Hi Brian:
Thanks for a good critique of my good critique. Rather than another "thought experiment", I suggest someone with engineering skills, who thinks it's worth the time, can easily run the numbers:
1) start with the thrust force of a G.E wind turbine, at a given windspeed, say 25 MPH. Easily calculated based on swept area, using common tables or formulae used in wind energy
2) Modify (lower) that thrust rating for a turbine traveling on rails downwind
3) Subtract the force needed to move the upwind-traveling turbine against the wind, though its blades may be feathered.
4) calculate the resulting power, which is energy per unit time, with energy being force x distance
5) see where you stand compared to the 1.5 MegaWatts any single one of these turbines could be making if left to operate as intended by the educated wind turbine designers.

Compare the cost, including all modifications, with output.
Know why wind energy works? Because it can compete with natural gas-fired power plants. If your power costs more than what you can get out of the wall, forget it. If your power costs more than what the electric company normally pays for power, you will still not be able to get a power purchase agreement, normally required for serious producers of wind energy.

If there's any lesson we learn building turbines and fixing them when they break, it is keep it simple and keep it beefy. Every potential added system or component introduces more failure modes.

And, never assume a turbine can handle high winds without overspeed protection.

--- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@... *** You are funny! Yeah "Professor", I think you are the only one who "understands" it... (he he he)***

This is why so many biological systems use reciprocating motion with elastic materials like resilin, with no necessity for rotation. The output is smoothed, with high overall efficiency preserved.

***interesting - and I always assumed animals don't have wheels because blood vessels would not be able to connect from the axle to the tire. Hey give evolution another billion years and maybe animals will have wheels!"***
***Yeah, you should contact machinery designers and the American Wind Energy Association and put them on notice that you are about to make rotation obsolete! (hope they don't laugh)***

In fact, only one major instance of biorotary actuation exists, the microscopic flagellum motor. Above this scale the penalty of scaling torque drives grows drastically such that the great structural engineering writer, Gordon, proclaimed- "Nature abhors torsion".

***Wow you know some big words. Yeah, I'd forget about using anything that rotates... (insert laugh track here)***

***Sure Dave, keep fixating on that "torque tube", as though I don't have many other ways that also work well***

***The professor has spoken - "hardly seem"is really convincing!***

- that Let Doug try to do rotating AWES to even 200ft without excess weight or hockling defeating him.Doug has never faced that AWES is not just windpower but also aviation, and that power-to-weight is the dominant flight design parameter.

***Yeah I've never faced it. That's it. If I "faced it" I'd be flying reciprocating kites...***

"Overspeed" in the conventional HAWT sense is a lesser issue, with new operational means to tame it.

***Dave your delusion is matched only by your focus on somehow rebutting every idea I have ever introduced. Yes, overspeed protection is not a factor at all for people who only imagine they are working in wind energy***

***Once again, professor, you speak with such authority - let's see an example lest we begin to doubt your veracity...***

***There is nothing so laughable in wind energy as people who cannot produce ANY wind energy whatsoever, despite years of attempts, endlessly deriding all that IS, in lieu of all they promise to create. One thing we notice though is the statements of superiority always refer to future activities. They kick and scream for years, and always end up sulking away with tail between legs and head hung low, with the attitude of "What are you still bringing that up for?"***

***Yeah "likely this" and "likely that" - Dave, unknown to you, you are one of the greatest comedy routines to ever besmirch wind energy. Really, thanks for endless laughs! You have me rolling around on the ground almost every day! :)))***
Doug Selsam

Power kite kayak sailing fast in Goa   

Thanks for the assurance that we have got at least something right.

Having spent over 20 years in "undeveloped" areas I have a good idea
what does and does not work in such places. Certainly good technology is
good everywhere and likewise for rubbish. However, there is presently a
very large disparity between the earning potential of people in
different places, but the cost of diesel generators and fuel is much
less variable. Manually operated AWE systems will therefore be
economical first in poor areas. It is our expectation that AWE systems
will gradually get increasingly automated. In the meantime we think we
have an idea worth starting with.

