Solar Energy

Solar energy is the sun’s rays (solar radiation) that reach the earth. This energy is received in many forms such as ultraviolet light, infrared right, and many more forms of light on the color spectrum. This energy can be converted into other forms of energy, such as heat (thermal energy) and electricity. Today, people use the sun's energy for lots of things. Solar energy can be converted into electricity in two ways.

1. Photovoltaic devices or solar cells change sunlight directly into electricity. PV systems are often used in remote locations that are not connected to the electric grid. They are also used to power watches, calculators, and lighted road signs. Unfortunately, this way to capture solar energy is very inefficient (about 10% efficiency!) because a lot of energy is not absorbed.
2. Solar Power Plants generate electricity when the heat from mirrors or solar thermal collectors is used to heat a fluid, which produces steam that is used to power generator. Out of the 15 known solar electric generating units operating in the United States at the end of 2006, ten of these are in California , and five in Arizona . These plants are more efficient than their Photovoltaic counter parts because the thermal conductors take in little heat.

The process on converting the sunlight to energy is different in a Photovoltaic device. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the size of the wavelengths, which is determined by what kind of light it is. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide the energy to generate electricity thus making photovoltaic devices inefficient. When enough energy is absorbed by the material, electrons are dislodged from the atoms. These electrons migrate to the surface because of the material of the photovoltaic devices. When the electrons leave their position, holes are formed. When many electrons travel toward the front surface of the cell, the atoms become imbalance in their charges between the cell's front and back surfaces. When the two surfaces are connected through an external load, electricity flows. However, one cell about foursquare inches to one square foot only produces 1 or 2 watts. To increase power output, cells are electrically connected into a packaged weather-tight module. There modules can be connected to form arrays, thus producing more energy.

As with any fuel, there are some disadvantages to solar energy. The most obvious is that sunlight arrives in different amounts at different times. It is inconsistent and depends on location, time of day, time of year, and weather conditions. Another disadvantage is that the sun does not deliver that much energy to any one place at any one time so a large surface area is required to collect the energy at a usable rate. Moreover, there are useful sides to solar energy such as the fact that Conversion from sunlight to electricity is direct, so that the use of mechanical generator systems is unnecessary. Another advantage is that PV arrays can be installed quickly and cheaply in any size required or allowed. Furthermore, the environmental impact is minimal, requiring no water for system cooling and generating no by-products except for energy.

The solar power plants get their energy differently. The most commonly used method is a parabolic trough. In this kind of plant, numerous glass in the shape of a parabola reflect energy to a think wire full of oil. This oil flows into a plant and make water boil, therefore making turbines turn. The turbines power a generator thus producing electricity. The other most common way to produce electricity is through a solar power tower. This new type of method is coming out just recently. It has a central receiver that generates electricity from sunlight by focusing concentrated solar energy from numerous flat sun-tracking mirrors called heliostats. The energy can be concentrated as much as 1,500 times that of the energy coming in from the sun! Energy losses from thermal energy transport are further minimized as solar energy is being directly transferred by reflection from the heliostats to a single receiver. This is more efficient because the thin stream of oil loses heat energy as it moves. Power towers must be large to be economical as with the parabolic troughs, therefore both are somewhat expensive to build. Whether it is through solar power plants or through p hotovoltaic devices, solar energy is a free form of energy and its supplies are unlimited. As a relatively new field in renewable energy, solar energy is still at its beginning stages, imagine what it will be like in a few more years.