Wind not blowing 50 to 70% of the time? Say what? Where are you at? I conclude you are not in western Texas or elsewhere on the Great Plains.
I live in a great plains state and haven’t been to West TX since graduating from UPT at Webb AFB back in the sixties.
...and the issue isn’t the percentage of time wind blows. The mere fact it doesn’t blow all the time is reason enough to question why anyone would consider wind or solar to be the answer to reliable energy production. The sun doesn’t shine at least eight hours a day, not counting overcast days, and wind is unreliable not to mention the wind generator itself being but thirty percent efficient.
All this means the coal fired plants remain on line regardless of available wind or solar. No savings whatsoever. Gas fire generating sources are up to ten times the cost of coal fired plants and natural gas itself is an historically price volatile fuel compared to coal.
In closing, our energy production industry has not been stupid when they put their efforts into coal fire plants. They are by far the least expensive way to produce clean safe reliable power, to meet the twenty four seven demand. EPA and presidential efforts to kill the industry not withstanding.