https://en.wikipedia.org/wiki/Wind_power_in_Texas
tl:dr if they didn't have batteries, they could only run stuff while the wind was blowing. I don't explain it well, but you have to have them in a 'renewable' system, and while you don't HAVE to mine the stuff in a far away country you don't mind ruining, you do have to perform a bunch of ruinous mining to get it.Future developments
An energy storage system is being developed for West Texas. The system allows excess wind energy to be stored, making wind energy more predictable and less variable.[41] This 36 MW battery facility became operational in December 2012