The sources of renewable energy depending on interpretation are somewhat wide ranging since they consist of energy derived from numerous natural resources. Generally speaking, energy generated without using fossil fuels (coal, natural gas, or petroleum) or that is non-carbon emitting is said to be green, renewable energy. This broad definition could allow for conventional nuclear reactors to be classified as renewable energy. However, typically legislation excludes nuclear as renewable energy due to obvious controversy. Some also argue that biomass, along with waste to energy processes, should not be classified as renewable due to carbon being released into the atmosphere during combustion. In the United States, the federal government has defined incentive eligible renewable energy technologies as the following:
• Solar Water Heat • Solar Space Heat • Solar Thermal Electric • Solar Thermal Process Heat • Photovoltaics • Wind • Biomass • Geothermal Electric • Fuel Cells • Geothermal Heat Pumps • Combined Heat and power (CHP)/Cogeneration • Solar Hybrid Lighting • Fuel Cells using Renewable Fuels • Microturbines • Geothermal Direct-Use
2.1 SOLAR PHOTOVOLTAICS
Solar photovoltaics, or PV, would not be able to work were it not for the photoelectric effect. The photoelectric effect is a physical process whereby the energy of photons of various wavelengths strikes a material and the solid material gives off energy in
the form of electrons. Nearly all materials exhibit this effect for certain wavelengths of electromagnetic radiation. Photovoltaic solar technology absorbs photons in the range of the electromagnetic spectrum we call light; light that consists of electromagnetic radiation with wavelengths of 10−8 to 10−3 meters and a frequency of 1016 to 1011 Hz.