Bifacial Solar Panel Guide + Insight Into ‘Bifacialize’ & ‘Bifaciality’

The quest for higher-efficiency solar panel technologies has been relentless since the advent of solar panels. The bifacial solar panel is one of the higher-efficiency advanced modules and has been constantly evolving for the past several decades.

This article will help you get to know bifacial panels inside out. Meanwhile, you will have a better sense of their adoption in projects, and how this technology is fused with other innovations.

What Is the Bifacial Solar Panel?

Actually, bifacial solar panel technology has a richer history than you may imagine, with the concept of it being first researched in the early 1960s. Then a prototype bifacial cell was developed in 1966. After more than a decade of endeavors, the first commercial production and commercialization of bifacial photovoltaic panels began in the early 1980s.

It's worth mentioning upfront that, as of now, the bifacial technology is primarily applied to traditional c-Si-based solar panels.

Structure of Bifacial Panels

Unlike traditional monofacial c-Si panels, which only harness sunlight from the front side, bifacial panels have a simple yet innovative design that allows them to generate electricity from both the front and rear sides.

In most cases, bifacial solar panels are single-junction panels, and their absorption or photovoltaic layer is composed of the same materials, arranged in a similar architecture as in monofacial panels.

The key difference between typical bifacial and monofacial panels lies in their backsheet.

In contrast to traditional panels that use an opaque backsheet, bifacial panels feature either a transparent backsheet or a dual-glass design. Generally, the front glass is thicker for enhanced durability while the rear glass is thinner for optimal light transmittance. This design is crucial for capturing light from both sides, thereby enhancing the panel's ability to capture both direct and reflected sunlight (albedo) efficiently. 

Beyond the dual-glass design, the other parts are basically the same. The cells are first sandwiched between encapsulation layers before being secured with glass. While a frame provides additional structural integrity, it is not a must-have. Some bifacial panels have a frameless design to suit particular applications.

How a Bifacial Solar Panel Works?

One round of operation ends for a monofacial panel after the incident light strikes the front side of the panel and is absorbed and converted into electricity.

For a bifacial solar panel, in addition for front-side conversion, part of the direct light would pass through the panel and be reflected back to the rear side by the surface below. On the other hand, ambient diffused and reflected light can also arrive at the rear side. Together, these types of light can participate in the energy conversion process from the rear side of the panel.

By capturing light from both sides, bifacial panels can increase energy production by 5-30% compared to monofacial products, depending on installation conditions and surface reflectivity.

When to Use Bifacial Panels?

These panels are particularly advantageous in certain scenarios due to their ability to capture sunlight from both sides. Here are some situations where using them is most beneficial:

Ground-Mounted Solar Farms

Bifacial panels have been proven well-suited for ground-mounted installations. These sites are generally large open fields where there is sufficient space for light to reflect off the ground, which can significantly boost the efficiency of bifacial panels.

Highly Reflective Environments

Highly reflective surfaces, such as snow, sand, water, white roofs or light-colored surfaces, can reflect a substantial amount of light upwards, which helps to maximize the energy-generating potential of bifacial panels.

Of greater significance is that installing bifacial panels over water bodies and crops contributes to the merits of floatovoltaics and agrophotovoltaics, respectively. These practices showcase how solar technology can create synergistic benefits for other sectors.

Elevated Installations

Bifacial solar panels can be effective when installed on elevated structures such as solar carports, canopies and pergolas. Elevation allows more sunlight to reflect off surrounding surfaces and reach the underside of these panels, increasing energy production.

In addition, the employment of bifacial panels can minimize the use of supporting structures or parts, which potentially lowers the cost of the project.

Vertical & BIPV Applications

Bifacial solar modules can capture sunlight from both sides, reducing their heavy reliance on optimal tilting angles. This feature enables them to be installed vertically to harvest energy at various angles of light paths.

When configured with high-strength structural glass, they can turn out to be one type of ‘solar facades’. Additional niche applications include integrating bifacial panels into vertical solar street lights.

Unleashing the Potential of Bifacial Panels: Things to Consider

To unleash the potential of bifacial solar panels, several things need to be considered, which influence their performance, energy yield, and also their overall economic viability.

Surface Albedo & Light Diffusion Level

The rear side gains of bifacial panels are greatly influenced by the albedo, which is the reflectivity of the surface beneath the panels.

Among all, snow has one of the highest albedo values, reflecting 80% to 90% of sunlight. Other surfaces above which bifacial modules are commonly installed above include new concrete, sand and green grass. These surfaces have albedo ranges: 0.40-0.55, 0.30-0.40, and 0.20-0.25, respectively.

White gravel or reflective roofing materials boast high albedo values as well. When planning to use bifacial panels for rooftop projects, it's suggested to choose these materials.

Furthermore, diffuse light also plays a role in the energy conversion of the rear side. Hence, projects located in areas with high levels of diffuse light can also get good outcomes from the use of efficient bifacial panels.

Height, Orientation & Tilt Angle

In general, a higher installation of the panels or array allows more reflected light to reach the rear side. The orientation with respect to the sun’s path and geographical location also has a huge impact on bifacial performance. Ideally, bifacial panels should be aligned to ensure maximum sunlight exposure on both sides throughout the day. Plus, the tilt angle should be optimized based on the local latitude to maximize solar radiation capture.

