Washington Post: A tidy village dedicated to the future of green, solar-powered living has taken over the heart of the National Mall, where 20 teams of college students are vying to see who can build the most appealing energy-efficient home. The teams, from universities in North America and Europe, are competing in the Department of Energy’s biennial Solar Decathlon, which runs through next weekend. The challenge: design and build a prototype house that can provide the comforts of home while …