I've been following that one, and it's 4500psi all right.
What worries me the most is that it's made by Tata motors. I've seen their construction quality first hand at a warehouse in Bridlington in England that housed a stack load of brand new Tata utes. You'd swear they were second hand and had done 100,000km before they rolled out the door.
Anyone remember the psi used in the Mythbusters "air cylinder rocket" episode that shot a cylinder through a concrete wall?
You just have to do the maths to see that it's either a complete con or close to it. You won't get far on a realistic sized storage tank at 300 bar. Also, the energy loss in compressing air to that pressure for storage is considerable, so OK the car irself might be efficient, but the refuelling system is unlikely to be.
OTOH, the promotion of the thing has been very clever, treading a fine line between feasible, practical and useful. Lots of suckers will part with their dough. WC Fields would be pleased.
Not that one, but it's something I've discussed a number of times. Unfortunately the skeptics are right about the efficiency problems. There are two real issues, and neither of them is about efficiency of filling the tank (the excess heat can be recovered).
First issue is that to get down to a pressure you can use in an engine, you have to pre-expand the air... and that discards the energy. Only way to recover half(*) the stored energy is to drive the equivalent of a high-pressure pump in reverse, and probably use hydraulics from there.
Second issue is that adiabatic expansion means the whole thing freezes, and you lose pressure ratio at much more than the volume ratio, due to the temperature drop. If freezing isn't an issue, you can only recover half the stored energy even theoretically. The temperature of normal air expanded from 25C at 4500 PSI to ambient drops to somewhere around 11 Kelvin. Try to stop *that* from freezing things.
Good points. I did a quick OOM calc based on a 200 litre tank (huge for a small car), 300 bar when full and 10KW at the wheels. Assuming 100% availability of the stored energy, which as stated in previous post you won't get anywhere near, you get about 10 minutes run time. Not much of a journey.
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