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Re: [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion

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  • dave santos
    Pierre (and DaveN),   WindLift is the third company to post flight video with realtime power data overlaid (TUDelft and Makani already have).   WindLift is
    Message 1 of 20 , Aug 26, 2011
      Pierre (and DaveN),
       
      WindLift is the third company to post flight video with realtime power data overlaid (TUDelft and Makani already have).
       
      WindLift is not an ideal model to extrapolate from. The prototype designs flew very low and had a lot of avoidable internal friction for later optimized models to reduce. Flying higher in much stronger winds will really make a difference in your power calculations.
       
      Perhaps the strangest misconception in AWE circles is that crosswind power is not possible at high altitudes, but there are multiple design paths open, such as autogyros, wingnills, and cross-country crosswind shuttling,
       
      A new misconception is that flygens are somehow inherently higher L/D than groundgen ideas. Ampyx's glider-like kiteplane has a much higher L/D potential than any comparable flygen due to a thinner cable and lack of rotor disks. Also, very generally, an AWECS forced to carry more weight aloft (like generators and conductors) has less lift available for power output,
       
      daveS

    • Pierre BENHAIEM
      DaveN, What I try to know is the real power from crosswind motion.What is common from all systems using crosswind motion (reel-out/in and other groundgens and
      Message 2 of 20 , Aug 26, 2011
        DaveN,

        What I try to know is the real power from crosswind motion.What is common from all systems using crosswind motion (reel-out/in and other groundgens and flygens) is the irregularity (all curves show it) of power and an output in conformity with Diehl's-Loyd's formula but only on the tiny peak.The average power is several times lower.If you see the trajectory on FlygenKite,kite wind turbine for lighting you can see (during 1 seconde) the light does not work then works:though wind speed being 5-6 m/s and L/D of my kite being 3-4 with turbine,kite speed is at least 14 m/s (my piloting by foot is not precise),and by car the light works from 10 m/s.

        It would be interesting to obtain a standard value of the average power from crosswind motion,according the real irregularities, and perhaps according to other losses the formula does not give (perhaps hysteresis Bob Stuart mentions for another aspect).

        After it we can know what L/D is needed for mass production,and other needed parameters.If the power from crosswind motion is not so high L/D will must be very high,with the limit of the drag of line increasing with its length and the altitude.

        PierreB 




        > Message du 26/08/11 15:47
        > De : "North, David D. (LARC-E402)"
        > A : "AirborneWindEnergy@yahoogroups.com"
        > Copie à :
        > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
        >
        >  

        >

        Pierre,

         

        Your last post is very insightful and asks many of the questions that I have been pondering. Here at NASA Langley, we are working on improving the L/D of kites (or as I like to call them “tethered flight vehicles”, it seems to get a better reception with the aero folks here at NASA!) . I realized a couple of years ago that the low L/D of existing surf kites and arc kites was going to need improvement if ground-gens were going to be competitive with higher performance aircraft-like fly-gens. I also realized from many years of kite flying that “unscheduled” landings are common and sometimes violent, so the kite construction would need to be very robust, at least during the development phases. Our first attempts are using materials like EPP foam with fiber reinforcement and coatings. The idea is to have an airfoil that can hold a much better profile tolerance than a ram air nylon kite or LEI single skin nylon surf kite and have a thinner section (maybe an 8% thickness-to chord ratio). We built a small 2kW ground-gen unit this summer to start getting test data. We just started testing last week and are starting to get data (kite speed, wind speed, line tension, line reel out/in speed, kite position data via video tracking, servo motor regen power, etc.). We’re flying “manually” now with a joystick controlling the servo motors, but plan to switch to automated flight with video tracking shortly.

         

        Our main focus is in two areas:  1) improvement in system L/D (kite and line) and 2) development of simple video tracking and kite control software for automated flight.

         

        Will keep you all posted on progress.

         

        Dave North
        >
        Aerospace Engineer
        >
        Systems Analysis and Concepts Directorate
        >
        1 North Dryden Street, Building 1209, MS462
        >
        NASA Langley Research Center
        >
        Hampton, VA 23681-2199
        >
        Phone: (757) 864-7285
        >
        Cell: (757) 771-5367
        >
        Fax: (757) 864-1975
        >
        Email: david.d.north@...

         


      • North, David D. (LARC-E402)
        DaveS, Agree on all points. You are right that reel-in / reel-out ground-gens can use high L/D glider-like kiteplanes . And I like Ampyx s solution. My
        Message 3 of 20 , Aug 26, 2011

          DaveS,

           

          Agree on all points. You are right that reel-in / reel-out ground-gens can use high L/D glider-like “kiteplanes”. And I like Ampyx’s solution. My premise is that there may be a middle ground between low L/D surf kites and high L/D glider-like craft where the cost is still very low, but performance is medium to high. And in the short term , while we get our autonomous flight controller up and running and “bullet-proof”, we need to be able to tolerate slamming into the ground many times without damage to the craft (thus the use of reinforced EPP). I am also interested in exploring the catenary / tensairity  design space of the arc kites in order to get to very low mass and simple tensile membrane designs.

           

          Dave North
          Aerospace Engineer
          Space Mission Analysis Branch (E402)
          Systems Analysis and Concepts Directorate
          1 North Dryden Street, Building 1209, MS462
          NASA Langley Research Center
          Hampton, VA 23681-2199
          Phone: (757) 864-7285
          Cell: (757) 771-5367
          Fax: (757) 864-1975
          Email: david.d.north@...

           

        • Joe Faust
          , and cross-country crosswind shuttling, daveS ... Responsive brief sketch of a CCCWS by JpF, Aug. 26, 2011:
          Message 4 of 20 , Aug 26, 2011

            , and cross-country crosswind shuttling,> daveS

            -------------------------

            Responsive brief sketch of a CCCWS by JpF, Aug. 26, 2011:
          • North, David D. (LARC-E402)
            Pierre, This is exactly the kind of data that we intend to generate over the next 1-2 years. There are many variables involved with cross wind power (see Loyd
            Message 5 of 20 , Aug 26, 2011

              Pierre,

               

              This is exactly the kind of data that we intend to generate over the next 1-2 years. There are many variables involved with cross wind power (see Loyd paper). We are trying to get actual test data to try to understand what the real-world “coefficients” are that need to be applied to Loyd’s ideal equations. And also try to understand where to focus the technology effort. Just from the physics L/D is an obvious area to focus for improved power output per unit area.

               

              Dave North
              Aerospace Engineer
              Space Mission Analysis Branch (E402)
              Systems Analysis and Concepts Directorate
              1 North Dryden Street, Building 1209, MS462
              NASA Langley Research Center
              Hampton, VA 23681-2199
              Phone: (757) 864-7285
              Cell: (757) 771-5367
              Fax: (757) 864-1975
              Email: david.d.north@...

               

            • Pierre BENHAIEM
              Stefano, Pag.27-28 Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground level. Kite effective area: 10 m2, maximum line length:
              Message 6 of 20 , Aug 26, 2011
                Stefano,

                Pag.27-28  "Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground

                level. Kite effective area: 10 m2, maximum line length: 800 m"

                shows with AWE it is possible to produce a good amount of energy with quasi no wind at ground.Another thing is trying to know the real output from crosswind motion (not only the peak),according to the variables indicated in M.Loyd's paper,according to eventual other parameters.

