12 hours is how much you need to get through a windless night. So I am calling bullshit on 5 hours of storage. The model also requires mathane peakers. The model claimed to include transmission costs into the final costs, but that's bs. Since solar/wind is much more widespread, a high-adoption rates increases transmission costs significantly. Just the increase in copper wires and transformers would push it past his estuimates. There was nothing about mantaining grid momentum or frequency.
Australia is dirty as all fuck. Even South Australia, with a low population and renewables, is dirty. Coal and methane overcome the intermittency of solar and wind. The rest of Australia relies on coal.