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.
"bad" solar areas are actually amazing for 9 months, and if you heating needs are met by other means, then winter can keep the lights on and still do cooking. The path to meeting winter heating needs is hot water and "heated dirt/sand" storage with hydronic floor heating (where more water is delivered at 30C is easier to manage than radiators at 80C) that can be stored during ample fall solar with no heat or cooling load.