Idaho Power says it already gets nearly half its energy from hydroelectric dams such as the Swan Falls Dam on the Snake River, just south of Boise. The utility plans to phase out its use of coal power plants. Education Images/UIG via Getty Images hide caption
Kelp plants grow on a 30-foot-long, white PVC pole suspended in the water. If this is successful, instead of just one row, there would be a whole platform, hundreds of meters across and hundreds of meters deep, full of kelp plants. Courtesy of David Ginsburg/Wrigley Institute hide caption
Solar Impulse 2, the solar powered plane, flies above Giza Pyramids as it finishes its penultimate flight, landing in Egypt on Wednesday. Anadolu Agency/Getty Images hide caption
U.S. Energy Secretary Ernest Moniz takes part in a press conference at the end of the 2015 meeting of the International Energy Agency Governing Board on Nov. 18, 2015 in Paris. ERIC PIERMONT/AFP/Getty Images hide caption
Vera Cole is president of the Mid-Atlantic Renewable Energy Association, a group arguing against proposed rules in Pennsylvania that would put stricter limits on how much grid-connected solar power homeowners can produce on their property. Jeff Brady /NPR hide caption
The new rules' would reduce harmful emissions, the EPA says. David Paul Morris/Getty Images hide caption
Greenpeace's annual report ranks Internet companies based on the efficiency of their cloud facilities. szaz/iStockphoto.com hide caption