If the stroke is too short you cannot go to high altitudes for the
reasons Bob pointed out. We are agreed that very long strokes also have
problems. One is the change in wind speed that must be accommodated.
Another is that if the tether is wound onto tether already on the reel
you get tether to tether wear. As I pointed out a few months ago this
can be avoided using a moderate stroke constant altitude strategy.
The kite is flown at constant altitude from one side of the power window
to the other. At the end the kite does a steep constant altitude turn
towards the ground station. It is just like an aircraft doing a constant
altitude turn towards the airport. The tether is rewound until the reel
is covered by a single layer of tether. The kite then turns again to
start another generation stroke in the other direction. That way tether
wear is very low because it is always under significant tension and it
experiences limited friction against anything.
In a farm setting each kite sweeps across its own limited altitude
range. All the kites and groundgens are mass produced to a standard
design. The high altitude ones have more tether on the reels. Kite size
will also be adapted to suit the wind speeds at the chosen altitude. The
groundgens will be designed to make reel changes quick and easy and
fully automated. Each reel will have its own kite so even though kites
can only take limited use the set will last years. That way the farm as
a whole will be able to make good use of a wide range of weather
conditions, and be robust and reliable.
On Tue, 2012-10-16 at 11:14 -0700, dave santos wrote:
> There is no one optimum AWES stroke-length. In engine mechanics we see
> short stroke proportions in racing cars and long stroke in utility
> vehicles. AWE design will show similar sensitivity to application
> Long-cycle AWES storage burden drives capital cost higher than
> short-cycle, whether by springs, flywheels, capacitors,
> compressed-air, pumped-hydro, etc.
> Making grids absorb a highly fluctuating supply is not ideal. A smooth
> on-demand variable output from a kite farm is optimal to a grid.
> There is plenty of airspace, carefully used. AWE will not so much
> "compete" for airspace with existing aviation, as much as "share"
> airspace. After all, AWE is a branch of aviation, with its rights to
> airspace based on safety compliance.
> Long-reeling is the most wasteful use of airspace of all AWES
> Many AWES crosswind designs are not flygens.
- 54 teams without a single wind energy person, no doubt... (you can't make this stuff up!) Well certainly with 54 teams, there can be NO DOUBT that they are on the right track, right? I think any bureaucrat would agree with that! Funding please!...
Just remember the joke about the drunk looking for his keys under the lamppost. Why is he looking under the lamppost even though he dropped them somewhere else? The light is better there. (punchline)
Why do people want to make power (force x distance / time) by the pull of a (normally stationary) string? They have flown kites and that pull on the string is what they know. That is the extent of the light of their old, reliable lamppost, and they are stuck under that lamppost because what is beyond the light of the lamppost is unknown. To them.
--- In AirborneWindEnergy@yahoogroups.com, Gaetano Dentamaro <bittertooth@...> wrote:> "[... M.Ippolito:] in the whole world, there are 54 subjects, > Universities, research centers and private firms, who are pursuing, with
> methods identical or very similar to ours, strategies to exploit
> airborne wind energy.
> Q. Among these competitors, did you notice promising technologies?
> A. Not too much; some are too similar to ours (some indeed have built
> machines identical to our first prototype), hence those will be
> short-lived because of the patents, others are too much inferior in
> terms of potentialities."