Flying Electric Generators

Discussion in 'Science' started by HereWeGoAgain, Apr 1, 2019.

  1. WillReadmore

    WillReadmore Well-Known Member

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    The strength of this cable is going to have to be pretty incredible.

    It has to carry the load for flight, the thrust of the gigantic blades, the wind power against the cable (which would tend to lower the angle), the lighting infrastructure along the cable, the weather/abrasion proofing, the weight of the cable itself.

    Plus, the lower bound of the jet stream is more like 5 miles, so I think 20k feet isn't enough altitude. My private plane cruises at 20K to 25k feet, and I certainly can't count on catching the jet stream, including over the western mountains.
     
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  2. modernpaladin

    modernpaladin Well-Known Member Past Donor

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    I suspect the continued developement of these will not only advance power generation, but technology conducive to space elevators as well. I support!
     
  3. WillReadmore

    WillReadmore Well-Known Member

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    Possibly, but let's remember that this is looking at 5 miles while space is more like 60 miles.
     
  4. modernpaladin

    modernpaladin Well-Known Member Past Donor

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    Of course :)
     
  5. WillReadmore

    WillReadmore Well-Known Member

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    I should have included that there would have to be a reasonable margin to account for factors such as wind velocity changes and changes to mode of operation (such as starting or stopping the blades or generator) that would create significant surges of cable tension.
     
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  6. WillReadmore

    WillReadmore Well-Known Member

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    Space elevators seem to be gated by the cable, which is a far bigger problem than this one, maybe.

    Stuff like kevlar is not even close to working.

    There might be solutions involving nanotubes, graphene ribbons or diamond nanothreads.

    The problem there is that there would still need to be a large cable, but it would have to be nearly perfect at the microscopic level. I don't believe that has been accomplished.
     
  7. modernpaladin

    modernpaladin Well-Known Member Past Donor

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    Not yet.

    Heres to hoping the FEGs become popular enough to drive demand for lighter, stronger tethers that could do the trick.
     
  8. WillReadmore

    WillReadmore Well-Known Member

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    Amen - there are probably other applications, too!
     
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  9. Derideo_Te

    Derideo_Te Well-Known Member

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    There can be weight savings via dual purposing components. A generator is also an electric motor. A turbine blade can also be a propeller. Wing angles can be varied from lift to drag and back to lift again. NASA has a test drone where the wings tilt to vertical so that the propellers can do a vertical take off and then transition to horizontal to provide lift in flight.

    https://en.wikipedia.org/wiki/NASA_GL-10_Greased_Lightning

    https://www.nasa.gov/langley/ten-engine-electric-plane-completes-successful-flight-test

    [​IMG]

    So to answer your question there are several parts that need to be addressed. The first is take off and reaching the jet stream. The tether cable could provide electricity to run the generators as motors in order to achieve the desired altitude. Once in the jet stream the FEG needs to essentially have enough power from the rear pusher propellers to remain in one constant position while the forward turbine blades turn the generators to make electricity. Optimizing the lift/drag from the wing would take advantage of the tilt feature and thereby ensure that least amount of power would be consumed by the motors while also reducing the strain on the tether.

    In summary it would be a balancing act between minimizing the consumption of power while generating an excess of power. This is why small scale testing would be essential for feasibility studies.

    I am also wondering about the use of different configurations for the turbine blades themselves.

    [​IMG]

    It might even make more sense to develop a ducted turbine mounted horizontally in order to obtain maximum generation.

    The basis concept is fascinating and I think that a lot of experimentation would be needed to find the optimal design.
     
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  10. roorooroo

    roorooroo Well-Known Member Past Donor

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    I found a good document concerning the FEG idea and the literature. It is interesting to say the least. It is fairly long and detailed, but it is readable.

    Anyone interested in this field should check it out - whether one is a physicist, or just a dummy like me.

    It is a PDF that can be found by googling "mindmeister the flying elec steven kambouris"

    The Flying Electric Generator: Evaluating the claims of a largely ignored proposal for generating
    electricity from high-altitude winds


    Steven Kambouris
    orcid.org/0000-0002-3876-7472
    Master of Science
    September 2015
    School of Historical and Philosophical Studies
    School of Earth Sciences
    The University of Melbourne
     
  11. roorooroo

    roorooroo Well-Known Member Past Donor

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    Since this thread has about run its course - here is one last attempt to determine whether the OP is being truthful and whether he has actually done serious research into FEGs: Concerning 500,000 volt and 1,000,000 volt generators that would be suitable for producing millions, if not billions, of watts:

    Do 500,000 volt or 1,000,000 volt generators suitable for producing millions of watts exist?
     
