Re: [AWECS] The Power of Rope must be Double, for Power Generation?
- The good news is no one need needs Magen's incredibly expensive and poor performing AWECS. We know savonius LTA is the least efficient and most expensive of any "leading" scheme. Its been proven on paper and in the pathetic demos where the Magenn device fizzles on camera. I think Harry maybe used it just as strawman, as it is trivial to use a real HAWT for rope power loops such as he describes. An simple obvious enabling method is to use Corner Blocks, pulleys that are set to turn rope power around bends. KiteLab's KiteMotor HAWTs use corner blocks. Similarly, if we need LTA lift, there is no need to use a terrible sideways-barrel shape, as profile/form drag is critical. A conventional aerostat is far better, and its COTS, with many vendors. Harry need not to open himself to (Doug's) opportunistic critique of peripheral detail.Doug should realise that the question of ropepower, which easily pulls loaded supertankers, is for him the core challenge to show his rigid driveshaft is even marginally workable. Once again Doug pretends he did not hear the shaft questions. Like Magen LTA, the SuperTurbine driveshaft is marginal AWE technology. It has no potential to do the job rope does; to transfer force over long distance at minimal weight and cost. Doug is right that there are definite limits to rope (and all engineering structure), but the good news is that these extreme limits allow for great performance; nothing else we know of can tap high altitude wind so convincingly, either in practice or in calculations.Reeling is another AWE straw man, just a brief historical phase. While reels are simple and hold the land-based AWE peak-power record, the best informed researchers know that it is wholly unnecessary and was just a method in early AWE to quickly show powerful results. KiteLab has publicly demoed numerous prototypes pumping the line to levers/cranks in short strokes, without reeling.Besides excessive mass, vulnerability, and high capital cost, a major defect of a driveshaft v. kiteline is that the thick cross-section of the driveshaft angled down into the wind develops large downforce. I pray Doug will soon see that phased collective-pitch multiturbines on a line is the only way an AWECS resembling his SuperTurbine AWE vision can triumph in upper-wind. These Turbine Trains can even be dense arrayed under a Control Mesh of lifter-kites. He should be seeking to partner with the teams entering that design space.
- There he is again, "the Nostradamus of AWE".
Sweeping pronouncements. Ultimate authority. Unlimited veto power. The final authority on all questions. (!)
OK Dave if you, and these multi-million-dollar players, are so on top of it all, why exactly IS Magenn a "leading" scheme? Why, if it's such a complete losing proposition, does NASA piggyback on Magenn's renderings? Why is Magenn shown in all the AWE PR? Doesn't ARPA-E, with all those "scientists" and millions of dollars, use it? Do real wind energy efforts show pictures of Savonius turbines? Could it be that these people are complete idiots on another Solyndra mission?
Why is a sideways barrel shape "terrible?" It's not the shape, it's because they use Savonius rather than Darrieus, which would be merely "suboptimal".
Oh and the main method all the big players are pursuing: reeling kites is now "just another brief historical phase". Why don't you call them up and tell them their next step?
Dave if you have ALL the answers, why not use that crystal ball and show us something workable beyond a toy for light winds that could briefly light an LED or two?
What I say about reeling pulling down on a machine that we are trying to keep up, applies also to pulsating pull. You know why you are talking about pulsating? Because as long as there is something that nobody wants to bother to build, including you, it can be talked about as though it's "the answer"
Build them and run them and see what the problems are. (Oh darn this is work!) Then you'll be on to the next phantasy like the dual-kite world-wandering system using microwaves to fry the populace - er um I mean "beam the power to power plants" (again, any economical examples?) that I heard another equally emphatic hypothesizer at the first ever AWE conference promote endlessly.
In wind energy there are knowns, ignored by newbies at their own peril. Magenn for example is popular because they actually built one and it can actually fly and so photos are available, yet it's a typical know-nothing newbie idea that ANY wind energy person can tell you sucks and not only that it sucks, but exactly WHY it sucks. All known. Why people are not building flying wind turbine is beyond me. I have plenty of designs that have NOTHING to do with Superturbine(R) and if I had even a spare day or two I could build them.
I think you and most of these "big players" are somewhere between lazy and completely asleep.
:) Doug S.
