[miahi]

You need a lot of batteries to store the energy needed overnight and you have to plan for (lots of) days without sun. At my latitude (45N) the difference in solar production between summer and winter is 5x. Even with batteries, you still need a backup for a week of bad weather; so you have to choose between increasing the solar production 20x to have enough power generated in cloudy days or have a backup coal/gas/something else plant.

[citrin_ru]

In regions where winters are dark windy places tent to be not too far away. If both solar and wind both overbuild to the extent it makes sense (say 5x for solar and 2x for wind) and batteries cover a normal daily cycle you probably will need to burn gas on 10-20% of days which is not net zero but way way better than the current situation.