Solar energy is the primary source of energy on the earth. This energy is derived from the thermonuclear reaction of fusing hydrogen atoms to form helium, a reaction responsible for driving the suns existence. During this reaction a very small amount of mass is lost. It travels to the earth as pure, radiant energy. Less than 1% of this energy reaches the earth and is enough to provide all of our energy needs. This energy travels as waves of photons, which are easily absorbed or reflected. Heating is important at the earth’s surface. When heat is absorbed by land it provides the major heat input into the lower atmosphere. This solar energy fuels the kinetic energy for wind generation of the great trade winds. The combination of solar energy, gravity and the rotation of the earth are responsible for oceanic movement relating to ocean energy. Heat absorbed by the ocean gives surface water molecules enough energy for evaporation to occur. The water vapor is then lifted by rising heated air and is carried by the winds until it falls as rain. By this lifting of great masses of water away from the earth the surface of the earth this solar energy is converted to gravitational potential energy. Some of this gravitational potential energy is then converted to mechanical energy when the water returns to the earth in the form of rain or snow, which move to rivers and streams. The flowing water is used to turn a turbine. 1
Radiant energy from the sun is absorbed by plants and used to break up the molecules CO2 and H2O and rearrange them to form carbohydrates. The carbohydrate formed with the help of the suns energy is either food or fuel. Eating or burning the carbohydrates form CO2 and H2O while releasing energy in the process.5
Humans have found ways to use the sun’s energy directly to provide heat and hot water for homes, offices and factories. In an active system solar energy is collected in a special device used to store and distribute the energy. This solar collector absorbs solar energy and converts it into heat energy. Water circulating through the collector increases in temperature and is used to run a home heating system. In a passive system solar architecture converts a building structure such as a home into a solar energy collector. The home is designed to allow large amounts of heat in while trapping the energy and heating the home.
Solar energy is also used to produce electricity. Photovoltaic (PV) cells originally used for space applications are now use to power solar calculators, toys and roadside telephone boxes. This is accomplished by transforming light directly into electricity with the use of a crystal emitting electrons into a system. Solar electricity production also occurs in solar thermal-electric systems. In these systems collectors concentrate the sunlight into a receiver to superheat a liquid used to produce steam to power electrical generators.6
The potential for solar energy is enormous and should represent a major percentage of our future energy throughout the U.S. It is an unlimited supply of energy and causes no air or water pollution. However the amount of energy received by a solar collector is affected by geographic location, time of the day, seasonal variations and atmospheric conditions. This may cause unreliability and a necessity for storage or backup sources due to the sporadic availability of sunlight.