nowadays the position of the renewable energy is so important because of the environment pollution and the limitation of fossil fuels in the world. energy can be generated more and more by the renewable sources, but the fossil fuels are non-renewable. one of the most important renewable sources is the wind energy. the wind energy is an appropriate alternative source of fossil fuel. the replacem...

using photovoltaic systems is gradually expanded by increasing energy demand. abundance and availability of this energy, has turned to one of the most important sources of renewable energy. unfortunately, photovoltaic systems have two big problems: first, those have very low energy conversion efficiency (in act between 12 and 42 percent under certain circumstances). second, the power produced b...