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Kite Arches for Crosswind Power

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  • dave santos
    Here are some notes toward a formal theory of operation for Kite Arches, extending Loyd s crosswind power concept to crosswind arches, and equating the
    Message 1 of 9 , Apr 2, 2012
      Here are some notes toward a formal theory of operation for Kite Arches, extending Loyd's crosswind power concept to crosswind arches, and equating the flight characteristics with Culp's "staked-out" stability principle. Basic geometric proof, covered elsewhere, applies in showing that arched structures far outperform single tether AWECS by airspace/land-footprint scope to power ratio.
       
      Miles Loyd famously coined the term "Crosswind Power" to describe crosswind sweeping wings like a HAWT blade or looping kiteplane, but the essence of Crosswind Power is broader than that, as every WECS requires a crosswind extent to operate. Crosswind Power is really a continuum, from high-speed sweep to static lift. A parachute decelerator works by spreading area across its apparent wind, and so is seen as the lower tech boundary of Crosswind Power. Decelerator-based AWESs exist, from spin-canopies to pulsing varidrogues. The lowly varidrogue is wrongfully objected to as more downwind than crosswind in operation, but a close look at virtually all AWES concepts reveals considerable depth-of-section downwind. There is seemingly no purely crosswind WECS.
       
      The unique virtue of Kite Arch engineering physics is to resist cross-field forces by a balanced minimal geometry of catenoids, a set of curves. To compute an ideal compressive arch, merely hang a chain and use that catenary curve upside-down.
       
      A Kite Arch essentially eliminates common tether drag, by being quasi all-wing. By contrast, a static single-line kite tether is fairly high drag, with some down force (negative lift). Worse, a looping single-tether kite inscribes a troposkein, the form encompassed by a jump-rope, "harvesting" high drag.
      Vertical Shunting Arches is the latest Kite Arch method. A VSA inscribes a catenoid minimal-surface in the sky. Special magic emerges when mathematical perfection is approximated in the real world. Catenoids may prove to be the optimal wind harvesting geometry, using the least material for maximal output. KiteLab had been for years hanging WingMill arches from lifter kites and shunting or tacking them crosswind horizontally, also inscribing a catenoid.
       
      Suddenly the Kite Arch emerges as a competitive AWES architecture, but there are key antecedents. We first note primitive arches from multi-line kites from traditional Polynesia, then into the 19th Century Kite Golden Age, with even manlifting accomplished (Baden-Powell), but it seems only in recent decades did the Kite Arch emerge as a well defined category. The first Kite Arch i learned about was my net friend Anders Ansar's Ribbon Arch, followed by Peter Lynn and Dave Gomberg's kite show arches flying multiple theme soft-kites closely together off a common gangline set crosswind. George Peters also did great work on Ribbon Arches, before Anders. 
       
      The World Kite Museum then opened up to me a whole world of special Kite Arches, seemingly tracing from Ohashi's 1980s discovery that he could bend a certain kind of Kite Train (diamond kites) almost 180 degrees into an arch set crosswind, and it would continue to fly. Some unknown person at about that time seems to have figured out how the diamond kites could be fully integrated into the arch line, eliminating all the cross-sticks. Since then hundreds of kitemakers have made such arches, generally without tinkering with the design. Other arch variants emerged, from rotating SkyBows. In all cases Kite Arches set crosswind.
       
      When Dave Culp at KiteShip first informed me in 2007 that "staking out" a large kite tames it, i did not make the connection  to Kite Arches. It was only last week that this mentally clicked into place. Not only is the Kite Arch a Crosswind Power device, but it incorporates a powerful kite stabilizing principle, that the ground surface itself is the most robust and stable kite structure possible. One even sees this principle in the common arched traction kite parked at zenith off its control bar. A fantastic advantage to Kite Arches is the ability to kill them in a controlled progressive linear fashion by slacking on side. The arch lays down from its windward point. By contrast, "kite killing" single tether AWES is always more complex or risks retract winch saturation.
       
