As of 2017, only 2 CAES installations are operational world-wide, one in Germany, one in the US.
Huntorf, Germany. Operational since 1978, output 290 MW daily or 321 MW max for 2 hours, thanks to storage, consisting of 2 135,000 m3 large underground cavities, at a depth of 650-800 meter, with air pressures of up to 50-70 bar. Efficiency at 42% if compression heat is not used (adiabatic compression). For the future, efficiencies of up to 70% are to be expected.
McIntosh power plant in Alabama, operational since 1990. Output from CAES storage 110 MW over 26 hours, with heat recuperation, leading to an efficiency of 54%. The 2015 video confirms that until 2015 there were only two CAES plants in the world and only one in the US (the other Huntorf in Germany)
Currently underway is a project in Northern Ireland, funded by the EU and hopefully survives the Brexit drama; 330 MW from storage for 6 hours:
[deepresource] – Europe Chases CAES GWh Energy Storage