From backyard tinkerers to big corporations, inventors have been struggling to find a way to store solar, wind and other renewable energy so it can furnish electricity when the sun doesn’t shine or the wind doesn’t blow. Now California is offering businesses a big incentive for success—contracts that the utility industry estimates could total as much as $3 billion for successful, large-scale electricity-storage systems. Starting this year, big utilities that do business here must begin adding enough battery systems or other technology so that by 2024 they can store 1,325-megawatts worth of electricity—nearly 70 times the amount that the handful of mostly experimental systems in the state store now. Regulators are also requiring municipal utilities to buy or lease energy-storage equipment. The storage systems California wants don’t exist on such a scale, so the new rules amount to a big bet—paid for by utility customers—that creating demand will […]