Hot seat occupant:

Cross-winding wing of L/D of  1 tethered non-powered kite system wing (tethered flight vehicle) (option choice of at-sea hydrogen aerostat lifter-keeper) using counter-weighted boom traverse to wind for driving groundgen (or seagen) has tiny non-power phase and long power phase without the need for drum or reeling-in or reeling-out actions.   Use sea water to get hydrogen to recharge the slow-leak optional hydrogen aerostat lifter-keeper.    Simple wing design for the L/D of  1 wings.   The L   and  the D  contribute to the force vector that drives the boom that drives the generator shaft.   Tipping-boom technology ...

 

Stefano,

Pag.27-28  "Test performed near Casale (IT), in January 2008. Wind of about 1-2 m/s at ground

level. Kite effective area: 10 m2, maximum line length: 800 m"

shows with AWE it is possible to produce a good amount of energy with quasi no wind at ground.Another thing is trying to know the real output from crosswind motion (not only the peak),according to the variables indicated in M.Loyd's paper,according to eventual other parameters.

I took Windlift video for the datas allowing to begin knowing what crosswind motion can produce by itself.

PierreB 

DaveN,

Another example:Makani choices a loop-path for its (relative) regularity.The curve seems to be a regular oscillation of irregularities.
And Makani explains loop allows more regular conversion.So it is possible that peak power is lesser but average power is higher.By putting aside higher L/D it seems (according to datas) that output is closer to what gives the (for peak?) formula (among other numerous formulas from M.Loyd's paper);something like 1/2 or 1/3 instead 1/5 and less.My idea is that different positions in the window of flight in regard to real or apparent wind,deformations of soft kites,optimization of piloting yes or no,are not enough to explain such a difference.A crosswind kite is a little like a rotor which works then stops then works etc.Nevertheless crosswind kite could be a winning combination.

PierreB

Wherever a foil is getting flipped to travel in the opposite direction as with these arms or a whale's fin, we have a chance to go Ma Nature one better.  A flexible foil, made of rubber or gristle, takes a shape with the opposite camber to what is wanted - like flying a non-aerobatic aircraft upside down.  Instead, we can use strong spars near the leading and trailing edges, with flexible ribs or whatever in between.  This gives a beneficial camber for each direction.

"Establishing this credibility
will have to be done through a centralized scientific establishment
providing peer-reviewed publications and periodicals."  ~ J. Breukels, M.Sc. (now Ph.D)

PAST, PRESENT AND FUTURE OF KITES AND ENERGY

GENERATION   [PDF]

HAWEG   high altitude wind energy generation      Thesis2009LF  
Note: The author uses also "HE" for short form of "HAWE".
Click the "qui" link at the showing preamble page for reaching a quality robust 246-page thesis by Lorenzo Fagiano.

1.     See: Project Sea Tree introduction  (now 8 pages).

2.  See: Moving Root versus Dynamic Sheeting 

 

PierreB,

So that will be one of my main goals in the next couple of years....to get a better understanding, for reel-in/reel-out ground-gen, of the "real-world" knock-down factors that need to be applied to Loyd's ideal power equations. Variables will include L/D, flight path, altitude, tether length, kite design [ram air, inflatable,semi-rigid, rigid], reel-out/in speed vs. wind velocity, etc..

The ultimate goal is to determine if a ground-gen can really compete with tower-based turbines (I respectfully disagree with some assessments in the AWE community that it cannot). I believe that it can compete at a minimum , in the short term, in certain "niche" markets and maybe, long term, on a grand scale with AWE being a significant portion of wind energy production. As DougS says, the commercial viability of AWE will be determined not by "government bureaucrats" like me (it's pretty funny that Doug characterizes me like that, because I identify more with the inventor types) but by the doggedly determined inventor/entrepreneurs. We at NASA are just trying to help the effort by doing whatever we can by getting a better understanding of the real-world factors through experimentation.

