Battery storage for bulk power has been talked up for years. Mostly by the wind industry. With solar power, you get peak power and peak air conditioning load around the same time. Wind varies about 4:1 over 24 hours, even when averaged across big areas (California or the eastern seaboard). So the wind guys desperately need to store power generated at 4AM, when it's nearly worthless, so they can resell at 2PM. When the wind farm companies start installing batteries at their own expense, this will be a real technology.
With the US glut of natural gas, this isn't needed right now. Natural gas peaking plants aren't all that expensive to build, and make money even if they only run for maybe 6 hours a day. That covers most peak needs.
There are other ways to store energy. Some of the dams of the California Water Project have reversible turbines, which can run either as pumps or generators. They pump water uphill at night, when power is cheap, and let it down during the afternoon to generate power. Since the dams and pumps are needed for water handling anyway, this adds little cost.