sentence: One recent calculation led by Vasilis M. Fthenakis, an environmental engineer at Columbia University's Center for Life Cycle Analysis, found that it would take covering 16,602 square miles[pdf] of land in the southwestern desert with solar energy converters like cadmium telluride photovoltaic panels to generate the 3,816,000,000 megawatt-hours of electricity that is used in the U.S. ever year.