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How Cheap Can Energy Storage Get? Pretty Darn Cheap

5 points by ph0rque 11y ago

infogulch 11y ago
I'm surprised Nickel-iron batteries[0] aren't used for this type of grid-scale storage. They are extremely time and cycle-durable: 20-50 years, almost immune to repeated deep discharges, relatively cheap and simple to produce. Cons: they need a bit of maintenance (not a big deal at grid scale), and have a less-than-stellar efficiency. The problem with compressed air is that the Ideal-gas law [1] actively works against you to reduce efficiency, assuming it will be kept at ambient temperature. Inserting energy by compressing gas heats it up, which increases the pressure of the gas in the tank, which makes you work harder to put more gas in. Extracting energy cools the gas down, which reduces the pressure of the gas, which reduces the amount of energy you can extract from it. You can mitigate these issues by carefully controlling the temperature of the gas (more energy) or having a much much bigger tank so a single cycle only thermally cycles by a small amount (more $$). Another option I hadn't considered until now is to let it heat up -- and insulate it to let it stay hot. It will cycle in both pressure and temperature on a nearly daily basis so you may not lose all that much energy in heat. But I doubt this is an original idea. [0]: https://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery https://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery [1]: https://en.wikipedia.org/wiki/Ideal_gas_law https://en.wikipedia.org/wiki/Ideal_gas_law
- ph0rque 11y ago
  Regarding the compressed-air problem you mentioned, have you seen LightSail Energy's (http://lightsailenergy.com http://lightsailenergy.com) solution to it? "Our innovation: an elegant method of capturing this heat energy and regenerating useful energy from it. We inject a fine, dense mist of water spray which rapidly absorbs the heat energy of compression and provides it during expansion." Maybe one of the founders, @DaniFong (https://news.ycombinator.com/user?id=DaniFong https://news.ycombinator.com/user?id=DaniFong), can chime in.
  - DaniFong 11y ago
    You've pretty much got it. The author mentions us actually. The parent commenter does accurately locate the challenge to date with compressed air energy storage, but we've directly and successfully targeted that loss channel :-)
    - infogulch 11y ago
      Thanks for replying. Most compressed air systems attempt to pull as much moisture out of the air as possible to prevent corrosion, but your solution to the heat problem means actively making the air and interior even more wet. This wouldn't be a problem in the short term, but your product is meant to be used over a very long period (~20 years); how are you approaching the issue with corrosion?

5 points by ph0rque 11y ago

I'm surprised Nickel-iron batteries[0] aren't used for this type of grid-scale storage. They are extremely time and cycle-durable: 20-50 years, almost immune to repeated deep discharges, relatively cheap and simple to produce. Cons: they need a bit of maintenance (not a big deal at grid scale), and have a less-than-stellar efficiency. The problem with compressed air is that the Ideal-gas law [1] actively works against you to reduce efficiency, assuming it will be kept at ambient temperature. Inserting energy by compressing gas heats it up, which increases the pressure of the gas in the tank, which makes you work harder to put more gas in. Extracting energy cools the gas down, which reduces the pressure of the gas, which reduces the amount of energy you can extract from it. You can mitigate these issues by carefully controlling the temperature of the gas (more energy) or having a much much bigger tank so a single cycle only thermally cycles by a small amount (more $$). Another option I hadn't considered until now is to let it heat up -- and insulate it to let it stay hot. It will cycle in both pressure and temperature on a nearly daily basis so you may not lose all that much energy in heat. But I doubt this is an original idea. [0]: https://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery https://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery [1]: https://en.wikipedia.org/wiki/Ideal_gas_law https://en.wikipedia.org/wiki/Ideal_gas_law

ph0rque 11y ago
Regarding the compressed-air problem you mentioned, have you seen LightSail Energy's (http://lightsailenergy.com http://lightsailenergy.com) solution to it? "Our innovation: an elegant method of capturing this heat energy and regenerating useful energy from it. We inject a fine, dense mist of water spray which rapidly absorbs the heat energy of compression and provides it during expansion." Maybe one of the founders, @DaniFong (https://news.ycombinator.com/user?id=DaniFong https://news.ycombinator.com/user?id=DaniFong), can chime in.
- DaniFong 11y ago
  You've pretty much got it. The author mentions us actually. The parent commenter does accurately locate the challenge to date with compressed air energy storage, but we've directly and successfully targeted that loss channel :-)
  - infogulch 11y ago
    Thanks for replying. Most compressed air systems attempt to pull as much moisture out of the air as possible to prevent corrosion, but your solution to the heat problem means actively making the air and interior even more wet. This wouldn't be a problem in the short term, but your product is meant to be used over a very long period (~20 years); how are you approaching the issue with corrosion?