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 "

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?