  12. HereWeGoAgain

    HereWeGoAgain Banned

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    Jesus, give it a rest. This is a brainstorming thread. I am exploring the limits of the technology as a back-of-the-napkin problem. How this actually falls out into a real design takes a lot of engineering. I don't know what the limits may be yet. No one does. I would have to consult with engineers who design high-voltage systems to determine what the limits for custom generator builds might be. But we do transmit on long distance power lines at 500 KV. A quick google shows that easily enough. + and - 500 KV is 1 million volts. But you want to drive the idea to the highest voltage possible to minimize the current. That is a starting point.

    I also stated that a typical FEG might have two or four turbines. Do you know how to divide?

    I also was using 1 GW as the standard for consideration. I was simply comparing the required scale to match the output of a typical nuclear reactor. I said that. Did you simply choose to ignore what I said?

    I even stated specifically that the examples chosen were arbitrary and only intended to provide a sense of scale. Was that too complicated for you or did you simply choose to ignore it?
     
    Last edited: Apr 13, 2019
  13. roorooroo

    roorooroo Well-Known Member Past Donor

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    I can understand that this would be uncomfortable. Therefore, I will give it a rest at this point. I found out what I needed to know, and will consider this knowledge when reading your posts in the Science forum in the future. Thank you.
     
  14. HereWeGoAgain

    HereWeGoAgain Banned

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    If the wing provides lift, it may not be required to be subtracted from the turbine power if properly designed. The skypower people use the turbine itself to provide lift. To me it seems clear that it is preferable to mount the turbines on a wing capable of providing all required lift at a standard air speed of 110 mph [the average speed in the jet stream].

    The drag force comes back to the tether.
     
    Last edited: Apr 13, 2019
  15. HereWeGoAgain

    HereWeGoAgain Banned

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    Cool!

    Yes, I have wondered a lot about that as well. Clearly the example of 90-meter turbines wouldn't work here. :D I was looking at large helicopter blades for comparison. They probably operate near the envelope of the requirements here. And they do make some very large helicopter rotors.
     
  16. HereWeGoAgain

    HereWeGoAgain Banned

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    https://en.wikipedia.org/wiki/Electric_power_transmission

    So cut the crap.
     
  17. HereWeGoAgain

    HereWeGoAgain Banned

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    1 Billion Watts /1 million volts is 1000 amps.

    That lands in the range of 1500 kcmil MCM, which has a diameter of 31 mm, for copper wire.
     
  18. roorooroo

    roorooroo Well-Known Member Past Donor

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    Crap? Nowhere in that link does it say anything about 500,000 or 1,000,000 volt generators. Yet you claimed you have seen them. The link supports the fact that generators do not produce the high voltages that are placed on the power lines.

    Yes, let's cut out the crap.... FEGs are obviously feasible because they have already been done. But how much power can a single FEG produce? You seem very optimistic that a single FEG can produce a huge amount of power - that they could replace 2000 LBTs. I am very skeptical - the electrical aspects just aren't working out. If te following does not interest you, then you have no business discussing large scale FEGs.

    You wrote: "So just one FEG having the same effective area as one of the largest land-based wind turbines in use, can produce 160% as much power as the largest nuclear power plant in the US." (6.4 GW) In another post, you lowered that figure to 4 GW.

    It is my assertion that you are being overly optimistic about the possible size of a single FEG. Regarding the large scale FEG concept, one needs to have at least a rudimentary knowledge of the electrical/mechanical requirements of producing huge amounts of power before making claims. My direction is to be realistic about the potential power that can be derived from a single FEG. Once we get that down to a realistic number, then we can actually decide the feasibility of the idea. My apologies for upsetting you, but, surely you would agree that a bit of skepticism is a good thing?

    [​IMG]

    The item in the photo is an example of a 3-phase "step-up" xfmr that receives somewhere in the range of 12KV to 28KV depending on the generator output and converts that to a higher voltage. The xfmr can be built to provide as much as 765KV depending on the requirements of the transmission lines.

