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Re: [AWES] AWES Solidity Factors

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  • dave santos
    We are faced with an over-simplistic conventional approach to solidity as it was taught to us in HAWT design. The shortcomings include-   -Overemphasis of
    Message 1 of 23 , Apr 11, 2012
      We are faced with an over-simplistic conventional approach to solidity as it was taught to us in HAWT design. The shortcomings include-
       
      -Overemphasis of solidity/sweep of the turbine disc area, while ignoring overall solidity/sweep of the entire kite farm airspace.
      -As Robert properly points out, failure to see that there is no one ideal solidity (or sweep) ratio across the wind spectrum.
      -Failure to account for factors that may drive solidity/sweep away from simplistic predictions. For example, a high solidity to maintain flight thru lulls can count for more, operationally, than ideal solidity at the working windspeed.
      -Failure to keep ROI foremost, in seeking abstract performance ideals like optimal solidity. Capital cost and lifecycle cost relate to factors like solidity, but look how many designers skip the holistic analysis.
       
      As agile engineers, we modify any existing concept when it stops moving us forward. We constantly refine or expand the previous standard of understanding, and do not let complaints from orthodox objectors hold us back. That is why we are free to define the new projected solidity/sweep area as the entire kite window*, rather than follow old HAWT norms, as the new view tends toward better maximizing kite farm performance over the previous idea.
       
      * Re: Overlapping kite windows- They violate the empirical principle, "if two kites can interfere, they will interfere". It will be a while before anyone has a system robust enough overcome this "classic kite reality".
       
      Note: Large open kite loop sweep patterns as represented by Makani/Joby clearly let a lot of wind pass thru the hollow center of the pattern untapped, missing the bulls-eye in the Power Zone. A quantification of such sweep/solidity efficiency needs to calculate this center bypass loss.

       
    • Doug
      Yeah a kixel: get yer kixels on route sixty-sixel... Kixel: An addressable kite graphic unit for showing pictures in the sky at kite festivals. The term
      Message 2 of 23 , Apr 12, 2012
        Yeah a kixel:
        "get yer kixels on route sixty-sixel..."
        Kixel: An addressable kite graphic unit for showing pictures in the sky at kite festivals. The term kixel suggests a new kite-based outdoor graphics display. There Dave you now have a job. Not sure what that has to do with AWE...
        In wind energy, the proper terminology for the addressable energy producing unit, after 3000 years, is "blade".
        :)
        Doug S.

        AWE: still learning basic wind energy terms, arguing about terms that may be extraneous, with little flying, and nothing producing...
        NASA: Nothing Airborne Still Analyzing?
        Or were they reeling in and out last I heard? With a multi-year plan to crash lots of kites?

        --- In AirborneWindEnergy@yahoogroups.com, Robert Copcutt <r@...> wrote:
        >
        >
        > >
        > > *poor step to AWE: argue about vocabulary and invent new words
        > > *poorest step to AWE: argue about whether one should be doing poor
        > > step above.
        > >
        >
        > Which is why I let 99.9% of the mistaken thinking I see on the internet
        > slide by. However, sometimes when I think I can bring about useful
        > change I speak up.
        >
      • blturner3
        Yes ROI ROI ROI. I see differences in our viewpoints that has led us to different conclusions. It seems that your working to get the most from low wind speeds
        Message 3 of 23 , Apr 19, 2012
          Yes ROI ROI ROI.

          I see differences in our viewpoints that has led us to different conclusions. It seems that your working to get the most from low wind speeds that I have chosen to ignore. The whole point of going higher is to get away from those low wind speeds. low wind speeds are far more expensive to harvest. I believe there is an ideal target windspeed for a given turbine system at a specific location. I think we naturally tend to design for the locations that we are thinking of at the moment. The location in my mind seems to be windier and more remote than the one your thinking of.

          You seem to be attempting to optimize ground space usage while keeping kites from having any possibility of conflicting. I believe that ground space is not that big an expense compared to the rest of the system, and that the control systems will mature to allow much closer spacing. We let kids drive on the public roads at some experience level. So will we let robot kites fly together.

          As to the hole in the middle. Regular wind turbines are less efficient toward the middle of the hub. The tips do most of the work. I do think that some of your proposals make better use of this space but at the expense of less efficient use of the wind passing through this space. If this is better ROI or not is, in my opinion, an unproven point.

          Brian

          --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...> wrote:
          >
          > We are faced with an over-simplistic conventional approach to solidity as it was taught to us in HAWT design. The shortcomings include-
          >  
          > -Overemphasis of solidity/sweep of the turbine disc area, while ignoring overall solidity/sweep of the entire kite farm airspace.
          > -As Robert properly points out, failure to see that there is no one ideal solidity (or sweep) ratio across the wind spectrum.
          > -Failure to account for factors that may drive solidity/sweep away from simplistic predictions. For example, a high solidity to maintain flight thru lulls can count for more, operationally, than ideal solidity at the working windspeed.
          > -Failure to keep ROI foremost, in seeking abstract performance ideals like optimal solidity. Capital cost and lifecycle cost relate to factors like solidity, but look how many designers skip the holistic analysis.
          >  
          > As agile engineers, we modify any existing concept when it stops moving us forward. We constantly refine or expand the previous standard of understanding, and do not let complaints from orthodox objectors hold us back. That is why we are free to define the new projected solidity/sweep area as the entire kite window*, rather than follow old HAWT norms, as the new view tends toward better maximizing kite farm performance over the previous idea.
          >  
          > * Re: Overlapping kite windows- They violate the empirical principle, "if two kites can interfere, they will interfere". It will be a while before anyone has a system robust enough overcome this "classic kite reality".
          >  
          > Note: Large open kite loop sweep patterns as represented by Makani/Joby clearly let a lot of wind pass thru the hollow center of the pattern untapped, missing the bulls-eye in the Power Zone. A quantification of such sweep/solidity efficiency needs to calculate this center bypass loss.
          >
        • dave santos
          Brian,   We agree on the obvious fact that low wind hardly pays in terms of direct production. What thousands of technical kite flight hours have suggested
          Message 4 of 23 , Apr 19, 2012
            Brian,
             
            We agree on the obvious fact that low wind hardly pays in terms of direct production. What thousands of technical kite flight hours have suggested to me is the operational advantage of coping well with lulls between useful gusts. So while you "believe there is an ideal target windspeed for a given turbine system at a specific location", i think in terms of wind spectrums and kite systems able to handle non-ideal wind speeds in non-specific locations.
             
            Regarding cost  and specific locations, you "believe that ground space is not that big an expense compared to the rest of the system". I believe in systems so cheap compared to ideal market locations near cities and grids, that location is indeed a driving cost. Space wasting systems face a severely limited applicability. Makani's model requires tens or hundreds of acres as a total no-go zone for very small amounts of power, and my rough estimates predict real world land costs will often exceed the base cost of even their high-price AWES, except in the cheapest imaginable spaces without grids, where no one lives. I won't repeat the basic numbers here (see TACO 1.0), but if you have some better calculations showing land use (and airspace use) to be a negligible cost, then please share them.
             
            Its true that common rotors do little work toward the center, but the Makani/Joby geometry hits a deep new low in this regard, letting far more energy pass thru the center than they tap from the circle swept. All this hype about replicating the power of HAWT tips without any offsetting downsides is deeply misleading. Its a subtle point related to tensile v. cantilever structure just why a tethered kite accesses so much power in the center of its power zone pattern, while a HAWT does so away from its axis. Makani/Joby loops are large to counter the centrifugal forces of high-speed high-mass loops with wing lift; not the best use of lift, which is to make net power out,
             
             
            daveS
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