Last summer, as the price of oil was peaking at more than $145 a barrel, legendary oilman T. Boone Pickens Jr. emerged as an unlikely clean-energy pitchman. The 81-year-old investor was trumpeting a novel plan to build a wind farm in his home state of Texas that would produce 4,000 megawatts of electricity, enough to power 1.3 million homes, which he figured would free up natural gas to run cars more cleanly and help slake Americans’ seemingly unquenchable thirst for foreign oil. Just a few months earlier, Pickens had put his money where his mouth was: His Dallas-based company, Mesa Power, paid $1.5 billion for 667 General Electric Co. wind turbines, slated for delivery in 2011 and expected to generate 1,000 megawatts of clean energy. By 2014, Pickens reckoned, the additional turbines he needed would be in place and the initiative, dubbed the Pampa Wind Project, would be fully operational. ...