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Catching Up with the Wind

windturbinestva.jpgEverybody's talking about wind power right now, and it's easy to see why -- a combination of new developments, high energy prices and (in the northern hemisphere) the return of brisk fall breezes put us all in the wind turbine frame of mind.

While we've all been busy getting WorldChanging: The Book completed (can WorldChanging: The Motion Picture be far behind?), a number of wind-related stories have piled up on my desktop. Rather than let them go to waste, I thought I'd give you an old-fashioned bullet point rundown of the developments.

  • Piezoelectric Wind Power
  • Do home turbines make economic sense?
  • Floating Wind Power
  • Vertical Turbine Design
  • Guandong's Wind Energy Potential
  • UK Wind Energy Potential

  • Micro-Wind Power

    Micro-micro-wind Nature News reports on the development of a tiny wind turbine (about 10cm in diameter) able to produce a surprisingly large amount of power for its size. The reason? Instead of the wind turning a conventional generator -- which, at that size, would be able to convert at best about 1% of the wind energy into electricity -- the system uses a piezoelectric generator, converting turbine vibrations into electricity using piezoelectric materials, which produce power when under mechanical stress. This gives the tiny turbines an efficiency of about 18%, comparable to much larger systems. In turn, these micropowerhouses can be used to power wireless sensor networks.

    (As noted in the comments, the Nature News story has been changed from free access to premium-only, and sites with more information than a link back to Nature were hard to find. I found one, though: INDOlink, a site focusing on news for Non-Resident Indians. Their article, Shashank Priya Invents Wind-Powered Wi-Fi, has a somewhat deceptive title -- the power from the piezoelectric turbines is not likely to be enough for standard wifi networks -- but gives most of the details of the Nature News story.)

    Home Wind Turbine BBC's The Magazine asks, Can a home wind turbine make money? The answer is a qualified "maybe," which is about as good as you're going to get right now. Wind intermittency is the greatest factor -- even turbines built in blustery areas will fall victim to extended calm periods. People who build home turbines shouldn't do so expecting to be able to live off the grid; instead, home wind power lets users cut their overall power bill by covering some portion of home use and, where allowed, selling excess power back to the grid. Regular readers will not be surprised to learn that the best thing one can do to increase the return of a home turbine is to increase the efficiency of energy use.

    Large-Scale Wind Power

    Floating Offshore Wind Traditional offshore wind farms are less-than-ideal for a few reasons. They are arguably visually unattractive, and may put shore birds at risk (depending upon turbine placement and height). Moreover, it's just not very efficient -- winds are less powerful close in to shore than they are in the open ocean. That's why Thomas Lee has designed a floating wind turbine platform intended for use dozens or even hundreds of miles out to sea. The turbines could be used to produce hydrogen or electricity cabled back to land, and would be able to move out of the path of major storms. This is still very much a paper design, not something currently being built; however, the US National Renewable Energy Laboratory has done a preliminary evaluation of floating platform wind farms (PDF), and concluded that they would be able to produce power for as little as $0.05/kWh.

    Vertical Turbines Deep-offshore wind still too conventional? A company called Terra Moya Aqua has come up with a vertical axis wind turbine (VAWT) design that they claim is somewhat more efficient than equivalent horizontal axis wind turbines (HAWT) -- 43-45% efficient, compared to the 20-40% of conventional systems. The TMA design is supposed to handle high winds better than conventional HAWTs, be quieter, and result in fewer bird kills (as they will be more visible than spinning horizontal blades, apparently). The first production model is supposed to be available by next summer; TMA claims that commercial models should produce power at a cost of $0.025-$0.035/kWh.

    VAWT designs aren't new, and previous iterations have fallen victim to higher mechanical stresses than traditional HAWT systems. I'm encouraged to see that TMA doesn't claim outrageous efficiency numbers or that this VAWT design will replace traditional towers. It remains to be seen how the TMA version will fare, but I look forward to hearing the results. (Via Treehugger)

    Wind Potential

    Guandong Wind Power The Worldwatch Institute has just published a lengthy examination (PDF) of the wind power potential for the Guandong region in China, near Hong Kong. Using studies from Stanford University and the UN Environment Program (probably SWERA), Worldwatch estimates that Guandong could build 20 GW of wind energy capacity by 2020, supplying about 17% of the region's demand. To accomplish this, Guandong would have to install a bit more than a gigawatt of wind power, on average, every year -- a rate that's slower than is typical for many similarly-sized European nations.

    UK Wind Power OxfordÂ’s Environmental Change Institute has now completed a study of the wind power potential in the United Kingdom, and has good news: it's the best in Europe. Jolly good!

    According to the report, wind turbines in the UK produced around 27% of their maximum possible energy, compared to 20% in Denmark and only 15% in Germany, the country with the greatest wind power use. Moreover, the wind coming in off the Atlantic was extremely predictable and dependable, and the likelihood of either wind calms or overly-high winds causing wind farm shutdowns across the UK was extremely low (one hour every five years and one hour every ten years, on average, respectively). More importantly, peak wind availability coincides with peak demand periods in the evening and in the winter.

    Comments (7)


    The article on the piezeoelectric wind turbine is behind a subscription wall.

    Odd. It wasn't earlier. I'll see if I can dig up an alternative source.

    Sorry about that.

    Well, as far as I can find right now (4:50 pm), the only references to the story are links to the Nature article -- which, as I said, was completely open earlier today.

    This is exactly the kind of thing I'd expect the BBC (among others) to pick up, though, so as soon as I can find a valid open link, I'll add it.

    Kirk Sorensen:

    Don't forget to consider high-altitude wind power, which may have more potential than ground-based wind power:


    There's another floating wind turbine design developed by Hydro, a Norwegian energy and oil company. I blogged about it here not to long ago.

    Also, Barco WM, a Spanish R&D group has been developing a vertical axis wind turbine design similar to the one above. Their design features four flat arms rotating around a central vertical axis. Each arm is made up of a number of panels which lie perpendicular to the wind to offer the greatest resistance to the wind when they are located in the front rotation area and then turn parrallel to the wind to offer practically no resistance when they are in the generatorÂ’s return area. (Check out the site for pictures and animations, it will make more sense then).

    Like the above design, they claim lower cut-in speeds and significantly higher max wind speeds with a greater efficiency than normal horizontal axis turbines (~40%). The higher max speeds are important for high wind areas as the power curve of turbines typically rises exponentially with wind speed until it reaches a cut off (max) speed at which the blades are rotated parallel to the wind and locked to prevent damage. Barco's design can run in very high winds (they even claim hurricane-force winds) and will continue to generate electricity. The combination of higher efficiency, lower cut-in speed and much higher max speed means these turbines should be able to generate significantly more megawatt-hours annually than horizontal axis designs.

    Also, like the above design, they do not need to rotate to track the wind like horizontal turbines as any wind direction works the same.

    The final advantage of vertical axis designs (which is a big one) is that the generator for these turbines can be installed at the ground rather than up in the nacelle on top of a tower like horizontal designs. There is simply little one can do to miniaturize or make lighter the dense coil of wires and large magnets that the generators consist of. Having to suspend all this weight in the air atop a tower is a significant engineering issue, necessitates large, expensive and very strong towers and puts a limit to the maximum size horizontal axis turbines can grow to. Vertical axis turbines avoid this issue as they can place the generator on the ground.

    I'll put money on the proposition that the overturning moment from wind pressure on a turbine, whether horizontal or vertical axis, requires more structure than supporting the weight of a generator.  Compression loads from a mass at the tower-top have no moment arm.


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