Well, no. The round trip efficiency of pumped hydro is terrible. And flywheels aren't scalable. 72% is pretty decent and I'm sure that can still be improved.

[–] Skua@kbin.social 5 points 6 months ago* (last edited 6 months ago) (1 children)

Round trip efficiency of modern pumped storage hydro is about 80%. How is that horrible if 72% is decent?

Pumped hydro obviously does have drawbacks in that it requires you to have the water and suitable landscape available to dedicate to it, but efficiency doesn't seem to be one of them

[–] wewbull@feddit.uk 4 points 6 months ago* (last edited 6 months ago)

Energy density is terrible of pumped hydro, plus you have the environmental impact; tunnel out the inside of a mountain, place a generator hall in there, and then flood a valley. Sure it look ok at the end of it, but huge damage has to be done each time. All of that coats large sums of money too, and it can only be done in a relatively small number of locations. Step 1. You need a mountain to pump the water up.

Compressed air batteries are a lot more energy dense, so smaller footprint, so much lower environmental Impact / cheaper and they don't rely on particular geographic features to work. They might be a bit less efficient, but that seems like a good trade to me.

[–] threelonmusketeers@sh.itjust.works 3 points 6 months ago (1 children)

If you have a good heat exchanger, don't you get most of that energy back when expanding the gas?

[–] captain_aggravated@sh.itjust.works 1 points 6 months ago

What does "a good heat exchanger" look like in this case? You compress air, the pump heats up, so you ventilate it to keep it cool. The air in the tank is hot, and starts to cool as it sits in the tank, and this causes a decrease in pressure, which is why even with no leaks a shop air compressor will run for awhile, stop, then after awhile cut back on again.

I get that I'm applying a shop tech's "machines that I can move with a hand truck" understanding to factory-size operations here but...