      Kite arches and trains naturally combine by setting the trains across the arches, from lower to upper. Multiple arches sum tremendous lift, while also stabilizing close-set trains from interfering. Fry and Hines naturally envisioned trains of WECS in their rigid wind power arch structure, set crosswind. We now see how a Kite Arch can do the job cheaper and better by going higher. A growing list of methods exists to rotate a Kite Arch to match wind direction-- Hauling and Belaying around an Anchor Circle, Anchor (ground) Vehicles, Giant Carousel, Giant Control Bar, Circular Track, Circular Cableway, Buddy Boats, etc.
       
      In summary, there are many bulk advantages to Kite Arches. The challenges with arches are mostly in the details. An "anchor field" is a key arch requirement. Kites in a network can tangle badly if poorly designed and carelessly operated. The Bow-Tie failure mode is most characteristic of a high AR arch wing; deep-section bridling, foil section reflex, and/or tails constrain a wing arch from flipping; local swivel sections can recover a BowTie flip.
       
       
    • Doug
      Traveling across the wind to make power could only considered a revelation by someone who was clueless as to the basics of wind energy. That was worked out
      Message 2 of 9 , Apr 3, 2012
        Traveling across the wind to make power could only considered a revelation by someone who was clueless as to the basics of wind energy. That was worked out over 2000 years ago. Can you say "The blind leading the blind"?
        :)

        --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...> wrote:
        Loyd's crosswind power concept to crosswind arches,�...
        > Miles Loyd famously coined the�term "Crosswind Power" to describe crosswind�sweeping wings like a HAWT blade or looping kiteplane,
      • blturner3
        Dave, All things being equal, the more wind area you can sweep per pound material the better. I don t see that kite arches do well here. The catenary increases
        Message 3 of 9 , Apr 3, 2012
          Dave,
          All things being equal, the more wind area you can sweep per pound material the better. I don't see that kite arches do well here.

          The catenary increases the tension in the lines for the amount of lift vs a windward line. That means larger line is needed.

          If we take a 7:1 L/D as a good amount of sweep and 1/2 wind speed as the reel out speed then the arch has 14 times higher reel speed. That is probably not good, but I guess it could be. I am not sure I see the same vision as you. It seems utterly uncompetitive.

          Brian

          --- In AirborneWindEnergy@yahoogroups.com, "Doug" <doug@...> wrote:
          >
          > Traveling across the wind to make power could only considered a revelation by someone who was clueless as to the basics of wind energy. That was worked out over 2000 years ago. Can you say "The blind leading the blind"?
          > :)
          >
          > --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@> wrote:
          > Loyd's crosswind power concept to crosswind arches,�...
          > > Miles Loyd famously coined the�term "Crosswind Power" to describe crosswind�sweeping wings like a HAWT blade or looping kiteplane,
          >
        • Joe Faust
          ... Brian, are you seeing the shunting vertically which is stark cross-winding sweeping. Mine the displacements of the vertically-shunting arch segments.
          Message 4 of 9 , Apr 3, 2012
            On Tue, Apr 3, 2012 at 8:30 PM, blturner3 <yahoo2@...> wrote:
            can sweep

            Brian, are you seeing the "shunting" vertically which is stark cross-winding sweeping. Mine the displacements of the vertically-shunting arch segments.

            Reach for lifted laddermill of vertically shunting arches and enter a special realm of continuous arch-fan-belting. 

          • dave santos
            Brian,   You seek to reason from-  All things being equal , when they are never equal in real-world engineering, which is based on careful trade-offs. To
            Message 5 of 9 , Apr 3, 2012
              Brian,
               
              You seek to reason from- "All things being equal", when they are never equal in real-world engineering, which is based on careful trade-offs. To then claim, on supposed equal grounds, "the more wind area you can sweep per pound material the better," compounds confusion.
               
