By Ryan Collins, Bloomberg News As attractive a renewable-energy concept as wind power is, it’s plagued by a fundamental flaw. It blows the most in the dead of night, precisely when there’s the least demand for electricity. That’s true for just about every windblown spot nationwide, from the foothills of the Tehachapi Mountains in California to the coastal plains of North Carolina. And then there’s South Texas. It is to wind, engineers have discovered in recent years, a bit like what Napa Valley is to wine and Georgia is to peaches.