Scientific American: A blue-black field of 5.2 million solar panels tilted toward the Arizona sun might just be the Hoover Dam project of the Great Recession. The Agua Caliente Solar Power Project hosts nearly 300 megawatts of silicon photovoltaics (PV) that turn sunshine into electricity. That made the Yuma County facility the largest working solar farm in the world when it opened in April 2014. But when it comes to mega--energy projects, Agua Caliente has competition, including four of the world's largest solar-power...