Power Storage in a wobbly flywheel

Discussion in 'Propulsion' started by rwatson, May 28, 2013.

  1. rwatson
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    rwatson Senior Member

    Possible marine use - IF the flexibility isnt affected by severe motion. Might make collecting solar power less of a weight issue too.

    http://www.kickstarter.com/projects/1340066560/velkess-energy-storage

    "Velkess's Technology – The Flexible Flywheel While Velkess's technology will replace batteries, "

    "How is Velkess's Flywheel Different?
    Velkess's flywheel was conceived from the very beginning up to provide dramatically lower cost for performance. .......

    Flexible vs. Rigid

    Traditional flywheels are designed and built like the turbines of high performance jet engines. They use super rigid materials and super high precision fabrication to very tightly control the powerful natural dynamics that are characteristic of all high energy spinning rotors. These materials, precision, and control techniques are all very expensive, so you simply can't use the traditional rigid approach to make a low cost system.

    Velkess's flywheel is flexible and works very much like a cowboy's lasso. Our flexible system embraces the natural dynamics of the rotor, redirecting any stray energies into stabilizing counter forces. By working cooperatively with these natural rotor dynamics we gain excellent control of the rotor system without having to crush out its irregularities. Because of this we can use much less expensive materials and don't need nearly as much precision as rigid designs."
     
  2. Petros
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    Petros Senior Member

    many years ago read about the efficiency of storing energy in a flywheel and thought how it could work in a car. There are a number of very large problems associated with flywheel storage in something that moves like a car or a boat. The most efficient in terms of energy density would be a very light weight hub and rotor with all of the mass out at the perimeter, and operating in a vacuum chamber (much reduced aerodynamic losses).

    On a moving vehicle you have the weight of the vacuum chamber, and it must be reliable, if it gets leaks you loose energy to the aero losses. One really big issue is you have VERY LARGE gyroscope loads every time you move the axis of rotion, and on a moving vehicle, it could cause you to loose control of the vehicle or vessel. for example if you had a horizontal flywheel spinning under the floor, if you pitched the nose up the Coriolis effect would cause the vessel or car to suddenly yaw or slew to the right. One way to deal with this is to use to counter rotating flywheels one on top of the other. But this nearly doubles the cost of making it, but it would reduce the size of axle and bearings you need since the yawing Coriolis forces would cancel and effectively go away. This would not work with the flexible flywheel arrangement in the link above since if they flexed the two flywheels would contact each other and likely explode (remember they are storing all your energy).

    You could make it work that way with rigid flywheels, but it would take up a very large space below decks, or in a car a chamber under the floor boards. With a car you have the very real possibility in a bad accident the camber would be breached and the flywheel explodes, releasing all that stored energy in the flywheels.

    A boat with solar panels could possibly spin up the flywheels and store it, the lower the friction bearings the better. However, unlike a car, you have no way to recover the energy when you slow down, and put it back in the flywheels. Seems to me a conventional desiel with a fuel tank would be safer and less troublesome.
     
  3. daiquiri
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    daiquiri Engineering and Design

    In my opinion, the energy-storage systems based on classical mechanics have no future. They are all very limited by weight and by material strength - besides already having been explored and examined in nearly all directions, so there's really no new things left to discover. Hence, I personally have no trust in bombastic claims related to some new mechanical energy storage devices for transportation purposes. :rolleyes:

    The next big step in energy storage will probably come from quantum mechanics and nano-technologies. Perhaps something could pop up from the Casimir effect, but that's not my field and is over me (for now ;) ).
     
  4. SamSam
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    SamSam Senior Member

    That would seem to be counterproductive. Plus it sounds like gobbelygook.

    That makes as much sense as me saying I could stop a steer with that engine but that plane won't fly using a rope for power. The only difference is I'd be telling the truth.

    http://www.google.com/patents/US20110175371?cl=en

    Mass/inertia isn't important in a flywheel?