Hugh Piggott has had some success introducing self-built turbines to
poor communities. There is a recent video of him at a conference talking
about his experiences. I can dig out the URL if anyone is interested.

Olly has posted a video from the test day here
http://www.youtube.com/watch?v=4ryOlAG2V80&feature=youtu.be

Robert.

Joe,

Thanks for passing on Dave Culp's interesting reply. The end of his
message seems to have been chopped off.

According to this
http://en.wikipedia.org/wiki/Cuben_Fiber
Cuben fiber has been around 20 years. The fact it is not more widely
used by now suggests it is yet another example of innovators not being
able to get their inventions launched to their full potential.

Robert.

On Thu, 2012-05-31 at 09:49 +0200, Theo Schmidt wrote:
I doubt it is a fantasy, just a few years into the future. Highly
automated robots will knit or weave high strength fibres into highly
optimised shapes to create kites with superb properties and low cost.

Yet another advantage of reel in/out systems is that the hazard area is
tiny. Use 2 or 3 tethers. If one breaks simply use the others to reel
the kite in faster than its free-fall velocity. It can then be safely
docked without anything falling in inconvenient places.

Robert.

On Sun, 2012-06-03 at 13:34 +0000, Doug wrote:
Efficiency is of tiny consequence. What matters is cost of energy. Costs
are very hard to predict but my bets are on pumping cycle systems.

Again, of tiny importance compared to cost of energy.

As I have pointed out before nearly all AWES will be connected to the
grid or batteries so intermittency is of no problem.

With groundgen systems the gearbox, or chain drive, can be built bulky
enough to be reliable.

Does not matter.

It is tension which is by far the most cost effective.

Can be speeded up.

It can be done in many ways.
1) Change kites to suit conditions.
2) Change flight altitude.
3) Change angle of attack of kite.
4) Put a torque limiting clutch between the reels and generator

Skysails have already demonstrated an automated system.

It will come as confidence in the computer algorithms grows.

Simply reel the kite in to its docking station.

Robert.

On Tue, 2012-05-22 at 13:26 +0000, Doug wrote:
Actually I have built several, including the Hugh Piggott design turbine
that can just be seen on the horizon of some of the Visventis first test
pictures.

That is a popular way of doing things but usually major innovations come
from taking the trouble to understand the theory in great detail.


Reliable protection of all wind energy generators (turbines or AWE)
requires sophisticated electronic circuits. Grid-tie often involves
maximum power point tracking (MPPT) circuits that have the intelligence
to protect the generator.

Agreed that the ability to shrug off strong winds is critically
important. Modern electronics allow us to build systems that do it more
reliably.

Robert.

The full reply from Dave Culp shows on the online view of the forum message: 

--- In AirborneWindEnergy@yahoogroups.com, Robert Copcutt <r@...
***Wait a minute - weren't you the one denying that power was proportional to RPM squared? So you understand in great detail, and I don't? Are you serious? Are you making a better alternator than me with your "advanced understanding"?****

***Yeah sure, we real wind energy people are presently in discussion of why half of the Skystream turbines in the Sam's Club parking lot in Palmdale, California, have been non-operation for the past 2 years. The Skystream was developed by Southwest and NREL, using just such circuitry as you mention. They are famous for failure. Electronics can only save you up to a certain windspeed***

You are still in discussion which means you don't know the full story
yet. Small turbines have to take short-cuts to keep costs down. MW level
turbines use electronics to turn their blades so that they receive
minimum force from storm winds. It already works at the MW level. The
cost of control electronics is dropping fast so even small wind power
systems will soon have no option but to embrace it. To survive in
industry we have to watch the trends and keep up with the important
ones. AWE without computer control will always be a sidelined
technology.

Robert.

It's come to this...before you all start.. this is very relevant.