              Serious AWE is a branch of aviation, and safety-critical reliability drives what is "competitive", meaning ROI. Remember, the whole safety regulatory side is your blind spot; you have a strong allergy to standard aviation safety culture. Its ExtractedPower-to-WeightAloft, not sweep-to-weight that is more favored. Low Weight, we both agree, is a key requirement. But Sweep too fast and you get regulated far more painfully, due to inherent risk. Fast is dangerous.
               
              You are failing to see the incredible lifting power in cheap thin membranes on rope loadpaths arched crosswind. Even the King of Sweep, Miles Loyd, makes a great case for the effectiveness of classic kite structure in his famous paper. An ideal lifting arch operates with all its structural molecules worked just as hard as an ideal sweeping wing. Arched kite structure can potentially lift huge HAWTs with high tip-speed ratios, but such hybrid schemes don't seem to figure in your straw contest. Note that reeling was not a subject or factor in the Kite Arch for Crosswind Power thesis.
               
              You conclude, "I am not sure I see the same vision as you. It seems utterly uncompetitive."
               
              Well, i am quite sure we do have far different visions. You could do a far better job presenting your "competitive" vision in detail, by working prototypes, measured specifications, and concept studies. It will be fantastic to see something better than Crosswind Arch AWES; please don't just tease us :)
               
              daveS
               
               
               
               

               
                  
            • blturner3
              Sorry, I should not have used the word utterly. I did not mean to get you going. I jumped in to the arch discussion because I see possible potential. I seek to
              Message 6 of 9 , Apr 10, 2012
                Sorry, I should not have used the word utterly. I did not mean to get you going. I jumped in to the arch discussion because I see possible potential. I seek to understand the concept.

                Here is my suggestion. Take the tarp kite concept and apply it to the arch. Put multiple tarps between two lines staked out across the wind to where it is a continuous swath of fabric. When the upper line is advanced windward the long soft airfoil will climb. When the lower line is advanced the kites dive. Just as you showed for the diamond kites. I think you called this shunting. The airfoil created this way should be more efficient than the diamond kites. Some ribs could be added to further improve the airfoil.

                A fifth line attached to the trailing edge of the arch goes to a generator. Generating as the kites climb. The line will need to spread the load so it will need to be a bridle of sorts. The line will need a high speed retract.

                A set of three or more arches turning the same generator would provide constant output at the generators max rating. Actually sets of three or more makes sense to me for many of the kite concepts we discuss here.

                I see plenty of problems with the concept, but plenty of advantages.

                Cheers,
                Brian

                --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...> wrote:
                >
                > Brian,
                >  
                > You seek to reason from- "All things being equal", when they are never equal in real-world engineering, which is based on careful trade-offs. To then claim, on supposed equal grounds, "the more wind area you can sweep per pound material the better," compounds confusion.
                >  
                > Serious AWE is a branch of aviation, and safety-critical reliability drives what is "competitive", meaning ROI. Remember, the whole safety regulatory side is your blind spot; you have a strong allergy to standard aviation safety culture. Its ExtractedPower-to-WeightAloft, not sweep-to-weight that is more favored. Low Weight, we both agree, is a key requirement. But Sweep too fast and you get regulated far more painfully, due to inherent risk. Fast is dangerous.
                >  
                > You are failing to see the incredible lifting power in cheap thin membranes on rope loadpaths arched crosswind. Even the King of Sweep, Miles Loyd, makes a great case for the effectiveness of classic kite structure in his famous paper. An ideal lifting arch operates with all its structural molecules worked just as hard as an ideal sweeping wing. Arched kite structure can potentially lift huge HAWTs with high tip-speed ratios, but such hybrid schemes don't seem to figure in your straw contest. Note that reeling was not a subject or factor in the Kite Arch for Crosswind Power thesis.
                >  
                > You conclude, "I am not sure I see the same vision as you. It seems utterly uncompetitive."
                >  
                > Well, i am quite sure we do have far different visions. You could do a far better job presenting your "competitive" vision in detail, by working prototypes, measured specifications, and concept studies. It will be fantastic to see something better than Crosswind Arch AWES; please don't just tease us :)
                >  
                > daveS
                >
              • dave santos
                Brian,   Tarp Kixels are a core arch strategy, but they won t do shunting well without sticks, but tend to tuck/luff or lumber along semi-stalled. Sticks can
                Message 7 of 9 , Apr 10, 2012
                  Brian,
                   
