Why can't we run on 100% renewables?

No country has completely decarbonised with only intermittent solar and wind. When the sun isn't shining and the wind isn't blowing solar panels and wind turbines aren't generating electricity. In addition to meeting demand from our current grid, there are many challenges preventing a 100% renewable grid in Australia: 

Firstly, electricity consumption is expected to double by 2050 to support electrification and electricity users such as data centres. This means that in addition to replacing current generation with renewables, we would have to double that again with more solar panels and wind turbines across the country. 

Secondly, high energy users such as aluminium smelters cannot rely on the intermittence of solar and wind. With 10% of Australia's emissions traced back to the industry sector, this is a critical gap in the plan for decarbonisation. 

Whilst storage and firming solutions do exist they're too expensive at the scale required (batteries & pumped hydro) and can sometimes do more harm to the climate than good (gas peaking). 

There is therefore a critical role for a flexible source of clean energy like nuclear power alongside renewables in the energy mix.