Renewables: Firming/Base Load

Was speaking to me brother in law over the festive season and he mentioned how renewables in Australia will be hard to transition without maintaining coal for base load power, and that batteries although can hold decent amount of power, are only good for an hour or two during peak.

Any arguments/counterpoints to this? I read Hydro might be another answer to firm market during peak however unsure if can get over the hour or two hump.

He's an exec at an energy company so trust what he says pretty well.