Solar Power Plants

Solar power is the conversion of energy from the sun to electricity. The process involves the use of photovoltaics or concentrated solar power or both. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaic cells convert light to an electric current using the photovoltaic effect . Photovoltaic cells where meant to power small devices like calculators and remote homes powered by an off grid photovoltaic system mounted on the rooftop. Commercial concentrated solar power plants were first developed in the 1980s and have continued to expand since.

Types

They are basically two types:

1. Photovoltaic systems

2.Concentrated Solar Power.

Photovoltaic Systems

Photovoltaic systems use solar panels placed either on rooftops or ground mounted solar farms converting sunlight directly to electrical power. This system consist of a photovoltaic cell that converts light into electric current using the photovoltaic effect. The photovoltaic effect is the creation of voltage and electric current in a material upon exposure to light. It is a physical and chemical phenomenon. The photovoltaic effect is similar to the photoelectric effect. In either of these cases, light is absorbed causing the excitation of an electron or charge carrier to a higher energy state. The difference between the two is that the photoelectric effect is used when the electron is ejected out of the material. Photovoltaic effect is used when the excited charge carrier is still contained within the material. In most photovoltaic applications the radiation in sunlight,and the devices are called solar panels. The array of a photovoltaic power system produces direct current (DC) power which fluctuates with the Sun’s intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC) through the use of inverters. Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter which produces power at the desired voltage and for AC the desired frequency or phase.

Concentrated Solar Power.

Concentrated solar power also called concentrated solar thermal uses lenses or mirrors and tracking systems to concentrate sunlight,then using the resulting heat to generate electricity from conventional steam driven turbines. A wide range of these technologies exist among which are the parabolic trough, the compact linear Fresnel reflector, the Stirling dish and the solar power tower. In all of these systems a working fluid is heated by a concentrated sunlight and then used to generate electricity or store power. Thermal storage efficiency allows up to 24 hour electricity generation.

Hybrid Systems

A hybrid system combines photovoltaic and concentrated power system with one another or with other forms of generation such as diesel,wind and biogas. The combined form of generation may enable the system to modulate power output as a function of demand or at least reduce the fluctuating nature of solar power and the consumption of non- renewable fuel. Hybrid systems are most often found on Islands.

A solar power plant.

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