And yet the existing battery facilities that could keep a smallish region (or a single city) supplied for 15 minutes or more are exceedingly rare.
Maybe they aren't as cheap as you claim. Australia is recently building a 1200 MW battery in New South Wales for 2.4 billion dollars - a cost comparable to a new nuclear reactor.
https://www.theguardian.com/australia-news/2021/feb/05/world...
Even the battery factories are in their early stages right now.
Do you have a reference for the storage capacity of that NSW battery? Because every newspaper I’ve found talking about it, only talks about megawatts (power) not megawatt-hours (energy), and it’s the latter which is expensive for batteries, not the former.
"The 300 MW / 450 MWh battery will consist of 210 Tesla Megapacks covering an area smaller than the football oval at Geelong’s GMHBA Stadium"
20 million cars in the UK are parked on peoples drives overnight. Vast majority don't need a full charge for the following day and people will be delighted to buy electric during the day for 10c/kWh and sell it overnight for 20c/kWh
If they were all electric with 60kWh of storage and can drop to 30kWh that's 600 GWh of storage. The UK's grid usage overnight is about 20GW from memory, so over 16 hours is in the order of 300-400GWh of overnight storage.
Assuming Germany has similar car and demand characteristics, as long as there's enough power during the day to cope with demand and recharging, there should be plenty of storage for overnight usage.
It is doable, yes, but I cannot concur with the OPs idea that it is cheap.
The other problem with using cars to feed the grid is that you need inverters large enough to do so in each house. That's not a cheap solution and it takes a lot of space.
https://reneweconomy.com.au/too-slow-too-expensive-why-nucle....
https://www.engineersaustralia.org.au/sites/default/files/re...
"The spread of projected and reported capital costs is unsurprisingly broad. In Australia the most recent public assessment is provided by the GenCost2018 report by CSIRO and AEMO.10 It assumes the capital costs for SMR technology is $16,000/kW in 2020 (and experiences no major price decline over time). We note this number is more than double other cost estimates worldwide. We have sought additional clarification on the basis for this costing. Initial advice is that the number is based on a GHD estimate for AEMO of costs for a future Gen IV reactor to be constructed in 2035 and not for the type of reactor which would most likely be deployed in Australia."
Anyhow, that 16k estimate is for power, not for energy... It's unclear over which timespans comparisons are being made (since a lot of it depends for how long power plants will be kept operational... A huge cost is the initial investment).
I've seen energy estimates as low as 30$ per MWh, for Nuclear energy plants built with interest rates of 3%