The thing about cloudy no wind days is: 1. These are conditions that don't coincidence as often as one would think 2. If they do happen at the same time they

The thing about cloudy no wind days is: 1. These are conditions that don't coincidence as often as one would think 2. If they do happen at the same time they are limited to certain places Now the only thing you need to have your solar and wind installations not in one place and make sure it is unlikely enough to have all of them inoperational at once. If you have the proper energy storage and a big enough grid that can balance itself this is totally doable.