Shading Management

Bifacial solar panels are more sensitive to shading on either side. Otherwise, it might be not necessary to switch your choice from monofacial to bifacial technology.

Make sure surrounding trees, buildings or other obstructions that could cast shadows should be minimized. Also, adequate spacing between bifacial panel rows is crucial to prevent shading.

Electrical Design

Like monofacial solar panel projects, being equipped with module-level power electronics such as microinverters can leverage the benefits of MPPT technology for module-level optimization and monitoring. This configuration further facilitates the optimization for the height, orientation and tilt angle of panels, helping to elevate the efficiency and production of the system.

Economic Considerations

Bifacial panels generally have a higher upfront cost compared to traditional monofacial panels. However, the increased yield can offset these costs over time, especially in large-scale projects with high electricity rates or limited space.

In some regions, bifacial panels may benefit from tariff exemptions, making them more economically attractive compared to traditional panels.

Summing up the Pros and Cons of Bifacial Panels

Now, let’s revisit a matter that’s been top of mind for many people: what are the pros and cons of bifacial solar panels?

Pros of Bifacial Panels

• Higher Efficiency & Increased Output: Bifacial solar panels have the ability to capture and convert not only direct sunlight but also reflected light from the ground. Their dual-side capability also makes them perform better in diffuse light conditions such as during cloudy days or early mornings. By harnessing additional light, bifacial panels provide increased overall efficiency and output. Manufacturers specify that these panels can harness up to 30% more energy than traditional monofacial panels.
• Enhanced Durability & Longevity: These panels are often constructed with tempered glass on both sides to provide extra protection against environmental factors and physical damage, resulting in enhanced durability and longevity.
• Vertical & Special Installations: With relatively less reliance on direct light, bifacial panels can be installed vertically, which is particularly beneficial in special installations such as vertical street lights, bifacial solar fences and bifacial solar facades.
• Aesthetic Appeal: These panels not only provide exceptional performance but also a sleek and sophisticated aesthetic. This makes them an attractive choice for architectural features like pergolas and canopies, adding a touch of elegance to outdoor space.

Cons of Bifacial Panels

• Higher Costs: These advanced panels tend to be more expensive to produce due to their unique design. The additional costs also stem from the need for specialized mounting systems and potential surface modifications (to increase reflectivity).
• Shade Sensitivity: To maximize their energy output, bifacial solar panels require minimal shading. Similar to surface albedo, the shading matter of the site is another key factor to weigh up whether it’s economically beneficial to go for this technology.
• Installation Considerations: Surface albedo and shading considerations, increased weight and relevant associated issues make bifacial solar panel installation more complicated, increasing project costs and potentially limiting their use.

Bonus #1: What Is the ‘Bifaciality’ of Bifacial Panels?

Up until now, we’ve covered principal topics about bifacial solar panels. Here we offer a couple of bonuses to help you dive deeper into this realm.

First comes the term you might have spotted on the spec manual of these panels: ‘bifaciality’.

It refers to their ability to generate electricity from both sides. This characteristic is quantified by the ‘bifaciality factor,’ which is the ratio of the efficiency of the rear side to that of the front side under the same irradiance conditions. It is a key metric used to measure the overall efficiency of bifacial panels, providing a benchmark to assist in evaluating whether this specific model of panel is suitable for that certain project or not.

The bifaciality factor can be determined using the following formula:

This calculation typically involves a combination of field measurements and computer simulations. Typically, this factor is less than 1, indicating that the rear side is generally less efficient than the front due to factors such as different optical properties and shading issues.

Bonus #2: What Does ‘Bifacialize’ Mean?

The term ‘bifacialize’ isn't widely used in the industry, but it refers to the process of designing and manufacturing solar panels to harness energy from both the front and back sides, boosting overall efficiency and energy output.

While the bifacialization of traditional monofacial is a mature process now, scientists and manufacturers are trying to add bifacial ability to current high-end products.

Although the bifacialization of traditional monofacial cells has become a well-established process, researchers and manufacturers are now focused on integrating bifacial capabilities into advanced high-performance products for a further boost.

Industry practices have shown that it is feasible to bifacialize most of current advanced high-efficiency solar panel technologies.

For example, the integration of bifacial technology into PERC panels enables the absorption of scattered and reflected light on the back of the module, providing a bifaciality close to 80% and increasing power output by up to 30%.

Beyond bifacial PERC modules, other high-end panels such as IBC, TOPCon and HJT can be integrated with bifacial technology as well. During the process, new materials, extra layers (e.g., coating and passivation), new architecture (e.g., multi-junction) and other necessary modifications would be utilized.

Final Words

Bifacial solar panels are poised for a bright future, with their market share on the rise.

However, whether they can realize their nominal bifaciality factor and expected resulting enhanced efficiency and energy yield closely relate to a series of environmental and installation factors.

Simply put, bifacial panels offer compelling benefits, but they may not offer a universal impressive ROI for every project.

Interested in exploring other high-efficiency solar panel solutions? Check out this roundup post.