It takes energy to re-compress that gas. I don't see how this is economical.
True, use renewables to ... No?
Chad and Peter,
It's pretty simple - energy prices vary throughout the day, and across days. You compress the CO2 when the energy is cheapest (perhaps around noon because potential solar generation is higher than usage), and decompress at periods of high demand like the early evening when you can sell the electricity at a higher price.
It wouldn't have to be renewables used to charge, but as there is no fuel cost it's solar and wind pricing that is the most variable.