                I took Windlift video for the datas allowing to begin knowing what crosswind motion can produce by itself.

                PierreB 

                > Message du 26/08/11 16:17
                > De : "stefano.cianchetta"
                > A : AirborneWindEnergy@yahoogroups.com
                > Copie à :
                > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                >
                >  

                > Pierre,
                >
                > I found in my archive these two documents, you may also try to elaborate these old experimental data!
                > They look more favourable (10m2 kite area, wind speed 3-4m/s at 500m altitude, output during production phase 1.5kW )
                >
                > pag. 27-28
                > http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                >
                > pag. 11-13
                > http://lorenzofagiano.altervista.org/docs/FaMiPi_TR_27082009.pdf
                >
                > I found also this Laddermill video:
                > http://www.youtube.com/watch?v=mChu9MxDeIA
                >
                > What about skysail-power?
                > http://www.skysails.info/english/power/development/2-demonstrator-1-mw/
                >
                > Stefano C
                >
                > --- In AirborneWindEnergy@yahoogroups.com, "Pierre Benhaiem" wrote:
                > >
                > >
                > > Windlift testing - 12 sq. m. wing
                > > <http://www.youtube.com/watch?v=FsBhBtt8RWI> .It is one on the first
                > > times when we can read one,even two energy curves in real time of
                > > flight.Datas are wing 12 m²,wind speed being 10 m/s at an altitude of
                > > 10 m.I suppose ratio L/D could be something like 4.
                > >
                > > The red curve shows instataneous (positive or negative) power during
                > > reel out and in,and is like toothes (irregularity of power the sound
                > > also shows). During the better time power is about 5 kw,the global
                > > average (before recovering phase) is about 2.5 kw.The global cycle
                > > produces 30000 J as indicated by the blue curve going from 110 000 to
                > > 140 000 J.The time is 55 secondes.30 000/55 = 545 W for the average of
                > > the complete cycle.
                > >
                > > We can see and listen the recovery period takes much energy,but it is
                > > not the most important problem:Windlift will can bring down these
                > > values.
                > >
                > > But with Diehls-Loyd formula, P = 2/27. air density.kite area.cube of
                > > wind speed.CL (CL/CD)². So a 12 m² wing should produce something
                > > like 20 kw.Yes but only on power peak,not as average apparently.
                > >
                > > So the best period,5 kw,(and a fortiori the average 2.5 kw) shows a
                > > power far to expected (at least on a better point of the croswind
                > > trajectory) 20 kw.
                > >
                > > So to produce 2.5 MW it would need 12 000 m² of kites (it is too much
                > > in regard to ROI), or for the better 2000 m² of rigid kites (it is
                > > also too much).
                > >
                > > What can be improved to maximize crosswind motion?
                > >
                > > Dr Breukels' thesis can produce answers by studying the way to benefit
                > > from control of flexibility of a kite.
                > >
                > > But the question is:is it really possible to project GW scale (with reel
                > > or flygen and crosswind motion) by multiplication of actual low output?
                > >
                > > Or AWE should be limited to precise targets like facilitating wind
                > > access in regions without grid? (projects for jet stream are not
                > > concerned since crosswind motion is not used).
                > >
                > > PierreB
                > >
                > > http://flygenkite.com <http://flygenkite.com>
                > >
                >
                >


              • Pierre BENHAIEM
                DaveN, Another example:Makani choices a loop-path for its (relative) regularity.The curve seems to be a regular oscillation of irregularities. And Makani
                Message 7 of 20 , Aug 26, 2011
                  DaveN,

                  Another example:Makani choices a loop-path for its (relative) regularity.The curve seems to be a regular oscillation of irregularities.
                  And Makani explains loop allows more regular conversion.So it is possible that peak power is lesser but average power is higher.By putting aside higher L/D it seems (according to datas) that output is closer to what gives the (for peak?) formula (among other numerous formulas from M.Loyd's paper);something like 1/2 or 1/3 instead 1/5 and less.My idea is that different positions in the window of flight in regard to real or apparent wind,deformations of soft kites,optimization of piloting yes or no,are not enough to explain such a difference.A crosswind kite is a little like a rotor which works then stops then works etc.Nevertheless crosswind kite could be a winning combination.

                  PierreB



                  > Message du 26/08/11 18:20
                  > De : "North, David D. (LARC-E402)"
                  > A : "AirborneWindEnergy@yahoogroups.com"
                  > Copie à :
                  > Objet : re: [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                  >
                  >  

                  >

                  Pierre,

                   

                  This is exactly the kind of data that we intend to generate over the next 1-2 years. There are many variables involved with cross wind power (see Loyd paper). We are trying to get actual test data to try to understand what the real-world “coefficients” are that need to be applied to Loyd’s ideal equations. And also try to understand where to focus the technology effort. Just from the physics L/D is an obvious area to focus for improved power output per unit area.

                   

                  Dave North
                  >
                  Aerospace Engineer
                  > Space Mission Analysis Branch (E402)
                  >
                  Systems Analysis and Concepts Directorate
                  >
                  1 North Dryden Street, Building 1209, MS462
                  >
                  NASA Langley Research Center
                  >
                  Hampton, VA 23681-2199
                  >
                  Phone: (757) 864-7285
                  >
                  Cell: (757) 771-5367
                  >
                  Fax: (757) 864-1975
                  >
                  Email: david.d.north@...

                   


                • Pierre BENHAIEM
                  Stefano and DaveN, Some aspects from my precedent (and perhaps present!) messages are wrong.Miles L.Loyd indicates on Crosswind Kite Power : The power
                  Message 8 of 20 , Aug 27, 2011
                    Stefano and DaveN,

                    Some aspects from my precedent (and perhaps present!) messages are wrong.Miles L.Loyd indicates on

                    Crosswind Kite Power :"

                    The power produced by either crosswind mode increases as

                    the square of L/DK.

                    The potential of these crosswind modes of kite operation is

                    shown in Fig. 5, where power output vs L/DK and wind

                    velocity is shown. A kite the size of the C-5A with a wing area

                    of 576 m2 and a minimum fuselage might have an L/DK of

                    20. From Fig. 5, this kite would produce 22 MW in a 10-m/s

                    wind. Actually, this is an upper bound that cannot be

                    achieved because the motion cannot be purely crosswind, the

                    tether has drag, and both the kite and tether have significant

                    weight. Even so, approaching this potential power output

                    seems very attractive for a single wind machine."

                    I put again the extract:"Actually, this is an upper bound that cannot be

                    achieved because the motion cannot be purely crosswind, the

                    tether has drag, and both the kite and tether have significant

                    weight."

                    I put again the extract:"because the motion cannot be purely crosswind".


                    On table 1 Examples of calculation.The table indicates 6.7 MW for the wind area of 576 m² ,lift-to-drag ratio being 20.

                    If one makes calculations with a lift-to-drag ratio of 4 which seems +- the ratio of used wings for Windlift,and Laddermill (with a better optimization for both power and retrieval phases due to the work of kite deformation Dr Breukel details in his thesis) one  can get closer more on the measured values indicated in the videos.Of course more performant wings will be used.For Makani it is the same with a higher ratio L/D.

