Cheap Practical AWE
AWE research has tended to envision high-altitude energy kites as based
on sport-style or aerospace-composite traction wings sweeping
figure-eights under active robotic UAV control. This mindset enabled
valuable analysis and demonstrations but technical kiting and
experimental robotics experience suggests that such schemes are
only about a tenth as reliable as advanced UAVs, which are themselves
about a hundredth as reliable as human piloted aviation . Most of the
causes of failure are inherent in the immature technology and will
persist for years. Capital and maintenance costs are particularly high
for aerospace airframes, active controls, and high-altitude flight. An
Low altitude Passive Flight Automation (PFA) based on traditional
single-line kite stability is proposed as a way forward. Passive
methods are cheap, have major performance and safety advantages,
and don't need batteries or many other active-control failure points.
PFA is the lowest-mass aloft solution, essential in good kite
systems. KiteLab has proven that a PFA based lifter kite can hold aloft
unstable hot power generating elements that would otherwise crash far
Low altitude research is also essential to move forward rapidly. Low
altitude kite flight is preapproved by US standards and can be rapidly
adopted by small players everywhere. KiteLab has working systems
operating under the 150 ft FAA approved kite ceiling, while performing
numerous small-scale experiments aimed at higher altitudes with active
elements. Low altitude practice is a vital stepping stone to
Micro-actuation trim-forces applied to a PFA lifter can
begin to bring back active approaches for eventual wide adoption. What's
desired is an actuation-starved agent for a tiny bit of "chaotic
control" over a real-world wind-field case-base for a
PFA lifter-kite. Even a primitive low-dimensional sampling of the Inflow
Wind Field may give such a controller a chance to poise the kite against
perturbation by inflow turbulence or to make small kicks to
dampen threatening aeroelastic oscillations. Kite-killing in runaway
event will be an essential safety function of minimalist actuation.
Considerations for Operation of Different Classes of UAVs in the NAS
~Dave Santos Apr
Comment and development of this topic will be occurring here.
All, send notes, drawings, and photographs!
Terms and aspects:
Commentary is welcome:
- I'm somewhat leery about excess complexity such as computer control
over kite-electric technology. My preference would be to keep the
technology as uncomplicated and as straightforward as possible. Less
complex technology almost consistently delivers higher reliability and
lower long-term operating costs. ~ Harry
- Hey Harry, a generator system I am developing is designed to be a
modular type of device such that it can work on the simplest pulsating
power input like the flipper wings Dave Santos prefers to the much more
complex multi inputs from tower turbine, solar steam, and pretty much
any type of mechanical energy. On the simplest level it can be
completely self governing by mechanical means or with the more complex
multi input arrangements it can be computer controlled to manage the
power ins and outs as programmed for priority needs. I'm still working
to get the prototype built as my finances will allow and will make
public the details when I can get the proper IP stuff documented. I do
intend to make all my stuff open source but I want to make sure that it
is covered first so as to not let it be taken over by those who are not
as willing to share the tech with the rest of the world.
- I am surprised at the absence of standard aerodynamic terminology in
the models described. I would like to hear about your; span, wing
loading, air foils, cables, speeds, power, L/D, weight, scale limits and
materials; these are the main issues I deal with in my designs.
The referenced post was a semantic abstract, not a technical
specification. Specs are available online off JoeF's AWE site.
If you are asking about Lifter Kites, standard types like Morse Sled &
KiteShip's OL are used. Specs are published. DaveC or I can answer
If you are asking about Membrane Wingmills- practical spans range from a
few cm to several hundred m.,
composite membrane & carbon battens preferred but even cardboard &
bamboo is practical.
my biggest membrane wingmill has been 3 m span, 50 cm at max chord, a
new wing under construction is 10 m
foil type is curved plate with turbulators & other tricks.
"cables" are SpectraŽ or DacronŽ.
Power has ranged from milliwatt to a couple of hundred watts, these are
small fast & cheap experiments, kw prototypes are under construction.
Membrane Wingmill concept intended to scale beyond all others.
L/D of most of the wings are in the 4-8 range, some are close to 15 or
so, torsional dampening by swept battens is allowing higher L/D.
What sort of AWE designs are you working on?
- Sounds interesting, Brooks . . . I wish you success. At the present
time there seems to be great merit in combining airborne aeronautical
working apparatus with ground-based electrical generation equipment.
Large generators/alternators would yield greater output and increased
longevity over small, lightweight airborne electrical equipment.
Ground based electrical equipment may also be easier to insulate/isolate
from lightning at some locations.
- Excellent point on the lightning issue although now you just
triggered the gerbil in my head spinning on some new ideas on how that
power could be harnessed. My dad worked with some folks who had made
some attempts many decades ago but I just had an idea that they may not
have tried regarding the many ways to store and convert energy. I'll
keep you posted.
-brooks (and the gerbil that controls him)
- Hi Brooks, You'll need some incredibly large capacitors to
store a charge of lightning . . . . or even multiple strikes.
- When I said "new ideas they may not have thought of " it was
a hint to the common method of extracting/storing energy via direct
electric energy is not the only form of energy that can be extracted
from a lightning strike. Giant capacitors would probably be the most
efficient if they could be charged fast enough to absorb that energy but
as someone who has restored old buildings with damaged lightning rods I
can tell you energy can be take many forms. I'll have to check my my
chief number cruncher to see if the projects he worked on could do the
job as well as the methods that have been tried by the electrical
extract/storage method. There has been some research in the direction
I'm thinking, but not public common knowledge. I'll have to check
on how public before I say more.
The fatal problem with lightning power is low capacity factor and high
capital cost of the equipment, which overwhelmingly sits idle but has
to be massive to handle brief peaks.
Persistent atmospheric charge across altitude seems too diffuse to
usefully collect by any sort of flying conductive web. Convective
cells are big capacitors & might conceivably be discharged at
a reasonable capacity factor (pulsed ionizing energy beams)?, but not
Synthetic lines in a non-saline atmosphere are not lighting
attractive. Aerostats have woven metal jackets on their tethers to
handle lightning. Lightning arrestors are bypass conductors that will
protect a kiteboat or ground generator from damage.
Ultra capacitors are generally only cost effective as load/supply
buffers, not as primary storage. Composite structure can double as
capacitor. Ultra capacitor airframes might charge/discharge by
contacting along skycable networks.
Wind power AWE will be far more practical for a long time than
secondary energy harvests such as from solar thin-film or
static-charges. Piezo hummer ribbon mesh might be a "solid state"
collector someday. A wing yanking on a generator is current best
- No debate here on all these points, Harry just got the gerbil
running on that treadmill in my head, but I have some new ideas on the
storage and transmission of energy. Actually old ideas revisited with a