Hello Geoff, pleased to see someone else come to the same conclusions
that I have. Interestingly I was never in a position to be able to
conclude what the duplication factor might be.
I notice that you have decided on 12 times to be a good starting point.
I have seen another study on the US that came up with 12 times.
The best figure for the cost of batteries that I have seen is about
$1.35 per watt/hr.
If a battery pack to store the grids demand for one day is needed
then the cost becomes astronomical.
I was pleased to see your conclusion that a separate generation
system is needed to recharge the batteries.

It seems to be that every article pushing battery backup never takes
into account of "Where and when do you get the power to recharge the battery" ?

24/7 renewables power is just not going to happen. Renewable power is unreliable and expensive.

However, the wankerati among the powerful rich, and the political class think otherwise, so there is no point in discussing it. We will all have to end up in deep trouble before the penny drops, particularly in Australia, where people making the decisions are much dumber than anywhere else in the world.

Now we have ministers insisting that firmed renewables are cheapest. I doubt that has fully included subsidies, the high capital cost of long term storage, frequency correction, the rising price of gas backup and unsightly new transmission for Renewable Energy Zones. A recent US estimate put the cost of net zero as $433 trillion. Earlier I saw on NEMwatch that SA the vaunted renewables leader was getting 1500MW out of 1900 MW demand from gas fired electricity.

I fear we are being led up the garden path by dreamers that now have the ear of government. The joint AEMO and CSIRO GenCost study insists that small modular reactors will have an electricity cost of over $300 per Mwh. Several manufacturers give cost estimates well under $100. Evidently the GenCost authors think we don't need baseload power despite the obvious fact it still generates most of our electricity.

Solar thermal is the only renewable worth considering for a number of very valid reasons. First is the location out in our vast inland where the sun shines but for a few days. And because molten salt is the medium it can be stored for several days in large vacuum vessels to store useful heat for up to a week.

That said, nothing beats 24/7 MSR thorium (nuclear) for cost effective power generation. Moreover, this technology is the safest, the cheapest, the cleanest available, and is carbon-free!

Can be re-tasked to burn and burn other folks nuclear waste where, it is mostly unspent fuel! Is reliable, dispatchable 24/7!

As a thorium burner, costs can be as low as 1 cent PKWH! As a waste burner all but free given the millions other folk pay us to take this free fuel off of their hands. With routine maintenence, these systems ought be good for 100 years.

Just 8 grams of thorium contains enough recoverable energy to power your house and car for 100 years! The cost of mining and refining 8 grams of thorium 100 dollars, meaning you can run your house and car for 1 dollar a year! And that's why prices as low as 1 cent PKWH are not just feasible, but guaranteed.

Funded and facilitated energy co-ops competing for your energy dollar will ensure these or lower costs. And energy that cheap will have the high tech manufacturing beating a path to our door!

All we need do is ensure we build enough houses (a million) to house the workers we will need to make it happen!

As for transmission, a cling wrap thin layer of graphene laid under our highways and byways will be the new (poles and wires) transmission of the future. And given graphene is a superconductor and 200 times stronger than steel, almost eliminate current transmission and distribution losses, especially if microgrids are the order of the day and planned for!

And a planned energy paradigm would make a very nice change from the last generation of political polly waffle. Wouldn't?
Alan B.

If sanity does not prevail and we are forced by asinine government policy to waste billions on intermittent renewables, then the battery of choice will be the sand battery. Simple, ultracheap and able to hold heat (500C) for many moonlight hours. Can be as big as whole block, office blocks! And an ideal companion for very large inland solar thermal projects! TBC.
Alan B

Solar thermal is something we can build here with materials and resources that are locally available, don't have to be imported! Economies of scale and automation of the steel mirrors production and polishing, will ensure construction costs compete with new coal-fired power! The difference, the power is forever free!
Alan B.