Dave North
NASA Langley

To keep in this topic thread the dynamic air version base; Dale's sketch at mid-tether could have a control cabin attached. Click through image for his full application:

Betz did his calculations for the swept area of any wind energy device.
Applying his equation to the area of a kite will lead to false
conclusions. For instance, if the kite moves into air that has been
disturbed by its previous passage through a nearby point in space its
power output will drop. ie. the Betz limit cannot be fooled.

With turbines it is the swept area and not the area of the blades that
dictates how much power can be generated. It is the potential ability to
sweep a much larger area for a given cost that makes AWE so attractive.

Organisations such as the AWEA
http://www.smallwindcertification.org/for-applicants/awea-standard/ ,
the BWEA etc. have already considered this topic in detail. Their
conclusion is that it is best to measure the power curve. We should use
the work already done by these agencies and not try to reinvent the
wheel with a separate AWE standard.

The process of turning a power curve into a predicted energy generation
figure can be a bit involved but spreadsheets like the one I have
developed at
http://www.copcutt.me.uk/WindDistribution.html
make it easier.

Robert.

Via smart soaring:: Use slope lift, thermal lift, wave lift, etc.  to drive turbine in glider and have no tether to ground or even to another wing. Send energy to self-system or to ground by microwave, battery exchange, or laser.  Bizjak sent the energy to the self-system's batteries.  Freeflight AWE or FF-AWE has many categories; this belong in one of the categories where the the tether is absent.  Differently is a category where the free-flight tether is winged at the tether's both end and there is no tether to ground or sea (there are water analogues to a tether with active hull or paravane at both ends of the tether. And recently our group has been discussing the bi-media bi-wing system of similar dynamics).

  Click through text image for full patent filed in June 3, 1938.

To correct the indicated link of topic's starting post:

http://www.google.com/patents/about?id=kSheAAAAEBAJ&dq=2368630

If I am interested in a kite system for harvesting wind power, or some other AWE system, what good would it be to have a standard to generate a power curve for a horizontal-axis wind turbine? If I want to buy a HAWT, I could use that standard to compare it to others on the market, but what good is it when I am interested in AWECS? An involved spreadsheet for turning the power curve into predicted energy generation will not help much more.
Probably the most convincing factor for a new endever is ROI. When I was in industry, operating for profit, If I wanted to buy a piece of equipment, the rule of thumb was that I needed to convince management the invested capital would be recoverd in 2, maybe 3 years. If I convinced my boss that I could get a pay-back in one year, he would scream "GO DO IT, IMMEDIATELY". Pay-back time is a convincing number; even more convincing than a Betz Area Ratio. But, pay-back time is a difficult number to get. If I showed him a chart with a rectangle representing the wing area of the proposed AWECS superimposed on a circle representing the swept rotor area of a state-of-the-art wind turbine big enough to generate the same power as the AWECS, he might at least want to get more information if the circle were sufficiently large compared to the rectangle (even if he were a bean counter). But, if I were to show him a HAWT power curve, he would probably say "Why do I need to know this?" Maybe total system mass is a better parameter for comparison than area...I don't know. I just hope people are not trying to avoid comparison.
Dennis

An extract from  Crosswind Kite Power:

"The criteria for the efficiencies of a kite or its turbine are

somewhat different from those used by Betz.20 The kite wing

sweeps out an annulus that may be compared to a turbine

disk. If the slowing of the wind in this annulus is small, the

kite's efficiency will be low in the Betz sense. However, the

power produced is higher than it would be if the kite were

flying in wind that had been slowed more. Betz's analytical

approach shows that slowing the wind by 5% results in a

9.5%

recovery of the wind energy passing through the annulus.

Since calculations of kite performance have resulted in

Betz efficiencies of a few percentage points, the induced

effects of the kite slowing the wind are assumed to be

negligible in this paper.

