Consider what happens when megawatts of grid-tied PV arrays are humming along and a cloud passes by or the sun sets—the utility has to compensate with a steep ramp-up of conventional power generation (commonly via natural gas “peaker” plants) to handle that decrease in available power. For the sun and wind to compete with conventional power sources, energy storage is needed to smooth out variations in energy availability.

The utilities are moving toward large-scale energy storage. In California, a mandate requires 1.3 gigawatts of storage by 2020. Under the mandate, approximately 100 MW of storage came online in this first quarter of 2017 by Southern Cal Edison (SCE) and San Diego Gas and Electric (SDG&E). Interestingly, the rapid deployment of those southern California storage projects was a response to a fossil fuel disaster: the methane gas leak at Aliso Canyon near Los Angeles.

Outside of California, since 2012, 250 MW of energy storage have been added to the PJM Interconnection grid in the Midwest and Mid-Atlantic regions. Other pending large-scale energy storage projects include:

•           The Kauai Island Electric Cooperative developing 20 MW of energy storage (with 28 MW of PV arrays) in Hawaii

•           20 MW of energy storage (total) to support two Texas wind farms (446 MW total)

•           10 MW of storage to support a 2 MW PV array for Tucson Electric Power in Arizona.

According to the Energy Storage Monitor: 2016 Year in Review, by 2022, energy storage deployments are projected to reach 2.6 GW per year over all sectors—that’s about 12 times the size of the 2016 deployment.