Battery storage: it’s back to the future. More than 120 years ago, batteries were commonplace on the power grid. Thanks to Thomas Edison’s vision, many central station power plants and distribution networks utilized battery systems in the 1890s.
Today, battery-based energy storage is again becoming vital to our power system. Storage is needed for load balancing and a great deal more. Batteries can help achieve the reliable, affordable, and clean power grid of the future, in the U.S. and around the world.
See http://blog.aesenergystorage.com/after-a-100-year-hiatus-batteries-are-helping-the-grid-again 
After a 100-Year Hiatus, Batteries Are Helping the Grid Again
After a 100-Year Hiatus, Batteries Are Helping the Grid Again