Bifacial gain

11.6 Bifacial gain

The software supports calculating bifacial gain for: fixed tilted plane and Tracking, horizontal N-S axis. Before setting the "Bifacial gain", users should check whether the "Array type" is set correctly in the "Create array" interface.

11.6.1 Bifacial modules

When the users selects the checkbox on the right side of "Double-sided components", the software will recognize all modules in the model as bifacial modules and calculate the bifacial gain based on the current interface parameter settings.

"Bifaciality factor": The bifaciality factor of bifical module is usually 0.7-0.9, and specific values need to be referred to in the module specification mannul. Please refer to the following formula for calculating the bifaciality factor, where the peak power is the output power of the module under STC conditions.

"Structure shading factor": Considering the shading caused by external factors such as combiner, inverter and rails of bracket, for the installation of side installed combiner or the use of bifacial module dedicated PV brackets, the shading factor of the structure can be set to 0 to avoid the shading of the back battery by the rails. However, in the N-S horizontal axis tracking bifacial power generation system, due to the longitudinal installation of PV modules along both sides of the main axis, the main axis is adjacent to the back of the module, resulting in a small distance between the back of the module and the main axis, which may cause shadings. Therefore, it is necessary to perform calculations and fill in the corresponding factor accordingly.

"Ground albedo": In practical projects, due to the presence of different ground characteristics such as snowfall, grassland, yellow sand land, cement land, etc., the albedo of the ground will exhibit specific characteristics with seasonal and temporal changes. The difference in ground albedo will affect the selection of the optimal radiation surface inclination angle and the calculation of power generation in the design scheme, especially in the case of using bifacial modules, where the ground albedo has a significant impact on the gain of power generation on the back of the bifacial modules. It should be noted that the "Gound albedo" set in the "Bifacial gain" is only used to calculate the bifacial gain.

Currently, numerous research institutions both domestically and internationally have conducted in-depth studies on the power generation performance of bifacial PV modules. In actual operation, the efficiency gain of bifacial modules on different floors is different compared to polycrystalline modules installed on cement floors. For example, on the ground painted with white paint (with high albedo), the power generation gain is the highest; Next is the aluminum foil floor; On grasslands (with lower albedo), the power generation gain is the smallest. Please refer to the table below for the albedo of different materials or environments.

"Mismatch loss factor": The current mismatch loss caused by uneven reflection of light on the back side, currently recommended by the software to be set to 10%. The mismatch loss is related to ground albedo, ground clearance height, and support form. The mismatch loss of the N-S horizontal axis tracking system is greater than that of the fixed array system, and it gradually decreases with the increase of ground clearance height.

11.6.2 Support Form

To calculate the bifacial gain effect on the back of the "Unlimited sheds 2D" or "Unlimited trackers 2D", users must select the corresponding checkbox for "Unlimited sheds 2D" or "Unlimited trackers 2D".