The issue with using compressed air as 'fuel' for any sort of portable power is it's
terrible energy density.
At 150 bar (2175 PSI) you have an energy density of only 17 Wh/liter. (Gasoline has an energy density of
9000 Wh/liter, for comparison...)
This means that, if you want to run a 1 HP, 100 percent efficient (obviously, not possible) pneumatic motor for 1 hour, you would need a 44 liter (12 gallon) air tank at 2175 psi. (actually, it would need to be quite a bit larger, as the energy density of compressed air falls as the pressure in the tank drops.
When you factor in both air motor inefficiencies, and energy density drop with pressure drop, you would be doing very well to get 1 HP for 1 hour using a 50 gallon, 2175 PSI tank. Which is the volume of a decent water heater.
Now, despite what you believe, air at over 2000 psi does not just 'pop.' There can be shrapnel; there can be a tank (or regulator) shooting off like a rocket. If you're in the way of shrapnel, tank or regulator, you could easily end up in the morgue. There's some members here who are welders by trade; they could tell you more about the characteristics of metal pipe and/or tanks at scuba-type pressures.
A 50 gallon (185 liter) 2175 PSI tank is also VERY heavy. It would be roughly 20 inches in diameter by 40 inches in length, with a steel wall thickness of
at least 1/2 inch. The reasons that the tank would have to be so strong, is 2175 pounds per square inch, spread over roughly 2400 square inches, means that there's 5.3 million pounds of force against the walls of the tank!
(You could get a tank made from exotic materials (spun carbon fiber/epoxy over a thin stainless liner, for instance - it's similar to what NASA uses for Xenon tanks on ion drive rockets - they only weigh about 25 pounds for a 50 gallon tank... but the cost of a tank like that is probably more than a new car...)
