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Fundamentals in layman's terms:So with renewables you either firm with fossil fuels, nuke or hydro?
What was the plan for 100% renewables if that is the case?
How would it even be done with renewables- every house gets a battery or something. Or just huge batteries (that I can't imagine would be feasible)?
Electricity production and consumption needs to match precisely and it needs to do so in real time.
I'll use the analogy of sound. If you want to hear it then it has to be produced in real time. Produced from a recording it could be yes, but the recording isn't storing actual sound, it's just storing a means of recreating specific sounds. What you hear still comes out the speakers in real time.
Electricity is the same. A pile of coal, a tank full of oil or gas, water behind a dam etc are all storing an energy source that can be turned into electricity but the electricity itself must be produced in real time.
The problem with wind and solar being simply that they're highly variable at or close to ground level and we have no workable means of storing the wind and sun itself. At best, we can harness the wind and sun when they're available and use them to produce something else which can be stored or, alternatively, we use something else (eg gas, diesel) as a backup. Or a combination of both approaches.
Batteries work, there's no question about that, but the problem is scale. The entire worldwide battery production in 2023 is forecast at 555 GWh. To put that into perspective, that's less than 4% of the storage capacity of the Tasmanian hydro system and it's outright trivial compared to hydro globally.
So batteries are just fine for short duration storage, eg to meet the evening peak demand, and there's quite a few companies (including AGL, Origin and Energy Australia among others) instaling them for that reason but they're not up to the task of maintaining supply during prolonged periods (days) of overcast, calm weather.
For that the options are far more limited - hydro or fuel of some sort. It's not that engineers love dams, gas turbines or diesel engines, just that they're the available fix for the problem.
In the context of hydro, either pumped storage or on river dams are both technically viable options so long as there's a surplus of energy at some other time with which to run the pumps. The key is finding places where they can be built large enough at a low enough cost - that's the hard bit which rules many out.
It's a scale of economy thing basically. What it needs to be viable is high energy storage volume relative to the civil works and transmission required including all roads, dams, tunnels or other water conveyance and transmission. The power station itself being more of a constant. Same with any resource. There's plenty of coal or iron ore for example that's worthless in practice since the cost to get it out of the ground is too high. Etc.
Failing that, it's gas turbines or diesels. Trouble is, those also come with a very real environmental impact and that's a key point of all this.
There is no "do nothing" option that maintains a functioning modern society.
There is no option that does not impact the environment in some way.
Or as an analogy, we have no choice other than to break some eggs and make the omelette. All we're choosing is which eggs we break. Trouble is, every egg has someone arguing why it ought be saved.