    Notice the three large "bushings" that extend up and to the left in the photo. Those are the high voltage output terminals/insulators sometimes called "stress cones." Notice how big and how far apart they are. There is a reason for this. Look up "corona of high voltage terminations." This is also one of the reasons that an electromagnetic generator has an upper limit of around 30KV.

    Okay, sure, so instead of using the fabled 500,000 volt generators on the FEG, we can use, say, 26,000 volt generators and a step-up xfmr to get the 500,000 volts. Yes we can. However, a 500MVA xfmr with output voltage of 500,000 volts will weigh approximately 300 tons. (google on "large power transformers and the u.s. electric grid" and you will find a PDF detailing all this.)(also, please note that for our discussion, VA and W can be interchanged, although VA is proper)

    If we run with the 4GW suggestion, and considering that you posted specs for a 1,300MVA generator which provided a weight of 390 tons. We need 3 of them to get close to 4 GW as you suggested. 390 tons x 3 = 1,170 tons. Speculating that we can build them a bit lighter, perhaps we can do away with the cooling systems because they will be in a cooler environment, let's knock off 10% and get that down to 1,053 tons for just the generators.

    Now the xfmers - the largest step-up transformer I can find is 1,510MVA.
    http://www.mitsubishielectric.com/bu/powersystems/products/transmission/transformers/index.html

    It doesn't list weight, but if a 500MVA xfmr weighs 325 tons, and it is 3 times smaller than the 1,510 MVA unit, let's assumethat the weight is doubled. I won't triple it, let's assume that it only doubles. Therefore, a single 1,510 MVA xfmr will weigh 700 tons. We need 3 of them, 1 for each generator. That is 2,100 tons for the xfmrs. Again, I'll knock off 10% because perhaps we can omit the cooling systems. This leaves us at 1,990 tons for the transformers.

    Total weight of generators and xfmrs equals 3,043 tons. Note that we really need 4 generator/transformer units for symmetry on the FEG. So we use 4 smaller units of 1,000 MW each instead of 3 larger units of 1,300 MW each. I don't believe this will lower the weight.

    A supporting structure to hold this massive amount of weight together will be significant, especially considering that the generators will be at least 200 feet apart. Add in the stresses from the torque required to turn the generators, and it will have to be quite massive. Regardless of whether the structure is a wing, or a supporting framework, I am making a total WAG of 150 tons (probably low).

    This brings us up to 3,193 tons. We still have to have control systems and blades and gear boxes.

    Speaking of gear boxes: I doubt that the blades will rotate at the exact speed needed for the generators, so we need gear boxes. These gear boxes would have to withstand in the neighborhood of 1,340,000 HP each. The largest wind turbine gearbox is for a LBT that produces 8 MW. It weighs 86 tons.

    http://www.offshorewindindustry.com/news/worlds-biggest-wind-turbine-gearbox

    A gearbox for a system producing 1,000 MW is going to be large and heavy indeed. I will be extremely extremely conservative and guess that it will weigh 125 tons. We need 4. That is another 500 tons.

    Gross weight at this point is 3,693 tons.

    The blades will have to have, at minimum, a "collective" control system. It may also need a variable pitch system. These items will have to be extremely robust and this means more weight. I won't even bother adding it into the total.

    The most powerful helicopter to date has a max take-off weight (craft and load) of 40 tons. The most powerful fixed wing plane has a max take-off weight of 640 tons. Our 4 MW FEG will weigh 3,693 tons.

    Are we still convinced that a 4 GW FEG is possible? If not, how much do we need to scale down? We may as well be realistic.

    There are still many more issues. We can discuss them if anyone would like.

    I would also like to repost this: Please check it out. it details many of the discrepancies, omissions, and unsolved issues with the literature concerning FEGs.

    It is a PDF that can be found by googling "mindmeister the flying elec steven kambouris"

    The Flying Electric Generator: Evaluating the claims of a largely ignored proposal for generating
    electricity from high-altitude winds

    Steven Kambouris
    orcid.org/0000-0002-3876-7472
    Master of Science
    September 2015
    School of Historical and Philosophical Studies
    School of Earth Sciences
    The University of Melbourne
     
  19. Derideo_Te

    Derideo_Te Well-Known Member

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    Been giving the concept of a FEG some thought and I have a different design in mind to what you envisioned. Not sure if you ever played with one of these toys as a child but this is the basic concept behind my idea.

