The article doesn't provide much details about installed solar, wind capacity, installed battery capacity, electricity produced each month, and so on. But this is data that Ukraine would not like to get public.

The biggest issue is only hinted in the article:

> ‘There’s just enough sun [in January/this winter thus far] to make it work,’ says Olena Kondratiuk

Solar+batteries work well in summer months, but for winter months, solar has much lower output. This is why Russia is attacking thermal plants especially in winter.