                    PierreB  

                     

                     




                    > Message du 26/08/11 16:17
                    > De : "stefano.cianchetta"
                    > A : AirborneWindEnergy@yahoogroups.com
                    > Copie à :
                    > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                    >
                    >  

                    > Pierre,
                    >
                    > I found in my archive these two documents, you may also try to elaborate these old experimental data!
                    > They look more favourable (10m2 kite area, wind speed 3-4m/s at 500m altitude, output during production phase 1.5kW )
                    >
                    > pag. 27-28
                    > http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                    >
                    > pag. 11-13
                    > http://lorenzofagiano.altervista.org/docs/FaMiPi_TR_27082009.pdf
                    >
                    > I found also this Laddermill video:
                    > http://www.youtube.com/watch?v=mChu9MxDeIA
                    >
                    > What about skysail-power?
                    > http://www.skysails.info/english/power/development/2-demonstrator-1-mw/
                    >
                    > Stefano C
                    >
                    > --- In AirborneWindEnergy@yahoogroups.com, "Pierre Benhaiem" wrote:
                    > >
                    > >
                    > > Windlift testing - 12 sq. m. wing
                    > > <http://www.youtube.com/watch?v=FsBhBtt8RWI> .It is one on the first
                    > > times when we can read one,even two energy curves in real time of
                    > > flight.Datas are wing 12 m²,wind speed being 10 m/s at an altitude of
                    > > 10 m.I suppose ratio L/D could be something like 4.
                    > >
                    > > The red curve shows instataneous (positive or negative) power during
                    > > reel out and in,and is like toothes (irregularity of power the sound
                    > > also shows). During the better time power is about 5 kw,the global
                    > > average (before recovering phase) is about 2.5 kw.The global cycle
                    > > produces 30000 J as indicated by the blue curve going from 110 000 to
                    > > 140 000 J.The time is 55 secondes.30 000/55 = 545 W for the average of
                    > > the complete cycle.
                    > >
                    > > We can see and listen the recovery period takes much energy,but it is
                    > > not the most important problem:Windlift will can bring down these
                    > > values.
                    > >
                    > > But with Diehls-Loyd formula, P = 2/27. air density.kite area.cube of
                    > > wind speed.CL (CL/CD)². So a 12 m² wing should produce something
                    > > like 20 kw.Yes but only on power peak,not as average apparently.
                    > >
                    > > So the best period,5 kw,(and a fortiori the average 2.5 kw) shows a
                    > > power far to expected (at least on a better point of the croswind
                    > > trajectory) 20 kw.
                    > >
                    > > So to produce 2.5 MW it would need 12 000 m² of kites (it is too much
                    > > in regard to ROI), or for the better 2000 m² of rigid kites (it is
                    > > also too much).
                    > >
                    > > What can be improved to maximize crosswind motion?
                    > >
                    > > Dr Breukels' thesis can produce answers by studying the way to benefit
                    > > from control of flexibility of a kite.
                    > >
                    > > But the question is:is it really possible to project GW scale (with reel
                    > > or flygen and crosswind motion) by multiplication of actual low output?
                    > >
                    > > Or AWE should be limited to precise targets like facilitating wind
                    > > access in regions without grid? (projects for jet stream are not
                    > > concerned since crosswind motion is not used).
                    > >
                    > > PierreB
                    > >
                    > > http://flygenkite.com <http://flygenkite.com>
                    > >
                    >
                    >


                  • North, David D. (LARC-E402)
                    PierreB, So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the
                    Message 9 of 20 , Aug 27, 2011
                      PierreB,

                      So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the "real-world" knock-down factors that need to be applied to Loyd's ideal power equations. Variables will include L/D, flight path, altitude, tether length, kite design [ram air, inflatable,semi-rigid, rigid], reel-out/in speed vs. wind velocity, etc..

                      The ultimate goal is to determine if a ground-gen can really compete with tower-based turbines (I respectfully disagree with some assessments in the AWE community that it cannot). I believe that it can compete at a minimum , in the short term, in certain "niche" markets and maybe, long term, on a grand scale with AWE being a significant portion of wind energy production. As DougS says, the commercial viability of AWE will be determined not by "government bureaucrats" like me (it's pretty funny that Doug characterizes me like that, because I identify more with the inventor types) but by the doggedly determined inventor/entrepreneurs. We at NASA are just trying to help the effort by doing whatever we can by getting a better understanding of the real-world factors through experimentation.

                      Dave North
                      NASA Langley
                    • dave santos
                      DaveN,   It will be hard to wait two years for your findings, which hopefully will settle many open questions.   Two top reasons that AWE can far outclass
                      Message 10 of 20 , Aug 27, 2011
                        DaveN,
                         
                        It will be hard to wait two years for your findings, which hopefully will settle many open questions.
                         
                        Two top reasons that AWE can far outclass conventional turbines are the superiority of the upper wind resource and the practicality of aggregating kite capacity to drive the largest generators by stringing together arrays. The low-capital-cost AWE advantage is largely negated by higher operational cost, so we must plan for "nuke-priced" energy in the early years.
                         
                        Please note that an advanced groundgen concept to include for study is a "short-stroke" power cycle (with little or no reeling) occurring at the natural kite orbit (loop or eight) frequency, with a brief elastic recovery phase at the top of each orbit. Line slack (Bob's hysteresis) is a limiting factor, but as the kite arrays grow in size, so grows the altitude potential of "short"-stroke, even to the Jet Stream.
                         
                        KiteLab and Makani independently identified specific advantages of this groundgen cycle over long-stroke reeling, but it has long existed as an AWECS principle, without the comparative analysis. Most long-stroke designs are so 2004, with many known disadvantages (lower overall efficiency, airspace hog, high line wear, long recovery phase power smoothing, etc,),
                         
                        daveS
                         
                      • Pierre BENHAIEM
                        DaveN and all, I agree.As I am not a scientific after trials of FlygenKite last days I am surprised the light does not work at a velocity which nevertheless
                        Message 11 of 20 , Aug 27, 2011
                          DaveN and all,

                          I agree.As I am not a scientific after trials of FlygenKite last days I am surprised the light does not work at a velocity which nevertheless seemed sufficient.I tried to extrapolate from the following estimations:  

                          see p.7  KiteGen project: control as key technology for a quantum leap in ... (2007):
                          "In particular, a

                          single 500 m2 kite with 12 m/s nominal wind speed and

                          aerodynamic efficiency (i.e. CL=CD) equal to 12 would be

                          able to generate 10 MW mean power.".This estimation seems work within the formula:power = 2/27.air density.kite area.cube of wind speed.Cl (CL/CD)².My system produces it only on peak,and less by far in average.After I read curve from Windlift and it is also less by far.I read again (what I can understand!) Loyd's paper "Crosswind kite Power" and it is interesting to see there are 2 parts:"Simplified Analysis" where the power of kite (576 m²,L/D = 20) is 22 MW,wind speed being 10 m/s.This result seems to go with the precedent (500 m² kite).BUT there is a second part "Detailed Analysis" which takes into account other parameters among which in first:"motion cannot be purely crosswind".In the end kite average power is only 6.7 MW instead 22 MW.But "it is a reasonable fraction of that predicted by the simplified analysis".

