1. SubscriberPonderable
    chemist
    Linkenheim
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    31 Oct '12 08:491 edit
    Hi,

    I came across this:

    YouTube&feature=youtu.be

    EDIT: Their homesite: http://www.energycache.com/

    They suggest to store electrical energy in gravel. So the principle is old and tested with water.

    Their point is that the density of gravel is a factor of 2.5 of water, and any hill can be converted into a gravel-based storage.

    Opinions?
  2. Cape Town
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    31 Oct '12 15:53
    I don't see the density having any major benefits here. Simply make the buckets a bit bigger, and you can use water. Water is probably also much easier to handle in general and can be run through pipes rather than complicated bucket systems. It is also easier to make a large reservoir of water. Gravel reservoirs would be limited in size - hence the need for the whole array shown in the video.
  3. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
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    31 Oct '12 22:531 edit
    Originally posted by twhitehead
    I don't see the density having any major benefits here. Simply make the buckets a bit bigger, and you can use water. Water is probably also much easier to handle in general and can be run through pipes rather than complicated bucket systems. It is also easier to make a large reservoir of water. Gravel reservoirs would be limited in size - hence the need for the whole array shown in the video.
    One thing about gravel in its favor is it won't flow out of a bucket with tiny holes in it. Water buckets have to be very well sealed. Also, in our territory, if it were water, it would freeze in the winter here in Pa. The gravel idea would never have problems with freezing, unless the lube froze.

    The one thing I don't see it saying is this: the prototype is listed as storing 50 Kw. Does that mean the prototype as seen there generates 50 Kw for one hour? Or does it generate 50 Kw for 10 minutes? Or 2 hours? It doesn't say the Kwhr rating.
  4. Subscriberjoe shmo
    Strange Egg
    podunk, PA
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    01 Nov '12 00:19
    Originally posted by sonhouse
    One thing about gravel in its favor is it won't flow out of a bucket with tiny holes in it. Water buckets have to be very well sealed. Also, in our territory, if it were water, it would freeze in the winter here in Pa. The gravel idea would never have problems with freezing, unless the lube froze.

    The one thing I don't see it saying is this: the prototyp ...[text shortened]... e hour? Or does it generate 50 Kw for 10 minutes? Or 2 hours? It doesn't say the Kwhr rating.
    I would imagine it is just stating the maximum power of the plant. I suspect it could sustain that power as long as it takes to empty the gravel dam at the top. But how long is that? Depends on the size of the dam.
  5. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
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    01 Nov '12 00:55
    Originally posted by joe shmo
    I would imagine it is just stating the maximum power of the plant. I suspect it could sustain that power as long as it takes to empty the gravel dam at the top. But how long is that? Depends on the size of the dam.
    I was thinking about the usability of this system in Pennsylvania winters and thought it would get clogged up if it were in a freezing rain, the gravel would be stuck together.
  6. Subscriberjoe shmo
    Strange Egg
    podunk, PA
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    01 Nov '12 01:21
    Originally posted by sonhouse
    I was thinking about the usability of this system in Pennsylvania winters and thought it would get clogged up if it were in a freezing rain, the gravel would be stuck together.
    Yeah, your probably correct...our state doesn't seem to be the optimum state to implement the system in.
  7. Cape Town
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    01 Nov '12 13:11
    Originally posted by sonhouse
    One thing about gravel in its favor is it won't flow out of a bucket with tiny holes in it. Water buckets have to be very well sealed.
    But as I pointed out, the usual system for water, is pipes and generators. The whole bucket system is only necessary because of the change to gravel.

    Also, in our territory, if it were water, it would freeze in the winter here in Pa. The gravel idea would never have problems with freezing, unless the lube froze.
    I don't know whether hydro electric plants have problems with freezing.

    The whole thing seems overly complicated to me. Why not simply have one large weight that is raised or lowered as needed? It can be on rails with a cable for lifting. Far less moving parts, less wear and tear, less frictional losses etc.
  8. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
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    01 Nov '12 16:531 edit
    Originally posted by twhitehead
    But as I pointed out, the usual system for water, is pipes and generators. The whole bucket system is only necessary because of the change to gravel.

    [b]Also, in our territory, if it were water, it would freeze in the winter here in Pa. The gravel idea would never have problems with freezing, unless the lube froze.

    I don't know whether hydro elec ...[text shortened]... ith a cable for lifting. Far less moving parts, less wear and tear, less frictional losses etc.[/b]
    I don't think there are any hydro dams in Pa, except maybe private small ones generating a few Kw.

    Why do we need to lift weights at all? Why not just pump air into an underground sealed cave and use the pressurized air to run a turbine? The amount of moving parts goes down drastically, it can work even in Antarctica where the temperature gets cold enough to make dry ice snow.

    It can work there because the building housing the parts can be insulated and heated with not a whole lot of energy needed. The better the insulation the less energy needed to keep things from freezing.

    You would need to build a structure a kilometer high to get any kind of real energy storage, that alone would push the price in to the hundreds of millions of dollars if not more.

    A hundred million bucks will buy a lot of lithium ion batteries!

    BTW, here is a link to an article about tripling or more, the power density of Li Ion batteries using silicon as part of the anode. Silicon can absorb a lot of lithium but it expands to triple its size in doing so, and like water freezing in a bottle, can destroy the battery just as water freezing in a glass bottle will break the bottle when it expands.

    They have found a way to control that expansion.

    http://phys.org/news/2012-11-boost-silicon-based-batteries.html
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