Renewable energy’s storage problem

Steam vents from the top of a tower at the Ivanpah Solar Electric Generating System in the California Mojave Desert. Gov. Jerry Brown wants to increase the state’s reliance on renewable energy.   (Mark Boster / Los Angeles Times)

At the Ivanpah Solar Electric Generating System in the California Mojave Desert, some of the plant’s 347,000 garage-door-sized mirrors used to generate power can be seen. California is looking for a reliable way to store green energy for when customers need it.  (Mark Boster / Los Angeles Times)

Terra-Gen Power representatives walk past the Alta East wind energy project in the Tehachapi Mountains. Peak demand for electricity rarely coincides with the brightest sunshine or the strongest winds, so finding a way to store clean power and deliver it when needed is critical.  (Irfan Khan / Los Angeles Times)

Wind turbines at the Los Angeles Department of Water and Power Pine Tree Wind Farm spin in the Tehachapi Mountains. California is looking for a reliable way to store clean energy.   (Al Seib / Los Angeles Times)

Experimental batteries are being tested as a means of storing and integrating renewable energy into California’s power grid at the Vaca-Dixon PG&E substation in Vacaville, Calif.  (Robert Durell / For the Los Angeles Times)