J.E. Gordon tells us that back in the 50's, when adjusting the helical winding angles on a cylinder became part of rocket science, two separate lines of investigation were both inspired by the bias-cut dresses of Mlle Vionnet.  The first spectacular demonstration of properly minding the fiber orientation in engineered textiles resulted in a certain piece of silverware becoming known forever after as "the America's Cup, since she so thoroughly pwned the British fleet.  Since then, fiddling with those angles also became familiar to the makers of rubber tires.  

Perfect Rod. Thanks. 

Couple of methods for long inflatable spars: 

Here is a german patent Rotor blade for wind farms  see fig.1 and 2.See also Winflex Wind Turbine . 

Blades should be enough rigid to keep a good profile in spite of air pressure due to apparent wind speed,but it is not obvious;is it possible?

PierreB

http://flygenkite.com 

Interesting discussion! I am a bit of a speed kiter myself, and would like to go to the Walvis Bay speed week this year. This is the safer, less extreme one with a squarer to the wind course. The Luderitz course in a channel is for the mad men. I think the innovation potential for Luderitz is small, but wide open for the squarer safer Walvis course.

If there are any ideas someone wants me to try should I go, let me know. At the moment, I believe that the board technology is the bottleneck for speeds. As Dave says, we should use a fin instead of the less efficient board edge, but I do not know whether fins would work (or what type of fins would work) at those speeds since cavitation becomes a huge problem. I was hoping to make a board that uses two fins as the lift element, and was looking for inspiration from the sail rocket (http://www.sailrocket.com/) but it sounds like they are also still trying to solve the cavitation issues.

The next step I thought that would increase the board performance if a fin can't work is to go for two rails in stead of one rail. Ski's in other words. I see the records for snow kiting is far higher on skis than on snow boards, and since water gets so hard at speeds over 50knots, maybe it reacts similar to snow and skis will work more efficiently? I know ski's have been tried for speed, but I don't think enough effort was spent on them. Any thoughts?

Concerning kites, I would love to try make a kite similar to an inflatable, but with large hollow spars instead of tubes. The diameter should be such that it allow the kite to float (hollow spars), but is much thinner than todays inflatable kites' tubes. The thinner leading edge should equate to less drag. Most probably the kite will have so little drag that it flies over your head and falls to the ground in any wind turbulence, but by sheeting in/out on the bar, one can move to a different AOA and hence l/d and hopefully control the kite in such a way until you start going for speed. Any thoughts? Anyone know where I can get materials/advice to make my own fiberglass/carbon spars?

One last question: Why do you say the mass of the kite is critical to L/D? I do not get it.

A ski is a single-surface foil with a terrible aspect ratio.  It should be possible to reduce cavitation on hydrofoils by using a non-lifting angle of attack at the surface, and/or by adding plates to prevent spanwise flow.  Use surface-following sequences of spoon, lead foil and main foil to simplify control, and don't use your body to transmit major loads or maintain balance -  use control inputs for that.  

This German patent starts out, in the first couple of lines, acknowledging that my U.S. patent 6616402 introduced the concept of inflatable blades:
http://translationportal.epo.org/emtp/translate/?ACTION=description-retrieval&COUNTRY=EP&FORMAT=docdb&KIND=A2&LOCALE=en_EP&NUMBER=2025928&OPS=ops.epo.org&ENGINE=google&SRCLANG=de&TRGLANG=en&W=1339421362469
:)
Doug Selsam

• http://en.wikipedia.org/wiki/Donald_Sadoway
• http://lmbcorporation.com/
• http://lmbcorporation.com/news/

On any airborne platform: 

Robert: To this date, all turbines have physical overspeed protection. The only small turbines that consistently survive have ONLY physical overspeed protection. The large turbines ALSO have physical overspeed protection. Of course, at the MegaWatt level, software and electronics play a role in deciding WHEN such physical controls are actively triggered. nevertheless, the entire windfarm thrived for many years with "The Danish Concept" in which blades had no pitch control and there were no electronic controls of the physical configuration. In my book, develop something first that is stable, period, Then we can add Siri at a later date.
Doug S.

