Choosing between a Short-Stroke or Crosswind Cableway
Long-stroke "yo-yo" reeling
is nearing the end of its early proof-of-concept usefulness in AWES R&D,
as modes emerge that better conserve airspace and output smoother power.
Two leading superior modes are Short-Stroke pumping and Crosswind Cableway
travel. These are current KiteLab Group AWES down-selects.
Short-Stoke AWES for electrical generation, involves a high-ratio step-up
transmission to convert kite "grunt" power into high generator speed.
Insofar as the kite sweeps "approximately transverse to the wind" during
the stroke, this is "crosswind kite power", as defined by Loyd. One
limitation is that the kite cannot be maintained aloft in lulls by
back-driving the system. The transmission requirement is a significant
capital cost or life-cycle issue. This is a single anchor solution, so
scaling requires going longer and higher with a bigger kite or kite stacks
The crosswind cableway AWES was documented by Dave Lang, as conceived by
Joe Hadzicki (DF 2004). A kite buggy hauls a crosswind cable back and
forth to turn a generator at high-speed, without need of a step-up
transmission. KiteLab replaces the buggy with a flying "pod". In
principle, the crosswind cableway can be back-driven to tow the kite back
and forth in lulls. As the prevailing wind direction shifts (i.e., around
weather front passage), the cableway needs to be rotated, or perhaps the
kite moves to an upwind crosswind leg of a polygonal layout. Capital cost
can be kept low, but maintenance and operational overhead is fairly high.
To scale up the crosswind cableway, many kites can operate side-by-side,
driving the cableway as a gang-line.
Either AWES option can be favored, depending on particular conditions.
Land foot-print and airspace utilization seems like the major factor of
which to choose in a given context. Important secondary factors include
kite control preferences. Capital cost variation does not seem to be the
major decision driver between Low Complexity AWES options like these.
Comment and development of this topic will be occurring here.
All, send notes, links, drawings, papers, videos, plans, safety-critical
findings, and photographs!
- Terms and aspects:
- Related links and concepts:
- Commentary is welcome:
Land footprint for some crosswind-cableway AWES could approach zero.