Solar cells or photovoltaic cells are small silicon wafers used to convert sunlight into electricity. Actually, they are small bricks that constitute solar panels.
Currently the most efficient cells are based on crystalline silicon with their production cost being relatively low. At the same time this technology can offer high reliability with the cell service life at least 25 years. In a lab environment cells show 44% efficiency of light conversion but the efficiency of serial solar cells is from 12% to 19%.
Any solar panel consists of solar cells and their type defines total capacity and service life of the overall system. Depending on their quality, light cells can be split into 4 categories or so-called grades.
- Grade A – the top quality cells. It does not permit any defects, even minute ones. In addition to high efficiency (16-19% and above) all cells are sorted by color and capacity. All NEOSUN Energy solar modules use Grade A cells.
- Grade B – is similar to Grade A. The only difference is that such cells may have slight visual defects such as color shades, stains, spots, etc. The efficiency of these cells is also at around 16-19% but minor difference in cells’ capacity can lead to slightly lower total capacity of such solar module in comparison with the panel made of Grade A cells. Therefore suppliers of high-quality solar modules never use Grade B for panels with the capacity above 100W while they are appropriate for production of panels below 100W.
- Grade C and Grade D – cells may have fractures, micro-cracks as well as other serious defects and actually are rejects to be recycled after sorting. Large companies never use such cells for their solar panels but some smaller businesses buy the waste and salvage it for a low price. They cut them into small pieces and solder into modules to sell much below market price. Aside from the fact that their efficiency is below 10-14%, such panels can be dangerous for the entire system. In fact, these panels require much soldering because of a large number of fragments. Wrong soldering may lead to local short-circuits and significant difference in capacity of each separate module can result in local overheating and so-called Hot Spot effect. High-voltage systems temperature can be up to 300C, which is fraught with danger for the entire solar module and might put you at a risk of fire.
How to identify the module made of Grade C and D elements? There are three main attributes:
- All high-quality modules are made of square cells with standard size 125х125mm or 156х156mm. If panel cells have another size or they are rectangle-shaped, then you are sure to have Grade C or D.
- Pay attention to modules’ dimension to capacity. The rated capacity of the right solar panel is at around 145-155W per 1 sq. m of module area.
- Manufacturer’s guarantee should be at least 10 years.
Example of cut solar cells: