In the fast-changing world of renewable energy, bifacial solar panels are becoming a revolutionary technology set to transform how we use solar energy. Unlike conventional photovoltaic panels that capture sunlight only on one side, bifacial panels are designed to harness light from both their front and back sides. This innovation is a game-changer, promising higher power output and improved efficiency. As the world increasingly adopts renewable energy, bifacial panels will be crucial in helping us transition to energy independence.

What are Bifacial Solar Panels?

Unlike traditional solar panels, bifacial panels have active solar cells on both sides and can absorb sunlight from the front and rear. This bilateral ability is a breakthrough with the conventional monofacial panels that are only intended to absorb direct sunlight that falls on their upper surface. This means that bifacial technology has the potential to harness both direct incident light and reflected light (albedo) to produce electricity and can increase the overall energy production.

Bifacial panels typically use a dual-glass or transparent backsheet design, unlike the opaque backsheets of traditional panels. This durable construction enhances resistance to environmental elements like hail, snow, and wind. This structural strength also aids in combating some of the usual degradation problems like potential induced degradation (PID), further prolonging the life of the panels.

PERC (passivated emitter and rear cell) technology is a crucial enabling feature in bifacial solar cells. PERC cells use a dielectric passivation layer on the rear side to reduce electron recombination and reflect more light into the cell. This design allows the rear side of the solar cell to capture diffuse and reflected light that would otherwise be wasted, converting it into usable energy.

This invention converts a formerly passive surface into an active power-producing participant.

The Science of Bifacial Panels and Their Power Generation

The enhanced power output of bifacial solar panels is primarily due to a phenomenon called albedo. Albedo, in particular, is the extent to which a surface reflects solar radiation instead of absorbing it. In the case of bifacial technology, light reflected from the ground or nearby surfaces hits the back of the panel and is converted into additional electricity, supplementing the energy generated from direct sunlight on the front. This is the bifacial gain, which is a direct consequence of the ability to capture light that conventional panels cannot.

The success of bifacial panels is, thus, highly dependent on the reflectivity of the surface underneath. The higher the albedo value of the surfaces, the more the light will be reflected to the rear side of the panel, resulting in increased energy production. For example, bifacial panels installed on snow-covered ground can produce much more power than on dark asphalt, as the reflective property of these surfaces is exceptionally different.

To understand the effect of various surfaces, here is a look at the average albedo values based on the surface:

  • Snow — 80 to 90%

  • White roof — 70 to 85%

  • Dry concrete — 40 to 50%

  • Grass — 20 to 25%

  • Asphalt — 5 to 10%

These values explain why strategically placing bifacial panels is crucial to maximize performance. Installers can realize these dual-sided energy collectors' full potential by maximizing the light reflected onto the rear surface. As a result, the surrounding environment is just as important as the panels in determining total energy output.

Bifacial Vs Monofacial

The decision to use bifacial or monofacial solar panels comes with several considerations that all affect a solar energy system's economic and practical feasibility. Although both technologies have the same purpose of converting sunlight into electricity, the differences in the design result in different advantages and drawbacks based on other performance parameters.

Monofacial panels capture only direct sunlight from the front, while bifacial panels generate power from direct and reflected sunlight. This design difference affects efficiency: monofacial panels perform well but are limited to single-sided capture, while bifacial panels are 5% to 30% more efficient due to their dual-sided design.

Monofacial panels generally have a lower upfront cost per watt. While bifacial panels are initially more expensive, their higher energy output can reduce the levelized cost of energy (LCOE) over time, making them more cost-effective in the long run.

In terms of durability, typical monofacial panels with glass and backsheet constructions are not as resistant to environmental effects as bifacial panels, which are commonly constructed with a more durable dual-glass construction. This improved design makes bifacial panels more resistant to degradation and offers more extended performance warranties in many cases. However, this extra durability is achieved at the expense of weight, and bifacial panels are heavier than monofacial panels, requiring more robust racking.

Aesthetically, the monofacial panels are usually opaque in the back and traditional-looking. Bifacial panels may be transparent, making them more modern and sleek. This can be an advantage in an application where visibility through the panel is desired, like in a carport or pergola.

Furthermore, the ideal use cases for each technology vary significantly. The monofacial panels are most applicable on residential rooftops or other space-limited locations where the main objective is to capture as much direct sunlight as possible. Bifacial is good in large-scale ground mounts, carports, flat commercial rooftops, and agri-voltaics, where the albedo effect can be maximized to utilize reflected light on the ground or reflective surfaces.

Advantages and Disadvantages of Bifacial Solar Panels

In the case of bifacial solar panels, it is crucial to know the pros and cons of the panels to decide whether they will suit a particular project. These panels have significant advantages, but they also have some considerations.

Bifacial Panels Benefits

Some of the common benefits of bifacial panels include:

Increased Energy Output

The primary advantage of bifacial panels is their ability to generate significantly more electricity. They can gain up to 5 to 30 percent more power output than monofacial panels with the same rating, based on the albedo of the ground surface and the installation configuration, by intercepting light on both sides. This results in more electricity being generated per square foot of the installed panel area.

Improved Durability

Most bifacial modules have a strong two-glass design, with the front and back sides being coated with tempered glass. This design offers better resistance to the environmental conditions like strong winds, heavy snow loads, and drastic temperature changes. The dual-glass encapsulation also seriously minimized the chance of Potential Induced Degradation (PID) and micro-cracks, typical of conventional panels using polymer backsheets. This inherent benefit contributes to a longer lifespan.

More Extended Warranties

Top-tier manufacturers often provide longer performance warranties on bifacial panels, exceeding the standard 25-year warranty. This gives investors and owners of the system more confidence about the longevity and performance of their solar array.

