Renewables don't need more "storage" than nuclear grids, though this is a bafflingly common belief.
See France, for example, which tops up its nuclear grid with gas, hydro, import/exports etc.
Storage only becomes an issue when you get to the last 20% or so of decarbonisation and if you're down at 5% you're better to focus on electrification of fossil fuel using industry than worry about that last 5% of gas used for electricity.
They've been publishing stories like this for years. They'll generally not mention that they are still burning fossil fuels.
You'll notice the headline isn't "Czech Republic runs on 100% carbon free energy", which would be a much more interesting headline.
I'm not sure how to check Czech Republic generation mix at that time but I wouldn't be surprised to see fossil fuels still being burnt for "contractual reasons". (edit: I'm estimating that there was at least 1.5GW of coal generation at the same time this solar was curtailed, so about 10x as much coal being burned as solar curtailed)
But, even if it was curtailed for genuine reasons, that still doesn't mean storage would make financial sense. See France, where they 'curtail' nuclear power. Does that mean they "need" batteries?
See France, for example, which tops up its nuclear grid with gas, hydro, import/exports etc.
Storage only becomes an issue when you get to the last 20% or so of decarbonisation and if you're down at 5% you're better to focus on electrification of fossil fuel using industry than worry about that last 5% of gas used for electricity.