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Power-Out Intermittency Notes
The problem of inherent Wind Intermittency v. Baseload is
not our central AWE problem. Thousands of engineers with billions in
investment are working on utility-scale storage, so we need only await the
winners.
Most intermittency is a trivial design issue. KiteLab's AWECS with a Seiko
self-winding chronometer "ground station" produces super-smooth output
from the wildest input. "Clockwork" is legacy tech.
Our problem is AWE power-cycle intermittency. Pierre is right that
its mostly just a cost, but any cost is bad. If a generator is inherently
only producing 60% of the time and motoring retract 40%; that is not great
ROI compared to a continuously driven generator.
Running generators hot with lots of cycling loads, G-forces, etc, will
greatly reduce reliability and life due to accumulating mechanical wear of
the insulation in the coils. The best and most profitable generator regime
is steady operation at just the right temperature.
Looping kiteplanes, as we have seen them so far, have high amplitude
variation in power-out during the loop. The solution is counter-intuitive:
the loop must be laid back downwind just as Dutch windmill rotors are
tilted back (and also angled sideways to cancel g-force asymmetry). One
needs a lifter kite (incl. arrays) to hold up tilted-back loops and it is
the kite's "jellyfishing" that buffers the power signal. The reason for
back-tilt is the surface wind gradient. Only a back-tilted loop
experiences a level "apparent crosswind". The side angle needed allows the
(struggling) rising kiteplane to see more apparent wind, while mostly just
using free-fall force for the descending side.
Figure-of-eight patterns are best with a brief retract at the top of each
ear of the eight. Pump-retract optimal frequency is at the fundamental
harmonic of the kite-tether, based on biomimetic models.
CoolIP
~Dave Santos May
15, 2011
M3576
Comment and development of this topic will be occurring here.
All, send notes, drawings, and photographs!
Terms and aspects:
- Distinguish between variability and intermittency.
- Distinguish between AWECS production of energy and the problem of
storage of energy.
- Smoothing electricity characteristics from intermittent and variable
inputs for feed to a consumption grid
- g-force
- AWE power-cycle intermittency
- jellyfishing
- power signal
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Related links:
Commentary is welcome:
- Recall that an AWECS may be designed to produce electricity or heat
or traction or fluid pumping or lifting of objects (for transport,
moving position, or storage of potential energy). Intermittency and
variability of wind plays differently as challenge in the various types
of energy production or task set for an AWECS.
JpF May 15, 2011
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M3575 PierreB brings forward the period
of time for storage of energy as a special consideration.
May 15, 2011
- The very tether set of a KES stores some potential energy in its
elasticity. Consider how bungee launch of a glider works: store energy
in the stretched bungee and then release the anchored glider and watch
the glider use the stored potential energy for its kited launch; the
elastic potential energy is converted mostly to increasing the kinetic
and positional potential energies of the glider for airspeed increase
and altitude increase. JpF May 15, 2011
- DougS supports focus on AWE, not the storage challenge:
HERE. May 15, 2011
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