Renewable energy advocates are looking to geothermal sources like this plant in Calipatria, Calif., to provide electricity to help California meet its goal of generating 33 percent of its power from renewable sources by 2020. But some conventional geothermal sites are, quite literally, running out of steam. David McNew/Getty Images hide caption

itoggle caption David McNew/Getty Images

The Campo Kumeyaay Nation, a desert tribe east of San Diego, currently leases land to the only large-scale renewable power facility on tribal land in the country. Amy Standen/KQED hide caption

itoggle caption Amy Standen/KQED