February 13, 2012. Renewable-energy companies are losing their allure with top executives after profits and stock prices collapsed across the industry, making it more difficult for boards to replace underperforming managers. First Solar Inc., the biggest U.S. solar company, ousted its chief executive officer in October and is still seeking a replacement. At Vestas Wind Systems A/S, the largest turbine maker, the chairman and finance director are leaving after the company cut sales forecasts twice in three months and CEO Ditlev Engel said his own job is safe.