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Some key insights from the article:
Basically, what they did was to look at how much batteries would be needed in a given area to provide constant power supply at least 97% of the time, and the calculate the costs of that solar+battery setup compared to coal and nuclear.
It sound impressive, until you read it's Las Vegas. In places like Germany you have several weeks per year with neither enough sun nor wind. With backup power like gas turbines which run few weeks per year you have to subsidize the operators. And if you want run them on green hydrogen, massively overbuild the renewable capacity so that you can fill up gas storage during summertime.