Flywheel energy transfer mechanism

Discussion in 'General Electronics Chat' started by RogueRose, Apr 7, 2016.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
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    I've seen reports that state that flywheels can be used to store energy for use in quick discharge (basically like a capacitor). I'm wondering how this is achieved and whether something like a generator is used. I know large resistors are/were used as brakes in trains but I'm unsure what tech is used to convert the mechanical to electrical in such a fast manner?
     
  2. Kermit2

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    Feb 5, 2010
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    Just like the Alternator in your car. The rotor spins but does nothing until the field coil is energized. At that time it becomes an electrical generator and supplies power derived from the flywheel.
     
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  3. mcgyvr

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    Oct 15, 2009
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    link to said report so we can remove the marketing/blah blah from the facts for you..
     
  4. nsaspook

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    Aug 27, 2009
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    From a Brake Resistor Design Doc:
    http://www.hilkar.com/inverterbreakingresistors.html
     
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  5. DGElder

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    Apr 3, 2016
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    You would add a flywheel to a a system to store energy. - the kinetic energy can be used to store energy for latter use or to smooth out the delivery of power to the system - the analog of a capacitor in a power supply.

    The energy delivery configuration depends on what the system designer is trying to accomplish - store or dissipate the flywheel inertia in the system. If a flywheel is mechanically coupled to a generator with no load on it, it can spin with little loss of energy through friction and eddy current losses. Or even less if it is mechanically decoupled from the flywheel. But then if you electronically switch in a load to the coupled generator, such as a resistor bank, the generator will dissipate the kinetic energy from the flywheel by generating heat in the resistor. The same generator could then be switched in as a motor to spin the flywheel back up to speed. Alternatively, the generator could charge a battery or capacitor bank so as not to waste the energy.
     
  6. RogueRose

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    Oct 10, 2014
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    I've heard of large flywheels powering trollies or buses over a century ago (read it many times, think it was in San Fran, don't have link but will look). I understand how the energy is stored in the wheel and transferred in this scenario. What I'm unsure of is when flywheels are mentioned to replace capacitors for powering things like large railguns, launch devices, CERN, etc.

    Since a cap discharges in fractions of a second for those devices, and at high current/voltages, I just didn't see how that would be possible with a normal generator powered from the flywheel. I know the one rail gun was supposed to require 32 -64 MJ of energy (or that was delivered energy -on target - so much more would be needed to launch with losses).

    I was trying to figure out how to deliver 5-10 KJ with a flywheel (not going to produce IRL, but for comparison numbers).
     
    Last edited: Apr 7, 2016
  7. DGElder

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    Apr 3, 2016
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    I don't know much about rail guns but obvious source of energy would be capacitors to deliver high power for a fraction of a second. They use the same principle to power lasers in fusion reactors. They could also couple a pulse generator to a flywheel. The flywheel allows you to power up the system with a relatively low power source - storing and accumulating the energy in the flywheel as it spins up ever faster. Then the pulse generator is switched on and all that energy is dumped into the rail gun as a massive pulse of current.

    A flywheel makes sense for cable cars in SF because of all the hills. You can use the energy from the cars going downhill to add energy back into the wheel to pull the other cars up hill. You only need to add enough energy to overcome friction losses. I imagine the cars had a clutch operated by the conductor to grab the cable.
     
    Last edited: Apr 7, 2016
  8. cmartinez

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    Jan 17, 2007
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    A few years ago what you're mentioning was thoroughly researched and tested in the lab for automotive use. But it failed to function in the real world, mainly because of the friction forces at its bearings, and the dangerous speeds involved. Also, the gyroscopic effects when turning the wheel around would add to the problem.
     
  9. hrs

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    Jun 13, 2014
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    There are these things:
    [​IMG] [​IMG]
    These are from Hitec power protection, a company near where I live, but I'm sure there are other manufacturers with similar products. I had a factory tour there some years ago and if I remember correctly these systems can sustain up to several megawatts of power for about 5 seconds while the back-up diesel kicks in.
     
  10. kubeek

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    Sep 20, 2005
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    Flywheels are quick, asi in a few seconds quick to give out all the stored energy, but you can´t really expect them to dump it in a few miliseconds or faster, as you would need for a railgun. Even at extremely high RPM the torque on the shaft would be enormous to deliver that amount of power, and the generator attached would be enormous as well since it needs to provide many MWs even if just briefly.
     
  11. shortbus

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    Sep 30, 2009
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  12. nsaspook

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    The mechanical forces from a very quickly stopped flywheel can be enormous and dangerously explosive if not contained. These little devils (MagLev Hi-Vac turbo pumps) both suffered a fraction of a second stoppage failure at ~50,000RPM. It sounded like a bomb exploding.
    [​IMG]
    [​IMG]
     
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  13. RichardO

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    May 4, 2013
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    cmartinez may like this but it saddens me greatly.
     
  14. cmartinez

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    Jan 17, 2007
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    I liked the picture... not the disaster... I still have some hope in this technology, my guess is that if it ever works out, new and advanced metallurgical science is going to have a lot to do with it in the end.
     
  15. RogueRose

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    Oct 10, 2014
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    Crystaline carbon /graphene nano tube possible?
     
  16. cmartinez

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    Possibly... it would have to be a material capable of withstanding large vibration amplitude, with no imperfections... maybe a monocrystaline steel alloy...
     
  17. ronv

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    Nov 12, 2008
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