                  Tarp Kixels are a core arch strategy, but they won't do shunting well without sticks, but tend to tuck/luff or lumber along semi-stalled. Sticks can be added, but diamond kites seem more sweep efficient until spar scaling penalties kick in. The swept LE/TE is a nice speed feature. An opened-up two-stick sled would be an intermediate design, more tarp-like, a higher skin-to-stick ratio.
                   
                  Many of your ideas on how to tap a multi-arch are sound, and similar rigs are seen here-
                   
                  Be sure to zoom in, many details are tiny,
                   
                  daveS
                   
                  PS A funny thing about the "utterly" usage was the echo re: Kixels as "utterly useless". Utterly repetitive, or not :)
                   
                   

                   
                • Joe Faust
                  Consider a stable lifter arch below which have integrated shunting arch; as the shunting arch drives up, the lifter rises also to a high position; when the
                  Message 8 of 9 , Apr 10, 2012
                    Consider a stable lifter arch below which have integrated shunting arch; as the shunting arch drives up, the lifter rises also to a high position; when the shunting arch drives hard down, then the lifter arch acts as anchor to permit mining the down-going shunting arch. Mine the up stroke of the shunting arch and mine the down stroke of the shunting arch.   
                    JoeF
                  • dave santos
                    Dear Lorenzo,   You asked- I d like to see some document giving the details of this idea   While [Dave Lang, DF, 2004] clearly described crosswind
                    Message 9 of 9 , Jun 4 10:31 PM
                      Dear Lorenzo,
                       
                      You asked- "I'd like to see some document giving the details of this idea"
                       
                      While [Dave Lang, DF, 2004] clearly described crosswind anchors as the basis for Joe Hadzicki's AWES concept, there have also been many AWES Forum messages elaborating on the idea. Lang, 2004, and many more messages  also document the intuitive idea of "pilot-kite" based passive-control as an AWES basis. Comparable (or even superior) control performance to active-control implies a formal computational equivalence, but I leave it to you to find this for yourself within your expertise.
                       
                      This is an "old" diagram of a piloted "imposed crosswind motion", which Rod Read later modeled in 3D-
                       
                       
                      A search on crosswind arches and anchor-fields on the AWES Forum got 171 hits. Its strange that Pierre seems to have missed these reports,
                       
                      daveS
                       
                      The following message is just a sample, but contains many specific references and key ideas-

                       
                      ----- Forwarded Message -----
                      From: dave santos <santos137@...>
                      To: AWE <AirborneWindEnergy@yahoogroups.com>
                      Sent: Monday, April 2, 2012 1:08 PM
                      Subject: Kite Arches for Crosswind Power

                      Here are some notes toward a formal theory of operation for Kite Arches, extending Loyd's crosswind power concept to crosswind arches, and equating the flight characteristics with Culp's "staked-out" stability principle. Basic geometric proof, covered elsewhere, applies in showing that arched structures far outperform single tether AWECS by airspace/land-footprint scope to power ratio.
                       
                      Miles Loyd famously coined the term "Crosswind Power" to describe crosswind sweeping wings like a HAWT blade or looping kiteplane, but the essence of Crosswind Power is broader than that, as every WECS requires a crosswind extent to operate. Crosswind Power is really a continuum, from high-speed sweep to static lift. A parachute decelerator works by spreading area across its apparent wind, and so is seen as the lower tech boundary of Crosswind Power. Decelerator-based AWESs exist, from spin-canopies to pulsing varidrogues. The lowly varidrogue is wrongfully objected to as more downwind than crosswind in operation, but a close look at virtually all AWES concepts reveals considerable depth-of-section downwind. There is seemingly no purely crosswind WECS.
                       
