Factors Affecting Yield Gain Using Bifacial Modules
- Mar 23, 2020 12:32 pm GMT
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Bifacial modules are modules that can produce power from both sides, thus increasing total energy generation. They expose both the front and backside of the solar cells to the sun light. Some manufacturers claim up to a 30% increase in production just from the extra power generated.
However, this extra gain is affected by many factors
The irradiance received by the rear side is directly proportional to the ground albedo, in other words the higher the albedo, the higher the bifacial gain in a linear correlation
Increasing the height of the modules will increase the incident irradiance on the rear side of the module, however this increase is not linear in nature, it has been noticed that the power gain from the rear side increases significantly between 0-1 meter in height. After 1 m the gain slows down. Another point here is the irradiance uniformity, it has been shown that increasing the module installation height above 1m makes the irradiance uniform, which allows the module to yield more energy.
Ground Coverage Ratio (GCR)
GCR is the ration of module to land area, when GCR decreases, the irradiance reflected on the rear side will increase. Some conducted studies, have shown that when the GCR increases from 0.25 to 0.5 the correlation is linear. However, when the GCR increases from 0.1 to 0.25, the slope of the yield increase decreases. To conclude, the bifacial gain increases with the increase of array pitch.
In most of the installation, shading cannot be eliminated from the rear back of the modules. The thickness of the supporting rails and height will cause shading, which will affect the irradiance on the rear side of the module.