Renewable energy is defined as “energy derived from resources that are regenerative or for all practical purposes can not be depleted.” Renewable energy, also called alternative energy, is generally thought of as an alternative to conventional energy usually supplied by the combustion of fossil fuel such as oil, coal or natural gas. The prime source of renewable energy is solar radiation, i.e. sunlight. The Earth-Atmosphere system receives approximately 5.4 x 10^24 joules per year in the solar radiation cycle (Sorensen, 2004). The solar irradiance at the top of the atmosphere is on average 1366 watts/meter-squared.