When a turbine is used on a kite to produce shaft power, the

efficiency of the turbine is the fraction of the load on the kite

that is delivered to the shaft. For example, a turbine disk area

equal to 11 % of the kite's wing area results in 90% efficiency.

A large-diameter, lightly loaded turbine is efficient in this

sense, but it is not efficient in the Betz sense."

 

PierreB

Interesting concept but what happens when the wind dies? I've been in the Atlantic in flat calms many times. Also I've been in the Atlantic in 70 foot seas and 80 knot winds. How do we make this concept work in both. Also am very interested in estimated upwind performance. Down wind and off the wind these things are great but I'm not sure how high they'll point. I'm not saying it isn't a good idea just wondering how to deal with some real world problems.

Pierre,
I tried to look a bit at those data from Milanese et al:
Milanese reported "37 Wh" produced by a 10m2 kite in about 100sec of active phase. This corresponds to an average power of 1.3 kW during the active phase (530W during a full cycle! similar to windlift but in a weaker wind), infact elsewhere (for the experiment near Casale)they reported 3-4m/s wind speed at 500m.
They claimed these experimental values are in agreement to their predictions (thus Megawatt scale reached by a 500m2 kite with L/D=12 at a wind speed of 10m/s appears plausible).
Notably these claims (as order of magnitude) appear to be consistent with the results reported by skysails (as far as I can understand).
Unfortunately actual data from skysails are not available (I did not find publications yet).
It appears to me that skysails could potentially answer in deep to our doubts about scalability and real performances...
I'll wait also for DaveN conclusions!!

Stefano C

Stefano,

In case of 3-4 m/s wind speed the power of 1.3 kW during the best period of the active phase is huge,except if L/D is very high (6 or 7 instead 4,or if wind speed is a little higher,5 m/s for example).A common point of all curves:power is not regular (you can hear that).And if you pilot a kite by eight-figure you feel the irregularity of the traction.

The value of 10 MW for 500 m² with 12 m/s nominal wind speed and L/D = 12 roughly corresponds to the "simplified analysis" from Loyd's paper,or to a peak of power.But in Presentazione di PowerPoint p.18 wind speed is 15 m/s,other datas being identical.Power increasing by the cube of wind speed,so 10 MW for 15 m/s wind speed induces half of the output of the same with only 12 m/s wind speed.This value is closer of the result on the "detailed analysis",or of the average power.

However crosswind kite power can be very promising for a mass production,with kites with higher L/D,and thiner lines,and now can be useful for some niche markets.

Note:it will be interesting to know results for retrieval phase during glide maneuver according to KiteGen systems .

PierreB 


 

http://energykitesystems.net/images/gangedtrainsToOneGen.jpg

Use AoA alternations for the trains for yo-yo.  Cross-winding  available. Smart sepration?  Netting? Separations?  Multiple lines of shown could blanket large acreage. Mechanical engineers called to solve the ganged drives   : ).   

If you have saved a copy to your local computer, then please note that a change on one page has been made; consider overwriting your study copy of the file:

 

Project Sea Tree introduction

Pierre,
I agree with you. look here at page 20!! http://homes.esat.kuleuven.be/~optec/events/20090526_milanese.pdf
Cable drag and recovery almost halved the power in this simulation!
The output is not regoular for sure, the kitegen group is still working with supercaps to smooth the power output (as far as I know).
I am curious too about the glide manouver; I have been told that it could significantly reduce the useful life of the kite fabric, but unfortunately I had no real data and this could be just a guess.

Stefano

Will study. Great post, DaveS. Thanks.

The preview has ""a total of 22 active companies"  which to me says that the report is 1/5  th of what it could be.   I just sent them our link where they might mine the Stakeholders page; maybe.       GL has no equity hold in any company of interest. However, GL is a neighbor to SkySails.