Better Performance

Bifacial panels tend to perform better under low-light and diffuse light conditions. Even during cloudy weather or early morning and late afternoon, diffused light reflected from the ground or scattered in the atmosphere can still reach the rear side and contribute to energy generation. This extends their operating window.

The Challenges of Using Bifacial Panels

There are some downsides of opting for bifacial panels that you should consider. They include:

Higher Upfront Cost

A significant consideration is the price of the panels. Bifacial panels generally cost more up front per watt than monofacial ones. The long-term energy savings can counter this, but the higher upfront investment may be a limiting factor for certain projects.

Site Dependency

Bifacial gain depends heavily on the installation site's characteristics. The ground's reflectivity (albedo) is the most crucial factor beneath and around the panels. Unless there is a very reflective surface, the extra energy harvested on the backside will be minimal, and the economic benefit of using bifacial technology will be minimal.

Installation Complexity Cost

Bifacial panels have special installation practices to optimize the performance of the rear side. This involves providing adequate ground clearance (to enable light to be reflected well) and racking systems that do not create much shading on the back side of the modules. These unique requirements could increase installation costs, as standard mounting equipment or site surfaces may not be suitable. Hence, these added complexities have to be considered during planning and implementation.

Are Bifacial Solar Panels Right for You?

Whether bifacial solar panels are the best option for a particular project depends on understanding their ideal applications and what conditions they need to be in to perform to their full potential. They are particularly suited to some situations because of their exceptional power to absorb light on either side. Here are a few considerations:

The Best Fit

Large-scale ground-mounted solar farms are among the most suitable environments for bifacial panels. When placed on light-colored gravel, sand, or snow-covered fields, the large albedo of these surfaces enables large amounts of energy to be harvested on the rear side. These setups are free from structural constraints and allow optimal panel spacing and tilt, maximizing reflected light and reducing the levelized cost of electricity (LCOE) over time.

Excellent for Commercial Use

Flat, white membrane commercial rooftops (like TPO or EPDM) provide another excellent potential for implementing bifacial. These roofs have a highly reflective surface, making a perfect albedo backdrop. Furthermore, commercial rooftops often offer ample space for optimal panel spacing and elevation to have minimum self-shading, maximizing rear-side light reflection. This is why they are a good option for businesses that want to optimize energy independence and reduce operational costs.

Great for Creative Projects

Bifacial panels are ideal in any project where diffused light capture or translucency is preferred. Solar carports, pergolas, and canopies are especially useful, as they generate energy while providing shade. These panels are also more aesthetically pleasing in their transparent quality than opaque traditional panels.

Bifacial panels are also ideal for agrivoltaics, where they can be tilted to allow crops to grow underneath, providing shade while generating electricity, which gives shade to the crops and, at the same time, generates power, showing a synergistic land use.

Conditional for Residential Premises

In the case of residential applications, the applicability of bifacial panels is more subtle. They perform best in homes with ground-mounted systems or homes with flat roofs that are highly reflective and white or light in color. The ground clearance or the required reflective surface can be easily achieved. Nevertheless, bifacial panels are generally not ideal for typical residential installations with dark, sloped asphalt shingle roofs.

The low albedo of asphalt and the ground clearance of angled roofs block most reflected light from reaching the rear side, negating the main advantage of bifacial technology and making them not worth the additional cost and installation complexity.

How to Get the Best of Your Investment

A bifacial solar installation needs to be optimized by carefully considering certain practices to maximize the amount of reflected light and guarantee long-term operation. These best practices can increase the energy yield considerably and the total investment payback.

Surface Preparation

The ground beneath the panels should be as reflective as possible to maximize the albedo effect. In the case of ground-mounted systems, it is possible to consider placing light-colored gravel, sand, or a white reflective membrane. In agricultural environments, having light-colored soil or planting techniques that do not pose heavy shade directly underneath the panels may also help enhance the rear side's performance. A white or light-colored roof membrane is highly recommended for rooftop applications to enhance reflectivity.

Maximum Ground Clearance

A bifacial panel requires adequate ground clearance. A minimum ground clearance of 1 meter (approximately 3 feet) is typically recommended beneath the panels. This height provides a wider reflection angle and allows more light to reach the rear side of the panel without obstruction from the ground or nearby structures. Inadequate clearance will significantly reduce the reflected light and compromise the advantages of bifacial technology.

Appropriate Racking

The racking system used is essential. Bifacial panels need a racking system that reduces shading on the backside. This means not using thick, opaque rails right behind the cells. Instead, use racking systems designed for bifacial panels, featuring thinner support profiles or suspended structures that enable maximum rear surface exposure to reflected light.

Panel row spacing should also account for potential self-shading between rows.

Tilt Angle

While standard tilt angles optimize direct sunlight capture, slightly steeper angles may increase rear-side exposure for bifacial panels, especially in high-albedo settings, like in areas with high-albedo surfaces like snow. This adjustment allows reflected light to strike the rear side more effectively. This, however, should be balanced against direct sun capturing and overall performance of the system because too steep an angle will minimize front-side gains. Site-specific simulations are essential to determine the optimal tilt angle that maximizes front and rear energy production.

Find a Solar Expert Near Me

Bifacial solar panels represent a significant advancement in photovoltaic technology, enabling greater energy production and extended service life. Their ability to capture both direct and reflected sunlight makes them increasingly attractive for a wide range of applications, including large-scale solar farms and innovative commercial and agricultural projects. As the world moves toward a more sustainable future, adopting technologies like bifacial solar will be key to maximizing our renewable energy potential.

If you plan to incorporate this innovative technology into your energy strategy, contact Sun Solar Electric at 707-658-2157. Our Bay Area and Northern California team will guide you on the best solar panel solutions tailored to your needs.