Here’s One That really Exists! ‘CAES’
If you want to know something about electrical energy production, ask the experts who make it at the wholesale level.
Notice their mention of efficiency. We need understand that they are declaring their CAES system efficient relative to other energy storage schemes, and with the help of their huge economies of scale and possibly a huge amount of waste heat from an adjacent convention natural gas turbine to help heat the compressed air coming out of storage. The losses in such a system are still significant, but they are charging their storage facility with surplus (inexpensive) KWHs off peak, and they are selling the peak hours for far more money than most people understand.
Glue Sniffers and Flower Children alike are attracted to the Indian Air Powered Tata Nano, a car that was announced to go into production some years ago, but still a pipe dream do to the fact the car is totally impractical. For those who measure the losses in the overall effort to charge the air powered car, they understand the staggering losses, and just how much fuel you still need to burn aboard the car to put the compressed air to work.