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alternative energy solar wind geothermal biofuel
http:__environment.nationalgeographic.com_environment_energy_great-energy-challenge_personal-energy-meter_
https:__docs.google.com_file_d_1meY4Af-y2g29RdiMvpTs4dRXDY1eVzTei59v6VZ9kdz0vFAnGIOAniZBeBfR_edit