Uses solar energy to heat expanding gas in CAES rather than natural gas. Of note, the company claims they need a peak to off-peak price premium of $0.07/kWh to be viable.
If long lifetime (20 years) batteries become available at $250/kWh, batteries will be a much better choice ($0.04/kWh). Even at $500/kWh and 20 year life, batteries would be close to viable at a $0.07/kWh price differential. They could also reliably handle voltage regulation, so could serve double duty.