California’s Push for Clean Energy Has a Problem: No Place to Store It

For 90 minutes, clean energy production was slashed 1,142 megawatts, enough electricity for hundreds of thousands of homes, while dirtier power from less flexible sources stayed on to keep the system stable. . . It was the largest curtailment of green energy last year, according to grid operators, and it highlights a hurdle for Gov. Jerry Brown’s plan to increase the state’s reliance on renewable energy. 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 will be critical as California relies more on renewable energy.