U.S. wind power has more than tripled over the last decade, surpassing hydropower to become the nation's single-largest source of renewable capacity, and that's due in no small part to federal tax incentives. The industry is now poised to enjoy one last hurrah from the tax program as the expiration of the credits this year is setting in motion a rush to build about 11 gigawatts of new projects, accounting for the largest expansion of the sector since 2012.