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recycling process of solar cell

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In this article- Module performance, Aging, Recycling and Production would be explained in short. Hope you would find it useful in school projects, Engineering projects and assist you in making your thesis or report on solar energy.

Module performance 

-is normally rated under standard test conditions STC which is the irradiance of 1000 watt per meter square, solar spectrum of AM1.5 and module temperature at 25 degree Celsius

How solar cell or solar module is produced?

  • The poly-silicon rock is melted until it forms white hot liquid. The molten material is then defused into a single giant crystal in which all the atoms are perfectly aligned and ordered in desired structure and orientation.
  • The 120 to 140 kg of poly-silicon pieces is then stacked in a quartz crucible. The silicon disc is soaked with tiny amount of boron. The boron is the doping substance here, which ensures positive potential electrical orientation of the resulting crystal. The crucible is encapsulated within thick walls of insulating graphite and locked within a cylindrical furnace.
  • The next step is melting the crystal. When the crystal glowing furnace heats up to the temperature of around 25,000 degree Fahrenheit, its silicon content melts and slurry is formed. The actual magic works, after computer monitor registers the right temperature and atmospheric condition is met. A silicon seed crystal is lowered into the melt.
  • The silicon melt freezes over the crystal seed, matching to the seed crystalline structure. The size of the crystal increases and stopped to the required dimensions. The next step involved cooling the crystal to 300 degree Fahrenheit which took around 2 to 3 days. The entire crystal is the form of big cylindrical structures.
  • Those cylinders thus formed, are cut into wafers with the appropriate cutting tools as required.

Recycling

Production of a device is crucial but it becomes extremely crucial to recover or recycle the devise if it failed to work properly. The advantage of solar module is that if it is not usable or failed to work properly, it can be recycled. Mostly upto 97 percent of the semiconductor, glass etc. part as well as large amount of the ferrous and non-ferrous metals.  Many private companies and NGOs are currently actively engaged in take –back and recycling operations for modules with ended life.

The recycling process depends on the type of technology used in the module –

The silicon based modules: – At the beginning of the process, aluminum frames and junction boxes are dismantled manually. The module is then crushed in the mill and the different fractions are separated viz. plastic, glass and metals etc. it is possible to recover more than 80% of the incoming weight. Process can be entertained by the flat glasses recyclers since the composition and morphology is similar to those flat glasses used in the building and automotive industry. There covered glass from this process is easily accepted by the glass foam and glass insulation company.

 

Non silicon based Modules: – For recycling the non-silicon based modules, less specific recycling technologies are required such as the chemical baths(dipping into chemicals and depositing on some other material) in order to isolate the different semiconductor materials. For cadmium telluride modules, recycling process starts with crushing the module and subsequently separating the different fractions. The recycling approach is designed in a way to recover glass upto 90 percent and 95 percent of the semiconductor materials contained in it.