Selsam's SuperTurbine (tm)

by Pierre Benhaïem in Airborne Windenergy Forum · · 6 Replies · View last reply Respond
Pierre Benhaïem
Pierre Benhaïem

After my and other analysis of numerous AWES, comprising my FlygenKite or Rotating Reel or OrthoKiteBunch or WheelWind, comprising other methods, it appears for me that SuperTurbine (tm) is a master component for any viable AWES. I will try to justify my statement later.  

Gordon Spilkin
Gordon Spilkin

I agree with you that a multiple turbine system on a common axis is suitable method for AWES.  The length of the torsion shafts or tensegrity elements between turbines is relatively short and so scale-up problems are not too severe.  The problem is the transfer of energy to the ground.  I favor using a rope driving system combined with a generator on the ground.  This system is light-weight and easily scalable, but requires a larger lifter kite to account for the differential forces in the cable drive system.

Doug Selsam
Doug Selsam

A rope-drive system seems advantageous, but bear in mind it can only bring power to the ground in proportion to how hard it tries to pull the apparatus toward the ground (out of the sky).  That means more lift is required to hold it all up.   It is noteworthy that those who endlessly talk of rope-drives, rotors on the ends of blades, etc. never show us a working model.  My take is most of what has lately been flagged as "Rube Goldberg" contraptions would not even work at all, due to unforseen effects the designers are not aware of, since they seldom build anything except in their minds and "on paper".  Drawings and renderings tend to "act" exactly as the designer wishes.  Kind of like Harold and his Purple Crayon drawing a landscape then walking iinto it.  Just drawing something and saying it works a certain way does not make it so.  Let's see smaller rotors mounted on the tips of a bigger rotor, spinning at a resulting speed approaching Mach 1, operating a rope-drive.  Mmmm-hmmm.....  There is a reason some designs remain forever on-paper only.

Pierre Benhaïem
Pierre Benhaïem

Right analysis as it specifies the likely practical impossibility of a rope-drive system connected to rotors on the ends of blades. So a system like KiteWinder is not directly concerned as the rotor is not on the ends of blades but is alone under the pilot kite, so the speed of its tips of blades is not so high.

Gordon Spilkin
Gordon Spilkin

I agree with you Doug about the necessity of testing a prototype. Nevertheless here is my idea to prevent the phenomenon which you describe as: "pull the apparatus toward the ground (out of the sky)".  Normally the tension in the rope drive system/turbine rotation speed tracks with the wind speed so the tension is usually adequate.   In the instance that the wind speed suddenly drops and the turbines are still turning, the tension in the slack side of the rope drive will drop to zero.  If we can monitor this tension or the sag of the low-tension rope and activate a clutch in the ground pulley, then we can avoid this problem.  I wonder what KItewinder does?

Pierre Benhaïem
Pierre Benhaïem

https://www.youtube.com/watch?v=h0IlGMW4E2o represents a KiteWinder video with a rope-drive system, also called loop belt. Currently this video seems to be the only one available video with a real device. It is a stationary device, like Gordon's device is. So these devices are not directly concerned with problems that Doug mentions when the rope-drive system is connected to rotors mounted of tips of a bigger rotor. However testing and data are needed as Doug and Gordon mention.

Doug Selsam
Doug Selsam

I am in favor of pursuing "rope drive", but also cognizant of weak points such as pulling itself downward, out of the sky, which requires more lift, likely entailing more apparatus and area aloft, which means more weight, and expense.  Mentioning this fact seems alarming to some, but merely mentioning a downside is not the same as saying the idea is no good or unworkable.  It's just reality.  Not only was my original AWE idea from the 1970's (later named "laddermill") a "rope-drive" device, but such a simple and basic idea as using a continuous loop as a tether, forms part of the hundred or so other simple AWE ideas I mention as no-brainers to at least try, that, amazingly, no AWE person or team pursues.  Having said that, I quickly saw SuperTurbine(R) as a successor to a laddermill configuration, still way back in the 1970's.  My education at the time consited mostly of a single pamphlet I had ordered from the U.S. Government Printing Office, but it only took a few pages to explain the simple facts of wind energy and to cover all the known variants at that time.  Still, as I've mentioned, I think it is tragic that UDelfts & Co. were unable or unwilling to even try to build a single laddermill after hyping it up so much.  Typical of AWE - lots of talk, but disappointing action.   I am happy to see "kitewinder" building and testing a "rope drive".  Easy to see it does work.  Hopefully they get something useful working and available without drowing in a billion dollars of debt based on false or overly-optimistic promises, like the rest of the field.  Let's remember, however, that as much as such rope-drives or belt-drives have always been talked about by amateur wind energy would-be inventors, the professionals seldom if ever utilize rope, belt, or chain drives.  Almost no turbines use them.  That should be considered significant, since ratio-gearing is so ubiquitous in wind energy, and belt drives offer such a simple implementation of ratio gearing, yet are never used.  Could there be a reason?  I've built a chain-drive turbine against the advice of veterans and found it too noisy and prone to wear and rust, as predicted.  I have only heard of one belt-drive turbine in my whole life (somewhere in Texas a few years ago) and (I think) it used one or more heavy-duty toothed industrial belts, like some heavy machinery, because the power level required more than just a typical fanbelt.  And it was not a huge, utility-scale turbine, but a smaller home-sized unit as I recall.  It was a prototype so I do not know if it worked out at all.  Not sure how long fishing line etc. would last in such an application, but you can imagine probably not very long.   Not sure if even that turbine is still operating, because most new turbine models fail pretty quickly, even if merely "standard".  Wind is brutal and destructively violent.  Consider replacing the fan belt in an old car with fishing line and see how long it lasts. Consider building a tower-mounted turbine with a rope drive to ground, just to show how great it works, and how long it will last.  Consider further, building a tower-mounted turbine with smaller propellers at the blade tips, spinning at almost supersonic speeds, using "rope" drives to transmit that power to a central axle, then another rope drive to take that cumulative power to the ground.  Don't forget - maybe another level of even smaller propellers on the blade tips of the blade-tip propellers is the answer - I mean, if the basic idea is "good" then another layer of the same might be "better", right?  What is the optimal number of "layers" of blades driving smaller rotors?  Three?  How about zero?  Possible?  It's amazing how easy it is to cite a back-of-the-napkin sketch and call it "obviously superior" if you never have to build or test any aspect of it.  If rope drives from tip-mounted, blade-driven, secondary propellers is a better way to design a wind turbine, maybe a tower-mounted turbine is the best place to first prove it.  Otherwise, maybe it does belong in the Rube Goldberg category...  I have noticed blade-mounted propellers are an idea commonly cited by wannabe inventors or innocent bystanders new to the field.  Ask why a car's fanbelt, transmitting so little power, is so thick and strong, yet still wears out.  Consider the size of "rope" required to reliably transmit 1 MegaWatt, which is about 1300 Horsepower(?), from a kite to the ground.  How much, or how many, "ropes" would you need?  How much would they weigh?  How long would they last?  How much tension might it require?  Anyway, after the recent 10 years of hype, and somewhere near a billion dollars spent so far, by so many AWE "teams", it's nice to see some kids with minimal funding, pursuing a simple, workable idea, that none of the highly-funded and highly-publicized teams has bothered with.  I hope they avoid drowning in debt like so many of the rest.