                          This result sounds like a real basis we can use for extrapolation (KiteGen,Delft,Makani and others probably made it to build their simulations).Windlift,Laddermill curves (and perhaps my trials) seems to confirm the validity of this result in a real world.And this paper was written in 1979! 

                          PierreB 
                             





                          > Message du 27/08/11 17:24
                          > De : "North, David D. (LARC-E402)"
                          > A : "AirborneWindEnergy@yahoogroups.com"
                          > Copie à : "mark.aull@..."
                          > Objet : re: [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                          >
                          >  

                          > PierreB,
                          >
                          > So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the "real-world" knock-down factors that need to be applied to Loyd's ideal power equations. Variables will include L/D, flight path, altitude, tether length, kite design [ram air, inflatable,semi-rigid, rigid], reel-out/in speed vs. wind velocity, etc..
                          >
                          > The ultimate goal is to determine if a ground-gen can really compete with tower-based turbines (I respectfully disagree with some assessments in the AWE community that it cannot). I believe that it can compete at a minimum , in the short term, in certain "niche" markets and maybe, long term, on a grand scale with AWE being a significant portion of wind energy production. As DougS says, the commercial viability of AWE will be determined not by "government bureaucrats" like me (it's pretty funny that Doug characterizes me like that, because I identify more with the inventor types) but by the doggedly determined inventor/entrepreneurs. We at NASA are just trying to help the effort by doing whatever we can by getting a better understanding of the real-world factors through experimentation.
                          >
                          > Dave North
                          > NASA Langley


                        • stefano.cianchetta
                          Pierre, I tried to look a bit at those data from Milanese et al: Milanese reported 37 Wh produced by a 10m2 kite in about 100sec of active phase. This
                          Message 12 of 20 , Aug 29, 2011
                            Pierre,
                            I tried to look a bit at those data from Milanese et al:
                            Milanese reported "37 Wh" produced by a 10m2 kite in about 100sec of active phase. This corresponds to an average power of 1.3 kW during the active phase (530W during a full cycle! similar to windlift but in a weaker wind), infact elsewhere (for the experiment near Casale)they reported 3-4m/s wind speed at 500m.
                            They claimed these experimental values are in agreement to their predictions (thus Megawatt scale reached by a 500m2 kite with L/D=12 at a wind speed of 10m/s appears plausible).
                            Notably these claims (as order of magnitude) appear to be consistent with the results reported by skysails (as far as I can understand).
                            Unfortunately actual data from skysails are not available (I did not find publications yet).
                            It appears to me that skysails could potentially answer in deep to our doubts about scalability and real performances...
                            I'll wait also for DaveN conclusions!!

                            Stefano C



                            --- In AirborneWindEnergy@yahoogroups.com, Pierre BENHAIEM <pierre.benhaiem@...> wrote:
                            >
                            > Stefano,
                            >
                            > Pag.27-28 "Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground
                            > level. Kite effective area: 10 m2, maximum line length: 800 m"
                            > shows with AWE it is possible to produce a good amount of energy with quasi no wind at ground.Another thing is trying to know the real output from crosswind motion (not only the peak),according to the variables indicated in M.Loyd's paper,according to eventual other parameters.
                            >
                            > I took Windlift video for the datas allowing to begin knowing what crosswind motion can produce by itself.
                            >
                            > PierreB
                            >
                            >
                            > > Message du 26/08/11 16:17
                            > > De : "stefano.cianchetta"
                            > > A : AirborneWindEnergy@yahoogroups.com
                            > > Copie à :
                            > > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                            > >
                            > >
                            > > Pierre,
                            > >
                            > > I found in my archive these two documents, you may also try to elaborate these old experimental data!
                            > > They look more favourable (10m2 kite area, wind speed 3-4m/s at 500m altitude, output during production phase 1.5kW )
                            > >
                            > > pag. 27-28
                            > > http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                            > >
                            > > pag. 11-13
                            > > http://lorenzofagiano.altervista.org/docs/FaMiPi_TR_27082009.pdf
                            > >
                            > > I found also this Laddermill video:
                            > > http://www.youtube.com/watch?v=mChu9MxDeIA
                            > >
                            > > What about skysail-power?
                            > > http://www.skysails.info/english/power/development/2-demonstrator-1-mw/
                            > >
                            > > Stefano C
                            > >
                            > > --- In AirborneWindEnergy@yahoogroups.com, "Pierre Benhaiem" wrote:
                            > > >
                            > > >
                            > > > Windlift testing - 12 sq. m. wing
                            > > > .It is one on the first
                            > > > times when we can read one,even two energy curves in real time of
                            > > > flight.Datas are wing 12 m²,wind speed being 10 m/s at an altitude of
                            > > > 10 m.I suppose ratio L/D could be something like 4.
                            > > >
                            > > > The red curve shows instataneous (positive or negative) power during
                            > > > reel out and in,and is like toothes (irregularity of power the sound
                            > > > also shows). During the better time power is about 5 kw,the global
                            > > > average (before recovering phase) is about 2.5 kw.The global cycle
                            > > > produces 30000 J as indicated by the blue curve going from 110 000 to
                            > > > 140 000 J.The time is 55 secondes.30 000/55 = 545 W for the average of
                            > > > the complete cycle.
                            > > >
                            > > > We can see and listen the recovery period takes much energy,but it is
                            > > > not the most important problem:Windlift will can bring down these
                            > > > values.
                            > > >
                            > > > But with Diehls-Loyd formula, P = 2/27. air density.kite area.cube of
                            > > > wind speed.CL (CL/CD)². So a 12 m² wing should produce something
                            > > > like 20 kw.Yes but only on power peak,not as average apparently.
                            > > >
                            > > > So the best period,5 kw,(and a fortiori the average 2.5 kw) shows a
                            > > > power far to expected (at least on a better point of the croswind
                            > > > trajectory) 20 kw.
                            > > >
                            > > > So to produce 2.5 MW it would need 12 000 m² of kites (it is too much
                            > > > in regard to ROI), or for the better 2000 m² of rigid kites (it is
                            > > > also too much).
                            > > >
                            > > > What can be improved to maximize crosswind motion?
                            > > >
                            > > > Dr Breukels' thesis can produce answers by studying the way to benefit
                            > > > from control of flexibility of a kite.
                            > > >
                            > > > But the question is:is it really possible to project GW scale (with reel
                            > > > or flygen and crosswind motion) by multiplication of actual low output?
                            > > >
                            > > > Or AWE should be limited to precise targets like facilitating wind
                            > > > access in regions without grid? (projects for jet stream are not
                            > > > concerned since crosswind motion is not used).
                            > > >
                            > > > PierreB
                            > > >
                            > > > http://flygenkite.com
                            > > >
                            > >
                            > >
                            >
                          • Pierre BENHAIEM
                            Stefano, In case of 3-4 m/s wind speed the power of 1.3 kW during the best period of the active phase is huge,except if L/D is very high (6 or 7 instead 4,or
                            Message 13 of 20 , Aug 29, 2011

                              Stefano,

                              In case of 3-4 m/s wind speed the power of 1.3 kW during the best period of the active phase is huge,except if L/D is very high (6 or 7 instead 4,or if wind speed is a little higher,5 m/s for example).A common point of all curves:power is not regular (you can hear that).And if you pilot a kite by eight-figure you feel the irregularity of the traction.

