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والان مع الموضوع..
Overview of the Photovoltaic Power System
At present, photovoltaic (PV) electrical power generation is a fairly costly technology. Recent developments have led to increased cell efficiencies at reduced costs. A lot of researches are ongoing targeting to make PV more and more efficient and to reduce its cost to a magnitude that is competitive to the generation of conventional power to enable widespread of this progressive technology to penetrate to the bulk power market.
In spite of all of this, even at this stage of the technology evolution, there are a lot of applications that photovoltaic is the only viable option. In some cases, it might be the only choice. Most of these applications, however, are small-scale power consumption applications. Larger scale power applications, especially if close to a utility grid, have not up till now been proven to be cost-effective.
Theory of Photovoltaics
The photovoltaic phenomenon is the process by which light is converted silently and directly into electricity without elaborate machinery which is usually associated with conventional generation of electricity.
A photovoltaic (solar) cell is typically made by placing a thin layer of phosphorus-doped silicon in intimate contact with a layer of boron-doped silicon. When light falls on the cell, photons are absorbed and electrons are set free. The excess electrons accumulate in the phosphorus-doped silicon, which is called n-silicon because electrons have negative charge. If one end of a wire is attached to this top layer and the other end is connected to the layer beneath, electrons will leave the upper layer, flow through the wire, and be absorbed by the boron-doped silicon, which is called p-silicon, meaning positive. Figure_1 demonstrates the process by which electricity in a photovoltaic cell is generated.