NearZero AWE Expert Elicitation Process (WindLift Role)
- Dear Rob,Its a still unresolved complaint that NearZero cooked its AWE policy poll results and particularly relied on your opinion in favor of rigid wings for AWES to help manufacture an expert "consensus" view in favor of rigid-wings for the purpose of informing US Government R&D priorities.* What could be worse than willfully perpetuating a mistaken technical opinion to trusting decision makers? Lets make sure we finally settle this controversy factually.Thanks for providing your specific basis for the NearZero cited opinion- that large soft-wings cannot be made to retract at an acceptably low CL,but large rigid wings can. The following facts are offered in rebuttal of this view-- All soft wings in principle can be folded or otherwise furled for zero CL.- Stability of a furled wing package is a unsolvable problem; in fact its been solved endless times (take sailing, skydiving, and aerospace-decellerators as examples).- AWES cycles requiring a retract cycle are obsolete in AWE thinking, however big a role they have played in early experiments. Long retract cycles waste critical airspace, with inherently uneven power output to correct. To presume a retract requirement exists is backwards AWE thinking.- The best AWES schemes do more-or-less constant crosswind motion; which soft wings manage just fine, with no furled-retract required. KiteLab Group has done many crosswind AWES designs with fabric wings, none of them retract-based. You only need to closely follow AWE conceptual progress to see the soft-wing "no-retract" paradigm thriving.- Rigid wings are in fact more severely scale-limited than soft-kites, by the far greater cubic-mass scaling penalty incurred (plus mass-velocity based regulatory safety restrictions). Soft-wings are predictably scaling far better, for greatest unit-power. This is why the largest wings ever made are soft, and AWES peak-power records are set by soft wings, while rigid wings are increasingly marginalized in R&D circles.Please reconsider your public opinion regarding soft-wing scalability in light of these facts, or at least allow that your 2011 opinion (as a wing non-specialist) is not a solid basis for US decision-makers to act on,Sincerely,Dave SantosPS NearZero is most faulted for manipulating the "voting" on the rigid v. soft question (purging experts like JoeF and me, while allowing a Makani pile-on). The elaborate new legal disclaimers on the Near Zero website do nothing to reduce NearZero's obligation to provide the best possible expert-elicitation process.* NearZero Final Report- "...Rob Creighton, CEO of Windlift, was quoted: “Fabric systems [suchas kites] will not scale well to grid scale electricity..."----- Forwarded Message -----
From: Robert Creighton <rob@...>
To: dave santos <santos137@...>
Cc: Joe Faust <joefaust333@...>; Steve Davis <sjdavis@...>
Sent: Thursday, September 13, 2012 7:13 AM
Subject: Re: Soft Wing Scaling
Dave,Fabric wings are great for pulling. It is difficult to get a fabric wing with a large enough Coefficient of Lift that can also achieve very low CL's during retraction without becoming unstable. I believe these challenges can be met on a smaller scale with semi-autonomy, but not on a larger scale.If you have a bridling scheme/control cycle which can achieve those goals, and have achieved reliable, continuous, autonomous net power production with a fabric wing, I would love to see it.Best Regards,RobOn Wed, Sep 12, 2012 at 4:39 PM, dave santos <santos137@...> wrote:
You are quoted in Near Zero's report regarding scaling of "fabric" wings. Are you aware of the counter-case for this opinion? Sky Sails farm concept is just one of many examples of superior scaling of soft tensile structure. Your comment seems to disregard these giant wings.
Why do you think rigid wings will scale better?
PS Here is my team's latest super-cheap 1/40 scale 300m2 soft wing power-kite in action. We will be lifting multiple WECS with it-
► 0:40► 0:40 Powerful Mega-kite MOTHRA1 shakes off wet sand...
youtube.comSep 3, 2012 - 40 sec - Uploaded by UtilMovement
In order to roll up and stow the giant kite arch, Dave Santos launches the sand covered MOTHRA1 in high ...--
Robert Creighton, President - WindLift, LLC - www.windlift.com - rob@... - (608) 332-7661 (mobile)