The Bifaciality of Solar Panels: A Comprehensive Guide from Principles to Applications

Introduction

As renewable energy rapidly evolves, photovoltaic technology continues to advance to meet the growing energy demands. Bifacial solar panels, as an innovative solar solution, are gradually becoming a popular choice in the market due to their ability to generate power from both sides simultaneously. Compared to traditional monofacial modules, bifacial modules can more effectively utilize ambient light, significantly improving energy generation efficiency, and thus play a crucial role in the global energy transition. This article will delve into the concept of bifacial solar panels, the different types available in the market, the factors influencing power generation gain, cost-benefit analysis, and their extensive application scenarios. The goal is to provide readers with a comprehensive understanding and insight into this cutting-edge technology. Through a thorough exploration of bifacial photovoltaic technology, we hope to inspire more attention towards sustainable energy solutions and promote the development of green energy.

What is the Bifaciality of Solar Panels?

Bifacial solar panels are solar modules capable of generating electricity from both the front and the back. They utilize bifacial solar cells, with the back typically encapsulated in transparent materials (such as glass or transparent back sheets). In addition to generating power from the front, the back can also capture ambient scattered and reflected light for additional electricity generation.

Due to the ability of bifacial solar panels to produce power from two directions, bifaciality has become an important metric for assessing their performance. Bifaciality, also known as the bifacial factor or bifacial ratio, measures the ratio of the power generation capabilities of the back and front of bifacial modules under standard testing conditions, playing a vital role in evaluating the performance of bifacial solar panels.

For example, under Standard Testing Conditions (STC), if the test power of the back of a bifacial photovoltaic module is 350 watts and the test power of the front is 500 watts, the calculation for bifaciality would be 350/500 = 70%. This means that the back contributes 70% of the power generation capability compared to the front.

Comparison of Bifacial and Monofacial Modules

When comparing the performance and characteristics of bifacial solar panels with monofacial modules, we can observe significant differences in multiple aspects. The following table provides a comprehensive comparison of the two types of solar panels, helping to clarify the advantages and limitations of bifacial solar panels compared to monofacial ones in terms of energy conversion, installation environment, power generation, cost, durability, appearance, and land usage efficiency.

Bifacial solar panels demonstrate clear advantages in power generation, adaptability to installation environments, and land utilization efficiency, especially in high-reflectivity environments where they can significantly enhance energy generation. However, initial investment and structural complexity are factors to consider. Therefore, when selecting the appropriate photovoltaic solution, users should assess the strengths and weaknesses of both types of modules in conjunction with their installation environment, budget, and power generation needs to make the most suitable decision for their circumstances.

Feature	Bifacial Solar Panels	Monofacial Solar Panels
Energy Conversion	Can absorb sunlight from both the front and back, resulting in higher energy output	Can only absorb sunlight from the front
Installation Environment	Suitable for high reflectivity environments to maximize power generation	Lower requirements for installation environment
Power Generation	Can produce 10-25% more energy compared to monofacial panels	Relatively stable power output
Cost	Higher initial investment	Lower initial investment
Durability	More complex structure; long-term stability is yet to be observed	Simpler structure; better long-term stability
Appearance	Modern and aesthetically pleasing	Traditional appearance
Land Area	Requires less land area for the same energy output	Requires relatively more land area

Types of Bifacial Solar Panels on the Market

Currently, there are various types of bifacial solar panels available in the market, including Passivated Emitter Rear Cell (PERC), Passivated Emitter Rear Localized Diffusion (PERL), Passivated Emitter Rear Full Diffusion (PERT), Heterojunction Intrinsic Thin Layer (HIT), Interdigitated Back Contact (IBC), and Tunnel Oxide Passivated Contact (TOPCon) modules.

PERC

Efficiency: Front 19.4–21.2%; Rear7–18.1%
Bifaciality: 70–80%
Main Application: Commercial; gradually being phased out, typically based on p-type monocrystalline silicon cells.

IBC

Efficiency: Front 22.0-23.2%; Rear1%-18.2%
Bifaciality: 70–80%
Mainly Based On: n-type monocrystalline silicon cells, with no metal gridlines on the front.
Main Application: Commercial; market share around 15%.

HJT

Efficiency: Front 22.1-23.7%; Rear4-23.3%
Bifaciality: 95–100%
Main Application: Commercial; market share around 10%, typically based on n-type monocrystalline silicon cells.

TOPCon

Efficiency: Front 22.0-23.3%; Rear4-20.3%
Bifaciality: 70%–90%
Based On: n-type monocrystalline silicon cells, featuring excellent photoelectric conversion efficiency and low temperature coefficient.
Gradually Achieving Commercialization: Market share around 70%.

