what is the most economical way to store electrical energy on a large scale?

General Questions
#1

suppose within a year the Alien Space Bats will teleport all evil-and-polluting power plants in (heavily dependent on such) Ruritania off to the other side of the Moon, leading to power shortages and exorbitant prices. In the meantime, for now electricity is still cheap and plentiful.

In such conditions, what technologies might the Ruritanian companies use to store energy for resale or consumption later on? I am guessing that part of the answer might be stockpiling of energy intensive commodities like aluminium and silicon. Nevertheless, that’s not quite energy storage per se. Let’s say maybe Ruritanian Motors needs actual electricity to run the factories so they want to be able to get some “out of thin air” once production is curtailed.

Well, so what are optimal technologies for storing a lot energy cheaply? Would that be pumped storage? Or emptied out gas wells filled with hydrogen under pressure? The same gas wells filled just with pressurized air that can be then run through a turbine? Some sort of cheap, massive batteries?

AFAIK, at least the pumped storage has been used to some extent in reality by the electrical infrastructure for load balancing purposes. Is this an efficient technology? Is its use heavily limited by absence of appropriate locations or are they in fact widespread and fulfilling all our load balancing needs?

#2

Electrical storage sucks. In your situation, you’d better off building windmills or solar cells that don’t pollute at all (once they’re made). I guess you’d want a few batteries to smooth out those systems. They should build dams too, if they can.

#3

IIRC: The best we have right now is pumping water up a hill and then using it to run a hydroelectric turbine.

#4

Flywheels can be 90%+ efficient, without the lifespan limits of chemical batteries. That’s going to be much better than hydro storage or some sort of weird gas well storage system.

Until we have superconductor storage, flywheeels are probably the best option.

BTW, they are considering using flywheels in Le Mans prototypes for regenerative energy storage, so it isn’t as if flywheels are a pie-in-the-sky tech.

#5

There is no way to store quantities of energy sufficient to supply Ruritania’s electrical demand for more than a few hours or days, even if every mountain was used for pumped storage and every cave was used for compressed air storage. Furthermore, these technologies could not be implemented in a year. Ruritania’s only hope is to commission as much non-polluting (defined as acceptable to the ASBs) generation as possible.

#6

hibernicus, that’s true, but then electrical consumption would also plummet and prices will be very high. So every extra cave full of whatever (or any other form of energy stockpile) might represent a big profit for the owners.

Ruritania will probably eventually rebuild its powerplants (once the ASB leave) rather than go back to the 18th century technology level. But that takes time and storing soon-to-be expensive energy wouldn’t hurt.

#7

Flywheels are a reasonable alternative for storing a limited amount of energy for a limited time. The big problem is they don’t scale well: a flywheel built on an automotive scale is somewhat challenging, but very feasible; a flywheel or series of flywheels built to hold enough energy to power a city is enormously complicated.

Although I don’t disagree with your conclusion, I suspect one could store more than just a few hours worth of energy using “every mountain.”