                              The value of 10 MW for 500 m² with 12 m/s nominal wind speed and L/D = 12 roughly corresponds to the "simplified analysis" from Loyd's paper,or to a peak of power.But in Presentazione di PowerPoint p.18 wind speed is 15 m/s,other datas being identical.Power increasing by the cube of wind speed,so 10 MW for 15 m/s wind speed induces half of the output of the same with only 12 m/s wind speed.This value is closer of the result on the "detailed analysis",or of the average power.

                              However crosswind kite power can be very promising for a mass production,with kites with higher L/D,and thiner lines,and now can be useful for some niche markets.

                              Note:it will be interesting to know results for retrieval phase during glide maneuver according to KiteGen systems .

                              PierreB 



                               


                              > Message du 29/08/11 12:51
                              > De : "stefano.cianchetta"
                              > A : AirborneWindEnergy@yahoogroups.com
                              > Copie à :
                              > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                              >
                              >  

                              > Pierre,
                              > I tried to look a bit at those data from Milanese et al:
                              > Milanese reported "37 Wh" produced by a 10m2 kite in about 100sec of active phase. This corresponds to an average power of 1.3 kW during the active phase (530W during a full cycle! similar to windlift but in a weaker wind), infact elsewhere (for the experiment near Casale)they reported 3-4m/s wind speed at 500m.
                              > They claimed these experimental values are in agreement to their predictions (thus Megawatt scale reached by a 500m2 kite with L/D=12 at a wind speed of 10m/s appears plausible).
                              > Notably these claims (as order of magnitude) appear to be consistent with the results reported by skysails (as far as I can understand).
                              > Unfortunately actual data from skysails are not available (I did not find publications yet).
                              > It appears to me that skysails could potentially answer in deep to our doubts about scalability and real performances...
                              > I'll wait also for DaveN conclusions!!
                              >
                              > Stefano C
                              >
                              > --- In AirborneWindEnergy@yahoogroups.com, Pierre BENHAIEM wrote:
                              > >
                              > > Stefano,
                              > >
                              > > Pag.27-28 "Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground
                              > > level. Kite effective area: 10 m2, maximum line length: 800 m"
                              > > shows with AWE it is possible to produce a good amount of energy with quasi no wind at ground.Another thing is trying to know the real output from crosswind motion (not only the peak),according to the variables indicated in M.Loyd's paper,according to eventual other parameters.
                              > >
                              > > I took Windlift video for the datas allowing to begin knowing what crosswind motion can produce by itself.
                              > >
                              > > PierreB
                              > >
                              > >
                              > > > Message du 26/08/11 16:17
                              > > > De : "stefano.cianchetta"
                              > > > A : AirborneWindEnergy@yahoogroups.com
                              > > > Copie à :
                              > > > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                              > > >
                              > > >
                              > > > Pierre,
                              > > >
                              > > > I found in my archive these two documents, you may also try to elaborate these old experimental data!
                              > > > They look more favourable (10m2 kite area, wind speed 3-4m/s at 500m altitude, output during production phase 1.5kW )
                              > > >
                              > > > pag. 27-28
                              > > > http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                              > > >
                              > > > pag. 11-13
                              > > > http://lorenzofagiano.altervista.org/docs/FaMiPi_TR_27082009.pdf
                              > > >
                              > > > I found also this Laddermill video:
                              > > > http://www.youtube.com/watch?v=mChu9MxDeIA
                              > > >
                              > > > What about skysail-power?
                              > > > http://www.skysails.info/english/power/development/2-demonstrator-1-mw/
                              > > >
                              > > > Stefano C
                              > > >
                              > > > --- In AirborneWindEnergy@yahoogroups.com, "Pierre Benhaiem" wrote:
                              > > > >
                              > > > >
                              > > > > Windlift testing - 12 sq. m. wing
                              > > > > .It is one on the first
                              > > > > times when we can read one,even two energy curves in real time of
                              > > > > flight.Datas are wing 12 m²,wind speed being 10 m/s at an altitude of
                              > > > > 10 m.I suppose ratio L/D could be something like 4.
                              > > > >
                              > > > > The red curve shows instataneous (positive or negative) power during
                              > > > > reel out and in,and is like toothes (irregularity of power the sound
                              > > > > also shows). During the better time power is about 5 kw,the global
                              > > > > average (before recovering phase) is about 2.5 kw.The global cycle
                              > > > > produces 30000 J as indicated by the blue curve going from 110 000 to
                              > > > > 140 000 J.The time is 55 secondes.30 000/55 = 545 W for the average of
                              > > > > the complete cycle.
                              > > > >
                              > > > > We can see and listen the recovery period takes much energy,but it is
                              > > > > not the most important problem:Windlift will can bring down these
                              > > > > values.
                              > > > >
                              > > > > But with Diehls-Loyd formula, P = 2/27. air density.kite area.cube of
                              > > > > wind speed.CL (CL/CD)². So a 12 m² wing should produce something
                              > > > > like 20 kw.Yes but only on power peak,not as average apparently.
                              > > > >
                              > > > > So the best period,5 kw,(and a fortiori the average 2.5 kw) shows a
                              > > > > power far to expected (at least on a better point of the croswind
                              > > > > trajectory) 20 kw.
                              > > > >
                              > > > > So to produce 2.5 MW it would need 12 000 m² of kites (it is too much
                              > > > > in regard to ROI), or for the better 2000 m² of rigid kites (it is
                              > > > > also too much).
                              > > > >
                              > > > > What can be improved to maximize crosswind motion?
                              > > > >
                              > > > > Dr Breukels' thesis can produce answers by studying the way to benefit
                              > > > > from control of flexibility of a kite.
                              > > > >
                              > > > > But the question is:is it really possible to project GW scale (with reel
                              > > > > or flygen and crosswind motion) by multiplication of actual low output?
                              > > > >
                              > > > > Or AWE should be limited to precise targets like facilitating wind
                              > > > > access in regions without grid? (projects for jet stream are not
                              > > > > concerned since crosswind motion is not used).
                              > > > >
                              > > > > PierreB
                              > > > >
                              > > > > http://flygenkite.com
                              > > > >
                              > > >
                              > > >
                              > >
                              >
                              >


                            • stefano.cianchetta
                              Pierre, I agree with you. look here at page 20!! http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf Cable drag and recovery almost halved the
                              Message 14 of 20 , Aug 30, 2011
                                Pierre,
                                I agree with you. look here at page 20!! http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                                Cable drag and recovery almost halved the power in this simulation!
                                The output is not regoular for sure, the kitegen group is still working with supercaps to smooth the power output (as far as I know).
                                I am curious too about the glide manouver; I have been told that it could significantly reduce the useful life of the kite fabric, but unfortunately I had no real data and this could be just a guess.

