The problem with this logic is that wind doesn't die down during the night.
Lets say that you build nukes equal to base load- they produce 100% of your nighttime demand, and 40% of peak daytime demand. This works out to some 50% of your total electricity carbon free and cheap. Now, how to cover day time peak: Cheap option is just to build gas turbines and run them during the day. This isnt green, but it works, and then you decide to reduce the damage your are doing by adding some windmills. During the day, all is fine and dandy- when the wind blows, you are burning less gas. But when the wind blows during the night, windmills still produce power, and there is no market for it, so now you got to loadfollow your nukes, and if you are willing to do that, why on earth build the gas turbines and windmills in the first place? it would be overall cheaper, and less polluting, to overbuild nukes and go to a wholly atomic gird...