In reply to David Riley:
> Obviously it can't. When it reaches the top of the dam that's it.
> Which is why the Dinorwig system can only run for a very short time.
Just as you can make the pile of weights bigger you can make the lake bigger. I said *practically* limitless, not that you can exceed the design parameters by piling more water in but that it's relatively easy at design time to add storage to suit your requiredments.
It'll run ~5Hrs flat out (1.8GW, 9GWH assuming they can keep it cool). I don't think that's a short time given it won't generally run flat out.
To store 9GWH (32,400GJ) of GPE in concrete on the same site would require
32400 * 10^9 / 10 * 520 = 6,200,000 Tons
2,500,000 cubic meters of concrete, roughly 33,000 shipping containers, roughly twice what the biggest ships on the seas can carry!
Plus all the handling equipment required to move that lot around.
> This is one of the main advantages of doing it with solid blocks. You would be able to have a considerably greater mass stacked much deeper to give more storage and longer working times without needing exactly the right hanging valley and a dam.
> No. The blocks would be packed together. So no more space would be used than for the water storage.
Lakes are a pretty natural looking unobtrusive addition to the mountain landscape. A huge freight yard and gantry crane aren't.
> Your objections seem to be based on a concept of how it would work which differs from mine and I don't understand what you are thinking.
I do tend to let my negativity get in the way of big ideas but I really don't get it. Stacked, handled, released, re-stacked how? All has to be done seamlessly in a hostile environment with minimal visual impact.
Water does all of this by itself without cranes and trains and all below the surface of a a pair of placid lakes.
> The potential energy storage is not changed just because the mass is solid rather than liquid, so theoretically do you not think the same results could be achieved ?
Of course you can store release energy by raising/lowering a solid mass. I'm not disputing that.
> You appear to have a negative view of the proposal and have come up with a vision of how awful it would be. My view is optimistic and I think I can envisage an elegant solution with no disadvantages. Of course it may ultimately prove impractical.
It already has proved impractical, pumped hydro won hands down. It's likely to be the grid-scale storage of choice in one form or another for a long time to come.
jk