    I think this guy has eggheaded his way into losing track of what he's doing.
    He starts with a red herring about a machined flywheel being too costly and then tunnel visions on to say that a machined, dense mass can be replaced with old underwear and dirty socks rotating in a vacuum. Well, I exaggerate, but not by much.

    These "kickstarter" type internet programs/sites where people try and get money to further their quests are studies in fraud, naivety, wrong assumptions, not researching what is already available etc. They are fun and interesting to pick apart.
     
  5. Petros
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    Petros Senior Member

    stored energy vs. cost is a valid metric, if weight and volume are not an issue. His proposal is a stationary generator type appliance. Anything that moves, like cars, boats and aircraft, weight and volume, become equally valid measurements.

    I think he acheives a lower cost storage by using more mass on a lower speed, less costly flywheel device to store the energy. It is not that it has not been done before, there was just no advange to it if you were trying to do it for transportation.

    I have even a better means of storing energy if volume and weight are not an issue. You recover almost 100 percent of the energy put into it, and it can store the energy indefinitely without any further loss at all. It is called a water tower. A large tank at the top of the hill or on a tower, when you have excess power you pump water into it. when you want to draw power out of it you use the pressure head to run a small hydraulic turbine that creates electricity (or mechanical energy if desired). As long as the water stays up high in the tank, there is no loss in storing it.

    Not practical for transportation, but it is safe and low tech. But it also takes up a lot of space too.
     
  6. daiquiri
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    daiquiri Engineering and Design

    Except for the problem that pumping the water up witha small-size pump will waste some 20-30% of the energy suplied to the pump, and a small turbine will be able to extract and convert around 80%-85% of the energy stored in the water. :p ;)
    So at the end you'll recover only around 60-65% of the initial energy fed into the pump.

    But... If you add wheels to the water tower, perhaps it could be used even for the transportation. Will leave a pretty wet trail behind... ;)
     
  7. DCockey
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    DCockey Senior Member

    A flywheel energy storage system was the group design project my senior year in mechanical engineering. My recollection is the energy which can be stored in a flywheel is a function of the flywheel's mass, tensile stress limit and a geometric shape factor. This assumes the speed of the flywheel is not constrained other than by the tensile stress limit.
     
  8. alan white
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    alan white Senior Member

    I can't imagine any flywheel storage device would ever be practical on a moving vehicle due to the relationship between weight (wheel mass) and storage capacity. One could substitute RPM for mass to reduce weight but then the material would have to be twice as strong in tensile strength. Regardless of the breakthroughs that will no doubt come, the math is pretty straightforward.
    Wheel speed and the material to withstand it are the limiting factors that are similar to the limitations we see in other devices. Some new invention may come along (not the wobble wheel) that allows incredible speeds but it would have to be a real breakthrough idea to make at least vehicular flywheels practical. Nothing of the kind appears to be in the offing.
    You could expect the same results from a huge wind-up spring, which would have almost infinite tension despite low weight.
    Vehicles of the near future will likely use electricity stored in efficient batteries, which is already possible in, e.g., the Tesla electric car. Flywheels are naturally limited by physical boundaries more problematic than any chemical boundaries would be.
     
  9. DCockey
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    DCockey Senior Member

  10. alan white
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    alan white Senior Member

    The article mentions that the flywheel had to be boosted at regular stops by means of electricity. Again, the storage capacity was ridiculously low.
    The bus probably traveled no more than a few blocks before the flywheel needed refreshing.
    Flywheels may indeed pay in situations where they are stationary. Then they can be truly massive.
    Another problem with a vehicle flywheel is the effect (for better or worse) of precession. Take a common woodworking router and get a feel for what happens when you run it in your hands and rotate it any way but around the motor axis. This could be a real problem when a boat reacts to waves in a seaway. It would change the natural movements of the boat which could cause the helm to do strange things.
     

  11. gonzo
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    gonzo Senior Member

    I think that a very large, low density system would work well in outer space where vacuum is free.
     
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