    [​IMG]


    The theory of an aerofoil is that the air must travel further over the upper surface which reduces the air pressure above the wing which means that the air pressure below the wing provides lift. If we build a longitudinal rotor into the top half of the wing where the blade protudes above the surface then the air flow will turn the generator.

    This design has two advantages in that it is enhancing the aerofoil concept and generating more lift by increasing the distance that the air must travel over the upper surface. The generator axle becomes the primary support for both the wing and generator itself. If the axle is made long enough then it runs across both wings and provides the strength to support the structure.

    The most obvious negative here is the generator torque factor that will attempt to pitch the nose up so this is where I needed to become creative. The concept of a Canard wing was introduced by the Wright brothers to provide pitch stability.

    https://en.wikipedia.org/wiki/Canard_(aeronautics)

    [​IMG]

    In essence the use of a Canard wing means that you set it at an angle of attack where it will stall and lose lift automatically before the pitch on the primary wing reaches the point of stalling. Placement far enough forward of the main wing axis of rotation will need to be determined so as to provide optimum stability while cancelling out the torque of the generators.

    Since the nose is now being used as a flight stabilizer a pusher motor will be needed at the rear to deal with wind gusts and maintain a steady pressure on the tether. My thinking here is that two smaller counter rotating motors will be optimal so as use them to help minimize any rotation that might occur. They will be powered via the tether to become airborne and then only be needed to maintain a constant GPS position since the wing generators will provide their own lift to keep the FEG airborne.

    While this design still needs a lot of math to become a reality it solves the primary problems that we encountered with the delta rotor design IMO.

    Do you see any serious flaws with this design?
     
  20. Derideo_Te

    Derideo_Te Well-Known Member

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    Not to nitpick but no one is suggesting a flying transformer unless I missed something.

    The generators are heavy enough without trying to keep a transformer airborne.

    Yes, I know, you were using it to illustrate the issues involved with high voltages so I thought that we had come to the conclusion that more smaller generators where preferable to a single larger one.

    I did read your link and it was a good paper. I did some more research based upon alternative means of generating mentioned in the paper and there are some ideas that look to be feasible.

    I think that we are at that early stage when heavier than air flying was first accepted as feasible and everyone was trying out new ideas. Most of them failed but what survived is how we travel long distances today.
     
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  21. roorooroo

    roorooroo Well-Known Member Past Donor

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    Concerning alternative means of generating... I agree there is some interesting stuff there. I especially like the one with the electrical equipment on the ground, and kites being controlled in a manner to turn a giant "disc" which turns the generator.

    Now, on to the transformer issue: I don't know if the OP has decided that 4 GW FEGs are infeasible. So I am still discussing large FEGS (more on smaller FEGs later). Transferring the power from the flying generator down to the earth is problematic. When we speak of wattage, or more correctly, volt-amps, the formula is as follows (please forgive me if you already know all this)

    Power (Watts or Volt-Amps) = Electromotive Force (Volts) x Current (Amps) (Watts and volt-amps are not necessarily the same thing, but for our purposes, we are safe to ignore the differences.)

    So there are various ways to transfer power: Example: Say we want to transmit 1,000,000 volt-amps to a distant factory that needs 480 volts. We could choose to simply send 100,000 VA at 480 volts. We would need to supply 2083 amps at 480 volts to give that much power. The conductors would be relatively "large" to carry the 2083 amps. Again, excuse me if you already know all this.

    However, if we raised the voltage to 100,000 volts instead of 480 volts, a current of 10 amps would supply the same power as the example above. The conductor could be quite "small." An additional benefit is there are less electrical losses with the lower current.

    Anyway, the magnitude of current is important because the electrical conductors affects the weight of the tether. The tether is going to be extremely problematic in the case of a large FEG, so any cable weight reductions are going to be helpful. This means that the FEG must send out power at a very high voltage, say 500,000 volts. This implies that the transformers must be up in the air with the generators if we want the tether to be as light as possible.

    Now, high voltages are no free ride like some on this thread seem to be thinking. Extremely high voltages create extreme issues with insulation. Look up "corona of high voltage cables."

    I have not mentioned this yet, as I am just sort of "following along" to determine who is who and who knows what in this thread, but the generators we are speaking of are actually going to be 3 phase alternating current generators. If this is the case, we can divide the above currents by 1.73. The OP suggested using 1000 HZ generators instead of 60 Hz, so he must have been speaking of alternating current. There was some mention of high voltage direct current later in the thread, and if that is the case, we omit the 1.73 divider.