JoeF

Per report's slant, it focuses on offshore HAWE. See for yourself; but
for me, the tone and slant leads me again to SkySails dominance. It does
not feel like they interviewed KiteLab Group ; )

Hi Dave North:
Thanks for posting here, communicating with the people, more than most "bureaucrats" do. I didn't mean that term "b-crat" in a perjorative way, as it is sometimes used. I just meant you work at a "bureau". Don't know a better term, but "government researcher" might be more appropriate.

From the beginning I have been puzzled by your role in AWE. The questions would be:

1) whether you represent NASA, or just work there and represent yourself as an independent inventor in AWE. both? cake'n'eat-it-too?

2) whether you can offer assistance to all AWE players equally, or whether you (or NASA) are in fact a player with your own interests. A Collaborator or a competitor? a bystander?

3) Whether you have indeed surveyed the space and technologies adequately, and assessed each. If so what are your results? Where can we read about the thought process leading to your current actions? Does NASA have a position on the viability of any technology? What has NASA now learned, that could help U.S. Citizens and companies, that could be said to be a result of the work performed so far?

4) What is the official NASA position on the various technologies? Let's just take the most famous example, with the most press releases: Magenn - does NASA have an official position on inflated, elevated Savonius technologies like Magenn?

5) Is there any concern that you (NASA?) could be duplicating the efforts of several high-visibility teams funded with millions of dollars that have produced no economically-workable technologies (product) yet for all those millions spent? Is there any concern that if the kite-reeling direction is not "the" answer, that NASA could turn out to be just one more misguided money-loser? Is there a desire on the part of NASA to try and play a role in whatever technology emerges with economically-useful products for power generation? Or is NASA interest restricted to just reeling kites?

6) Do you yourself, or does NASA, have an official position with regard to the only AWE technology demoed at the first world AWE conference in 2009 at Chico, the technology that was still up and running the next day after being left unattended overnight, built for a few hundred bucks, Superturbine(R)?

7) After I authored the AWE Primer for NASA, explaining the 3000-year history of wind energy that started with the pulling force on membranes in 1000 B.C and has transitioned to spinning airfoil blades (known as rotorcraft in the field of aviation), does NASA have any feedback on what I outlined as the proven false trails in wind energy and the tendency for newbies to gravitate toward "rediscovering" the entire progression of the art, starting at the pulling thrust force on membranes, and culminating on steady-state, spinning propellers? Where does NASA now feel that it is, in this well-known and oft-repeated historical progression? What year are you now at, in the well-worn 3000-year trail?

8) Does NASA have an official position on my assertion, in that Primer I prepared specifically for NASA, that a Venn diagram showing the intersection of the set of known, working aviation technologies, and the set of known, working wind energy technologies contains only one thing: a helicopter rotor in autorotation, also known as the autogyro rotor?

9) Is NASA aware that wind energy and helicopter technologies are so similar that a helicopter company was originally called on as the go-to obvious choice to build some of the first windfarm turbines in the U.S.?

10) You have indicated a future program to fly kites and extract power from spools and reels "for a few years" while you "learn". Is this now an official NASA program? Does it exclude other design directions than reeling kites? What decision points led to this kite-flying, reeling effort? What decision points led to the exclusion of other technologies? What decision points led to the decision NOT to work on a design direction that has been shown to work easily, now?

11) I'm building another flying wind turbine now. I could have it running in an afternoon. There is little doubt that it will work the first try. No computers are needed. Yes, learning is what we do, but learning whether it even has a chance to work is a hurdle we passed long ago. On paper, or in the field, this works, here and now. Does NASA have any interest in a technology that can work today, that is at the present intersection of known aviation technology, and known wind energy technology, rather than spending years "learning" about an as-yet uneconomical technology that may or may not eventually bear fruit?

11) Was there a process to NASA'a (or your) choice of what technology to pursue? Is this decision-making process public?

12) Does NASA (or you) see any obligation to completely survey the space and issue a report on the various technologies and their advantages/disadvantages?

13) At this point, what have we as taxpayers gotten out of the NASA effort in AWE?

