Exactly, though the US is only around 45% coal at this point, and dropping. Compressed air is a poor form of energy storage, period, end of story, do not pass go, do not collect $200. There is no such thing as perpetual motion anyway. Trying new ideas is great, but the physics has to make sense. A mechanical engineer should know that you don't get free energy and that the obvious losses in a compressed air system is simply a terrible use of electricity. Batteries have far better efficiency and density. Tesla is coming out with their Model S sedan this year which will have up to 320 miles of range,
http://www.teslamotors.com/ Nissan has the LEAF around 100 miles of range, and batteries are constantly improving. Meanwhile Tata and Midi build golf carts that barely have any range, little power, would not pass a crash test, and are a horrible waste of electricity. If you want a low cost form of low speed transportation for the Indian population something like this would be better and use no grid electricity: (broken link removed) I would seriously look into the actual physics of energy in compressed air before I invested in anything dealing with it. Tata may be a good investment but not because of their "air car".