I wonder what the energy loss to the ground would be; since compressed air is much hotter than the same mass of uncompressed air while containing the same amount of energy. How much of the energy are you going to loose to the surrounding, much cooler, earth.
Since the compressed air tends to cycle in and out, there isn't sufficient time for significant heat transfer to occur, per articles I read years ago. There is usually one period of time during the day when wind is high and another when it is low and demand also fluctuates daily, so these systems aren't intended for long term storage.
Remember, air is a good insulator (vs. liquids and solids), so these systems are still efficient.