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Kelvin water dropper generator

  1. Aug 29, 2012 #1
    I have only recently found out about this idea (many thanks m.e.t.a.) and I am curious about it. Could it be used to produce electricity on a mass scale, and if not, why not? Is the efficiency of conversion from gravitational potential energy into electric potential energy less that the conversion to kinetic energy in a hydroelectric turbine, for example? Or is it perhaps related to the discrete rather than continuous nature of the high potential difference?

    Thanks for your help,

  2. jcsd
  3. Aug 29, 2012 #2


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    Staff: Mentor

    I would expect that both the efficiency and the maximal flow rate (a small stream per device) are too small to be useful.
    You need several cubic meters per second to get any useful amount of power (with 100m height difference, 1m^3/s just corresponds to 100kW input power)

  4. Aug 30, 2012 #3
    Thanks mfb. The energy loss from impact is something I hadn't taken on board.
  5. Aug 30, 2012 #4
    I don't think there is a minimum to this loss, since the electric field between the ring and the bucket will counteract gravity, so the drops could theoretically hit the water with zero speed.
  6. Aug 30, 2012 #5


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    Please pay attention to two very different kinds of apparatus: Hydroelectric power generators and Kelvin Water-drop generators.

    Here are a few excerpts from the Wikipedia page on “hydroelectric generator”:

    “Hydroelectric generators are found world-wide. In China the Three Gorges Dam generates 20,300 Megawatts and in the USA the Grand Coulee Dam generates 6,809 Megawatts.

    Pico hydro is a term used for hydroelectric power generation of under 5 KW. It is useful in small, remote communities that require only a small amount of electricity. For example, to power one or two fluorescent light bulbs and a TV or radio for a few homes.[13]

    Even smaller turbines of 200-300W may power a single home in a developing country with a drop of only 1 m (3 ft). Pico-hydro setups typically are run-of-the-river, meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before returning it to the stream.”

    The purpose of the water-dropper is not to generate electric power. A Kelvin Water-drop generator generates a high voltage potential between its two electrodes. They may be buckets or spheres, but there is no significant amount of electrical power stored on the electrodes. A fully charged sphere, for example, may cause a few micro-amperes to flow during a short-circuit arc for a few microseconds. This is not a significant amount of power and would not power a load.

  7. Sep 1, 2012 #6
    Thanks for your help. I need to think about this a bit more!

    Cheers, Rooted
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