- Doug,Your questions have been covered before, but review hones the logic and catches details.The reason Magenn is called a "leader" (only in quote marks) is that Fred Ferugusen is widely considered "The Great Impostor" in LTA circles, going back decades. His Magnus Airship tapped tens of millions of "Star Wars" dollars (What idiots approved this funding?). It was the aeroengineer-predicted flop before being destroyed in a mysterious insurance fire. We long thought we we where done with this charlatan, but then he pops up with another "Magnus Effect" (Savonius actually) balloon, this time for AWE, and raises eight million from rubes, while claiming he will help Mayan villagers (my friends). After decades of following his shady carreer, i confronted Fred in public at HAWPCON09. To my memory (a video must exist), when he claimed a ridiculous advantage in that "no part of (his) turbine traveled faster than the wind", i pointed out that the return side buckets face almost 2x the windspeed and that here is where most of his power gets wasted, he looked stunned, bleating weakly, "2x the windspeed, yes" and sat down. Doug, beware becoming just like Fred. Run your numbers again and again and restudy your many driveshaft "flights", and how they break or grow too heavy; one need not be a Nostradamus to spot a marginal concept this way.We have found an interesting niche for Darrieus in the form of rotor kites like the Prism flip kite. Its true that a Darrieus is not as good as a HAWT, but its far better than a bad Savonius rotor or worthless Magnus rotor. The backwards looping rotor kite has the virtue of stability and a naturally strong pulse on the line along with self lift. Its not predicted to scale well, but it does suggest a Dynamic Soaring mode in the wind gradient that a hotter kite plane could exploit. Using the gradient in this way is much like a virtual return-side shield that boosts darrieus efficiency. Flip kite AWE is a great demo to the world of how you can walk into a kite store and buy a flying device ready to make micropower. The flip kite even turned a five pound flywheel and oversized generator for a trickle of power in Italy recently, but its best suited to a small cell-phone generator. I hope to show a flip kite at work soon when the video is hosted for linking (one of the many varied demos you are promised).Note that in the lofted turbine space, KiteLab Ilwaco favors a true HAWT under a stock kite or aerostat, with a moving line driving a generator on the ground, but tests all AWE concepts if possible, because even flops reveal good lessons. I fly large kites all i can (after all i did collaborate with KiteShip) and have flown giant kites, arches and trains regularly, and have been injured repeatedly in extreme kite sports, as is normal (be very scared). But i agree with Moritz ( a super bright guy!) that developing AWE at small scales is smart. Moritz's Leuven Lab has even committed to stay at the small scale for five years before scaling up! I am not that smart...Hope this answers your questions,daveS
- OK Dave S., can you give me the formula for how much a non-buoyant wind energy system can weigh versus its swept area and how much that further reduces the amount of energy that the betz coefficient allows?
OK now how about the formula for how much more energy is lost (required to maintain altitude) if the power is transmitted by pull up a tether (pulling the AWE device downward), based on tether travel speed? Thanks.
Oh what's the matter? No formulae to offer? No carefully-thought-through Betz-like mathematical thought-experiment derivation? Gee Dave with all your omniscient pontificating, I would have thought you had all this figured out, but nobody has even looked at the basics. Even you. We have no basic formulae to even start from yet.
See, the fact is you DON'T answer my questions. Nobody has. I don't see that anyone even RECOGNIZES the main questions. Airborne wind energy is not even up to where regular wind energy was when Betz first put numbers to the point of maximum energy extraction from a given area.
Carry on with your edible paste, round-ended scissors, and construction paper. No you should not eat the paste!
--- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...> wrote:
> Your questions have been covered before, but review hones the logic and catches details.
> The reason Magenn is called a "leader"ï¿½(only in quote marks) is that Fred Ferugusen is widely considered "The Great Impostor" inï¿½LTA circles, going back decades. His Magnus Airship tapped tens of millions of "Star Wars" dollars (What idiots approved this funding?).ï¿½Itï¿½was the aeroengineer-predicted flop before being destroyed in a mysteriousï¿½insurance fire. We long thought we we where done with this charlatan, but then he pops up with another "Magnus Effect" (Savonius actually)ï¿½balloon, this time for AWE,ï¿½and raises eight million from rubes, while claiming he will help Mayan villagers (my friends).ï¿½After decades of following his shady carreer, iï¿½confronted Fred in public at HAWPCON09. To my memory (a video must exist), when he claimedï¿½aï¿½ridiculousï¿½advantage in that "no part of (his) turbine traveled faster than the wind", i pointed out that the return side buckets face almost 2x the windspeed and that here is where most ofï¿½his powerï¿½gets
> wasted, he looked stunned, bleating weakly, "2x the windspeed, yes" and sat down. Doug, beware becoming just like Fred. Runï¿½your numbersï¿½again and againï¿½and restudy your many driveshaft "flights", and how they break or grow too heavy;ï¿½one need not be a Nostradamusï¿½to spot a marginal concept this way.
> We have found an interesting niche for Darrieus in the form of rotor kites like the Prism flip kite. Its true that a Darrieus is not as good as a HAWT, but its far better than a bad Savonius rotor or worthless Magnus rotor. The backwards looping rotor kite has the virtue of stability and a naturally strong pulse on the line alongï¿½with self lift. Its not predicted to scale well, but it does suggest a Dynamic Soaring mode in the wind gradient that a hotter kite plane could exploit. Using the gradient in this way is much like a virtual return-side shield that boosts darrieus efficiency. Flip kite AWEï¿½is a great demo to the world of how you can walk into a kite store and buy a flying device ready to make micropower. The flip kite even turned a five pound flywheel andï¿½oversizedï¿½generator for a trickle of powerï¿½in Italy recently, but its best suited to a small cell-phone generator. I hope to show a flip kite at work soon when the video is hosted for
> linking (one of the many varied demos you are promised).
