I know how much power can be stored in compressed air. I've used compressed air all my life. (Even drive nails & take off my lug nuts with it).
But, it would take a LOT of 3,000 PSI scuba tanks to get the kind of results you get
with one gallon of gas. One problem is the HPA tanks would all have to be made from
carbon fiber (which isn't real cheap). Or, the car would be way too heavy.
And if you wanted to maintain a smallish size, those tanks would need to hold a lot more than 3,000 PSI (200 bar).
More dangerous pressures and your home compressor would be VERY expensive.
Just check out the prices of a little home compressor to fill a 300 bar scuba tank..
My guess.. A car designed from the wheels up to be a plug-in EV would be < 1/2 the price of an air powered car with the same range and load capabilities.
When you added in the cost of compressor hardware, the air car becomes something that no one would buy.
Go Google up the all the news on the Indian air car. A lot of it is very old news. They were going to start full production a few years ago.
Why didn't they? My guess is, they just can't get the range they need,
at the price point they need.
Heck we could be driving EVs made out of carbon fiber and covered with
high output solar cells, but what would be the MSRP?
Cheers,
Rich