During winter, France uses ~50% more electricity per day than during summer.
And during cloudy days in winter, solar produces 10%-15% what it produces during summer.
If you don't have month-long battery storage, in order to be fully solar based France would need to produce 20 times more electricity than needed during summer.
> And during cloudy days in winter, solar produces 10%-15% what it produces during summer.
This doesn't matter. If you look at the monthly stats, solar panels in France produce ~3x more in the summer than the winter at a month by month view. As such, you only need 3x extra overall, and some day to day storage.
Or you use a different technology optimized for long term storage. Batteries are not that technology. Hydrogen (or other e-fuels) or long term thermal storage.
> Or you use a different technology optimized for long term storage. Batteries are not that technology
I've heard this before but can you explain why? A cursory web search tells me batteries hold charge pretty well for 6 months. And the new sodium batteries from CATL are certainly cheap enough.
For long term storage, capex is king, not round trip efficiency. The capex of batteries ($ per kWh of storage) is much too high. There aren't enough charge/discharge cycles to amortize that capex. This is unlike with diurnal storage, where there are many thousands of cycles over which to spread that cost.
To go into more detail: you want to really aggressively minimize capex, even at the expense of round trip efficiency, for long duration (like, seasonal) storage. The interesting example from Standard Thermal is something that could reach a capex of $0.10 per kWh-th of storage capacity (yielding heat at 600 C). This is three orders of magnitude better than batteries. Even tossing in 40% round trip efficiency from converting this back to electricity using steam turbines it would be vastly superior to batteries for seasonal grid storage.
There are varieties of batteries with somewhat lower capex and lower charge/discharge rates. Form Energy's iron batteries are of this kind. They would occupy an intermediate timescale, perhaps ~1 week, which could be good for leveling wind output.
During winter, France uses ~50% more electricity per day than during summer. And during cloudy days in winter, solar produces 10%-15% what it produces during summer.
If you don't have month-long battery storage, in order to be fully solar based France would need to produce 20 times more electricity than needed during summer.