We've read the press releases. "NASA now involved in AWE".
Well, it's been a few years now, and we've seen press-releases from perhaps 1000 entities purporting to either be entering the field, or more likely to have all the details sewn up, (well on paper at least), (and with regard to sexy renderings), in AWE.

I mean Honeywell, Boeing, now even NASA - is there any limit? Where's the beef? Where's that working system we can see operating today, like the several wind turbines on site here, spinning right now? Waiting for the Chinese to perfect it for you?

We can go back to the press releases of Magenn a few years back and read about problems solved and a new way to power our civilization from the sky. Only thing is, did any of it turn out to be true? Out of 1000 press-releases in AWE, how many turned out to be true? Well to judge from the field of wind energy in general, out of 1000 press-releases for new wind energy technologies, perhaps zero-to-1 will be true, if you are lucky.

So thanks for participating, thanks for breaking out of the mold of researchers who refuse to try anything new, thanks for communicating, and I'll be really eager to read back the answers to the questions I've posed above!
:)
Thanks
Doug Selsam

The first ocean current generators, using tidal flows, were and are slightly modified land windmill designs, generally including a tower extension to winch the works up to the surface for service.  This, of course, requires a very strong foundation for the cantilevered tower.  By contrast, ship moorings are a very well known technology that can anchor a kite-style generator, free from any difficulty over buoyancy or unpredictability.  Kites make even more sense for generators in water than in air.

The common element among AWECS is tether and needs searches for:
-lightness;
-low drag;
-protection against lightning both for flygens and groundgens;
-for that new materials or improvements of existing materials...

PierreB
http://flygenkite.com

http://www.ifandp.com/article/009950.html

SkyMill Energy

Extened Feb. 2011 article

Hopefully someone might bring forward copies of all the entries to the contest of 1896c.  
Boston Aeronautical Society might have archived entries.

 

     And the winning paper was ...

 

The most important quality of a tether is its price.

The only way to protect from lightning is to bring the kite back to
ground level.

I am compiling a spreadsheet with the properties of tether materials. I
do not get much time to work on it but will post a link when it is a bit
more advanced.

Robert.

At least we agree that ROI is the critical value to determine. However,
you misunderstand the proposed use of the existing Wind Energy
Association standards. The idea is that the kite energy device (AWECS)
is tested in a range of wind speeds and the power output at each wind
speed is recorded. The resulting power curve can be put into
spreadsheets like mine to predict energy output on a given site. If an
AWECS is for sale it has a price. Potential customers measure the wind
speed on their site (maybe using a small mobile AWECS) and then
calculate expected energy yield which leads them to an ROI. It is not
that difficult and leads to a much more accurate answer than trying to
put a single figure of merit on an AWECS.

Robert.

As discussed recently, aerodynamic tether drag decreases the potential
generating power of kites. A ribbon or tape or belt shaped tether
orientated in the right direction could largely eliminate this problem.

There are at least 2 ways to use a ribbon tether. One would be to have a
join, so the ribbon part would go from the kite down to a junction. The
junction would join the ribbon to an ordinary round tether that is wound
on the reel. However, an alternative where the ribbon is wound on the
reel has some interesting advantages. It would require a mechanism above
the reel to twist the tether 90 degrees but in the process of doing this
tether wear could be greatly decreased. The ribbon would be less likely
to slide on the surface of ribbon previously laid on the reel than would
be case with circular tethers. The contact pressures would also be
lower.

Steel and polymeric ribbons (tapes) are widely used in the packaging
industry so they are already available at low cost. Ribbons are easier,
and therefore cheaper, to manufacture than multi-core round cables.

It seems to me that using ribbons instead of round cable for the harness
of any kite, its lift could be increased and its drag decreased. It
would be easier to make too. If the ribbon is too thin and wide it will
flutter but there must be an optimum aspect ratio that delivers all the
advantages mentioned.

Robert.