An idea for mechanically storing energy

[JoeKing]

I think you overlooked my post. Before investing billions of dollars in your storage system, it would be far more economical to simply use existing transmission lines to send the power to some place where it would be much more feasible to use the natural terrain.

I'll run some numbers for you though:
http://en.wikipedia.org/wiki/Raccoon_Mountain_Pumped-Storage_Plant
http://www.tva.gov/sites/pdf/raccoonmtn.pdf

Or rather, I don't think we really need to run too many numbers - look at it this way - the reservoir is 528 acres. Think about what volume of water they're dealing with. They excavated 10 million cubic yards for the lake. Whatever the mass is that you're pushing up an incline... do you know how much 10 million cubic yards of water weighs? (Actually, I'm not sure what the water capacity of the lake is though.) The density of steel is about 8 times that of water. The density of concrete is less than 3 times that of water. Can your system lift 1 million cubic yards of steel to a height of nearly 1000 feet? (990 feet at Raccoon Mountain.) 1 cubic yard is 13000 pounds. You need to lift a MILLION cubic yards. Do you have any idea how large a hunk of solid steel that is? Or, another easier way to think about it is that you'd need to lift a solid block of steel 1000 feet; the block would be about one eighth the size of the capacity of that lake - 66 acres and 200 feet thick.

I think your tunnel would be woefully inadequate. Not to mention, water is pretty cheap vs. a shitton (a million shit tons) of steel.

Another point to make is that you want a shallower angle, rather than lifting vertically. A shallower angle is going to result in more frictional losses than lifting vertically.

Wouldn't the loss of power in transit to such "dam" sites be too great? Don't get me wrong I really like and believe in that method of energy storage, but I can't don't know if you can build those types of dams in many places.

As for my system I was thinking we could use many weights? But you do bring up a great point concerning the actual size the weights would have to be to make this work. I guess I grossly underestimated this.

I was thinking multiple weights like this, but on a much larger scale.

 

[Mark R]

Wouldn't the loss of power in transit to such "dam" sites be too great? Don't get me wrong I really like and believe in that method of energy storage, but I can't don't know if you can build those types of dams in many places.

No. Transmission of bulk electricity is extremely efficient. It costs about 2% to send bulk electricity about 300 miles; with even higher efficiency possible on special lines. The amount of energy lost in those high-voltage long distance lines is actually smaller than the amount of electricity lost carrying the power from the pole to houses, and powering the electricity meters.

Additionally, pumped storage hydro is very efficient as far as energy storage is concerned - with 'round trip' efficiency of about 75-80%. I.e. for every 100 kWh you put in, you receive 75-80 kWh back on demand.

There are few storage systems of comparable efficiency, at any scale. 75-80% is considerably better than is achievable with battery technology (except state of the art lithium-ion), better than compressed air, hydraulic, etc.

As for my system I was thinking we could use many weights? But you do bring up a great point concerning the actual size the weights would have to be to make this work. I guess I grossly underestimated this.

I was thinking multiple weights like this, but on a much larger scale.

The problem is simply one of scale - A silo like the one you show might weigh 100 tons.

A decent sized pumped storage hydro lifts 10 million tons - in other words, you would need 100,000 concrete weights the size of that silo. The other problem is height. A decent pumped storage plant might lift the water 3000 feet. Imagine a mile-long freight train, going up a high mountain - now imagine that you need something 1000 times that size.

The problem then becomes, how much will those weights cost (about $400/ton), let alone the machinery to move them, and the drilling of the massive shafts needed to allow them to drop.