Shining a Light on Bifacial Solar Modules: Unlocking the Potential of Two-Sided Solar Panels in the PV Industry

The photovoltaic (PV) industry has witnessed remarkable growth recently, with solar PV installations increasing exponentially worldwide. However, despite the significant improvements in efficiency, cost reduction, and reliability, the industry still faces some technical and economic challenges. One of the most pressing issues is how to improve the efficiency of solar panels and reduce the levelized cost of electricity (LCOE) without sacrificing the durability and reliability of the systems. Bifacial solar PV technology has emerged as a potential solution to these challenges, promising to boost the energy output of solar panels by absorbing light from both sides. Bifacial modules are designed to absorb light from both sides, increasing their energy output and providing more flexibility in system design. However, the effectiveness of this technology remains controversial, with some critics claiming that it is merely a marketing gimmick.?

The article focuses on bifacial solar PV technology's critical technical and economic aspects, including efficiency gains, durability, reliability, and cost-effectiveness. The article also evaluates this technology's potential drawbacks and limitations, such as the sensitivity to shading, weather conditions, and installation requirements. By the end of this article, you will have a comprehensive understanding of the role that bifacial solar modules can play in the solar PV industry and their potential benefits in helping to address some of the industry's key challenges.

Monofacial vs Bifacial

The main difference between bifacial and monofacial solar cells is how they capture and convert sunlight into electricity. Monofacial solar cells, the most common type of solar cell, feature a single-sided design that only captures sunlight from one side. The front side of the cell is coated with an anti-reflective material that helps to minimize reflection and maximize light absorption. The cell's back side typically features a metal contact grid that collects the electrons produced by the cell and carries them to the electrical contacts. On the other hand, bifacial solar cells are designed to capture sunlight from both the front and rear sides of the cell. Bifacial cells feature contacts on both sides, allowing them to produce electricity from light reflected off the ground or surrounding surfaces. Bifacial cells can also be made with a transparent backsheet, enhancing their ability to absorb light from both sides.

The critical advantage of bifacial solar cells is their ability to produce more electricity for a given area of the solar panel compared to monofacial cells. Overall, while monofacial solar cells remain the most common type of solar cell, the higher energy yield and improved performance of bifacial solar cells make them an increasingly popular choice for solar panel manufacturers and system designers.

The analysis reveals that bifacial solar PV technology has several advantages over conventional monofacial solar panels. Depending on factors such as the albedo, tilt angle, and shading conditions, bifacial modules can generate up to 30% more energy than monofacial modules. Bifacial technology also provides more flexibility in system design, allowing for better integration with different mounting systems and tracking technologies. Moreover, the durability and reliability of bifacial modules are similar to those of monofacial modules, and they have demonstrated resistance to degradation and long-term performance issues.

However, bifacial solar PV technology also faces some challenges that may affect its viability in the market. The main issue is the sensitivity of bifacial modules to shading, which can significantly reduce their energy output and affect the overall system performance. Other factors that may impact the performance of bifacial modules include weather conditions, dust accumulation, and installation requirements, which may increase the system's complexity and cost.

Cost Considerations

Bifacial solar PV technology is generally more expensive than monofacial technology due to the additional processing steps required in the manufacturing process. However, the cost difference decreases as the technology becomes more widespread and economies of scale are achieved.

Regarding the response of the spectrum, bifacial modules are more sensitive to the light spectrum than monofacial modules, as they can absorb light from both sides. This means that the spectral distribution of the incident light can affect the performance of bifacial modules differently from monofacial modules. Bifacial modules generally perform better under diffuse and reflected light conditions, such as in snowy or cloudy environments or on reflective surfaces, than under direct sunlight conditions.

Structural Requirements

Regarding weight and structural requirements, bifacial solar panels are generally similar to monofacial solar panels. Bifacial panels are typically slightly heavier than monofacial panels due to the additional layer of glass. However, the weight difference is generally insignificant and within the acceptable range for most mounting systems and applications.

Structurally, bifacial panels are designed to be compatible with standard mounting systems and installation practices. The additional glass layer on the rear side of the panel provides some extra strength and stiffness, which can help to reduce the risk of breakage or deformation. However, some specific installation considerations may apply for bifacial panels, such as the need for a reflective ground cover to enhance the rear-side energy generation and the optimization of the orientation and tilt angle of the panels to maximize the front and rear-side energy yields. The structural requirements for bifacial panels also depend on the specific application and environmental conditions. For example, bifacial panels may require a stronger frame or support structure if installed in areas with high wind or snow loads. Additionally, the installation of bifacial panels may require additional care and attention to avoid shading, which can reduce the energy yield of the panels and affect the overall system performance.

Overall, while there are some slight differences in weight and structural requirements between bifacial and monofacial solar panels, these differences are generally manageable and do not significantly impact the feasibility or cost-effectiveness of bifacial technology.

