Brian Hayden, 30, and Duncan Miller, 29
Concerned about global warming and U.S. dependence on foreign oil, Babson grads Brian Hayden and Duncan Miller founded the Heatspring Learning Institute in 2007 to train general contractors, engineers, architects, and other building professionals in the U.S. in how to design and install geothermal heating and cooling systems. The technology, which has existed for more than 50 years but is only now gaining popularity, works by pumping water through underground wells, where the stable temperature can heat buildings in cold weather and cool them in hot weather. Geothermal systems, which replace oil or gas furnaces in homes and commercial buildings, can cut energy bills by 30% to 70% and reduce carbon emissions from burning fuel, according to Hayden. So far, over 1,600 people have participated in the four-employee company's courses, which range from $300 online training to $1,500 three-day boot camps. The firm now offers training to building professionals in solar panel installation as well. Heatspring had sales of over $1 million in 2008, a figure Hayden expects to double this year.