How do they count battery storage as energy capacity? And it doesn't sound like they're comparing energy outputs, only nameplate capacity (not counting night or clouds etc)
Yes, their data does count battery storage as operating capacity. Isn't that a useful metric though, since batteries will complement the grid during solar downtime?
They'd need to assume a change discharge rate since battery capacity is measured in power time (kWh) instead of power (kW). Are they assuming 1C? Or higher? And battery capacity wouldn't be as useful as generation capacity, since you need to first charge it via other sources.