Indeed, some bifacial solar panel manufacturers are now producing panels without a rear glass layer. These panels typically use a transparent backsheet made of materials such as fluoropolymer or tempered glass, which allows sunlight to pass through to the rear contacts of the panel. The advantage of using a transparent backsheet instead of a glass layer is that it can reduce the weight and cost of the panel, which can be particularly advantageous in specific applications, such as building-integrated photovoltaics (BIPV) or other installations where weight or cost constraints are a concern. However, it's important to note that using a transparent backsheet instead of a glass layer may impact the durability and reliability of the panel, particularly in harsh or extreme environments. Without the additional protection of a rear glass layer, the panel's rear contacts and other internal components may be more susceptible to damage from factors such as moisture, temperature fluctuations, or physical impact.

In general, the choice between using a glass layer or a transparent backsheet in a bifacial solar panel will depend on the system's specific application and performance requirements, as well as the available materials and manufacturing processes.

Reflective Ground Covers

Reflective ground covers can be used with bifacial solar panels to enhance the energy yield of the rear side of the panels. The reflective ground cover reflects sunlight up towards the rear side of the panels, increasing the amount of light the panels can absorb and convert into electricity. This can result in a higher energy yield from the bifacial panels. Several types of reflective ground covers can be used, including:

1. White gravel or stones: These materials are often used as a low-cost and low-maintenance reflective ground cover. They can be easily installed and provide a high level of reflectivity.
2. White paint or coatings: Specialized reflective coatings can be applied to the ground beneath the solar panels to enhance the reflectivity. These coatings can be applied to various surfaces, including soil, concrete, or asphalt.
3. Mirrored surfaces: Mirrored surfaces can provide a very high level of reflectivity, but they are often more expensive and require more maintenance than other options.
4. Vegetation: In some cases, vegetation can be used as a reflective ground cover. White clover, for example, has a high albedo and can help to reflect sunlight up towards the panels.

The choice of reflective ground cover will depend on several factors, including the installation site's cost, maintenance requirements, and environmental conditions. In general, white gravel or stones are the most commonly used reflective ground cover for bifacial solar panels due to their low cost and ease of installation.

Installation

The optimal orientation for bifacial solar panels can vary depending on several factors, such as the latitude of the installation site, the time of day, and the desired energy yield. Generally, bifacial solar panels can be installed vertically or with a latitude tilt angle. A vertical orientation allows the panels to absorb light from the front and rear sides throughout the day. At the same time, a latitude tilt angle can help to maximize the energy yield during specific times of the year, such as the winter solstice.A vertical orientation may be preferred in installations with limited space or shading concerns, as this orientation can help reduce the impact of shading on the overall energy yield. However, a vertical orientation may result in a slightly lower energy yield than a latitude tilt angle, as the panels will not be optimized to capture the maximum sunlight during specific times of the year. On the other hand, a latitude tilt angle can help to maximize the energy yield of bifacial solar panels by optimizing their orientation to capture the maximum amount of sunlight during specific times of the year.

The height of installation for bifacial solar panels compared to monofacial panels can vary depending on several factors, such as the desired tilt angle, shading considerations, and the mounting system used.

One advantage of bifacial solar panels is that they can be installed at a lower height than monofacial panels while achieving high energy yields. This is because bifacial panels can absorb light from both the front and rear sides, allowing them to capture more sunlight even when installed closer to the ground.

However, the exact height of installation will depend on several factors, such as the tilt angle and the orientation of the panels, as well as any shading considerations. In some cases, it may be necessary to install bifacial panels at a higher height than monofacial panels to avoid shading from nearby obstructions.

Additionally, the height of the installation may be influenced by the type of mounting system being used. For example, pole-mounted systems may require a higher installation height compared to ground-mounted systems due to the need for clearance between the panels and the ground.

Overall, the optimal orientation and height of installation for bifacial solar panels will depend on the specific site conditions, the design of the solar PV system, energy yield requirements, and installation constraints.

Recycling

Recycling solar panels, including bifacial solar panels, is an important consideration for the sustainability of the photovoltaic industry. While solar panels have a long lifespan and generate clean energy, they eventually reach the end of their useful life and need to be replaced. Recycling can help to recover valuable materials and reduce waste, energy consumption, and environmental impacts.

Bifacial solar panels are generally composed of materials similar as monofacial solar panels, including glass, aluminium, silicon, and other metals. The recycling process for bifacial solar panels is similar to that of monofacial panels and involves several steps, such as collection, disassembly, shredding, and separation of the materials. The recovered materials can then be reused in manufacturing new solar panels or other products.

While recycling bifacial solar panels is technically feasible, the industry is still developing comprehensive and cost-effective recycling solutions. There are also some challenges and limitations to recycling, such as the lack of standardization, the variability of the panel designs and materials, and the potential loss of efficiency and quality of the recovered materials. Nevertheless, efforts are being made to improve the recycling infrastructure and processes for solar panels and to increase awareness and collaboration among stakeholders in the industry.

?Testing and Certification

There are some differences in the testing standards for monofacial and bifacial solar modules due to the differences in how they capture and convert sunlight.

