The current use of fossil fuels as our main energy source has two drawbacks: their inevitable depletion and the pollution associated with combustion. These two drawbacks in addition to the growing concern of global warming has pushed for the development of more sustainable sources of energy, namely solar energy and its derivatives (i.e. wind power). Solar energy is appealing for its potential to meet all our demands, while proving to be a pollution free resource.(Bohn, 2009)
Solar energy originates from the thermonuclear fusion reactions occurring in the sun. Leaving all the byproducts of the reactions behind in the sun, the energy that reaches the Earth is pure radiant energy. This energy represents the entire electromagnetic spectrum, ranging from x-rays to radio waves. Most of the sun’s energy, forty-three percent, is in the form of visible light, which can be harnessed for electrical production. The amount of energy hitting the Earth is incredibly large; by one calculation, a month of sunshine has the equivalent energy of all the planet’s used and unused fossil fuels.(Huang, 2007) However, the nature of solar energy has two disadvantages. The sun does not shine consistently throughout the day due to clouds and other atmospheric factors, which can be problem for constant electricity and heat production. Moreover, solar energy cannot be used for nighttime production. The other shortcoming is that the energy from the sun is a diffuse source, that is, it falls over a wide area. In order to utilize this energy, it must be concentrated into a form and amount we can use, such as heat and electricity. These problems are addressed in the three steps used to harness the sun’s energy: collection, conversion, and storage.
The sun’s energy that reaches the Earth does not completely reach the ground where we can use. The clouds absorb 10% off the energy, while reflecting about 25%, and allow about 17% to pass through. The atmosphere absorbs 9%, reflects 9%, and transmits 6% of the solar energy. Twenty-four percent of the solar energy directly reaches the ground. Overall, about 47% (17+6+24) of the sun’s energy striking the Earth reaches the ground, where it is collectable by solar devices. These devices are used generally for two purposes: to heat water and/or living spaces and to produce electricity.
Solar energy is used to heat water for homes and buildings. Two methods used to accomplish this are the passive system, which has no moving parts and strictly relies on the convection currents, and an active system which uses pumps to move the liquid. In both systems, a solar device called a flat bed collector absorbs the sun’s energy to heat the water. The collector consists of a thin, broad box with a glass or clear plastic top and a black bottom with water tubes embedded in it. The black bottom allows for the maximum amount of heat absorption while the clear cover and interior insulation prevent heat loss. As...