Factors Affecting the Power Gain of Bifacial Modules

Minimum Height Above Ground: Generally speaking, the higher the bifacial solar panels are installed above the ground, the more pronounced the gain effect from the back side. However, when the height exceeds 1.3 meters, the increase in irradiance received by the back side begins to plateau. Therefore, considering factors such as bracket load, cost, and maintenance, it is recommended that the height above ground be maintained between 0.7 to 1.2 meters.

Ground Reflectivity: The back side of bifacial solar panels can utilize reflected light from the ground for power generation. The higher the ground reflectivity, the stronger the light received by the back side, leading to better power generation performance. Compared to conventional module systems, bifacial modules experience the greatest power gain against a snowy backdrop, with approximate reflectivity ranking as follows: snow > sandy/cement ground > land > grass > water. The approximate reflectivity can be referenced from the following diagram:

From a rigorous perspective, different technology types (such as PERC, HJT, IBC, TOPCon, etc.) exhibit significant differences in back side gain for bifacial modules. The following table details the back side gain effects and associated reflectivity data for bifacial modules under various ground backgrounds:

表格模板

Surface Scenario	Reflectivity	PERC Gain	HJT Gain	IBC Gain	TOPCon Gain
Snow	80%-85%	20%-25%	30%-40%	25%-30%	28%-35%
Sand/Cement	20%-40%	10%-15%	20%-30%	15%-20%	18%-25%
Soil	20%-33%	5%-10%	15%-20%	10%-15%	12%-18%
Grass	15%-25%	3%-8%	10%-15%	8%-12%	8%-14%
Water	5%-12%	3%-7%	8%-12%	5%-10%	6%-10%

Based on the data in the table, it can be seen that HJT technology performs best in high reflectivity environments (such as snow), while PERC technology shows relatively average performance across all environments, but slightly underperforms in high reflectivity conditions. IBC and TOPCon technologies demonstrate stable performance in various reflectivity scenarios, especially in moderate reflectivity contexts (such as sandy/cement ground and agricultural land). Thus, when selecting installation locations, fully considering the ground reflectivity characteristics can effectively optimize the power generation efficiency of bifacial modules. Choosing suitable reflective environments in conjunction with the appropriate technology type will contribute to achieving higher power generation benefits.

Module Tilt Angle: During installation, efforts should be made to correct the module orientation to maximize exposure to solar irradiance. In Germany, where the latitude is higher, ranging from 47°N to 55°N, the impact of tilt angle is more pronounced. According to the rule of subtracting 10 degrees from the local latitude, the optimal tilt angle in the south, such as Munich (approximately 48° latitude), is 38°, while in the north, such as Hamburg (approximately 53° latitude), it increases to 43°. In Germany, modules are typically installed facing true south, but a slight tilt towards the southwest can capture more afternoon solar radiation effectively.

Module Spacing: Adequate spacing between modules helps reduce shading between them, ensuring that both the front and back sides of each module receive sufficient light. The greater the spacing between the module arrays, the more pronounced the gain effect on the back side. However, during actual installation, it is necessary to determine the array spacing based on the specific project conditions to balance power generation benefits and construction costs.

Bracket Structure Design: When installing bifacial modules, the support rails must be positioned at the edges of the modules to avoid shading on the back side, while also minimizing shading from other components (such as inverters) on the back side of the modules. The back side and surrounding environment can significantly impact the back side power gain, so thorough consideration of the back side light flux is essential during the initial design phase of the array.

Applications of Bifacial Solar Panels

Due to the bifacial power generation characteristics of bifacial modules, which absorb direct sunlight on the front side and receive reflected light from the ground and scattered light from the air on the backside, both sides can generate electricity. This allows for arbitrary installation orientation and angle settings, making bifacial modules suitable for various installation scenarios.

Ground-mounted Power Stations

Large-scale Deployment:Ground-mounted power stations typically cover a large area, allowing for optimal utilization of the bifacial modules’ dual power generation capabilities, thereby improving land efficiency.
Flexible Layout:The layout of ground-mounted power stations is relatively flexible and can be optimized based on factors such as terrain, sunlight conditions, and wind speed, maximizing the utilization of solar resources.
Integration with Energy Storage:Ground-mounted power stations can be combined with energy storage systems to achieve smooth power output, enhancing grid stability.

Agricultural Photovoltaics

Agricultural and Solar Complementation:Bifacial modules can be integrated with agricultural production to achieve agricultural and solar complementarity, enhancing land utilization.
Improved Planting Environment:The shade produced by bifacial modules can reduce surface temperatures, improving the growth environment for crops and increasing yield and quality.
Increased Farmer Income:Farmers can generate additional income by leasing rooftops or land for solar installations.

