this post was submitted on 20 Aug 2024
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Is pumped-hydro inefficient or something? All the arguments about flooding land and surveying geography seem bizarre if the alternative includes a big impermeable structure. We've got those, for water. They're called pools. They're nontrivial because you have to contain pressure that desperately wants to leak out, but holding compressed air is surely harder. Water also doesn't change temperature when you move it uphill.
Why is this better than two reservoirs with a pipeline between them?
The main reason is you can site it in a lot of places you can't put pumped hydro.
... what, just anywhere flat? Pumped hydro should be feasible wherever there's a hill.
If we're building big weird structures, even that is optional. You can put one pool above-ground and another in-ground. Deep and tall presumably beat wide.
To actually do the volumes that make pumped hydro practical you need not just a hill but a space which can hold a truly huge volume of water.
Yeah pumped hydro needs lakes, not pools, as far as I know. They flood entire mountain valleys, using the surrounding mountains themselves as the storage structure, because they need so much space.
But a warehouse-sized balloon works?
Yes, because phase transitions involve absolutely huge amounts of energy.
Don't get me wrong, I love me a good pumped hydro solution, but they do come with a couple of disadvantages:
a) as others pointed out, you need a somewhat steep gradient between two places. Preferably for a bit of distance so as to increase efficiency by putting more turbines in. Their need for a gradient limits their use in flat locations such as the entire US Midwest, for example.
b) comparatively expensive and longer construction process than other storage forms.
c) usually you have to build the upper reservoir. That's an environmental harm. IMHO not that big if a concern, but it's there.
d) if you don't build out a reservoir, but use an existing lake, you risk contaminating it with algae / cyanobacteria and wreaking havoc on fish and other wildlife.