on hills about 25-30 miles from the airport weather station reflecting the Doppler back.
  • wind speed sensors (Score:2, Interesting)

    by zogger (617870) on Sunday August 30, 2009 @04:54PM (#29254337) Homepage Journal

    Put simple wind speed sensors (and other weather reporting gizmos) at each big wind tower, have them automatically update that info upstream so it can be cross referenced. If the remote radar says tornado in the direction of a tower, but the tower only reports a 40 mile an hour wind...you can nail the false positives easier. Turn a liability into thousands of new weather reporting assets.

  • by overshoot (39700) on Sunday August 30, 2009 @04:59PM (#29254367)
    Is this a problem, or is it a Good Thing we're missing?

    All of those turbines make pretty decent wind speed/direction instruments, and they're all connected. How much would it cost to rig data feeds from them to the weather data collection system? I mean, if the weather computers are reading a Doppler shift from an area where there are wind farms but the wind turbines are all indicating 80 kph winds in the same direction it's not hard to figure out what's going on. Likewise if they're showing major surface-level wind shear around a vertical axis!

  • by Thelasko (1196535) on Sunday August 30, 2009 @07:29PM (#29255499) Journal

    There are lots of objects that cause the same types of problems, including rotating radar antennas and buildings.

    Yes, I heard this story last week at my local Fox affiliate, WFLD. The chief meteorologist stepped in at the end of the story and explained that there are lots of things that can cause these types of problems. He mentioned specifically that condensation from a cooling lake at a nearby nuclear power plant looks like a thunderstorm all of the time. But since they know about it, they can ignore it.

    He concluded that he felt this story was blown out of proportion.

  • Simple fix... (Score:3, Interesting)

    by Bones3D_mac (324952) on Sunday August 30, 2009 @09:18PM (#29256155)

    Have these wind turbines registered with the National Weather Service and mark the locations in the system. Also, place transponders on the turbines to verify their operational status. If a tornado is detected near a known turbine location and the turbine fails to report its status, there probably is "something" in the area bad enough to damage a turbine.

  • by Anonymous Coward on Sunday August 30, 2009 @09:47PM (#29256319)
    I work for NWS. False alarms are rare. The Mets know where the farms are and the signals are always there. While there is a chance of a mistake in the heat of battle - the duty Mets are usually overloaded with information during a convective event - they don't happen that often. A bigger issue is a farm degrades the performance of the radar around the farm. In other words, if there is weather right around the farm, you can't see it for noise.

    Here the real threat.

    Lawyers for wind farms who know they have a nimby problem know that one of the arguments will be the interference problem. The lawyers have learned that NWS/DOD/FAA (the radars are a tri-agency project) usually leased the land for the radars in the late 1980s/early 1990's for either 20 or 25 years, so the leases are coming up for renewal.

    In several recent cases, NWS/DOD/FAA have gone to the land holder to renew the lease only to find out the wind project has already leased the land for twenty years at 5x the rate of the government lease and get a notice the radar needs to be moved.

    Now moving a WSR-88D costs upwards of a million bucks. They are VERY large and engineering studies have to be conducted to locate a good location ... usually as high up as possible (but not too high), in a place that has as few places were the beam is blocked by terrain, where power and limited bandwidth can be had, etc. The studies done in the 1980's usually found that sweet spot, but it has just been taken away.

    So the radar could end up being moved at high expense to a not as good location. While the radar is down (there aren't any spares), coverage may not be available.
  • Air Traffic Control (Score:2, Interesting)

    by amiga500 (935789) on Sunday August 30, 2009 @10:55PM (#29256629) Homepage
    Having setup an ATC radar in Palm Springs, I can attest that the wind farms add a lot of noise to ATC radar systems as well as weather systems. Noise on the radar screen makes ATC more difficult, and increases the risk of accidents. The wind mills in Palm Springs are the small blade, fast moving type which birds like to fly into. I think the newer, larger wind farms are less of an issue for ATC radar. The slower moving blades can be filtered out. If they could build the windmills with flat edges, or use radar absorbing materials, they would become invisible to the radar.
  • by Ungrounded Lightning (62228) on Monday August 31, 2009 @02:32AM (#29257789) Journal

    For many years I lived on a sailboat with a wind generator which shorted the output to stop the blades as well as to KEEP them stopped.

    Worked fine even in gale force +++ winds.

    It worked fine because the turbine was small and the genny was powerful. It was able to produce enough drag torque to pull the rotor down to stall speeds even in a gale.

    Unfortunately, for big homebrew turbines the alternators can't be counted on to be sufficiently strong to accomplish this. (For starters ie means dumping the energy of the turbine's inertia, plus all the power the blades are pulling from the air before they get down to stalling speed, into the alternator coils as heat. On a big machine this may melt them.) Also: If the turbine is in stall and the wind gets high enough to overpower the genny if the turbine weren't in stall, a gust may start it spinning and pull it out of stall (or, as in your case, cause enough damage to the alternator to cause it to stop braking the blades effectively).

    One VERY dark night headed for Fiji though a magnet came loose in the generator and THAT was spectacular! ... I now understand that the bade was close to MACH 1 when it broke free!

    An important design parameter for wind turbines is TSR - Tip Speed Ratio. This is the ratio of the speed of the tip of the blade to the speed of the wind when the turbine is under load and achieving peak efficiency. (When unloaded, for instance if the battery came unhooked, the turbine will freewheel at something like twice that speed.)

    Horizontal axis wind turbines (the wind-facing "propellor" type) are most efficient when designed for a TSR in the vicinity of 6. (Slower and they waste more power "spinning the exhaust". Faster and they waste more power in drag - and the airflow over part of the blade may go supersonic in a storm, which is not good.)

    Speed of sound at 68F is about 768 MPH. That means a TSR 6 turbine will have the tips hit sonic speed at a wind speed of about 128 MPH under load or roughly 64 MPH freewheeling. (And that cube law means your genny will probably burn out in sustained winds approaching 128 MPH so you'll probably be unloaded at speeds well below 128.)

    Of course holding the blade to the hub when the tip is moving near the speed of sound (or fast enough that part of the airflow is supersonic and making the blade vibrate horribly) takes a LOT of strength - usually more than the parts have. This is why wind machines are designed to furl somehow before they get spinning that fast.

  • Re:Military issues. (Score:1, Interesting)

    by Anonymous Coward on Monday August 31, 2009 @04:09AM (#29258211)

    The actual solution is to forget using these stupid "wind farms". They are uneconomical - they can NEVER generate enough electricity to pay for their transportation, construction and operation in their lifetimes. They can also NEVER "repay" the carbon budget necessary to construct them. The only reason that they appear financially attractive is because of the government subsidies - we are ALL paying for a fundamentally defective, ill-thought-out technology that has no benefits.

  • by GPSguy (62002) on Monday August 31, 2009 @08:59AM (#29259339) Homepage

    Hmmm. A couple of thoughts.
    1. The tornado isn't a pressure-equalization tool. Were that so, prediction would likely be a bit easier.
    2. Yes, wind turbines do modify the landscape. More to the point they modify surface roughness, and research at the National Center for Atmospheric Research is looking at how these changes might affect local weather. It's not quantified yet, so useful conclusions are unlikely to be drawn at this early date.

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