You only see half of a system

In any wind powered system, in order to have power when the wind isn't blowing, you must have an energy storage system. Small systems, like for one house, will often have batteries. Other methods have also been tried such as flywheels, compressed air, and hydrogen production.

Along with all the thousands of wind turbines that have been and are being erected in the U.S.A., where is the energy storage? I have never seen or heard of any. Could it be underground? Like, maybe in an underground military base? I don't know, that is why I am asking. What I do know is that what the wind power companies build where I can see them is only half a system. Where is the other half? Where is the energy storage part?