27-07-2012, 12:52 PM
solar electricity
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SOLAR POWER
Solar power is the conversion of sunlight into electricity, either directly using photovoltaic’s (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics convert light into electric current using the photoelectric effect. Commercial concentrated solar power plants were first developed in the 1980s. The 354 MW SEGS CSP installation is the largest solar power plant in the world, located in the Mojave Desert of California. Other large CSP plants include the Solnova Solar Power Station (150 MW) and the Andasol solar power station (150 MW), both in Spain. The 200 MW Golmud Solar Park in China, is the world’s largest photovoltaic plant.
TYPES OF SOLAR CELLS
The most common form of solar cells are based on the photovoltaic (PV) effect in which light falling on a two layer semi-conductor device produces a photo-voltage or potential difference between the layers. This voltage is capable of driving a current through an external circuit and thereby producing useful work. The most common configuration of this device, the first generation photovoltaic, consists of a large-area, single layer p-n junction diode, which is capable of generating usable electrical energy from light sources with the wavelengths of solar light. These cells are typically made using silicon. However, successive generations of photovoltaic cells are currently being developed that may improve the photo-conversion efficiency for future photovoltaic. The second generation of photovoltaic materials is based on multiple layers of p-n junction diodes. Each layer is designed to absorb a successively longer wavelength of light (lower energy), thus absorbing more of the solar spectrum and increasing the amount of electrical energy produced. The third generation of photovoltaic is very different from the other two, and is broadly defined as a semiconductor device which does not rely on a traditional p-n junction to separate photo-generated charge carriers. These new devices include dye sensitized cells, organic polymer cells, and quantum dot solar cells.
APPLICATIONS OF SOLAR CELLS
The market for solar cells at presently is growing at over 30% per year, and the cost of panels is declining continuously in real terms, due to both new technologies and mass production. The need and possible applications for solar electricity is growing as follows: