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Problems with "Fly HAWT Blade Tips Only" AWES Concepts

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  • dave santos
    Many AWES R&D teams publicly assert a familiar logic, that the secret is to fly the blade tips only of a conventional wind turbine, so as to avoid massive
    Message 1 of 6 , Dec 24, 2012
      Many AWES R&D teams publicly assert a familiar logic, that the secret is to fly the "blade tips only" of a conventional wind turbine, so as to avoid massive tower and hub costs. None of these claims is accompanied by admission of problems with this paradigm, some of which are-


      1) Control is greatly complicated when the passive stabilities of towers and hubs are eliminated. The engineering problem is moerely shifted to the expense and risk of high-endurance aerobatic flight. The schemes with two or three kiteplanes looping together are particularly at risk.

      2) Nowhere do the believers show how they calculated relative capital costs of concrete and steel against the costs of complex aerospace platforms. Fort Felker [2010] estimates aerospace costs by unit mass as one hundred times those of conventional wind towers.

      3) The simple argument that the blade tips, as 20% of the rotor diameter, do 80% of the work ignores some bad news. An AWES "blade tip" aircraft creates a new wingtip on the inside of its loop pattern, which means higher induced drag. The blade root/hub area is helping maximise extraction within its disc area, maximising power from the occupied airspace. Its pressurizing the blade tip upwind and depressurizes the tips the downwind side, boosting them for max power extraction.

      4) Tether drag greatly cuts into high-speed flight efficiency. A wind tower has no tethers to slow its TSR.

      5) As these "flying blade tip" concepts seek to access upper winds higher than towers, they overshadow such a huge land footprint (and airspace volume) that they become uneconomic most everywhere. At a glance, one sees how sparsely these configurations tap the wind in the vast space they occupy.


      The "Kitelab conclusion" from consideration of both sides of the "blade tips only" AWES concept is that this is a highly  misleading and flawed paradigm to design from.
    • Joe Faust
      The message http://tech.groups.yahoo.com/group/AirborneWindEnergy/message/8254 is
      Message 2 of 6 , Dec 24, 2012
        The message
        is probably related to this topic thread. 
      • Pierre BENHAIEM
        Great analysis! ...6) Unlike HAWT kite flight is not completely crosswind,and there are variations of power inducing high losses (listen and see the variations
        Message 3 of 6 , Dec 24, 2012


          Great analysis!

           

          ...6) Unlike HAWT kite flight is not completely crosswind,and there are variations of power inducing high losses (listen and see the variations of turbine sound and light on http://flygenkite.com ).

           

          Possible conclusions:1) anchored AWES using crosswind kite power being often seen as the better possibility of AWE,AWE is not a scale-utility solution excepted for some commercial niche ,OR ;2) scale-utility AWES is not a crosswind kite anchored,but perhaps a travelling AWES like hydro-turbine from Jong Chul Kim,or a stationary scheme like autogyro-mode,perhaps an hybrid scheme mixing airborne and seaborne...

           

          Merry Christmas,

           

          PierreB

          > Message du 24/12/12 21:53
          > De : "dave santos"
          > A : "AWE"
          > Copie à :
          > Objet : [AWES] Problems with "Fly HAWT Blade Tips Only" AWES Concepts
          >
          >  

          >

          Many AWES R&D teams publicly assert a familiar logic, that the secret is to fly the "blade tips only" of a conventional wind turbine, so as to avoid massive tower and hub costs. None of these claims is accompanied by admission of problems with this paradigm, some of which are-

          >

          >
          1) Control is greatly complicated when the passive stabilities of towers and hubs are eliminated. The engineering problem is moerely shifted to the expense and risk of high-endurance aerobatic flight. The schemes with two or three kiteplanes looping together are particularly at risk.

          >
          2) Nowhere do the believers show how they calculated relative capital costs of concrete and steel against the costs of complex aerospace platforms. Fort Felker [2010] estimates aerospace costs by unit mass as one hundred times those of conventional wind towers.

          >
          3) The simple argument that the blade tips, as 20% of the rotor diameter, do 80% of the work ignores some bad news. An AWES "blade tip" aircraft creates a new wingtip on the inside of its loop pattern, which means higher induced drag. The blade root/hub area is helping maximise extraction within its disc area, maximising power from the occupied airspace. Its pressurizing the blade tip upwind and depressurizes the tips the downwind side, boosting them for max power extraction.

          >
          4) Tether drag greatly cuts into high-speed flight efficiency. A wind tower has no tethers to slow its TSR.

          >
          5) As these "flying blade tip" concepts seek to access upper winds higher than towers, they overshadow such a huge land footprint (and airspace volume) that they become uneconomic most everywhere. At a glance, one sees how sparsely these configurations tap the wind in the vast space they occupy.

          >

          >
          The "Kitelab conclusion" from consideration of both sides of the "blade tips only" AWES concept is that this is a highly  misleading and flawed paradigm to design from.
        • dave santos
          Joe, Wayne s Makani challenge and discussion of the general blade-tip model are mostly coincidence of timing, rather than closely related. A key difference is
          Message 4 of 6 , Dec 24, 2012
            Joe,

            Wayne's Makani challenge and discussion of the general blade-tip model are mostly coincidence of timing, rather than closely related.

