This concept has been used in the small scale by professional carpenters since the 50s, through the usage of pneumatic nail guns :-) There are also other power tools that can use compressed air as a power source. The average power consumption of a carpenter using a nail gun is lower than the 2 kW one can take from a completely ordinary electricity socket, but each nail requires reasonably high amounts of energy over a really short timespan, so a crazy amount of peak power. The carpenter may wish to "fire" multiple nails rapidly, possibly spending more than 2 kW over a minute or two - so it may be needed with a reasonably big "pneumatic battery" :-)