Is a 2 ply cylinder as strong as a 1 ply twice the thickness?

[sophiecentaur]

what maximum pressure you are designing for,

Yes; the details are very important. Springs and gravity stores have been used for hundreds of years for a good reasons.

I can only think of one example of compressed gas energy storage and that's in air guns. Apparently, a 12g CO2 cartridge can deliver up to 200 shots (maximum permitted is 10J a shot so a couple of kJ stored - that's one Watt for half an hour, minus the efficiency losses). I brought that up as a ball park figure for what can be done. Of course, that ignores the actual energy involved in filling up the cartridge which would be very relevant in terms of 'energy storage'. Also one would have to consider the health and safety considerations involved in the factory producing them and the very high spec needed for the canisters. [Edit: about 60Bar]

 

[DaveE]

I can only think of one example of compressed gas energy storage

I've been on dive boats that use a scuba tank to power the starter for their diesel engine, which seemed to work well. No dead battery issues. But it's telling that you only see this in a niche application where they had to have a bunch of high pressure cylinders onboard anyway.

 

[Baluncore]

But it's telling that you only see this in a niche application where they had to have a bunch of high pressure cylinders onboard anyway.

Many big diesel engines, in generators, HGV trucks, railway engines and ships, use compressed air to start.
https://en.wikipedia.org/wiki/Air-start_system

 

[sophiecentaur]

I've been on dive boats that use a scuba tank to power the starter for their diesel engine, which seemed to work well. No dead battery issues. But it's telling that you only see this in a niche application where they had to have a bunch of high pressure cylinders onboard anyway.

Now you’ve jogged my memory I remember starting aero engines with a blank cartridge.
Better than carrying a large battery. But I remember a light plane being forbidden to take off with its flat (lunch box size) battery. A jump start was’t allowed either.
No real excuse for a defunct dive boat battery though. Makes me wonder what else could have let them down in an emergency. But five bottles always(!) should have some air in them after a dive.
The numbers count in this project so other applications may not be relevant. Modelling does not always give valid conclusions in some engineering problems.