Storing Renewable Energy is a tough problem. Here is a wiki on Grid Energy Storage.
One I just found is Gravity Power.
Gravity Power, LLC, a spin-off of LaunchPoint Technologies, Inc., is developing a revolutionary grid-scale electricity storage system. The company's new Gravity Power Module(GPM) exploits the established principles of pumped storage hydropower, but extends the concept in a new direction: Down.
Here is a presentation if you are interested.