Comment by api
3 days ago
So… it’s a compressed air battery but with a better working fluid than air.
I remember wondering about using natural gas or propane for this a long time ago. Not burning the gas but using it as a compressed gas battery. It liquifies easier than air, etc., but would be a big fire risk if there were leaks while this is not.
Seems neat.
> Not burning the gas but using it as a compressed gas battery. It liquifies easier than air, etc., but would be a big fire risk if there were leaks while this is not.
FWIW Back in the day, Ammonia was used for refrigeration because it had the right properties for that process; I mention that one because while it's not a fire risk it's definitely a health risk, also it's a bit more reactive (i.e. leaks are more likely to happen)
> Seems neat.
Agreed!
Maybe use excess power to produce methane via the sabatier reaction, store that, and then burn it in turbines or use it in fuel cells when needed.
It’ll be interesting to see how the economics of these various solutions play out.
The problem with that is usually efficiency. Electrochemical or thermal production of methane from CO2 and H2O is not very efficient, and then you're burning it, which is only heat engine efficiency.
Batteries or direct mechanical storage (compressed gas, pumped hydro, etc.) are both a lot more efficient.
This would make sense if solar gets so cheap that it's something to do with the surplus, and it would be a way to electrify things like long haul aviation where batteries are too heavy. We are flying LNG rockets, so LNG planes are totally possible, or you could upgrade methane to butane or propane which are quite easy to compress to liquid form. Jet engines run great on light weight fuels like that.
Except you have to trap and recycle the uncompressed CO2, hence that enormous bag to hold all that gas. Color me skeptical.
With compressed air, you just release the air back to the atmosphere.
> With compressed air, you just release the air back to the atmosphere.
The issue with compressed air is that you have to build more of the system to handle higher pressures and/or have a more robust regulator design, plus the pressures required to compress CO2 back to liquid are typically lower than what you'd need to store a useful final volume compressed air...
Also, As far as having an 'open loop' (i.e. venting to atmosphere), that's typically got it's own problems, mostly that when you need new air you have to make sure it's 'pure', not just things like dust but even whether there's water vapor.
They mention that and say it fits in a huge inflatable tent, which rings true. CO2 is more dense than nitrogen and oxygen which are most of air, and if you're storing it at ambient pressure you don't need a super strong vessel.