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10398Re: [AWES] Summary of Tether-Angle "Non-Issue" for Utility-Scale AWES

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  • dave santos
    Oct 25, 2013
      Pierre,

      Megascale crosswind arches are designed as the primary scaling solution to create cheap bulk-lift in the smallest land-airspace. In principle, any kind of WECS can be raised on close-spaced halyards under an arch (cascade-launch). Rod's many versions of megascale arches cover many of the choices- HAWT flygens, looping foils, wingmills, and so on. The choice of WECS remains open, subject to years of compenent testing. Even a balloon can lift a WECS; giant arches just allow larger cheaper AWE, by lifting more.

      We also know several powerful inherent arch-oscillation modes (jellyfishing, Dutch-roll shimmy, phugoid). These exact modes are also seen in TUDelft kite-force numeric simulations and wind-tunnel testing of arched parafoils ("staked out" like an arch, without tethers). There is no scaling barrier seen to these phenomena operating at km scale, and the calculated power is monstrous. Mothra1, at 300m2, flew exactly as intended (under easy launch and land control), and could set the AWE peak power record by simply hoisting conventional small HAWTs.

      Rather than mock EBS as applicable to large kite lattice dynamics, you should try to make a small scale model of the offshore concept you are lately promoting. You are seeking to attract investors on the basis of naive engineering speculation, without bothering with even the smallest working prototype. This is a "Red Flag" by Mike's criteria.

      On the other hand, Mike will continue to uncover the vast body of foundational discussion and experiments showing just how open-source megarches can make mega-power, if simply by hosting dense WECS arrays cheaper and better than LTA,

      daveS


       







      On Friday, October 25, 2013 3:02 AM, Pierre BENHAIEM <pierre.benhaiem@...> wrote:
       
      "I don't understand how kites that sit in one place at moderate altitudes are going to generate power, especially in context of only rags and string aloft. Is it just lots of kites, hence lots of lift so a large mass rising slowly then controlled to fall slowly, pulling cable out through regenerative winches but with tons of torque geared up massively for electrical generation?"
      I either.See old posts about arches.Note that an arch has two anchors,so it is limited to dominant winds,excepted in case of implementation of a device such a circular track. A possibility:as static traction kite to carry turbines aloft.Another possibility is described in videos from Roddy:the arch is on a circular track allowind both adaptation to wind directions and making some power by being piloted from anchors,the generator being at ground. Other indication by DaveS on numerous posts:oscillating according to Bose-Einstein theories:I do not know anything about them but I think DaveS will be happy to explain the modus operanti.
       
      PierreB


      > Message du 25/10/13 11:25
      > De : "Mike Barnard"
      > A : AirborneWindEnergy@yahoogroups.com
      > Copie à :
      > Objet : Re: [AWES] Summary of Tether-Angle "Non-Issue" for Utility-Scale AWES
      >
      >  
      > Hi Dave et al . . .

      >
      In the interests of learning more and trying to understand Dave's suggestion below, I've been trying to dig into arch kite generation approaches.

      >
      So far I've found some pretty arch kites at kite festivals, a few 3d computer models without any working details, rotating ribbon kites and no documentation on how arch kites are expected to generate power.

      >
      - I understand fully how SkySails and similar pumping kites generate power via regenerative braking at the winch.
      - I understand how Makani and similar concepts fly small wind turbines at high speeds through the air to generate electricity on the kite.
      - I understand how Altaeros takes a ducted wind turbine embedded in a blimp to high altitudes to maximize wind speed over a small wind turbine.
      - I understand the purely mechanical concepts of having kites tow stuff uphill to create potential kinetic energy to generate power.
      - I understand how the Magenn aerial Savonius design generated power by have the blimp spin on an axis with electric motors.

      >
      I don't understand how kites that sit in one place at moderate altitudes are going to generate power, especially in context of only rags and string aloft. Is it just lots of kites, hence lots of lift so a large mass rising slowly then controlled to fall slowly, pulling cable out through regenerative winches but with tons of torque geared up massively for electrical generation?

      >
      I certainly see Dave's points regarding multiple tethering points having reliability and safety advantages. I'm less sold on the tether angle argument, in part because the linkage to power generation is not obvious.

      >
      Please help, perhaps by pointing to technical papers or articles I've been unable to find on the Yahoo group or using Google. Right now it looks as if it has similar problems to Savonius devices in concept: lots of torque, no fast movement, hence more useful for things other than generating electricity like pumping water. A working prototype, or published and peer-reviewed paper on the mechanics of the solution would be very advantageous.

      >
      Thanks,
      Mike

      >
      On 2013-10-23, at 11:36 AM, dave santos wrote:

       
       

      >
      The dire problem of over-long tethers causing airspace and land-footprint sprawl is only inherent to fixed single-anchor unit cells, and most AWES developers are stuck in this rut. The problem disappears in more advanced thinking; for example, crosswind arches of pure wing, shifting anchors to upwind locations in the cell, and dense arrays (crosslinked aloft) where the tether angle penalty is paid only once by the upwind lines, and all downwind array units share the single offset. This is how gigawatt unit-scale becomes practical.

      >
      Variations on these simple solutions allow >100x the spacial density of obsolete single-anchor architectures. These more-advanced AWES need not ever overfly field perimeters. Multi-anchor solutions also redundantly eliminate runaway risk. As true utility-scale solutions now become better known, early worries over AWES sprawl and runaway will dissipate. Long-term, based on heuristic Critical-Path Analysis of relentless aviation progress, highly-perfected AWES will be able to overfly dense populations, just as normal aircraft do, subject to standard aviation safety and reliability metrics (~2030).

      >

      >
      * Excess helium lift to secure a high elevation angle is especially misguided, as an aerostat is driven down by wind, compared to kites, with far greater costs.
       
       
       

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