Commercial and Industrial Rooftops

Angle Advantage:For commercial and industrial rooftops with an angle greater than 20 degrees, the backside of bifacial modules can receive more diffuse reflected light, further enhancing power generation returns.
Utilization of Rooftop Space:Bifacial modules can fully utilize rooftop space, increasing electricity output while also providing shading and thermal insulation.
Self-Consumption:Commercial enterprises can achieve self-consumption by installing bifacial modules, reducing electricity costs.

Carports and Parking Lots

Shade and Rain Protection:Bifacial modules can provide shade and rain protection for vehicles while also utilizing clean energy.
Aesthetic and Practical:Bifacial modules can blend with buildings, enhancing aesthetic appeal and elevating the quality of parking lots.
Value Addition:Parking lot operators can increase revenue by offering value-added services such as charging stations.

Building-Integrated Photovoltaics (BIPV)

Aesthetic and Functional:Bifacial modules can be integrated into building facades, roofs, etc., achieving architectural integration and enhancing visual appeal.
Energy-saving and Environmentally Friendly:BIPV systems can reduce energy consumption in buildings and lower carbon emissions.

Scenarios Where Bifacial Solar Panels Are Not Recommended

Bifacial double-glass solar panels are not suitable for residential rooftop photovoltaic systems and flat commercial and industrial rooftop projects, as these scenarios limit the performance and safety of the modules, preventing them from fully leveraging their technical advantages.

Weight Issues:Double-glass modules typically use 2.0*2.0mm semi-tempered glass, which is significantly heavier than the same-sized single-glass modules, increasing the load pressure on rooftops. If the rooftop’s load-bearing capacity is limited, it may not be suitable for installing double-glass modules.
No Backside Power Generation Gain:Due to the installation being flush against the rooftop, there is no opportunity to utilize light reflections, resulting in no additional power generation from the backside of the double-glass modules.
Self-Explosion Risk:Residential rooftop photovoltaic systems usually require complex transportation and installation environments. Compared to single-glass modules (3.2mm fully tempered glass), double-glass modules are more prone to breakage, increasing construction difficulties.
Poor Hail Resistance:The front glass of double-glass modules is 2.0mm semi-tempered glass, which has lower hail resistance than single-glass solar panels with 3.2mm fully tempered glass, making them more susceptible to damage in harsh weather conditions.
Poor Heat Dissipation:Residential sloped rooftops typically employ flush mounting, and the backside glass of double-glass modules does not dissipate heat as effectively as the backsheet of single-glass modules. This results in poorer thermal performance, causing relatively high operating temperatures and reduced electricity generation based on temperature coefficient principles.

Conclusion

As a significant development in modern solar technology, bifacial solar panels showcase enormous market potential and application prospects due to their ability to generate electricity from both the front and back sides. By assessing the bifacial rate, we can better understand their performance advantages, especially in terms of electricity generation capabilities under various environmental conditions.

Various types of bifacial modules are available in the market, such as PERC, IBC, and HJT, each with its own characteristics to meet different user needs. These modules are gradually becoming an important choice in the renewable energy sector due to their efficient photovoltaic conversion and flexible application methods in scenarios such as ground-mounted power stations, agricultural photovoltaics, and commercial rooftops.

Although the initial investment in bifacial modules is relatively high, the energy savings and environmental benefits they offer in the long run make them a worthwhile investment. With continuous technological advancements and gradual market maturation, bifacial solar panels are expected to lead the future trends in photovoltaic development and contribute to achieving sustainable energy goals.

Since 2008, Maysun Solar has been dedicated to producing high-quality solar panels, particularly bifacial modules. Our products include IBC, HJT, and TOPCon double-glass solar panels, all designed with lightweight construction and exceptional bifacial power generation performance to maximize sunlight utilization and improve energy efficiency. Additionally, our balcony solar power stations offer users flexible application choices. Maysun Solar has successfully established sales offices and warehouses in multiple countries across the EU and has formed long-term partnerships with excellent installers. For the latest quotes on solar panels or any inquiries related to photovoltaics, please contact us. We are committed to assisting you in making optimal choices regarding the use and selection of solar panels during system design and installation.

Reference：
Wikipedia contributors. (2024, September 6). Bifacial solar cells. Wikipedia. https://en.wikipedia.org/wiki/Bifacial_solar_cells
David, L. (2024, October 22). A guide to bifacial solar panels. https://www.marketwatch.com/guides/solar/bifacial-solar-panels/

2024年 10月 28日 No Comments

Learn about bifacial solar panels and the concept of bifaciality, explore the different types of bifacial modules available in the market and their applications, compare them with monofacial modules, analyze the factors influencing the power generation gain of bifacial modules, and understand their widespread applications across various fields.