Northwest Power and Conservation Council, Oct. 17, 2016, by John Harrison.
http://www.nwcouncil.org/news/blog/energy-storage-presentations-october-2016/

"As renewable energy, primarily wind and solar power, proliferates across the Northwest and increases our supply of low-cost, carbon-free energy, there also is a growing need to store energy so it can be released into the regional power grid when renewable generation declines, as when the wind doesn’t blow and the sun doesn’t shine. Consequently, research and development is focused on promising, utility-scale storage devices and also on identifying and resolving regulatory issues so that storage, like renewable energy, can proliferate. While there is progress, technological and policy hurdles remain, a panel of energy storage experts told the Council at a recent meeting."