'Dispatchable' power. I posted awhile ago the 2018 experience in the UK...a 13 day calm period eliminated all wind power there...had it not been for other sources, it would have required over $1T just to pay for enough battery power to last those 13 days...and then pray that the batteries could recharge before another calm period.
That being said, Coal isn't the answer to our energy future...and Utilities know it...they aren't going to invest in new coal plants; Trump is just chumming for votes from his uninformed base.
Note also that Texas...on its own volition...has built Wind Turbines for specific reasons...i.e. abundant and 'reliable' wind on its plains, plus a transmission infrastructure that's suitable.