That the problem you can't make it big enough with current tech.
The basis is to reduce the CO2 output, it you want renewables to cover your base load.
Pumped Hydo ..ppphhhttt. We don't even have enough water out west for towns to have drinking water, let alone water to create electricity. The number of places it is viable is limited to build in a big enough scale...It is a good idea, just won't scale to what we need for Australia. Plus transmission losses are too high to cover East coast of Aust, let alone all of Aust.
Portable mini Nuclear power stations on the back of a truck..... one for each town.
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( I Jest - wipe the coffee off your computer screen
one for each town.
