Solar Energy as the #1 renewable resource Ian Devito
             Photovoltaics(Solar cells) are probably the most efficient method of power generation known. They are silent, produce no emissions, and use no fuel other than sunlight, which is in endless supply. Manufacturers make extensive use of recycled materials and even use waste from other industries as raw material. While some hazardous materials (primarily strong inorganic acids and bases) are used in solar cell manufacturing, these substances are not released into the environment. PV technology is based on silicon, the second most common element on the earth's surface. As used in PV modules, silicon is non-toxic.
             To understand how a solar cell works, it is necessary to go back to some basic atomic concepts. In the simplest model of the atom, electrons orbit a central nucleus, composed of protons and neutrons. each electron carries one negative charge and each proton one positive charge, neutrons carry no charge. Every atom has the same number of electrons as there are protons, so, on the whole, it is electrically neutral. The electrons have discrete kinetic energy levels, which increase with the orbital radius. When atoms bond together to form a solid, the electron energy levels merge into bands. In electrical conductors, these bands are continuous but in insulators and semiconductors there is an "energy gap", in which no electron orbits can exist, between the inner valence band and outer conduction band [Book 1]. Valence electrons help to bind together the atoms in a solid by orbiting 2 adjacent nuclei, while conduction electrons, being less closely bound to the nuclei, are free to move in response to an applied voltage or electric field. The fewer conduction electrons there are, the higher the electrical resistivity of the material. In semiconductors, the materials from which solar sells are made, the energy gap Eg is fairly small. Because of this, electrons in the valence band ca...