A fire at a battery storage facility in Otay Mesa is out — but the stubborn nature of the blaze has sparked opposition from some residents about the relative safety of at least three other battery projects that developers want to build in other parts of San Diego County.

Renewable energy supporters say battery facilities are essential to meet California’s goals to develop a carbon-free electric grid. State policymakers and battery companies say the risk of future fires will decrease over time, counting on technological improvements in battery chemistries and better designs at the facilities housing the batteries.