(1) Solar energy is mass-produced on a large farm of solar panels. Learn more about solar power, solar farms and alternative energy in this video. http://videos.howstuffworks.com/howstuffworks/3910-solar-farm-video.htm

(2) Hydroelectric and geothermal energy are two examples of renewable sources of electricity. Learn more these sources and the physics behind them in this video. http://videos.howstuffworks.com/hsw/9616-physics-of-motion-renewable-sources-of-electricity-video.htm