Renewable energy sources are discussed. These include wind energy, solar energy, biomass energy and geothermal energy. Energy from wind is acquired through the use of large wind turbines. These turbines ideally need to be located in areas where there is strong wind and low atmospheric turbulence. Solar power is collected using both photovoltaic solar cells and concentrated solar power. Energy from biomass can be produced in two ways: burning biomass to generate electricity or fermentation to produce fuel ethanol. Geothermal energy is produced by pumping water below the earth’s surface into areas of hot rocks which heats the water and creates steam. This steam is then run through a turbine to produce power. Complete course materials are available at the Open Yale Courses website: http://oyc.yale.edu This course was recorded in Fall 2011.