Enthusiasts for overbuilding wind and solar say we can use the surplus energy to make electrolytic hydrogen and burn it for power during the calm and dark periods. Hellishly inefficient but.

Storage itself may be curtailed once the battery or pumped hydro dam is full. Build a bigger battery they say. Some say for 100% renewables we need static capacity 10X annual electricity demand. The Hornsdale SA battery of 129 Mwh was said to cost $50m. Call it $400 per kwh about half or less the cost of a home battery. In 2016 Australia used 257 Twh = 257 bn kwh of which 10% is say 26 bn kwh. Times $400 is $10.4 trillion. Those greenies must be rich.

The real question is
"Can we NOT afford a renewables only power supply".
Make your choice. Destroy this planet or not.

The short answer is NO! Renewables are the thing of greens and other un-informed, mis-informed or just plain arrogant fools who think they have the answers and understand the problems. They don't! I've said it before; A bunch of self anointed 'gardeners', think they have the smarts and the answers to a problem they have conjured up to elevate themselves into a position of 'experts' in the field, fall way short of the mark. First and foremost, we must be cautious about a bunch of people who have NO political experience and NO policies of any kind. They have appealed to a particular and peculiar group of people who are in fact, child-like in their thinking. I find it difficult to describe them because I cannot think so narrowly. This beat-up on CC is not going to end up killing us and destroying the Earth. So let's just keep throwing money at all these 'con-men' and the problems will all go away. It's an age old ploy. Make up some disaster stories, it never happens, then another excuse/reason is fabricated to justify the prediction never materialising. Just remember the Y2000 bug, mad cow disease and so on. You are trying to squeeze a square peg into a round hole. For renewables to be the most 'viable' source of power generation, we will need wait a little longer as the technology we seek is not yet invented. I desperately need for politics and personal agenda to go and get f#*&ed. We have Alan's passion for thorium as a true candidate for the job, but for the fact these mongrels haven't figured out how they're going to fleece money out the back door into their back pockets if they go down that path. Nuclear is also in with a very good chance. Now this one I think the pollies like because they know how to skim money out of it. Unfortunately, because the greens and other idiots have managed to polarise enough of the population that it is not a vote winner. Ultimately, that is the priority for the pollies. Not us!

The only guaranteed renewable is the continuing arrival of the power bill needing to be paid

Can we afford a Coal-only power supply? The answer to that would also be no.

Apparently we're not a smart as Albania, Iceland, Paraguay and Norway who get most (if not almost all) their energy from renewables.
We're also not like many other countries (Scotland, Sweden..even China) who are moving away from fossil fuels.

It's apparently smarter to dig up rocks and burn them, no matter what the long-term cost and as long as a few people can make an easy dollar out of it.

Coal comes in part from the remains of dinosaurs and so do some modern attitudes toward the future.

rache, your position is an old one and quite frankly, out of date. The CC is a beat-up and time will prove this. The world is going through one of it's growing periods. The Earth has been doing this for millions of years. How long do you have to wait and see that CC is just another con. People see something and along comes a 'motor-mouth' who can see a good con and gives this thing a reason, an explanation that the plebs all nod and agree, as if they are familiar with the science and technology of the implied problem. The same people wanting to not look as stupid as they really are, don't have the stones to say, 'I have no idea what he's talking about', so they all go around espousing the virtues of the con-men, all the while nodding to each other and agreeing with each other as if they have any idea about what the dirty little con-man said.
rache, try thinking outside the box. Take the box and crush it, then burn it. Then start questioning these claims. Don't take people's word as gospel. For a balanced discussion, you need both sides of an argument. Only then will you find flaws in these arguments which hopefully will get you looking for answers. And that is the best advise I can offer anyone.