I believe this design is super collectable and highly stackable:   http://youtu.be/wA4rYK_Ztyc
OK it needs a few patches sewing, bearings set to shafts threaded through sail and pulleys run and mounted collected to a bottom gen... but otherwise ...
Nothing that any robot worth it's grease cannot do
CC3.0 nearly commercial BY SA

Rod Read

Windswept and Interesting Limited
15a Aiginis
Isle of Lewis
HS2 0PB

07899057227
01851 870878

http://kitepowercoop.org

CC BY NC SA

•  ~ ~   12Feb2014           Discuss at: AirborneWindEnergy/conversations/messages/11529

Comment and development of this topic will be occurring here.       
All, send notes, links, drawings, papers, videos, plans, safety-critical findings, and photographs!

• Terms and aspects:  
  • ST    Superturbine®
• Related links and concepts:  
  •  
• Commentary is welcome:
  • Rod added a note:   |
    Nature's similarity case...
    Energy sourcing mounted on stacked wings
    http://www.underwaterphotography.com/Photo-Contest/underwater-photo.aspx?i=77306#.UvyB_LSLOM8
     
  • Rod,   You don't really show the massive torque drives in the Mothra-ST model, which are the ST problem part. You missed early discussions over why "rotating-tower" driveshafts won't scale like rope-driving.
    
    The turbine placement is curious; besides a forward leaning shaft, what advantage is there? The in-wing turbine disc location looks to add parasitic drag, spoil Bernoulli lift, and even develop negative lift. A seeming hot-spot for a kite "turbine on a wing" is just under the TE, counter-rotating against the vorticity of local span-wise flow.
    
    Keep in that pumping turbine stacks are a contender (SkyMill). You don't know our friend, Grant Calverley (DaveL you know), but it is easy to overlook the Skymill non-driveshaft autogyro option, in all the smoke.                      ~DaveS                   12Feb2014    
     
  • Thanks Roddy:
    My take(s) on this high quality rendering is:
    1) SuperTurbines(R) that slant upward exert positive lift. Slanting downward tends toward negative lift, tending to pull the whole thing down.
    2) The whole "Mothra" fixation thing is getting a bit overdone. Seems like it's mostly about pretending Dave S. is doing anything about airborne wind energy as he plays with tarp kites. As others have pointed out, nobody has really shown the pertinence or applicability of the arch kite configuration over other configurations. Sure it eliminates a lateral spar in favor of relegating that duty to the Earth, which could be a good feature. That assumes there is some advantage to a very wide kite in the first place, which there may be, but also maybe not so much... Unfortunately it loses the advantages most every other kite has, which are natural and passive downwind aim from a single pivot point, and the ability to travel across the wind, which many systems use to increase relative wind.
    
    All in all, while it seems like one of thousands of configurations that "technically COULD work OK", I don't see any compellingly advantageous use of material, use of space, nor any suggestion of superior performance, nor any particular suggestion that it would be easy to deploy, easy to un-deploy or stow, nor what one would do with it when the wind died, or if the wind gets extra-strong. I do see a large circular track. That looks expensive. Reminds me of the old joke about how many idiots does it take to change a lightbulb?    Answer: 1000, one to hold the lightbulb, and 999 to rotate the building. In this case it's how much material and infrastructure that same idiot might need to allow a wind turbine to change direction, when simply attaching a tether to a fixed point is normally all that is required (just unscrew the lightbulb - wait, just LET the lightbulb unscrew by itself...). Hey forget re-aiming individual turbines, let's re-aim the whole windfarm!
           Roddy you are great at rendering. Reminds me of the days when I used to say "I could live work, and shop in 3-D CAD", and the 3-D drawings did get me there, to a certain point. Plus the renderings of an artist from Dreamworks. Well after enough "conferences", articles in PopSci, PopMech, several green energy and wind energy magazines, a couple of Discovery Channel videos, and getting to meet some of the richest and most influential people in the world, I realized all the hype was just that: hype. No matter how much attention I was able to garner (and it got boring after awhile), the reality I saw was even companies who understood exactly how to do wind power nonetheless were going bankrupt, no matter how many grants and investment dollars they could take in. I realized the whole industry, VC people, multi-letter agencies, famous authors, and all the rest, there were only a very few who could actually create a RELIABLE wind energy system, of any kind, that did not break down. This seemed to be a rare talent, and it further became apparent that it was one more case of those who talk don't know, and those who know, don't talk". I decided to skip the hype and develop reliable solutions. So, render away, blog away, but in the end, a reliable and powerful wind energy solution will need to be constructed, produced, marketed, etc., and all the talk, blogging, internet debates, all the hype, all the conferences, all the grants, and all the multi-million-dollar cash influxes, and even Mothra renderings showing a circular track, will not change that simple fact.     :)     ~  Doug S.
     
  • Rod,
    Keep in mind that Mothra was born to scale beyond anything else flying, fundamentally, as a COTS soft-kite*. Adding ST drive-shafting negates the advantages. Using Mothra lift to overcome avoidable WECS mass is not synergy.
    
    The most promising WECS arrays for Mothras to host are also soft, perhaps a giant pair of opposed looping parafoils, or even a vast curtain of tiny flygen HAWTS. Big sticks (driveshafts, rigid-wings) are not just parasitic flight-mass, and poorly scalable, but something serious to break. Chordwise sticks, as the mash-up shows, want to act in compression, contrary to the usually supposed ST driveshaft pre-tensioning need. Mothra will do far better with no added brittle-structure failure-modes.
    
    The most predictive WECS bench-mark is highest power-to-weight. Mothra does this for lift-force, and the choice of WECS should be comparably potent. ~30% stream-tube conversion efficiency has been shown for membrane wing-mill variants [U. Maine], which may be a power-to-weight winner over even an ideal turbine. ~30% is a common range for "ugly" WECS to live (like the venerable Aeromoter). Evolved Mothras really might flap in monstrous wind-driven bulk motions, to outpower any adjunct method.
    
    ~ DaveS       12Feb2014
    
    * Tarps v. Formula Racer driveshafts in the prototypes underscores a stark philosophical divide between Mothras and STs.