                      The unique virtue of Kite Arch engineering physics is to resist cross-field forces by a balanced minimal geometry of catenoids, a set of curves. To compute an ideal compressive arch, merely hang a chain and use that catenary curve upside-down.
                       
                      A Kite Arch essentially eliminates common tether drag, by being quasi all-wing. By contrast, a static single-line kite tether is fairly high drag, with some down force (negative lift). Worse, a looping single-tether kite inscribes a troposkein, the form encompassed by a jump-rope, "harvesting" high drag.
                      Vertical Shunting Arches is the latest Kite Arch method. A VSA inscribes a catenoid minimal-surface in the sky. Special magic emerges when mathematical perfection is approximated in the real world. Catenoids may prove to be the optimal wind harvesting geometry, using the least material for maximal output. KiteLab had been for years hanging WingMill arches from lifter kites and shunting or tacking them crosswind horizontally, also inscribing a catenoid.
                       
                      Suddenly the Kite Arch emerges as a competitive AWES architecture, but there are key antecedents. We first note primitive arches from multi-line kites from traditional Polynesia, then into the 19th Century Kite Golden Age, with even manlifting accomplished (Baden-Powell), but it seems only in recent decades did the Kite Arch emerge as a well defined category. The first Kite Arch i learned about was my net friend Anders Ansar's Ribbon Arch, followed by Peter Lynn and Dave Gomberg's kite show arches flying multiple theme soft-kites closely together off a common gangline set crosswind. George Peters also did great work on Ribbon Arches, before Anders. 
                       
                      The World Kite Museum then opened up to me a whole world of special Kite Arches, seemingly tracing from Ohashi's 1980s discovery that he could bend a certain kind of Kite Train (diamond kites) almost 180 degrees into an arch set crosswind, and it would continue to fly. Some unknown person at about that time seems to have figured out how the diamond kites could be fully integrated into the arch line, eliminating all the cross-sticks. Since then hundreds of kitemakers have made such arches, generally without tinkering with the design. Other arch variants emerged, from rotating SkyBows. In all cases Kite Arches set crosswind.
                       
                      When Dave Culp at KiteShip first informed me in 2007 that "staking out" a large kite tames it, i did not make the connection  to Kite Arches. It was only last week that this mentally clicked into place. Not only is the Kite Arch a Crosswind Power device, but it incorporates a powerful kite stabilizing principle, that the ground surface itself is the most robust and stable kite structure possible. One even sees this principle in the common arched traction kite parked at zenith off its control bar. A fantastic advantage to Kite Arches is the ability to kill them in a controlled progressive linear fashion by slacking on side. The arch lays down from its windward point. By contrast, "kite killing" single tether AWES is always more complex or risks retract winch saturation.
                       
                      Kite arches and trains naturally combine by setting the trains across the arches, from lower to upper. Multiple arches sum tremendous lift, while also stabilizing close-set trains from interfering. Fry and Hines naturally envisioned trains of WECS in their rigid wind power arch structure, set crosswind. We now see how a Kite Arch can do the job cheaper and better by going higher. A growing list of methods exists to rotate a Kite Arch to match wind direction-- Hauling and Belaying around an Anchor Circle, Anchor (ground) Vehicles, Giant Carousel, Giant Control Bar, Circular Track, Circular Cableway, Buddy Boats, etc.
                       
                      In summary, there are many bulk advantages to Kite Arches. The challenges with arches are mostly in the details. An "anchor field" is a key arch requirement. Kites in a network can tangle badly if poorly designed and carelessly operated. The Bow-Tie failure mode is most characteristic of a high AR arch wing; deep-section bridling, foil section reflex, and/or tails constrain a wing arch from flipping; local swivel sections can recover a BowTie flip.
                       
                       


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