                                Stefano



                                --- In AirborneWindEnergy@yahoogroups.com, Pierre BENHAIEM <pierre.benhaiem@...> wrote:
                                >
                                >
                                > Stefano,
                                >
                                > In case of 3-4 m/s wind speed the power of 1.3 kW during the best period of the active phase is huge,except if L/D is very high (6 or 7 instead 4,or if wind speed is a little higher,5 m/s for example).A common point of all curves:power is not regular (you can hear that).And if you pilot a kite by eight-figure you feel the irregularity of the traction.
                                >
                                > The value of 10 MW for 500 m² with 12 m/s nominal wind speed and L/D = 12 roughly corresponds to the "simplified analysis" from Loyd's paper,or to a peak of power.But in Presentazione di PowerPoint p.18 wind speed is 15 m/s,other datas being identical.Power increasing by the cube of wind speed,so 10 MW for 15 m/s wind speed induces half of the output of the same with only 12 m/s wind speed.This value is closer of the result on the "detailed analysis",or of the average power.
                                >
                                > However crosswind kite power can be very promising for a mass production,with kites with higher L/D,and thiner lines,and now can be useful for some niche markets.
                                >
                                > Note:it will be interesting to know results for retrieval phase during glide maneuver according to KiteGen systems .
                                >
                                > PierreB
                                >
                                >
                                >
                                >
                                >
                                >
                                > > Message du 29/08/11 12:51
                                > > De : "stefano.cianchetta"
                                > > A : AirborneWindEnergy@yahoogroups.com
                                > > Copie à :
                                > > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                                > >
                                > >
                                > > Pierre,
                                > > I tried to look a bit at those data from Milanese et al:
                                > > Milanese reported "37 Wh" produced by a 10m2 kite in about 100sec of active phase. This corresponds to an average power of 1.3 kW during the active phase (530W during a full cycle! similar to windlift but in a weaker wind), infact elsewhere (for the experiment near Casale)they reported 3-4m/s wind speed at 500m.
                                > > They claimed these experimental values are in agreement to their predictions (thus Megawatt scale reached by a 500m2 kite with L/D=12 at a wind speed of 10m/s appears plausible).
                                > > Notably these claims (as order of magnitude) appear to be consistent with the results reported by skysails (as far as I can understand).
                                > > Unfortunately actual data from skysails are not available (I did not find publications yet).
                                > > It appears to me that skysails could potentially answer in deep to our doubts about scalability and real performances...
                                > > I'll wait also for DaveN conclusions!!
                                > >
                                > > Stefano C
                                > >
                                > > --- In AirborneWindEnergy@yahoogroups.com, Pierre BENHAIEM wrote:
                                > > >
                                > > > Stefano,
                                > > >
                                > > > Pag.27-28 "Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground
                                > > > level. Kite effective area: 10 m2, maximum line length: 800 m"
                                > > > shows with AWE it is possible to produce a good amount of energy with quasi no wind at ground.Another thing is trying to know the real output from crosswind motion (not only the peak),according to the variables indicated in M.Loyd's paper,according to eventual other parameters.
                                > > >
                                > > > I took Windlift video for the datas allowing to begin knowing what crosswind motion can produce by itself.
                                > > >
                                > > > PierreB
                                > > >
                                > > >
                                > > > > Message du 26/08/11 16:17
                                > > > > De : "stefano.cianchetta"
                                > > > > A : AirborneWindEnergy@yahoogroups.com
                                > > > > Copie à :
                                > > > > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                                > > > >
                                > > > >
                                > > > > Pierre,
                                > > > >
                                > > > > I found in my archive these two documents, you may also try to elaborate these old experimental data!
                                > > > > They look more favourable (10m2 kite area, wind speed 3-4m/s at 500m altitude, output during production phase 1.5kW )
                                > > > >
                                > > > > pag. 27-28
                                > > > > http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
                                > > > >
                                > > > > pag. 11-13
                                > > > > http://lorenzofagiano.altervista.org/docs/FaMiPi_TR_27082009.pdf
                                > > > >
                                > > > > I found also this Laddermill video:
                                > > > > http://www.youtube.com/watch?v=mChu9MxDeIA
                                > > > >
                                > > > > What about skysail-power?
                                > > > > http://www.skysails.info/english/power/development/2-demonstrator-1-mw/
                                > > > >
                                > > > > Stefano C
                                > > > >
                                > > > > --- In AirborneWindEnergy@yahoogroups.com, "Pierre Benhaiem" wrote:
                                > > > > >
                                > > > > >
                                > > > > > Windlift testing - 12 sq. m. wing
                                > > > > > .It is one on the first
                                > > > > > times when we can read one,even two energy curves in real time of
                                > > > > > flight.Datas are wing 12 m²,wind speed being 10 m/s at an altitude of
                                > > > > > 10 m.I suppose ratio L/D could be something like 4.
                                > > > > >
                                > > > > > The red curve shows instataneous (positive or negative) power during
                                > > > > > reel out and in,and is like toothes (irregularity of power the sound
                                > > > > > also shows). During the better time power is about 5 kw,the global
                                > > > > > average (before recovering phase) is about 2.5 kw.The global cycle
                                > > > > > produces 30000 J as indicated by the blue curve going from 110 000 to
                                > > > > > 140 000 J.The time is 55 secondes.30 000/55 = 545 W for the average of
                                > > > > > the complete cycle.
                                > > > > >
                                > > > > > We can see and listen the recovery period takes much energy,but it is
                                > > > > > not the most important problem:Windlift will can bring down these
                                > > > > > values.
                                > > > > >
                                > > > > > But with Diehls-Loyd formula, P = 2/27. air density.kite area.cube of
                                > > > > > wind speed.CL (CL/CD)². So a 12 m² wing should produce something
                                > > > > > like 20 kw.Yes but only on power peak,not as average apparently.
                                > > > > >
                                > > > > > So the best period,5 kw,(and a fortiori the average 2.5 kw) shows a
                                > > > > > power far to expected (at least on a better point of the croswind
                                > > > > > trajectory) 20 kw.
                                > > > > >
                                > > > > > So to produce 2.5 MW it would need 12 000 m² of kites (it is too much
                                > > > > > in regard to ROI), or for the better 2000 m² of rigid kites (it is
                                > > > > > also too much).
                                > > > > >
                                > > > > > What can be improved to maximize crosswind motion?
                                > > > > >
                                > > > > > Dr Breukels' thesis can produce answers by studying the way to benefit
                                > > > > > from control of flexibility of a kite.
                                > > > > >
                                > > > > > But the question is:is it really possible to project GW scale (with reel
                                > > > > > or flygen and crosswind motion) by multiplication of actual low output?
                                > > > > >
                                > > > > > Or AWE should be limited to precise targets like facilitating wind
                                > > > > > access in regions without grid? (projects for jet stream are not
                                > > > > > concerned since crosswind motion is not used).
                                > > > > >
                                > > > > > PierreB
                                > > > > >
                                > > > > > http://flygenkite.com
                                > > > > >
                                > > > >
                                > > > >
                                > > >
                                > >
                                > >
                                >
                              • Doug
                                Hi Dave North: Thanks for posting here, communicating with the people, more than most bureaucrats do. I didn t mean that term b-crat in a perjorative way,
                                Message 15 of 20 , Aug 31, 2011
                                  Hi Dave North:
                                  Thanks for posting here, communicating with the people, more than most "bureaucrats" do. I didn't mean that term "b-crat" in a perjorative way, as it is sometimes used. I just meant you work at a "bureau". Don't know a better term, but "government researcher" might be more appropriate.

