Just in case those little solar-powered garden lights are not cool enough for you: The George Washington University has installed a 100-square-foot stretch of walkway that's covered entirely in solar panels. In a year, the solar sidewalk should make about 470 kilowatt-hours of electricity, according to numbers from Onyx Solar, the walkway's maker. That electricity will power the 450 LED lights inside the panels that will light the walk at night.