            A key difference is that Wayne has not challenged any team except Makani, but many teams, for years now, use the "blade-tip" explanation in public. Lets all concede the "blade tip" example is OK for a lay-person's metaphor for a sweeping energy kite, without going into the detail of why its a poor specific engineering similarity-case. Wayne's biggest objection to Makani is the flygen aspect, rather than its widely shared use of the blade-tip metaphor. 

            Regarding his challenge, Wayne has not disclosed a reference design. His general contribution is to ponder general ideas, without providing the sort of details that would make his challenge a workable game. Unless he can provide convincing design specifics (or real cases) comparable to what Makani has disclosed, such challenges are meaningless,

            daveS

          • Pierre BENHAIEM
            Effectively the message can be related to the mentioned topic but can also favours some like-autogyro schemes comprising that from Sky WindPower or
            Message 5 of 6 , Dec 24, 2012

              Effectively the message can be related to the mentioned topic but can also favours some like-autogyro schemes comprising that from Sky WindPower or Selsam's,and also quite different even opposite schemes with short-strokes described by DaveS.

              PierreB



              > Message du 24/12/12 22:42
              > De : "Joe Faust"
              > A : AirborneWindEnergy@yahoogroups.com
              > Copie à :
              > Objet : [AWES] Re: Problems with "Fly HAWT Blade Tips Only" AWES Concepts
              >
              >  

              >The message

              is probably related to this topic thread. 
            • John Adeoye Oyebanji
              Sincere wishes to everyone for a most merry christmas and the happiest year yet in 2013. Best lifts, always. JohnO John Adeoye Oyebanji CEO, Hardensoft
              Message 6 of 6 , Dec 24, 2012
                Sincere wishes to everyone for a most merry christmas and the happiest year yet in 2013.
                Best lifts, always.
                JohnO
                John Adeoye Oyebanji
                CEO, Hardensoft International Limited
                FundNopolis Representative -
                Nigeria & West-Africa
                President-protem, Airborne Wind Energy Industry Association (AWEIA International)

                From: Pierre BENHAIEM <pierre.benhaiem@...>
                Sender: AirborneWindEnergy@yahoogroups.com
                Date: Mon, 24 Dec 2012 23:21:10 +0100 (CET)
                To: <AirborneWindEnergy@yahoogroups.com>
                ReplyTo: AirborneWindEnergy@yahoogroups.com
                Subject: re: [AWES] Problems with "Fly HAWT Blade Tips Only" AWES Concepts

                 


                Great analysis!

                 

                ...6) Unlike HAWT kite flight is not completely crosswind,and there are variations of power inducing high losses (listen and see the variations of turbine sound and light on http://flygenkite.com ).

                 

                Possible conclusions:1) anchored AWES using crosswind kite power being often seen as the better possibility of AWE,AWE is not a scale-utility solution excepted for some commercial niche ,OR ;2) scale-utility AWES is not a crosswind kite anchored,but perhaps a travelling AWES like hydro-turbine from Jong Chul Kim,or a stationary scheme like autogyro-mode,perhaps an hybrid scheme mixing airborne and seaborne...

                 

                Merry Christmas,

                 

                PierreB

                > Message du 24/12/12 21:53
                > De : "dave santos"
                > A : "AWE"
                > Copie à :
                > Objet : [AWES] Problems with "Fly HAWT Blade Tips Only" AWES Concepts
                >
                >  

                >

                Many AWES R&D teams publicly assert a familiar logic, that the secret is to fly the "blade tips only" of a conventional wind turbine, so as to avoid massive tower and hub costs. None of these claims is accompanied by admission of problems with this paradigm, some of which are-

                >

                >
                1) Control is greatly complicated when the passive stabilities of towers and hubs are eliminated. The engineering problem is moerely shifted to the expense and risk of high-endurance aerobatic flight. The schemes with two or three kiteplanes looping together are particularly at risk.

                >
                2) Nowhere do the believers show how they calculated relative capital costs of concrete and steel against the costs of complex aerospace platforms. Fort Felker [2010] estimates aerospace costs by unit mass as one hundred times those of conventional wind towers.

                >
                3) The simple argument that the blade tips, as 20% of the rotor diameter, do 80% of the work ignores some bad news. An AWES "blade tip" aircraft creates a new wingtip on the inside of its loop pattern, which means higher induced drag. The blade root/hub area is helping maximise extraction within its disc area, maximising power from the occupied airspace. Its pressurizing the blade tip upwind and depressurizes the tips the downwind side, boosting them for max power extraction.

                >
                4) Tether drag greatly cuts into high-speed flight efficiency. A wind tower has no tethers to slow its TSR.

                >
                5) As these "flying blade tip" concepts seek to access upper winds higher than towers, they overshadow such a huge land footprint (and airspace volume) that they become uneconomic most everywhere. At a glance, one sees how sparsely these configurations tap the wind in the vast space they occupy.

                >

                >
                The "Kitelab conclusion" from consideration of both sides of the "blade tips only" AWES concept is that this is a highly  misleading and flawed paradigm to design from.
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