Rob,
In
the last five years we have made great conceptual progress toward true
Megascale AWES based on fabric wing structure. This new work builds on
the legacy of megascale soft kite pioneers like Domina Jalbert, Harry
Osborne, Dave Culp, Peter Lynn Sr, Dave Gomberg, and many others. Many
of these folks are still actively advancing the art.
No such experts nor their grand discoveries were allowed to influence Near Zero's "rigid wing favored" scaling conclusion. Megascale soft wing expertise was even summarily removed from the Expert Panel. Instead,
your pessimistic opinion of fabric wing scaling was cited as if a
definitive conclusion (despite 4-0 disagreement with your quoted
comment during the panel discussion).
As
WindLift publicly stated at AWEC2012, your team is not really a
wing-expert circle (but your mechanical ground design is outstanding). KiteLab
Group's R&D includes advanced rigid AWES wings flown comparatively,
and in hybrids, with soft wings, across all existing scales. We are
true AWES wing experts, with many important innovations developed and
tested.
The
following fabric-based Megascale AWES ideas have emerged that address
every major concern about fabric wings such as you pose-
1)
Either by scaling law or existence-proof, tensile airborne array
structure is the most inherently scalable wing technology. Its the only
way to do gigawatt-unit scaling. The largest wings ever made are
cellular or modular soft kites ( york', times,
serif;background-color:transparent;font-style:normal;">2) By "staked
out" (multi anchor) arched methods, megascale fabric kite stability is
solved. The Earth itself between spread anchors is the ultimate rigid
"control bar". Graduated porosity is just one of many other
low-tech stability factors to engineer with. Runaway
risk is also mitigated by multi-lines. New methods were developed to
rotate arrays. Cascaded launch of large arrays from a single pilot unit
has been shown effective. Single-line jumbo rigid-wing concepts dependent on complex avionics are much more operationally and stability-challenged.
3)
Megascale actuation is best done by massive industrial ground winches,
rather than expensive super-light aviation-grade actuators with far
shorter lifecycles (<1000hr). Similar logic applies to keeping giant
generators on the ground v flying small generators. Large soft arrays
helping drive the largest legacy generator plants (coal, gas, and
hydro) as "Kite Hybrids" is perhaps the most promising AWES biz model
of all. Near Zero failed to understand how strategic such specific
ideas may prove.
4)
Simple geometric studies and many actual experiments show that dense
arch arrays use land and airspace at up to 100 times greater intensity
than single-line concepts with a comparable scope requirement.
Effective geoengineering to mitigate adverse climate effects is also
far more feasible by the ultimately more powerful dense-array fabric
methods.
5)
True crosswind AWE is just as good with soft or hard wings (by power to
airborne-mass). Yes, a comparative soft wing is bigger by wing area and
does not have so high a "TSR" for equivalent power, but is so-o-o much
cheaper and more robust. Its well worth testing both approaches
head-to-head in comparative trials (fly-offs) to help settle the issue.
6)
Regulatory certification is based on specific factors such as flight
mass/velocity categories, inspectability, and conspicuity. The FAA has
further cited as key issues runaway crash concerns and airspace
utilization efficiency. Megascale fabric and rope arch concepts seem
advantaged in every such requirement.
These
Megascale AWES research findings have plenty of supporting evidence.
For example, KiteLab Ilwaco has tested fabric kites repeatedly in real
icing conditions and found they reliably and continuously shed ice
flakes due to constant flexing, before build up occurs. Other teams validate the same observations about fabric self-deicing. Lift
is destroyed by ice far more readily with fine rigid-wings, requiring
avoidance or expensive added deicing systems (like inflatable rubber
boots or heaters).
To review your soft kite Cl return phase issue-
1)
Your logic is based on long-stroke reeling, an early AWES method widely
considered obsolete in the Megascale AWES study circle. Long-stroke
issues range form poorest airspace usage to high tether wear. A short
recovery phase at the top of a loop or figure-of-eight suffices
(short-stroke method).
2)
Soft Kites offer the most variable-geometry of any wing type, and
therefore the greatest possible control of Cl. Parafoil kites furl to
as little as 1/100 of inflated projected frontal area. Single skin
kites furl even more. These proven modes are available to long-stroke
designers. The gedanken proof offered you involved a hybrid concept- of
a rigid airframe stably ferrying a far more powerful packed soft kite
back along a return-phase. Purpose designed AWES along these lines are
possible, following the common example of roller-furling in sailing.
3)
All major stability concerns are resolved with multi-anchored
cross-linked arrays. One can even imagine the best of all worlds, a
megascale fabric-based vertical-lift arch hosting aloft large numbers
of smaller rigid wings operating crosswind. Chaos of any part is
cancelled by the bulk array, and the part recovers.
For lack of staff domain-expertise, Near Zero never understood the hybrid array concept space as a most strategic R&D option,
and obviously failed to comprehend the key importance of so many other
current ideas. They cherry-picked and cooked expert-provided data to
fit a novice conception of AWES scaling possibilities. Only the full
range of expert design choices allows the best R&D allocations.
Your
concern that no soft wing AWES is in continuous reliable operation is
even more true for rigid wings. A big reason is simply current
experimental logistics. Kitelab Ilwaco has at least demonstrated
continuous reliable self-operation of small AWES, including up to 40
self-relaunch cycles. No fabric element has ever worn out, given
simple maintenance and quick repair, despite some kites flown
relentlessly for five years. Only session constraints limited
operation. Lets
let third-party judged fly-offs determine if complex brittle rigid
wings can really compete with their simple tough fabric counterparts.
Let
me know if any point made here requires more substantiation. I tried to
keep the explanations short, but there is so much more supporting
evidence that could be offered.
Thanks again for elaborating your thoughts on AWES Megascaling theory,
daveS