                                  From the beginning I have been puzzled by your role in AWE. The questions would be:

                                  1) whether you represent NASA, or just work there and represent yourself as an independent inventor in AWE. both? cake'n'eat-it-too?

                                  2) whether you can offer assistance to all AWE players equally, or whether you (or NASA) are in fact a player with your own interests. A Collaborator or a competitor? a bystander?

                                  3) Whether you have indeed surveyed the space and technologies adequately, and assessed each. If so what are your results? Where can we read about the thought process leading to your current actions? Does NASA have a position on the viability of any technology? What has NASA now learned, that could help U.S. Citizens and companies, that could be said to be a result of the work performed so far?

                                  4) What is the official NASA position on the various technologies? Let's just take the most famous example, with the most press releases: Magenn - does NASA have an official position on inflated, elevated Savonius technologies like Magenn?

                                  5) Is there any concern that you (NASA?) could be duplicating the efforts of several high-visibility teams funded with millions of dollars that have produced no economically-workable technologies (product) yet for all those millions spent? Is there any concern that if the kite-reeling direction is not "the" answer, that NASA could turn out to be just one more misguided money-loser? Is there a desire on the part of NASA to try and play a role in whatever technology emerges with economically-useful products for power generation? Or is NASA interest restricted to just reeling kites?

                                  6) Do you yourself, or does NASA, have an official position with regard to the only AWE technology demoed at the first world AWE conference in 2009 at Chico, the technology that was still up and running the next day after being left unattended overnight, built for a few hundred bucks, Superturbine(R)?

                                  7) After I authored the AWE Primer for NASA, explaining the 3000-year history of wind energy that started with the pulling force on membranes in 1000 B.C and has transitioned to spinning airfoil blades (known as rotorcraft in the field of aviation), does NASA have any feedback on what I outlined as the proven false trails in wind energy and the tendency for newbies to gravitate toward "rediscovering" the entire progression of the art, starting at the pulling thrust force on membranes, and culminating on steady-state, spinning propellers? Where does NASA now feel that it is, in this well-known and oft-repeated historical progression? What year are you now at, in the well-worn 3000-year trail?

                                  8) Does NASA have an official position on my assertion, in that Primer I prepared specifically for NASA, that a Venn diagram showing the intersection of the set of known, working aviation technologies, and the set of known, working wind energy technologies contains only one thing: a helicopter rotor in autorotation, also known as the autogyro rotor?

                                  9) Is NASA aware that wind energy and helicopter technologies are so similar that a helicopter company was originally called on as the go-to obvious choice to build some of the first windfarm turbines in the U.S.?

                                  10) You have indicated a future program to fly kites and extract power from spools and reels "for a few years" while you "learn". Is this now an official NASA program? Does it exclude other design directions than reeling kites? What decision points led to this kite-flying, reeling effort? What decision points led to the exclusion of other technologies? What decision points led to the decision NOT to work on a design direction that has been shown to work easily, now?

                                  11) I'm building another flying wind turbine now. I could have it running in an afternoon. There is little doubt that it will work the first try. No computers are needed. Yes, learning is what we do, but learning whether it even has a chance to work is a hurdle we passed long ago. On paper, or in the field, this works, here and now. Does NASA have any interest in a technology that can work today, that is at the present intersection of known aviation technology, and known wind energy technology, rather than spending years "learning" about an as-yet uneconomical technology that may or may not eventually bear fruit?

                                  11) Was there a process to NASA'a (or your) choice of what technology to pursue? Is this decision-making process public?

                                  12) Does NASA (or you) see any obligation to completely survey the space and issue a report on the various technologies and their advantages/disadvantages?

                                  13) At this point, what have we as taxpayers gotten out of the NASA effort in AWE?

                                  We've read the press releases. "NASA now involved in AWE".
                                  Well, it's been a few years now, and we've seen press-releases from perhaps 1000 entities purporting to either be entering the field, or more likely to have all the details sewn up, (well on paper at least), (and with regard to sexy renderings), in AWE.

                                  I mean Honeywell, Boeing, now even NASA - is there any limit? Where's the beef? Where's that working system we can see operating today, like the several wind turbines on site here, spinning right now? Waiting for the Chinese to perfect it for you?

                                  We can go back to the press releases of Magenn a few years back and read about problems solved and a new way to power our civilization from the sky. Only thing is, did any of it turn out to be true? Out of 1000 press-releases in AWE, how many turned out to be true? Well to judge from the field of wind energy in general, out of 1000 press-releases for new wind energy technologies, perhaps zero-to-1 will be true, if you are lucky.

                                  So thanks for participating, thanks for breaking out of the mold of researchers who refuse to try anything new, thanks for communicating, and I'll be really eager to read back the answers to the questions I've posed above!
                                  :)
                                  Thanks
                                  Doug Selsam



                                  --- In AirborneWindEnergy@yahoogroups.com, "North, David D. (LARC-E402)" <david.d.north@...> wrote:
                                  >
                                  > PierreB,
                                  >
                                  > So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the "real-world" knock-down factors that need to be applied to Loyd's ideal power equations. Variables will include L/D, flight path, altitude, tether length, kite design [ram air, inflatable,semi-rigid, rigid], reel-out/in speed vs. wind velocity, etc..
                                  >
                                  > The ultimate goal is to determine if a ground-gen can really compete with tower-based turbines (I respectfully disagree with some assessments in the AWE community that it cannot). I believe that it can compete at a minimum , in the short term, in certain "niche" markets and maybe, long term, on a grand scale with AWE being a significant portion of wind energy production. As DougS says, the commercial viability of AWE will be determined not by "government bureaucrats" like me (it's pretty funny that Doug characterizes me like that, because I identify more with the inventor types) but by the doggedly determined inventor/entrepreneurs. We at NASA are just trying to help the effort by doing whatever we can by getting a better understanding of the real-world factors through experimentation.
                                  >
                                  > Dave North
                                  > NASA Langley
                                  >
                                • Pierre BENHAIEM
                                  The common element among AWECS is tether and needs searches for: -lightness; -low drag; -protection against lightning both for flygens and groundgens; -for
                                  Message 16 of 20 , Sep 1, 2011

                                    The common element among AWECS is tether and needs searches for:
                                    -lightness;
                                    -low drag;
                                    -protection against lightning both for flygens and groundgens;
                                    -for that new materials or improvements of existing materials...