Doug,

Let me explain in more detail. Large turbine have anemometers on them,
and computer/electronic control. When the wind is too fast the
electronics tells motors to turn the blades so that the forces on the
blades are minimized. They used to use stall control because it requires
less turning but modern turbines can react more quickly so they feather
their blades. This gives more protection. Even earlier this used to be
done mechanically. Electronic control enables greater capacity factors
and more protection from storm winds.

My belief is that large scale AWE is not viable using only clever
mechanical design. It is the main reason no one has done it yet.
Electronic control will be essential for progress.

Robert.

I'd like to thank Robert for some of the clearest explanations in our archives.  However, I don't think they contain any examples of Doug S. being swayed by any new information or logic, just many complaints from him about the volume of responses he elicits.  He is right that we would be better advised to go fly a kite.

Topic: 

Time lapse flow at just one point on earth: 

Sadoway has been a prominent figure in the global electrochemistry
community for some time. When my last boss's FFC invention was making
world news over 10 years ago he was one of many who jumped on the band
wagon for a while.

He gives a very convincing lecture but when you look at the details it
all falls apart. I too have been studying the period table for decades,
but my conclusions are very different. He has obviously had a lot of
trouble finding a suitable pair of metals. Let us look at the earth
abundance of the relevant metals.

Iron - 50 000 ppm
Magnesium - 20 900 ppm
Nickel - 80 ppm
Antimony - 1 ppm


How he can expect an Antimony based battery to compete with the Edison
battery (Nickel - iron) is a mystery to me.

The Mg is supposed to form a solution in the Sb. How much Mg can
dissolve in the Sb before it starts to float on the salt? How does he
mix the Sb so that the Mg does not concentrate on the top? These are
issues that could kill the project yet he ignores them.

He also tries to paint high temperatures as an advantage. He glosses
over the fact that molten salts are very corrosive. The Edison battery
has been demonstrated to last over 70 years. I cannot foresee his
batteries lasting that long. I have done lots of molten salt work and
corrosion usually destroys most apparatus within a year of careful
part-time use. He also fails to mention what salt he is using. His
patent covers every possibility (there are not that many) so the logical
conclusion is that the salt choice is giving him trouble.

One of my current projects is on cost reduction of the Edison battery.
His battery is unlikely to beat an existing battery yet he has attracted
funding of over $20M. Maybe I should learn to blow my own trumpet as
loudly as Sadoway does. Horrors!

Robert.

Thanks Bob, it is good to know I am getting some way to achieving what I
set out to do. If Doug's skim-reading misses a point I simply take it as
a warning that others may also have misunderstood. If I was writing for
him alone I would send a personal Email. One day a cat might learn to
use a remote control:-)

It seems to me AWE has so far not made nearly the progress it could so
my objective is to prevent, as far as possible, people chasing dead-end
ideas. Eg. flygen and LTA based systems. We need people to concentrate
on a few of the most promising concepts. We urgently need to attract
people with computer control skills to the community. If we can direct
newcomers to first read contributions from the best authors they will
get up-to-speed quicker.

Robert.

Clearly, any modern business needs either a stellar Renaissance man, or a team with a wide range of talents.  Management, promotion, finance and technical skills have to be combined.  The best designers know that there is not just one right answer for all situations, and are quite aware of the uncertainties ahead.  This attitude is anathema to the sales talent.  On one hand, they want to resonate with a simple message, but when they do encounter someone whose results generate word of mouth advertising, they turn away, so that their peers won't be able to say "Well, Anyone could sell That!" 

I have spent a lot of time hanging out with human powered boat developers.  Most determined builders are successful with hydrofoils, but even the most extreme efforts have not achieved normal planing.  

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June 14, 2012, paper received from
Drs. J. M. E. Beaujean
P.O. Box 3006 
NL  5902 RA Venlo      

Paper:    Sky Sails for Wind Turbines 2012   (PDF document)

My background holds  http://www.allaboutcircuits.com/