On the plains of West Texas, new wind farms can be built for just $22 a megawatt-hour. In the Arizona and Nevada deserts, solar projects are less than $40 a megawatt-hour. Compare those figures with the U.S. average lifetime cost of $52 for natural gas plants and about $65 for coal. Environmental rules and government subsidies are no longer the key drivers for clean power. Economics are. That’s why Donald Trump will have limited influence on…