In a thought experiment of building a mechanical battery I found the following calculation very sobering.

In order to simply store the equivalent of One Kilowatt-Hour of energy the following is required:

One Kilogram of water falling one meter produces:

(1 kg water)(9.8 m/s2)(1 meter) =  9.8 kg-m2/s2 which is equivalent to

9.8 Joules of energy

                       ------------------------------

1000J/s for one hour is One Kilowatt-hr of energy

(1000J/s)(60sec/min)(60min/hour)  =  3.6 million Joules .

In order to store this much energy by raising a weight to a height of  3 meters we would need a total weight of:

(3600000 kg-m2/s2)/ ((9.8 m/s2)(3 m))  =  122000 kg. raised to a height of 3 meters.

For those of us in the United States it is equivalent to approximately 134 Tons raised to a height of approximately 10 Feet.
                                  -----------------------------

Wet sand weighs approximately 2.3g/cm3 or 19.19 lbs/ gal

A single ton of this heavy stuff would require 53 cubic meters of volume. Multiply this by 134 and you can see why energy is never stored by raising a weight, and why a gravity-based battery has never been economically developed.

For the first time in my life, my old sore knees being now ignored, I am looking at the reality that the force of gravity is a very weak force indeed.

or using water instead of sand, 1 gallon weights 3.787 Kg

so,  1 KW-Hr is roughly 32,220 gallons per hour, or approx. 550 gallons per minute through an hydroelectric generator.
with a drop height of 9.8 ft.

size = its about a 20-ft by 40-ft / 5 ft deep swimming pool.
completely dumped in 1 hour.

Yes, but consider that such an eventuality is not really about gravity wheels at all....

But instead, certain tangential possibilities.

From there, a single great leap is possible.


TS

Hi all
Why not use water.
1 liter water = 1kg
1000 liter = 1000kg = 1t

to Spoondini:
Is that the idea you red somewhere?

http://www.overunity.com/index.php?topic=3422.0

Bye

Gravity wheels do not function. 

I’m not familiar with US system. In kgms, 1ton = 1000kg, math is easier.
In the above quote there is a math error. 2.3g/cm3 would be 2.3 tons/m3. 1 such ton would require only 0.43m3.

Instead of wet sand, one may better use lead. Or even steal. Gravitational batteries are still used today although not widely; check large bridges i.e. the famous London Bridge (before its refurbishment).

What?

Let's see, wet sand weighs about 19.19#/gal so a ton is:

2000#/(19.19#/gal) = about 104.2 gallons

A gallon is 3785 ml or 0.003785 m³

so (104.2 gal ) (0.003785 m³/gal) = 0.3944 m³ ... DOH!!

Leave it to a Chemist to screw that calculation up.

so 134 tons would be (134 tons)(0.3944 m³/Ton) = 53 m³.

OK so now is this right? I probably screwed it up again, but it looks OK to me now.

I also thought about lead or steel first, but I wanted to get as close to the same densities and be very, very cheap. You can't beat sand for cheap except with water, but the wet sand density is over twice the density of water, so I figured it was the best to use to get the most weight in the smallest volume at the cheapest cost.

Still, it is very disappointing for size vs. power storage.

Thanks for finding my error.

Mr. Rat,
I like your idea.
Sort of like a grandfather clock, only a lot bigger.

Taking the same idea & tweaking it - have a barge in a tidal area - have the barge act like a pontoon i.e. four poles in the sea floor & guides mounted on the barge so that it rises & falls with the tides but doesn't move laterally - either run a cable thru a sea floor mounted pulley to land &/or a cable to a pulley above the barge then to land - have both for max work capacity - the land based cables lift a weight via a pulley on top of a tower etc to raise the masses gravitational Pe [to do work when released, say driving a generator] - the buoyancy of the barge lifts the land based mass up the tower as the tide comes in - having a dual system allows another mass to be lifted into position when the tide goes out & the barge falls, lifting the mass - free energy 4 times a day limited only by the scale.