The main factors influencing the energy yield of bifacial solar panels include:
1. Albedo (Ground Reflectivity)
Albedo is a critical factor because bifacial panels generate additional energy from sunlight reflected off the ground onto their rear side. Surfaces with high reflectivity like white roofing, light-colored concrete, or white gravel significantly boost the rear-side energy capture. For example, white roofing membrane can have an albedo greater than 80%, while green grass has about 23%. Therefore, the type and color of the ground or surface underneath the panels substantially affect the energy yield.
2. Tilt Angle and Orientation
The tilt angle of bifacial panels affects both the front and rear side exposure to sunlight and reflected light. Increasing the tilt angle typically improves the rear side illumination due to better reflection angles, which enhances overall energy production. Proper orientation aligned with the sun’s path also maximizes sunlight capture.
3. Module Efficiency and Bifaciality Factor
The intrinsic efficiency of the solar cells and the bifaciality factor (the ratio of rear side efficiency to front side efficiency) influence the energy gain from the rear side. Different solar cell technologies have varying bifaciality factors: PERC+ cells have >70%, PERT >90%, HIT >95%, and IBC >70%. Higher bifaciality factors mean better energy yields. Also, bifacial cells unlike monofacial ones have a partially metallized rear, allowing rear-side generation without much additional manufacturing cost.
4. Elevation Height of the Panels Above Ground
The height of the solar panel structure above the ground affects how much reflected light reaches the rear side. Elevating the panels reduces shading and allows more reflected light to be captured at the back, positively impacting energy yield.
5. Ground Cover Ratio (GCR) and Row Spacing
GCR refers to the ratio of the panel area to the total ground area they cover. Wider row spacing increases the amount of reflected light reaching the rear side by reducing shading between rows. Optimizing the inter-row spacing allows more indirect light to reach the rear side and improves the energy gain.
6. Shading and Environmental Conditions
Shading from nearby objects or from adjacent panel rows reduces both front and rear side irradiance, lowering energy yield. Moreover, the amount of diffuse radiation in the atmosphere (affected by latitude and weather) contributes to the effectiveness of bifacial panels since diffuse light can illuminate the rear side better under certain conditions.
Summary Table of Key Factors
| Factor | Description | Impact on Energy Yield |
|---|---|---|
| Albedo (Ground Reflectivity) | Reflectivity of ground surface below panels | Higher reflectivity = more rear-side energy |
| Tilt Angle and Orientation | Angle and direction of panel installation | Optimizes sunlight and reflected light capture |
| Module Efficiency & Bifaciality Factor | Quality of cells and rear/front efficiency ratio | Higher values increase rear-side power output |
| Panel Elevation Height | Distance of panel from ground | Higher elevation improves rear-side irradiance |
| Ground Cover Ratio (GCR) | Panel layout density and inter-row spacing | Lower density/wider spacing increases reflected light |
| Shading and Environment | Shading presence, diffuse vs direct sunlight, atmospheric conditions | Affects total irradiance on front and rear sides |
In practice, combining these factors optimally can lead to energy yield gains from 3% up to 30% compared to monofacial modules, depending on site-specific conditions.
Thus, maximizing bifacial solar panel performance requires careful consideration of installation geometry, site surface properties, and module characteristics.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-are-the-main-factors-influencing-the-energy-yield-of-bifacial-solar-panels/
