Yeah I agree V2G will play apart in complete electrification of the grid, but I think other community or residential energy storage will be necessary too as EVs aren’t guaranteed to be connected to the grid during peak solar generation times. They will be good for supply during peak demand times though, especially as demand peaks when everyone gets home from work, at which time they will be grid connected and can discharge when necessary, with the EV the recharging overnight while energy is cheaper.
The only way I can think of making them a primary storage source is if absolutely every car park in the country has an V2G EV charger installed. That way the online time they would be disconnected I when they were in use. The complication I can see with this though is its hard to predict user habits so if the batteries discharge to the grid too much then the user will be limited to travelling shorter distances. A way around that would be to allow a maximum discharge amount be set I the EV, but this could lead to everyone setting it very high to limited energy is made available to the grid anyway.
Unfortunately 363GWh/60kWh = 6,050,000 cars, which goes to 18,150,000 cars if we only allow 1/3 of the battery charge be used, which is over 90% of the 20 million cars figure you mentioned.
We also havent considered things like big industrial loads, which can have very large energy demands. I think it will be more likely they would require energy storage closer to their location, as drawing power from distributed sources across the entire grid would lead to a lot of grid congestion, as well as higher resistive power losses from transmitting greater distances. Having batteries closer to the large loads would be more similar to how the grid operates now, as the big industrial loads often get their own distribution transformers and lines connected to the transmission system so they don’t negatively impact the distribution lines that provide population centres.
I think it is also worth taking into account the evolution of energy storage tech as well. There are far fewer limitations (size, weight) for land based energy storage types, and there is a lot of research going into more sustainable batteries, but these may not be suitable for EVs for some time. https://cosmosmagazine.com/technology/energy/sodium-ion-batteries/
You are right in the sense that as a significant percentage of the population owns a car, and therefore will forseably own an EV, it would be more sustainable to use that energy storage for the grid, rather than doubling up on energy storage devices.
I’d be interested to know what Australia’s annual energy use would be if the large industrial loads weren’t considered. It may even be that EVs could cover a considerable percentage of residential and commercial energy demand.
Either way, V2G will have an important role to play to completely electrify Australia and the rest of the state governments should pull their fingers out and allow it.