                                    PierreB
                                    http://flygenkite.com


                                    > Message du 31/08/11 17:38
                                    > De : "Doug"
                                    > A : AirborneWindEnergy@yahoogroups.com
                                    > Copie à :
                                    > Objet : [AWECS] Re: Irregularity and perhaps not so good output in crosswind motion
                                    >
                                    >  

                                    > Hi Dave North:
                                    > Thanks for posting here, communicating with the people, more than most "bureaucrats" do. I didn't mean that term "b-crat" in a perjorative way, as it is sometimes used. I just meant you work at a "bureau". Don't know a better term, but "government researcher" might be more appropriate.
                                    >
                                    > From the beginning I have been puzzled by your role in AWE. The questions would be:
                                    >
                                    > 1) whether you represent NASA, or just work there and represent yourself as an independent inventor in AWE. both? cake'n'eat-it-too?
                                    >
                                    > 2) whether you can offer assistance to all AWE players equally, or whether you (or NASA) are in fact a player with your own interests. A Collaborator or a competitor? a bystander?
                                    >
                                    > 3) Whether you have indeed surveyed the space and technologies adequately, and assessed each. If so what are your results? Where can we read about the thought process leading to your current actions? Does NASA have a position on the viability of any technology? What has NASA now learned, that could help U.S. Citizens and companies, that could be said to be a result of the work performed so far?
                                    >
                                    > 4) What is the official NASA position on the various technologies? Let's just take the most famous example, with the most press releases: Magenn - does NASA have an official position on inflated, elevated Savonius technologies like Magenn?
                                    >
                                    > 5) Is there any concern that you (NASA?) could be duplicating the efforts of several high-visibility teams funded with millions of dollars that have produced no economically-workable technologies (product) yet for all those millions spent? Is there any concern that if the kite-reeling direction is not "the" answer, that NASA could turn out to be just one more misguided money-loser? Is there a desire on the part of NASA to try and play a role in whatever technology emerges with economically-useful products for power generation? Or is NASA interest restricted to just reeling kites?
                                    >
                                    > 6) Do you yourself, or does NASA, have an official position with regard to the only AWE technology demoed at the first world AWE conference in 2009 at Chico, the technology that was still up and running the next day after being left unattended overnight, built for a few hundred bucks, Superturbine(R)?
                                    >
                                    > 7) After I authored the AWE Primer for NASA, explaining the 3000-year history of wind energy that started with the pulling force on membranes in 1000 B.C and has transitioned to spinning airfoil blades (known as rotorcraft in the field of aviation), does NASA have any feedback on what I outlined as the proven false trails in wind energy and the tendency for newbies to gravitate toward "rediscovering" the entire progression of the art, starting at the pulling thrust force on membranes, and culminating on steady-state, spinning propellers? Where does NASA now feel that it is, in this well-known and oft-repeated historical progression? What year are you now at, in the well-worn 3000-year trail?
                                    >
                                    > 8) Does NASA have an official position on my assertion, in that Primer I prepared specifically for NASA, that a Venn diagram showing the intersection of the set of known, working aviation technologies, and the set of known, working wind energy technologies contains only one thing: a helicopter rotor in autorotation, also known as the autogyro rotor?
                                    >
                                    > 9) Is NASA aware that wind energy and helicopter technologies are so similar that a helicopter company was originally called on as the go-to obvious choice to build some of the first windfarm turbines in the U.S.?
                                    >
                                    > 10) You have indicated a future program to fly kites and extract power from spools and reels "for a few years" while you "learn". Is this now an official NASA program? Does it exclude other design directions than reeling kites? What decision points led to this kite-flying, reeling effort? What decision points led to the exclusion of other technologies? What decision points led to the decision NOT to work on a design direction that has been shown to work easily, now?
                                    >
                                    > 11) I'm building another flying wind turbine now. I could have it running in an afternoon. There is little doubt that it will work the first try. No computers are needed. Yes, learning is what we do, but learning whether it even has a chance to work is a hurdle we passed long ago. On paper, or in the field, this works, here and now. Does NASA have any interest in a technology that can work today, that is at the present intersection of known aviation technology, and known wind energy technology, rather than spending years "learning" about an as-yet uneconomical technology that may or may not eventually bear fruit?
                                    >
                                    > 11) Was there a process to NASA'a (or your) choice of what technology to pursue? Is this decision-making process public?
                                    >
                                    > 12) Does NASA (or you) see any obligation to completely survey the space and issue a report on the various technologies and their advantages/disadvantages?
                                    >
                                    > 13) At this point, what have we as taxpayers gotten out of the NASA effort in AWE?
                                    >
                                    > We've read the press releases. "NASA now involved in AWE".
                                    > Well, it's been a few years now, and we've seen press-releases from perhaps 1000 entities purporting to either be entering the field, or more likely to have all the details sewn up, (well on paper at least), (and with regard to sexy renderings), in AWE.
                                    >
                                    > I mean Honeywell, Boeing, now even NASA - is there any limit? Where's the beef? Where's that working system we can see operating today, like the several wind turbines on site here, spinning right now? Waiting for the Chinese to perfect it for you?
                                    >
                                    > We can go back to the press releases of Magenn a few years back and read about problems solved and a new way to power our civilization from the sky. Only thing is, did any of it turn out to be true? Out of 1000 press-releases in AWE, how many turned out to be true? Well to judge from the field of wind energy in general, out of 1000 press-releases for new wind energy technologies, perhaps zero-to-1 will be true, if you are lucky.
                                    >
                                    > So thanks for participating, thanks for breaking out of the mold of researchers who refuse to try anything new, thanks for communicating, and I'll be really eager to read back the answers to the questions I've posed above!
                                    > :)
                                    > Thanks
                                    > Doug Selsam
                                    >
                                    > --- In AirborneWindEnergy@yahoogroups.com, "North, David D. (LARC-E402)" wrote:
                                    > >
                                    > > PierreB,
                                    > >
                                    > > So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the "real-world" knock-down factors that need to be applied to Loyd's ideal power equations. Variables will include L/D, flight path, altitude, tether length, kite design [ram air, inflatable,semi-rigid, rigid], reel-out/in speed vs. wind velocity, etc..
                                    > >
                                    > > The ultimate goal is to determine if a ground-gen can really compete with tower-based turbines (I respectfully disagree with some assessments in the AWE community that it cannot). I believe that it can compete at a minimum , in the short term, in certain "niche" markets and maybe, long term, on a grand scale with AWE being a significant portion of wind energy production. As DougS says, the commercial viability of AWE will be determined not by "government bureaucrats" like me (it's pretty funny that Doug characterizes me like that, because I identify more with the inventor types) but by the doggedly determined inventor/entrepreneurs. We at NASA are just trying to help the effort by doing whatever we can by getting a better understanding of the real-world factors through experimentation.
                                    > >
                                    > > Dave North
                                    > > NASA Langley
                                    > >
                                    >
                                    >


                                  • Robert Copcutt
                                    The most important quality of a tether is its price. The only way to protect from lightning is to bring the kite back to ground level. I am compiling a
                                    Message 17 of 20 , Sep 2, 2011
                                      The most important quality of a tether is its price.

                                      The only way to protect from lightning is to bring the kite back to
                                      ground level.

                                      I am compiling a spreadsheet with the properties of tether materials. I
                                      do not get much time to work on it but will post a link when it is a bit
                                      more advanced.

                                      Robert.


                                      On Thu, 2011-09-01 at 13:56 +0200, Pierre BENHAIEM wrote:
                                      >
                                      >
                                      > The common element among AWECS is tether and needs searches for:
                                      > -lightness;
                                      > -low drag;
                                      > -protection against lightning both for flygens and groundgens;
                                      > -for that new materials or improvements of existing materials...
                                      >
                                      > PierreB
                                      > http://flygenkite.com
                                      >
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