needtoknow.nas.edu http://needtoknow.nas.edu/energy/energy-use/home-work/ http://needtoknow.nas.edu/energy/energy-use/home-work/ http://needtoknow.nas.edu/energy/energy-use/home-work/ http://needtoknow.nas.edu/energy/energy-use/home-work/ http://needtoknow.nas.edu/energy/energy-use/home-work/ utilize this energy