The hydroelectric power plant on the Nevada side of Hoover D [Getty Images]

UNITED STATES - JUNE 03: The hydroelectric power plant on the Nevada side of Hoover Dam near Boulder City, Nevada, U.S., is shown on Wednesday, June 3, 2009. Investors poured $155 billion into renewable-power projects worldwide last year, exceeding for the first time new spending on fossil fuel-based technologies like coal-fired electricity plants, the United Nations said. (Photo by Ronda Churchill/Bloomberg via Getty Images)

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