America is facing unprecedented challenges--a collapsing economy, threats to national security, the climate crisis. The common thread running through them all? Our addiction to fossil fuels. So in July, Nobel laureate and former vice president Al Gore issued a challenge: generate 100 percent of our electricity from truly clean sources that do not contribute to global warming, and do it within 10 years.

Meeting this bold challenge will involve work on three technical fronts. One, get the most out of the energy we currently produce. Two, rapidly develop and commercialize the clean energy technologies that we know can work. And three, create a new integrated grid to deliver power from where it is produced to where people live (see "Lifeline for Renewable Power").