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Lumifer comments on Stupid Questions May 2015 - Less Wrong Discussion
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Following on from this question, since cheap energy storage is a big obstacle to using wind/wave/solar energy, why is gravity-based energy storage not used more?
Many coasts have some cliffs, where we could build a reservoir on top of the cliff and pump up seawater to store energy. What is the fundamental problem with this? Efficiency of energy conversion when pumping? Cost of building? The space the reservoir would take (or the amount of water it could hold)?
Cost. Wind/wave/solar energy is more expensive than fossil-fuel or nuclear energy to start with, and adding not-too-efficient storage mechanisms to even out the supply does not help it at all.
Really, the answer to most questions of this kind is "cost". It is the default and usually correct answer.
But "cost" isn't very specific. Is the major problem that it's too inefficient? That it takes too much to build? Too much to maintain?
Doesn't the energy grid need good storage anyway, to even out differences between day and night?
If it were cheap enough, maybe, but at the moment the demand fluctuations are covered by power generating plants which come online in times of high demand (e.g. day) and shut off during low demand (e.g. night). Typically these plants burn natural gas.
Sufficiently cheap storage would be very useful, yes.
Actually, pumped storage hydro is used for the purposes than DanArmak describes; see my post elsewhere in this thread.