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Summary of Methods to Modulate Kite Area
for Max Capacity Factor
AWECSs can be designed to handle a wide range of wind conditions by
traditional methods well known to sailing and aviation. Its rare to see a
new method, but flexible combination's of standard methods are common. The
basic principle is to keep wings within the maximum (Load Case) limits in
high-wind (airspeed), but to spread the most wing possible in low-wind.
Sweeping a wing effectively creates virtual area. Calibrated Kill-Lines
and Elastic Aft Bridling can prevent chaotic surge damage. In terms of our
abstract gel physics model for large kite lattices, Densification is the
state of the array when landed at the surface and Rarefaction (saturation)
is the low density extended state aloft. Densification and rarefaction can
be used locally at any fractal dimension.
Classical sailing is done by constant small changes in a sail's Angle-of
Attack (AoA). Sailing often depends on gross changes in the sails set;
increasing or reducing the number and type of sails according to
conditions. With kite systems the varied set of wings to match conditions
is a "Quiver". Dousing, Furling, Reefing (Slab, Jiffy, Roller) comprise
the major state transitions of individual sails. Sails commonly emerge
from Chutes, and a kite field might have underground silos in this role.
Sail pack bags called Turtles, or long Sleeves, are means to handle lots
of sail with less fuss. Packing soft-kites like parachutes is a practical
method, with Kite-Killers to douse. A parafoil or single-skin wing can
progressively reduce span by accordion pleating performed much as a
Braille theater curtain uses drawlines and grommets.
Lazy Jacks are a double "wall" of windwise preventer lines that keep a
sail within bounds as it is raised or doused. There is great potential for
staged Kite-Arrays to raise or douse along lazy-jack lines into narrow
surface corridors, avoiding the clutter of surface obstructions and the
need for extensive land area. Chafing Gear includes special pulley covers
and line sleeves that reduce the wear of rubbing lazy-jacks on sails. Lazy
Jacks are an instance of a "pulley whipple-tree".
Autogyro rotors have an exceptionally wide flight envelope within a
minimal state space. They do not completely cover extreme low-wind and
high-wind ranges, but everything in between is nicely handled by
modulating RPM and collective pitch. Soft rotor-blade roller-furling might
extend rotor wind range unbeatably.
KitePlane Hard-Wings are most at home at higher airspeed and face special
challenges in order to land slowly, especially at larger scales.
Hard-wings have many methods to handle broad conditions. They can stop
sweeping in high wind and "Park". Looping sweep is all-or-nothing between
the parked state ("pasted-to-the-sky"). Figure-of-eight sweeping allows an
intermediate range of Dutch roll sweep between parked no-sweep and
high-sweep. A very basic hard-wing control input is modulation of AoA by
feathering the wing with an Elevator wing or Trim-Tab surfaces, which
corresponds with powering/depowering a common traction kite with its
"Brake Lines". Folding Wings are an uncommon option, as flight balance,
actuation forces, wing mount design all tend to be more radical challenges
than just adding Leading-Edge Slats and Trailing Edge Flaps.
It can be confidently predicted that a successful utility-scale AWECS will
require adequate wing-area modulation means to maximize capacity factor
across the broadest wind and load conditions.
CoolIP
~Dave Santos 26Nov2011
AWE4881
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