One important difference is the need to account for the impact of reflected light on the performance of bifacial modules. Because bifacial modules can generate electricity from both sides, the amount and quality of the reflected light can significantly impact their overall performance. As a result, many testing standards for bifacial modules include provisions for measuring and accounting for the effects of reflected light on energy yield.

For example, the International Electrotechnical Commission (IEC) has developed specific testing standards for bifacial modules, including provisions for measuring the front and rear-side irradiance separately and the effects of different types of ground cover and reflectors. These standards are intended to provide a more accurate assessment of bifacial modules' energy yield and performance in real-world conditions.

In contrast, the testing standards for monofacial modules typically focus on measuring their performance under standard test conditions (STC), which assume a specific set of operating conditions, including a fixed angle and intensity of sunlight. While some testing standards for monofacial modules may include provisions for measuring their performance under different operating conditions, they generally do not need to account for the impact of reflected light in the same way as bifacial modules.

Overall, the testing standards for both monofacial and bifacial modules are designed to ensure that they meet certain minimum performance and safety requirements and to provide a standardized way of comparing the performance of different modules. However, the specific testing protocols may differ depending on the type of module and the performance characteristics being evaluated.

Several specific test standards for bifacial solar modules are designed to evaluate their performance and quality. Here are some of the most important standards:

1. IEC 60904-1: This standard specifies requirements for measuring the electrical performance of PV cells and includes provisions for measuring the response of bifacial cells to light from both the front and rear sides. It provides a standardized way of measuring cell efficiency and other performance metrics.
2. IEC 60904-8: This standard is specific to bifacial PV devices and provides guidelines for measuring the optical and electrical properties of the devices, including measurements of spectral response, quantum efficiency, and energy yield.
3. IEC 60904-9: This standard provides guidelines for measuring the angle-of-incidence dependence of the electrical performance of bifacial PV devices, which is an essential factor in determining their energy yield.
4. IEC 60904-10: This standard provides guidelines for measuring the temperature dependence of the electrical performance of PV devices, which is important for predicting their performance under different operating conditions.
5. IEC 61724: This standard provides guidelines for monitoring the performance of PV systems, including bifacial systems, in the field. It includes provisions for measuring the energy yield, performance ratio, and other metrics over time and identifying and correcting issues that may impact system performance.

In addition to these standards, there are also several test procedures and protocols that have been developed specifically for bifacial modules, which may be used by manufacturers, testing laboratories, and other stakeholders to evaluate their performance and quality. These may include tests for measuring the bifacial factor, the effects of different types of ground cover and reflectors, and other factors impacting the module's energy yield and performance.

Future Outlook

The future of the bifacial module market looks promising, with significant potential for further innovation and development in the coming years. One area of innovation is in the design and manufacturing of bifacial cells, which are the fundamental building blocks of bifacial solar modules. Researchers and manufacturers are exploring new materials, cell structures, and processing techniques that could improve bifacial cells' performance, durability, and cost-effectiveness.

Another area of innovation is developing new applications for bifacial modules. While ground-mounted systems are currently the most common application for bifacial modules, researchers and engineers are exploring new applications such as rooftop systems and building-integrated photovoltaics (BIPV). These new applications could open new markets for bifacial modules and help drive further industry growth.

Market trends and demand for bifacial modules are also positive. According to a report by Global Market Insights, the global bifacial module market is expected to grow from $5.7 billion in 2020 to $18.9 billion by 2027, with a compound annual growth rate (CAGR) of 17.7%. This growth is driven by increasing demand for clean, renewable energy and the advantages that bifacial modules offer over traditional monofacial modules.

Overall, the future of the bifacial module market looks bright, with significant potential for further innovation, growth, and impact in the solar PV industry. As the industry continues to evolve and improve, we expect to see further advancements in bifacial module technology and new applications that will help drive the industry's growth in the coming years.

Conclusion

In conclusion, bifacial solar modules are a promising technology that offers several advantages over traditional monofacial modules, including capturing light from both sides and increasing energy yield. Bifacial modules are typically more expensive than monofacial modules but can also provide a higher return on investment in suitable applications. Several different bifacial modules are available, including glass-glass and glass-back sheet designs. Depending on the specific application, they can be installed in various orientations and configurations. Testing and certification of bifacial modules are crucial in ensuring their performance and safety. Several standards and test procedures can be used to evaluate their quality and reliability. While bifacial modules may not be the best choice for every application, they represent an important development in the solar industry. They offer significant potential for improving the efficiency and effectiveness of photovoltaic systems.

Based on the available information, it is clear that bifacial solar modules are not just an industry gimmick. The advantages of bifacial modules are well documented and offer real benefits in terms of increased energy yield and improved performance under certain conditions. Additionally, the use of bifacial modules is becoming more widespread in the solar industry, and their performance and reliability are being demonstrated in a growing number of installations around the world. Therefore, it can be concluded that bifacial solar modules are a valuable technology that has a fundamental and vital role to play in the solar industry.