4 ms·

The main problem in my mind is not where to store the compressed air, but the poor efficiency of compressing/using the air. Compressing air produces quite a bit

The main problem in my mind is not where to store the compressed air, but the poor efficiency of compressing/using the air. Compressing air produces quite a bit of heat, and you have the opposite problem when using the air. For Thermal and other storage methods while the storage part might be more lossy, they are less lossy over all because they dont toss away 80% of the power before it can be stored. If it was more efficient, than we would see air powered cars (not the scam that surfaces every other year). Industry only uses it to power things because you can have simple & compact actuators and high rpm motors.

dredmorbius 11y ago
Realise that virtually all your energy storage options have hugely pressing cost, capacity, or storage stability problems. Pumped hydro's remarkably efficient, fast-responding (minutes), but extremely limited in scale. See Tom "Do the Math" Murphy, but I think you'd need ~1,500 or was it ~15,000 Hoover-dam sized project for US storage capacity. Batteries are fairly efficient, but respond slowly (you can neither charge nor discharge them rapidly), and at scale virtually all have massive substrate / materials shortages -- lead and lithium particularly. Iron-based batteries should be abundant, and liquid metal or molten-salt batteries seem to be the most abundant. Storage densities aren't great, but if you're building stationary facilities, that's not a concern. The 600C - 800C temperatures may be though. Having a neighbourhood melt-out wouldn't be pretty. Biomass might work for standby thermal generation. Thermal salt storage also pencils out. But any thermal storage system, that is, hot stuff you use to boil a working fluid that runs through a gas turbine, suffers from Carnot efficiency losses, about 35-45 max efficiency. If in a desert area, you've got problems of cooling your working fluid without venting too much of it (or the coolant). Not insoluble problems, but an issue. Heat also doesn't store indefinitely though it should be good for hours to a few days. Fuel synthesis has the advantage of scaling fairly arbitrarily large, particularly with liquid hydrocarbons. Put them in liquid-proof tanks and they'll stay there. Storage stability is proven to 100s of millions of years, so there's that. They're also transportable and can be utilised on-site. You lose 50% in hydrogen electrolysis, plus 65% on Carnot, for a net return of about 17%, but if you've sufficient peak surplus, that's viable. CAES has the hot/cold problem, but there's a lot of air, and there's a lot of underground reservoir. Again I'm not sold that it pencils out, but it's possible. Other options include direct banking of heat for buildings and/or industrial processes -- these use a lot of energy, and direct application and storage avoids electric or electric-to-fuel conversion losses. It'll be interesting.

dredmorbius 11y ago

Realise that virtually all your energy storage options have hugely pressing cost, capacity, or storage stability problems. Pumped hydro's remarkably efficient, fast-responding (minutes), but extremely limited in scale. See Tom "Do the Math" Murphy, but I think you'd need ~1,500 or was it ~15,000 Hoover-dam sized project for US storage capacity. Batteries are fairly efficient, but respond slowly (you can neither charge nor discharge them rapidly), and at scale virtually all have massive substrate / materials shortages -- lead and lithium particularly. Iron-based batteries should be abundant, and liquid metal or molten-salt batteries seem to be the most abundant. Storage densities aren't great, but if you're building stationary facilities, that's not a concern. The 600C - 800C temperatures may be though. Having a neighbourhood melt-out wouldn't be pretty. Biomass might work for standby thermal generation. Thermal salt storage also pencils out. But any thermal storage system, that is, hot stuff you use to boil a working fluid that runs through a gas turbine, suffers from Carnot efficiency losses, about 35-45 max efficiency. If in a desert area, you've got problems of cooling your working fluid without venting too much of it (or the coolant). Not insoluble problems, but an issue. Heat also doesn't store indefinitely though it should be good for hours to a few days. Fuel synthesis has the advantage of scaling fairly arbitrarily large, particularly with liquid hydrocarbons. Put them in liquid-proof tanks and they'll stay there. Storage stability is proven to 100s of millions of years, so there's that. They're also transportable and can be utilised on-site. You lose 50% in hydrogen electrolysis, plus 65% on Carnot, for a net return of about 17%, but if you've sufficient peak surplus, that's viable. CAES has the hot/cold problem, but there's a lot of air, and there's a lot of underground reservoir. Again I'm not sold that it pencils out, but it's possible. Other options include direct banking of heat for buildings and/or industrial processes -- these use a lot of energy, and direct application and storage avoids electric or electric-to-fuel conversion losses. It'll be interesting.