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光伏發(fā)電機的基本組件是光伏電池，在光伏電池中將太陽輻射轉化為電流。電池由一薄層半導體材料構成，通常經(jīng)過適當處理的硅，厚度約為0.3 mm，表面為100至225 cm2。硅有四個價電子（四價），通過在一個“層”上添加三價原子（例如硼-磷摻雜）和在另一個“層”上添加大量五價原子（例如磷-氮摻雜）來“摻雜”。p型區(qū)域有過多的空穴，而n型區(qū)域有過多的電子。在兩層不同摻雜（P-N結）之間的接觸區(qū)域中，電子傾向于從富電子半（N）移動到貧電子半（P），從而在P區(qū)域中產生負電荷的累積。電子空穴出現(xiàn)雙重現(xiàn)象，在區(qū)域N中積累正電荷。因此，在結上產生電場，阻止電荷進一步擴散。通過從外部施加電壓，接頭僅允許電流沿一個方向流動（二極管工作）。當電池暴露在光照下時，由于光伏效應1，在N區(qū)和P區(qū)都會出現(xiàn)一些電偶。內部電場允許多余的電子（從材料的一部分吸收光子而來）從空穴中分離出來，并將它們推向彼此相對的相反方向。因此，一旦電子通過耗盡區(qū)，它們就不能向后移動，因為磁場阻止它們反向流動。通過將接頭與外部導體連接，可以獲得閉合電路，其中只要電池被照亮，電流就從具有較高電勢的N層流向具有較低電勢的N層。有助于提供電流的硅區(qū)域是P-N結周圍的區(qū)域；電荷在遙遠的地區(qū)形成，但沒有電場使它們移動，因此它們重新結合。因此，光伏電池必須有一個大的表面：表面越大，產生的電流越大。5.2光伏發(fā)電廠的主要組件1當材料（通常為半導體）價帶中的電子由于吸收入射到材料上的一個足夠能量的光子（電磁輻射量子）而提升到導帶時，會發(fā)生光伏效應。事實上，在半導體材料中，就絕緣材料而言，價電子不能自由移動，但與絕緣材料相比，價帶和導帶（典型的導電材料）之間的能隙很小，因此當電子從外部接收能量時，可以很容易地移動到導帶。這種能量可以由光輻射提供，因此產生光伏效應。

The elementary component of a PV generator is the photovoltaic cell where the conversion of the solar radiation into electric current is carried out. The cell is constituted by a thin layer of semiconductor material, generally silicon properly treated, with a thickness of about 0.3 mm and a surface from 100 to 225 cm2 . Silicon, which has four valence electrons (tetravalent), is “doped” by adding trivalent atoms (e.g. boron – P doping) on one “layer” and quantities of pentavalent atoms (e.g. phosphorus – N doping) on the other one. The p-type region has an excess of holes, whereas the n-type region has an excess of electrons. In the contact area between the two layers differently doped (P-N junction), the electrons tend to move from the electron rich half (N) to the electron poor half (P), thus generating an accumulation of negative charge in the P region. A dual phenomenon occurs for the electron holes, with an accumulation of positive charge in the region N. Therefore an electric field is created across the junction and it opposes the further diffusion of electric charges. By applying a voltage from the outside, the junction allows the current to flow in one direction only (diode functioning). When the cell is exposed to light, due to the photovoltaic effect 1 , some electronhole couples arise both in the N region as well as in the P region. The internal electric field allows the excess electrons (derived from the absorption of the photons from part of the material) to be separated from the holes and pushes them in opposite directions in relation one to another. As a consequence, once the electrons have passed the depletion region they cannot move back since the field prevents them from flowing in the reverse direction. By connecting the junction with an external conductor, a closed circuit is obtained, in which the current flows from the layer N, having higher potential, to the layer N, having lower potential, as long as the cell is illuminated. The silicon region which contributes to supply the current is the area surrounding the P-N junction; the electric charges form in the far off areas, but there is not the electric field which makes them move and therefore they recombine. As a consequence it is important that the PV cell has a great surface: the greater the surface, the higher the generated current. 5.2 Main components of a photovoltaic plants 1 The photovoltaic effect occurs when an electron in the valence band of a material (generally a semiconductor) is promoted to the conduction band due to the absorption of one sufficiently energetic photon (quantum of electromagnetic radiation) incident on the material. In fact, in the semiconductor materials, as for insulating materials, the valence electrons cannot move freely, but comparing semiconductor with insulating materials the energy gap between the valence band and the conduction band (typical of conducting materials) is small, so that the electrons can easily move to the conduction band when they receive energy from the outside. Such energy can be supplied by the luminous radiation, hence the photovoltaic effect.