http://www.nu.com/northfield/tour.asp

There are peek hydro power stations operating like that.  They are called “reversible” as far as I remember.  During periods of low power demand they pump water in a reservoirs-lakes well above their level but at demand peeks they operate as turbines.  Therefore when operating as a pump that turbine/pump impeller should be coupled to a power source and when operating as a turbine to a generator.  Or maybe there is something like electrical motor/generator, which can be switched to either mode.

I haven’t seen that turbine/pump impeller but it could well be something resembling a centrifugal pump impeller and at the same time a centrifugal turbine rotor.  Maybe those two things don’t differ a lot (for incompressible fluid - water) in which case it was quite easy to design something in-between.