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This is what Danielle Fong at Lightsail has been doing since 2009. They've had investment from Bill Gates and Peter Thiel. They've developed a way to compress a

by artr 10y ago

This is what Danielle Fong at Lightsail has been doing since 2009. They've had investment from Bill Gates and Peter Thiel. They've developed a way to compress and decompress air efficiently by heating/cooling the air. by using a carbon fibre air canister they are able to store air at a much higher pressure than previously possible. Her Ted Talk[1] and their website[2] explains it much better than I do. [1] https://www.youtube.com/watch?v=hZiaTV6uvFQ https://www.youtube.com/watch?v=hZiaTV6uvFQ [2] http://www.lightsail.com/ http://www.lightsail.com/

extrapickles 10y ago
Compressed air storage rings of a scam to me. They never mention how efficient it is to compress the air and turn the air back into electricity. It's always how efficient their storage tank is, which on paper gives batteries a run for their money. When sizing an industrial air system a rule of thumb is to budget 7-8hp of compressor for 1 hp of air motor. That is 12% efficiency, or only worth it if you had no other source of power. I'll give them the benefit of the doubt and assume a tightly integrated system you could do 3x better, but it still doesn't come close to batteries. If someone has plug-plug numbers that are better, let me know.
- dredmorbius 10y ago
  My understanding is that the grid-scale stuff will be using natural geological reservoirs -- basically re-filling old gas wells with air. My understanding isn't particularly deep, and I'd like to run numbers on storage, volume, pressure, etc. But I suspect this'll have to be big enough that constructing cans really isn't viable.
  - evgen 10y ago
    Doesn't this run into insulating problems for the resevoir? How do you prevent the pressure from being lost as heat?
    - dredmorbius 10y ago
      Rock is a pretty good insulator. Anythhing exposed to fluid isn't. Groundwater flws, tanks in air. I'm not sure about possible ignition explosion risk from residual methaane or hyrogen, say.
  - extrapickles 10y ago
    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 10y 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.
- shalmanese 10y ago
  There's some secret magic going on using moisture and phase change to drastically up the efficiency and storage capacity. It's not just a simple compressed air system which, as you noted, doesn't work. No idea if their current system will work or not but it's complicated enough that they've spent 7 years trying to get it right.

by artr 10y ago

extrapickles 10y ago

Compressed air storage rings of a scam to me. They never mention how efficient it is to compress the air and turn the air back into electricity. It's always how efficient their storage tank is, which on paper gives batteries a run for their money. When sizing an industrial air system a rule of thumb is to budget 7-8hp of compressor for 1 hp of air motor. That is 12% efficiency, or only worth it if you had no other source of power. I'll give them the benefit of the doubt and assume a tightly integrated system you could do 3x better, but it still doesn't come close to batteries. If someone has plug-plug numbers that are better, let me know.

dredmorbius 10y ago
My understanding is that the grid-scale stuff will be using natural geological reservoirs -- basically re-filling old gas wells with air. My understanding isn't particularly deep, and I'd like to run numbers on storage, volume, pressure, etc. But I suspect this'll have to be big enough that constructing cans really isn't viable.
- evgen 10y ago
  Doesn't this run into insulating problems for the resevoir? How do you prevent the pressure from being lost as heat?
  - dredmorbius 10y ago
    Rock is a pretty good insulator. Anythhing exposed to fluid isn't. Groundwater flws, tanks in air. I'm not sure about possible ignition explosion risk from residual methaane or hyrogen, say.
- extrapickles 10y ago
  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 10y 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.
shalmanese 10y ago
There's some secret magic going on using moisture and phase change to drastically up the efficiency and storage capacity. It's not just a simple compressed air system which, as you noted, doesn't work. No idea if their current system will work or not but it's complicated enough that they've spent 7 years trying to get it right.