由于單晶硅電池片和多晶硅電池片前期生產(chǎn)工藝的不同，使它們從外觀到電性能都有一些區(qū)別。從外觀上看：單晶硅電池片四個(gè)角呈圓弧狀，表面沒有花紋;多晶硅電池片四個(gè)角為方角，表面有類似冰花一樣的花紋。

對(duì)于使用者來說，單晶硅電池和多晶硅電池是沒有太大區(qū)別的。單晶硅電池和多晶硅電池的壽命和穩(wěn)定性都很好。雖然單晶硅電池的平均轉(zhuǎn)換效率比多晶硅電池的平均轉(zhuǎn)換效率高l%左右，但是由于單晶硅太陽能電池只能做成準(zhǔn)正方形(其4個(gè)角是圓弧)，當(dāng)組成太陽能電池元件時(shí)就有一部分面積填不滿，而多晶硅太陽能電池是正方形，不存在這個(gè)問題，因此對(duì)于太陽能電池元件的效率來講幾乎是一樣的。另外，由于兩種太陽能電池材料的制造工藝不一樣，多晶硅太陽能電池制造過程中消耗的能量要比單晶硅太陽能電池少30%左右，所以多晶硅太陽能電池占全球太陽能電池總產(chǎn)量的份額越來越大，制造成本也將大大小于單晶硅電池，所以使用多晶硅太陽能電池將更節(jié)能、更環(huán)保。

9、逆變器的概念

逆變是針對(duì)整流而言的，整流器把交流電能變換成直流電能的過程稱為整流。那么把直流電能變換成交流電能的過程就稱為逆變了，把完成逆變功能的電路稱為逆變電路，把實(shí)現(xiàn)逆變過程的裝置稱為逆變器。

在太陽能光伏發(fā)電系統(tǒng)中為什么一定要采用光伏逆變器呢?目前我國發(fā)電系統(tǒng)主要是直流系統(tǒng)，即將太陽能電池發(fā)出的電給蓄電池充電，而蓄電池直接給負(fù)載供電，如我國西北地方使用較多的太陽照明系統(tǒng)以及遠(yuǎn)離電網(wǎng)的微波站供電系統(tǒng)均為直流系統(tǒng)。此類系統(tǒng)結(jié)構(gòu)簡單，成本低廉，但由于負(fù)載直流電壓的不同(如12V、24V、48V等)，很難實(shí)現(xiàn)系統(tǒng)的標(biāo)準(zhǔn)化和相容性。特別是家用電器，如日光燈、電視機(jī)、電冰箱、電風(fēng)扇和大多數(shù)動(dòng)力機(jī)械都是利用交流電工作的，即大多數(shù)為交流負(fù)載，所以利用直流電力供電的光伏電源，很難作為商品進(jìn)入市場(chǎng)。太陽能光伏系統(tǒng)設(shè)置逆變器的目的就是將直流電轉(zhuǎn)換為交流電，便于滿足大多數(shù)使用者負(fù)載的需要。

此外，如果電力線受到破壞或被迫關(guān)閉，逆變器就要停止向用電設(shè)備或電網(wǎng)供電。如果電力線電壓偏低或欠壓，或出現(xiàn)較大的擾動(dòng)時(shí)，要采用一種用于“非孤島”逆變器的傳感器來傳感這種情況。當(dāng)出現(xiàn)這種情況時(shí)，逆變器將自動(dòng)地關(guān)閉向電網(wǎng)供電，或把電力傳輸?shù)狡渌胤剑瑥亩乐顾蔀殡娏Πl(fā)電的“孤島”。所謂孤島效應(yīng)，即電網(wǎng)出現(xiàn)故障后，并聯(lián)在電網(wǎng)上的光伏并網(wǎng)發(fā)電系統(tǒng)依舊可以工作，處于獨(dú)立運(yùn)行狀態(tài)。

Because of the different pre-production technology of monocrystalline silicon cell sheet and polycrystalline silicon cell sheet, there are some differences between them from appearance to electrical properties.   From the appearance: the four corners of the monocrystalline silicon cell are arc shaped, no surface pattern;   The four corners of the polycrystalline silicon cell are square, and the surface has a pattern similar to ice flowers.  

 

 

 

To the user, there is not much difference between a monocrystalline silicon cell and a polycrystalline silicon cell.  Monocrystalline silicon cells and polycrystalline silicon cells have good life and stability.  Although the average conversion efficiency of monocrystalline cells better than the average conversion efficiency of polysilicon batteries around l %, but because of monocrystalline silicon solar cell can only be made quasi square (the four Angle is arc), when the solar battery components are part of an area of fill, and polycrystalline silicon solar cell is a square, there is no this problem,  So it's almost the same for the efficiency of the solar cell components.  In addition, due to the manufacturing process of two kinds of solar cell materials, polycrystalline silicon solar cell manufacturing process consumes less energy than monocrystalline silicon solar cell is about 30%, so the polycrystalline silicon solar cells account for a growing share of the total global solar cell production, the manufacturing cost will be much smaller than that of single crystal silicon cell,  So using polysilicon solar cells will be more energy efficient and environmentally friendly.  

 

9. The concept of inverter  

 

 

 

Inverter is for rectification, the rectifier to convert AC electric energy into DC electric energy process called rectification.  So the process of DC energy into AC energy is called the inverter, the completion of the inverter function of the circuit called the inverter circuit, the realization of the inverter process device called the inverter.  

 

 

 

Why must the photovoltaic inverter be used in the solar photovoltaic power generation system?  At present, the power generation system in our country is mainly a DC system, which is to charge battery with the electricity produced by the solar cells, and supply power to the battery directly. As the solar lighting system which is widely used in the northwest of our country and the microwave station power supply system are all DC system.  This kind of system has simple structure and low cost, but it is difficult to realize the standardization and compatibility of the system due to the different DC voltages of the load (such as 12V, 24V, 48V, etc.).  Especially household appliances, such as fluorescent lamps, television sets, refrigerators, electric fans and most power machinery are the use of alternating current work, that is, most of the AC load, so the use of DC power supply of photovoltaic power, it is difficult to enter the market as a commodity.  The purpose of setting inverter in solar photovoltaic system is to convert direct current to alternating current, which is convenient to meet the needs of most users.  

 

 

 

In addition, if the power line is damaged or forced to shut down, the inverter stops supplying power to the electrical equipment or grid.  If the power line voltage is low or undervoltage, or there is a large disturbance, use a sensor for "non-island" inverter to sense this situation.   When this happens, the inverter will automatically turn off its power supply to the grid or transmit it elsewhere, preventing it from becoming an "island" of electricity generation.   The so-called island effect means that the grid-connected photovoltaic power generation system connected in parallel to the grid can still work and operate independently after the grid fails.