    Back to the conductors from the FEG to the earth: If we are using extreme voltages, we are most likely going to have to separate the conductors by spacing them 20 or 30 feet apart, if not more (insulation issues with extreme high voltages in close proximity - see the picture of the high voltage transformer stress cones discussed in my previous post). This means instead of 1 tether, we will have 3 for a 3 phase AC system, and 2 for a DC system. This has the advantage of reducing the stress on each tether, but it may cause stability problems, mechanical problems, and electrical problems as the tethers twist and oscillate in the winds. Intuitively, the 3 tether design seems especially problematic.

    A quick side note: Long transmission lines do have "capacitance" issues. An increase in frequency to 1000Hz could be an issue because "capacitive reactance" increases linearly as the frequency goes up.

    In the paper by S. Kambouris, he discussed literature concerning a proposed 3 MW FEG. Off the top of my head, this rather "small" FEG was predicted to have a weight of 3000 pounds, and the predicted tether weight was as much as the FEG itself. Again, the tether is a very important concern. And, I will say this... if all we can hope for is 3 MW, we will be better off sticking to LBTs.

    My point all along has been to keep this thread realistic on the electrical side of things. The 4 GW FEG is obviously not feasible. I do think it would be profitable to discuss something that is realistic. Since some have mentioned the 747 in this thread, perhaps keeping our theoretical FEG within those weight limits would be a good starting point.

    What would be the electrical capabilities of an FEG that weighed about the same as a 747?
     
  22. Derideo_Te

    Derideo_Te Well-Known Member

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    Thank you for your detailed explanation WRT electricity. I only have a layman's understanding of it and do not have any expertise beyond household wiring. that said I am trying to learn more in order to convert at least some of my household usage into renewable energy. I installed a solar hot water heater and I am now looking into wind and solar panels.

    My own expertise tends towards mechanical engineering so those are the forces that I am trying to come to terms with. If the tether distance makes it prohibitive for a FEG to operate in the jet stream using a DC generator then why not just use an invertor instead of a transformer? That way the DC generator current could still be sent back down the tether as AC.

    Speaking of the tether needing more than one line and problems with twisting the use of triangular separators on a 3 wire system would have far more stability and resistance to tangling/shorting than a 2 wire tether. If you ran the load bearing cable up the center of the triangles with the wires at each corner that would be relatively stable and durable IMO.
     
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  23. roorooroo

    roorooroo Well-Known Member Past Donor

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    Any input you have on the mechanical aspects, forces, torque, I am all ears!

    Regardless if the generator is AC or DC, insulating the high voltages are problematic. I don't know this for a fact, but I am quite certain that a DC generator is going to have about the same voltage limitations as an AC generator. An inverter by itself can't raise the voltage up to extremely high levels. I don't see any benefits of using a DC generator and then an inverter to produce AC. We may as well use an AC generator and eliminate a component.

    Perhaps I misunderstood your point?

    Even with high voltage DC transmission systems, the generators produce 3 phase AC, the AC goes through a step-up xfmr just like with high voltage AC systems, but then there is an added step of rectifying the high voltage AC to high voltage DC. I don't see how this will eliminate any issues with the FEG.

    Interesting thoughts. Of course, if we are talking about high capacity FEGs and high voltages, the separators would have to be quite substantial and I have no idea how far apart they would need to be. This would add weight to the tether.

    Here is a photo of 132KV insulators. These seem somewhat larger than I expected for 132KV. The larger the voltage, the larger the insulators. For smaller, lower voltage generators, your idea may be the ticket.

    [​IMG]
     
  24. tecoyah

    tecoyah Well-Known Member Past Donor

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    The complexities and logistics behind this idea make it unlikely at best. The effort, resources and mental effort is better spent on Solar in Space and microwave transmission.
     
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  25. Derideo_Te

    Derideo_Te Well-Known Member

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    My understanding is that you need thicker cables with higher voltages.

    Why not just use lower voltages instead?

    Insulators are primarily used to prevent grounding shorts as far as I know. With the bulk of the tether suspended way above the ground the only insulators would be needed at the end nearest the ground. The triangular frames can be all be made with lightweight ceramic insulators bonded into carbon fiber frames.
     

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