Can we crowd-fund our way to a solar revolution? That's the vision of Billy Parish, the co-founder of Mosaic, an Oakland start-up that enables individuals to invest collectively in solar projects. So far, the company has channeled more than $1 million into solar panels atop housing complexes and community centers. The idea that crowd-funding could catalyze the shift to green energy was inspired by Parish's wife, Wahleah Johns, a founder of the Black Mesa Water Coalition, which advocates for a transition to renewables on the impoverished Navajo Nation in the Southwest. Decades of dirty-energy production on Navajo lands have left a legacy of pollution, even while thousands continue to live without electricity. "Solar can generate revenues for communities," Johns says. "But we have to find ways of financing these projects. Tribes don't have the capital." At current rates of traditional, top-down investment, a worldwide change to renewables will take about 400 years. Parish, who dropped out of Yale in 2002 to become a full-time activist, thinks his financing model could supercharge that process. "We're trying to find new capital but also get people invested in clean energy, literally."