CAMBRIDGE — Harvard University has entered into a 15-year agreement to buy power and renewable energy certificates from a wind energy farm to be built in Maine.

Harvard officials announced today that Stetson Wind II facility near Danforth, Maine, expected to go online in the middle of next year, will eventually provide more than 10 percent of the university’s electricity needs. Federal environmental regulators say that will make Harvard the largest purchaser of wind power by a university or college in New England.