Temporal Power has developed fly-wheel technology to store energy from generation.  Basically, it takes the electrical energy and converts it into rotational kinetic energy (stored in a rotating flywheel).  From my understanding, it provides a faster response than batteries but slower than super capacitors.

NRStor Inc. has just opened the first energy storage facility providing regulated service for the Independent Electricity System Operator (IESO).

Interesting to see how this evolves…