The cleanest energy is often referred to as renewable energy, and it is mainly hosources such as solar, wind and hydroelectric power. These sources are good in a way because they use natural processes for continual regeneration. Their major functions are to produce electricity, supply heat, and provide transportation fuel--none use greenhouse gas in the process. Technological fields divide along these lines: solar cells use sunlight as energy; windmills convert wind directly into power; while hydroelectric plants swish running water around a turbine which spins coils and thus generates electric current from potential energy. There are uses from small scale family self-powering regions up to general residential and commercial supply as well as largescale industry, with this level of energy sources we may get away from carbon fuel dependency.