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Thread: Capacitors

  1. #1 Capacitors 
    Forum Professor leohopkins's Avatar
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    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.


    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  3. #2 Re: Capacitors 
    Forum Ph.D. Leszek Luchowski's Avatar
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    Forget the capacitor, where do you get the wires that can carry a billion watts?


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  4. #3 Re: Capacitors 
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by leohopkins
    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.
    First off, a watt isn't a unit of energy, it is a unit of power. A watt-sec is a unit of energy.

    So assuming that you want to store 1 billion watt seconds of energy, then you would need about a 9000 farad capacitor.

    Now here's the kicker. I've found capacitors up to 5000 farads, but they are only rated for 5 volts.

    I've also found energy storage capacitors rated at about 1000 v, but they only have a capacitance of 200 uF (0.000002 Farad) so you would need some 45,000,000 of them to get your billion watt-sec storage.


    Quite frankly I don't think you are going to find anything that will meet your needs.

    For one thing, the highest energy density for capacitors presently produced is 30 Watt-hrs/kg, so you would need at least 9259 kg of capacitor (about the equivalent of 8 Honda Civics)
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  5. #4  
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    Your better off using a bunch of smaller caps at a relatively high voltage that are switched to a series circuit simultaneously producing an incredible amount of voltage and a decent amount of current. If your looking for crazy wattage I would go the voltage road before the current road as it's easier to transmit. You of course would need some good insulators.

    Perhaps something like this

    http://en.wikipedia.org/wiki/Cockcroft-Walton_generator

    Keep in mind also that the "Super capacitors" in the thousands of farads are often designed for backing up computing devices that require a fairly low current draw. I'm sure some can be had that will release massive amounts of current, but they tend not to last very long. Current rush is the next largest killer of capacitors next to heat.
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  6. #5  
    Forum Professor leohopkins's Avatar
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    Thanks guys, ill take a look.
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  7. #6  
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    Don't forget to order a few extra 5000 Farad capacitors, they'll come in real handy when you build your 2.5Hz radio transmitter......
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  8. #7 Re: Capacitors 
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    Quote Originally Posted by leohopkins
    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.
    A large circle of copper sheet metal, around a smaller circle of copper sheet metal, suspended by silk, separated by air as the dielectric will create a very high voltage very high capacitance if you make it large enough.

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    William McCormick
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  9. #8 Re: Capacitors 
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    Quote Originally Posted by William McCormick
    Quote Originally Posted by leohopkins
    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.
    A large circle of copper sheet metal, around a smaller circle of copper sheet metal, suspended by silk, separated by air as the dielectric will create a very high voltage very high capacitance if you make it large enough.

    Sincerely,


    William McCormick
    That's about as useful a reply as "you need some rocks and a smelter" when asked how to build a car.
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  10. #9 Re: Capacitors 
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    Quote Originally Posted by Megabrain
    Quote Originally Posted by William McCormick
    Quote Originally Posted by leohopkins
    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.
    A large circle of copper sheet metal, around a smaller circle of copper sheet metal, suspended by silk, separated by air as the dielectric will create a very high voltage very high capacitance if you make it large enough.

    Sincerely,


    William McCormick
    That's about as useful a reply as "you need some rocks and a smelter" when asked how to build a car.
    If you asked me how do I build a big electromagnet, I would reply with "you need a core or two cores and some magnet winding wire".

    If you have some specific size, we could probably guess at the size of the core and the number of the turns.

    If he had an exact figure, how many volts and at what amperage, and duration, he needs this capacitor to output, I can calculate to the square inch how many square inches he needs, and how far apart the plates have to be. It may be better to build a couple small ones.

    The size just requires the formula for capacitance. If he does not know it, my description is more then adequate. And if he knows it my description is more then adequate.

    I have been told I am not allowed to post pictures in Harolds forum by private message. Or I would post the pages I have on building capacitors. Very good stuff.

    On a side note I thought it was our forum.


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    William McCormick
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    well I support Harold 100% especially since all the pages you have printed so far are from books printed 90 years ago and so far out of date they must be crumbling in your hands, "British THermal Units" Foot Pounds" and a million others mean nothing to many people (no please DON@T explain, I know all about raising a pound of water by 1 deg F BUT today it's the Calorie, the energy required to raise a cc of water by 1Deg C, and the metric system a far superior 1=1=1 system whereas " A weight equal to no more than 3 straws of copper" (see if you can find that one in your book :wink: ) is outdated confusing and shows you and your answers are from an age that designed an unsinkable ship that sank.

    Now why don't you start a thread in History about ancient units of measurement and ancient scientific practices and I'd be glad to join in as might a few other old timers.
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  12. #11  
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    it was until the pictures you posted took the space of entire threads... plus, many of them are archaic, ancient, books that have been (seemingly?) scanned into a computer. If you are going to build a giant capacitor, silver plate your copper sheet metal, it adds a good bit to the conductivity and (I may be wrong) cuts down on the resistance of the capacitor. and, as posted earlier, the weight of such a monster would be calculated in tonnage, rather than pounds. I don't think a billion watts of power sustained for less than a second would be very useful, unless you are looking to make a massive electric arc or some kind of "super" taser...... Or you plan to reenact Tesla's Colorado Springs incident on grander scale.
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  13. #12  
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    Forget the silver plating, for high voltage capacitors a reduction in ESR of a few milliohms will make about as much difference as polishing a snail to reduce it's drag in still air.
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    William, here is a solution for you. Post your pictures in a thread in the trash forum and put a link to them here. That way nobody has to look at them unless they want to. And rest assured, nobody wants to.

    Also I wish you would keep the quoted material to a minimum. In fact, that's a new rule for you. No quoting previous posts.

    Megabrain, I tried to find out how many straws of copper are in a pound. All I learned was how much elemental copper per acre is needed to grow wheat.
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  15. #14  
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    Quote Originally Posted by Harold14370

    Megabrain, I tried to find out how many straws of copper are in a pound. All I learned was how much elemental copper per acre is needed to grow wheat.
    That's really meaningless Harold unless you quote variety.
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  16. #15  
    Moderator Moderator Janus's Avatar
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    [ BUT today it's the Calorie, the energy required to raise a cc of water by 1Deg C, and the metric system a far superior 1=1=1 system whereas [/quote]

    You probably shouldn't capitalize calorie here, as capitalization has been used to distinguish between the gram-calorie, of which you are talking about here and the kilogram-calorie which is a thousand times larger, and can go by "Calorie".

    It isn't a iron-clad rule, however.

    For instance, food calories are Kilogram-calories, though I've seen them as both calorie and Calorie. It is just understood which is meant by context.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  17. #16 Re: Capacitors 
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    Quote Originally Posted by leohopkins
    Does anyone know where I can buy or get hold of some capacitors that will store an extremely large amount of energy? - Id like something that I could charge up over time using standard 240v domestic supply, but when released could throw out around a billion watts of energy.
    What you want are batteries.

    The amp-hour rating will tell you how much energy you can store.
    P = [ amp-hr x voltage ] x time.

    And billions of watts is a bit ambitious, wouldn't you agree ?

    At a high energy physics lab, we store large amounts of energy in a
    massive flywheel called an MG Set [motor - generator].
    I doubt you want to build one of these unless it is a small demonstration model.

    ====================
    Why are my "quotes" coming out as pure text and not in a shaded box
    like most everyone else ?
    I click "Quote" and then add my reply.
    It seems to me that should work.
    What else must I do or refrain from doing ?

    Thanks
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