A. What Are Bi-Facial Solar Modules?
The energy output of a photo-voltaic solar plant is closely linked to the efficiency of the solar modules using which the solar panels are made. It is needless to mention that numerous designs and configurations are being developed and tried out to further enhance the output of the modules.
One such configuration, which has demonstrated positive results is bifacial solar modules. As we all know, the conventional modules have solar cells only on one side. This, in some way directly links the plant output to the total surface area of the solar panels. Bifacial solar modules have solar cells on both the sides – front as well as back.
This means, for the same surface area, we can have twice the number of solar cells. To put it simply bifacial solar technology allows us to put a double number of solar cells in the given surface area when compared with the conventional modules.
It is important to note that doubling the number of solar cells will not necessarily double the output of the PV panel as the output heavily depends on the radiant energy hitting the panels. While studies show that use of bifacial modules increases the output of the solar plant, the amount of increase in energy is determined by how the bifacial panels are installed.
B. How Are Bifacial Modules Installed?
Bifacial modules need to be installed in a special manner so that they function at peak productivities. Interestingly, the orientation and height of installation of these modules can sharply increase or decrease their output. Here are some positional as well as other factors which determine the output of the bifacial modules.
- Factors determining the energy output of bifacial Modules:
- The orientation of Installation: Since bifacial modules capture solar radiation from both the faces, it is crucial that they are installed in such a manner that both the surfaces are used efficiently. Normally, the bifacial modules are installed in a more vertical orientation than the mono facial or conventional modules. Many experts recommend installing these solar panels absolutely vertically so that energy is captured during first and the second halves of the day by the two sides of the panels.
- Diffused Radiation: In case of bifacial solar panels, while one side is exposed to the radiation, the other side will be deprived of it. However, the second side will still be getting a considerable amount of diffused radiation which actually results in the energy boost. Hence, the amount of diffused radiation plays a key role in determining the efficiency of the bifacial modules. Needless to say that in snowy regions and high altitudes, the energy boost due to bifacial modules will be much more. Researchers and manufacturers claim increments as high as 50% to 70% due to use of bifacial modules are diffused radiation is available in plenty.
- Height of Installation: The output of Bifacial panels increases as the height of installation is increased. As the height of installation is increased, the amount of diffused radiation reaching the backside of the modules will increase thereby increasing the output. At the same time, the height can not be increased beyond a certain limit as it will cause shadowing on other panels and will to solve that, the panels would need to be installed sparsely
- Albedo: Albedo refers to the reflectivity of the surface beneath the modules. As we have seen earlier, the output of bifacial modules will depend on how much diffused radiation the ground facing side will receive. Increasing the reflectivity of the surface bending it in white color or by using certain materials can drastically improve their output.
C. How Output Of Bifacial Modules Is Measured?
When it comes to actually measure the performance of the bifacial modules, a term – Bifaciality Factor needs to be considered. The bifacility factor is simply the ratio of power generated by the rear side of the panel to the power generated from the front side of the panel.
Bifaciality Ratio = Energy generated from the rear side/ Energy generated from the front side.
Higher the bifacility ratio, higher the energy boost received from the module.
- Benefits Of Bifacial Solar Modules:
- Increased energy generation: The obvious and most clear benefit of bifacial modules is the increase in the generated energy. Bifacial modules can lead to a 10% to 15% increase in energy production under normal circumstances. This can very easily change the profitability of the entire plant and can also bring down the payback period drastically.
- Balanced energy output: Normally, energy generation reaches a peak when the sun rays fall normal to the In case of bifacial modules if they are installed properly, the energy generation profile can be more uniform as it is the sum total of outputs of both the sides which determines the total energy output.
- Suited for places where space is a restriction: At many locations, lack of space limits the energy output and can be a deal-breaker for someone thinking of moving to Bifacial modules can be installed at such locations and deliver higher energy outputs.
- Limitations Of Bifacial Modules:
- Cost Of Manufacturing: Bifacial modules are costlier to manufacture and need advanced setup for manufacturing. Since this technology is not yet widely accepted, manufactures can not leverage the scales and bring the costs down.
- Lack Of Standards: Definitive standards are not available to rate the bifacial modules nor any certified method is available to measure their output and hence ROI conclusively. As this technology finds inroads, more of such data will be available which will further help buyers to move to this technology.