1. Principles of Solar Photovoltaic Power Generation

光生伏打效應(yīng)在液體和固體物質(zhì)中都會(huì)發(fā)生，但是只有固體（尤其是半導(dǎo)體PN結(jié)器件）在太陽光照射下的光電轉(zhuǎn)換效率較高。利用光生伏打效應(yīng)原理制成晶體硅太陽能電池，可將太陽的光能直接轉(zhuǎn)換成為電能。太陽能光伏發(fā)電的能量轉(zhuǎn)換器是太陽能電池，又稱光伏電池，是太陽能光伏發(fā)電系統(tǒng)的基礎(chǔ)和核心器件。太陽能轉(zhuǎn)換成為電能的過程主要包括3個(gè)步驟：

Photovoltaic effect can occur in both liquid and solid materials, but only solid (especially semiconductor PN junction devices) have higher Solar-cell efficiency under sunlight. The crystalline silicon solar cell is made by using the principle of Photovoltaic effect, which can directly convert the solar energy into electric energy. The energy converter of solar photovoltaic power generation is solar cells, also known as photovoltaic cells, which are the foundation and core components of solar photovoltaic power generation systems. The process of converting solar energy into electrical energy mainly includes three steps:

(1)太陽能電池吸收一定能量的光子后，半導(dǎo)體內(nèi)產(chǎn)生電子一空穴對(duì)，稱為“光生載流子”，兩者的電極性相反，電子帶負(fù)電，空穴帶正電。

(1) After solar cells absorb photons of a certain amount of energy, electron hole pairs are generated in semiconductors, known as "photo generated charge carriers". The polarity of the two is opposite, with electrons negatively charged and holes positively charged.

(2)電極性相反的光生載流子被半導(dǎo)體PN結(jié)所產(chǎn)生的靜電場(chǎng)分離開。

(2) Photogenerated charge carriers with opposite polarity are separated by the electrostatic field generated by the semiconductor PN junction.

(3)光生載流電子和空穴分別被太陽能電池的正、負(fù)極收集，并在外電路中產(chǎn)生電流，從而獲得電能。

(3) Photogenerated current carrying electrons and holes are collected by the positive and negative electrodes of the solar cell, respectively, and generate current in the external circuit to obtain electrical energy.

太陽能光伏發(fā)電原理如下圖所示。當(dāng)光線照射太陽能電池表面時(shí)，一部分光子被硅材料吸收，光子的能量傳遞給硅原子，使電子發(fā)生躍遷，成為自由電子，在PN結(jié)兩側(cè)集聚形成電位差。當(dāng)外部電路接通時(shí)，在該電壓的作用下，將會(huì)有電流流過外部電路產(chǎn)生一定的輸出功率。這個(gè)過程的實(shí)質(zhì)是光子能量轉(zhuǎn)換成電能的過程。

The principle of solar photovoltaic power generation is shown in the following figure. When light shines on the surface of a solar cell, a portion of photons are absorbed by the silicon material, and the energy of the photons is transferred to the silicon atoms, causing electrons to undergo transitions and become free electrons, which gather on both sides of the PN junction to form a potential difference. When the external circuit is connected, under the action of this voltage, a current will flow through the external circuit to generate a certain output power. The essence of this process is the process of converting photon energy into electrical energy.

在太陽能發(fā)電系統(tǒng)中，系統(tǒng)的總效率η由太陽能電池組件的光電轉(zhuǎn)換效率、控制器效率、蓄電池效率、逆變器效率及負(fù)載的效率等決定。目前，太陽能電池的光電轉(zhuǎn)換效率只有17%左右。因此，提高太陽能電池組件的光電轉(zhuǎn)換效率、降低太陽能光伏發(fā)電系統(tǒng)的單位功率造價(jià)，是太陽能光伏發(fā)電產(chǎn)業(yè)化的重點(diǎn)和難點(diǎn)。自太陽能電池問世以來，晶體硅作為主要材料保持著統(tǒng)治地位。目前對(duì)硅太陽能電池轉(zhuǎn)換效率的研究，主要圍繞著加大吸能面（如采用雙面電池減小反射）、運(yùn)用吸雜技術(shù)和鈍化工藝提高硅太陽能電池的轉(zhuǎn)換效率、電池超薄型化等方面。

In a solar power generation system, the overall efficiency of the system η It is determined by the Solar-cell efficiency of solar cell module, controller efficiency, battery efficiency, inverter efficiency and load efficiency. At present, the Solar-cell efficiency of solar cells is only about 17%. Therefore, improving the Solar-cell efficiency of solar cell modules and reducing the unit power cost of solar photovoltaic power generation system are the key and difficult points of the industrialization of solar photovoltaic power generation. Since the advent of solar cells, crystalline silicon has maintained a dominant position as the main material. At present, research on the conversion efficiency of silicon solar cells mainly focuses on increasing the energy absorbing surface (such as using double-sided cells to reduce reflection), using impurity absorption technology and passivation process to improve the conversion efficiency of silicon solar cells, and making the cells ultra-thin.

目前，太陽能光伏發(fā)電系統(tǒng)主要應(yīng)用于以下3個(gè)大的方面。

Currently, solar photovoltaic power generation systems are mainly applied in the following three major areas.

(1)為無電場(chǎng)合提供電源，主要為廣大無電地區(qū)居民生活生產(chǎn)提供電力，為微波中繼站和移動(dòng)電話基站提供電源等。

(1) To provide power for electric field free integration, mainly for the daily life and production of residents in areas without electricity, as well as for microwave relay stations and mobile phone base stations.

(2)太陽能日用電子產(chǎn)品，如各類太陽能充電器、太陽能路燈和太陽能草坪燈等。

(2) Solar daily electronic products, such as various solar chargers, solar street lights, and solar lawn lights.

(3)并網(wǎng)發(fā)電，即接入電網(wǎng)。我國(guó)光伏并網(wǎng)發(fā)電已經(jīng)很成熟了，從2013年開始，出臺(tái)了一系列的光伏發(fā)電促進(jìn)政策，鼓勵(lì)有條件的地區(qū)工商業(yè)和戶用、公共建筑等建設(shè)光伏發(fā)電設(shè)施。

(3) Grid connected power generation, i.e. connected to the national power grid. China's photovoltaic grid connected power generation has become very mature. Since 2013, the country has introduced a series of policies to promote photovoltaic power generation, encouraging the construction of photovoltaic power generation facilities for businesses, households, public buildings, and other areas where conditions permit.

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