> Note that in the lofted turbine space,ï¿½KiteLab Ilwaco favors a true HAWT under a stock kite or aerostat, with a moving line driving a generator on the ground, but tests all AWE concepts if possible, because even flops revealï¿½good lessons. I flyï¿½large kites all i can (after all i didï¿½collaborate with KiteShip) and have flownï¿½giant kites, arches and trainsï¿½regularly, and have been injuredï¿½repeatedly in extremeï¿½kite sports, as is normal (be very scared). But i agree with Moritz ( aï¿½super bright guy!) that developing AWE at small scales is smart. Moritz's Leuven Lab has even committed to stay at the small scale for five years before scaling up! I am not that smart...
> Hope this answers your questions,
- Given that a kite can't stay up without some tension on the tether, I don't see any problem with having that tension be on a moving pulley system. The return line may double the weight, but it can serve as an overload preventer as well. The power available will be the product of the available line tension times line speed.Bob StuartOn 5-Nov-11, at 9:02 AM, Doug wrote:
- Bob,Doug seemed tome to be asking for examples of power transmitted by cables, which were given. I missed his was really a demand for equations of motion. Surely he knows that failing to forward basic equations at the speed of unjustified impatience is not our fault. So you gave him a starting point. I think he is asking about overall L/D of an AWECS, which is very simple to calculate. The basic idea is for the useful load to account for most all of the drag. An overall L/D of one, as observable by a 45 degree tether angle, is close to optimal. Much higher and less power is extracted, and much lower and the kite rig sinks too low in the wind gradient for less power and is at risk of forced landing. NASA has great "high school level" material online on basics-of-flight equations comparable to Betz in WP.A further hint for Doug along the lines you began- Mass is an object's inertia; the proportion between force and acceleration as in Newton's Second Law. With such classic tools its possible to calculate that AWE is quite feasible, potentially revolutionary, especially using line to tap the upper-wind as no tower can.Doug please note the massive amount of basic and advanced math now found in the academic literature of AWE (start with Loyd!). My main job is rigging, performing, and reporting novel flight tests. Try to wait calmly for the new videos; the dozens of old ones were just a prelude, but they do show a reasonable proportion of action compared to talk compared to your Forum output,daveS
- Thanks Bob for a concrete answer, to back up Dave S.' assertion that there's no fundamental math that has been ignored in the talk-talk-talk field of wannabe AWE.
Yet Bob's answer implies that a kite's weight is the LIMITING FACTOR on power output from a kite. He seems to say it is not a factor and you can get as much power as you want and seems to agree with Dave S. that my concerns for a formula are baseless. But a closer examination reveals that if your tether reel speed is limited, your power output will be limited by the tension in the tether times the tether reeling speed. This might in turn be limited by, say centrifugal force, air friction etc. So the weight of a reeling system would seem to be a limiting factor in power output, as would reeling speed of the tether. That's just off the top of my (pointed) head.
I'd like to propose a thought experiment in response:
Say you have a kite energy system that is barely able to keep itself aloft in a given wind due to its own weight. Say the tension on the tether varies between 0 lbs and 100 lbs. How much power can this device now transmit by pulling upward on a tether, steady-state? The answer might be close to zero, since any pulling upward on the tether by the device will tend to want to pull the device downward out of the sky.
Obviously there must be some maximum amount of power that can be pulled down from the sky by this method before the device itself is pulled down from the sky. The power would seem to be limited by whatever extra lift the device has (extra tension on the tether) times the tether's speed. So if we merely increase the tether's speed to an unlimited speed, can we then extract unlimited power from the tether? How does that unlimited tether speed affect centrifugal force at the spinning, circular reels? See what I mean? Some numbers could be put to all this. And what about that dreaded return cycle? Ya know, where you gotta give some of the energy back, or at least not make any power, as the system retracts? Personally, I prefer a steady-stae system without a retraction cycle but there's more fodder for requisite equations.
This is similar to the realization Betz and others had that a wind turbine slows the wind by extracting energy, and that there is a maximum level of energy extraction that can take place before you are slowing the flow so much that you have less energy to extract from that slowed flow. It's a case of effect/counter-effect, or action/reaction.
Anyway in all the press-releases from the big players, and in all the pontificating and 5-second, grainy videos from the peanut gallery, I have seen no such basic mathematical derivation that would indicate that any serious player has done the slightest amount of "on=paper" homework seen in normal engineering efforts.