Wind generators at Pacific Hydro's Cape Bridgewater wind farm in Warrnambool, Australia, in May 2012. Each generator produces roughly enough energy to meet the annual needs of 12,000 households. Mark Dadswell/Getty Images hide caption

itoggle caption Mark Dadswell/Getty Images

Residents of Mutriku, a fishing village on Spain's northern coast, lounge at their local beach, protected from fierce Atlantic waves by a cement breakwater that also houses Europe's first wave energy plant. Lauren Frayer for NPR hide caption

itoggle caption Lauren Frayer for NPR

Austin Mitchell walks away from an oil derrick outside Williston, N.D., in July 2011. North Dakota is now the No. 2 producer of oil in the U.S. behind Texas. Gregory Bull/AP hide caption

itoggle caption Gregory Bull/AP

As U.S. coal consumption has fallen, its exports of coal have risen. Pictured, Midwest Generation's Crawford Generating Station, a coal-fired power plant in Chicago. The city's two coal-fired plants are closing under a deal with city officials and environmental groups. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP