The solar industry continues to innovate and strive to improve the efficiency and reliability of photovoltaic systems. One of the most promising developments is the development of bifacial modules in combination with tracking systems. These technologies aim to capture more sunlight and convert it into electricity, making solar energy more effective and affordable. IEA PVPS Task 13 is at the forefront of this innovation, working to improve the performance and reliability of PV systems. This article explores the concept of bifacial tracking, its benefits, challenges, market developments and the key contributions of IEA PVPS Task 13.
IEA PVPS Task 13 recently published a new report “Best practices for the optimization of bifacial photovoltaic tracking Systems” and a Fact sheet on bifacial tracking (available in several languages). The report, which includes contributions from international experts, provides an in-depth analysis of bifacial tracking systems and aims to offer best practices to optimize their performance. This comprehensive work includes reviews of recent literature, industry standards, and insights from interviews with leading tracker companies and PV system owners/operators around the world.
The report examines various technical aspects and innovations in the field of bifacial tracking. It covers different types of single-axis trackers, their components and design principles tailored to specific site conditions. Innovations in tracking technologies, such as backtracking to prevent shadows from row to row and active protection against extreme weather conditions, are also discussed.
Understanding bifacial tracking
Bifacial modules are PV panels that can collect sunlight from both the front and back. New cell designs allow light to reach the cell from the back with efficiencies ranging from 60% to more than 90% compared to the front. Unlike traditional monofacial modules that absorb sunlight on only one side, bifacial modules benefit from reflected light from the ground and other surfaces, increasing their energy output.
Tracking systems, which adjust the orientation of the panels to follow the path of the sun, can further improve the performance of bifacial modules. These systems are available in various configurations, such as single-axis trackers (SAT) and dual-axis trackers. Single-axis trackers rotate the panels around one axis, usually horizontally, to track the sun from east to west, while dual-axis trackers adjust both horizontal and vertical angles, ensuring optimal orientation throughout the day and year. Integrating these tracking systems with bifacial modules results in more consistent and higher energy production compared to static, monofacial systems.
Benefits of bifacial tracking
The synergy of bifacial modules and tracking systems offers remarkable benefits. According to the 2020 techno-economic study cited in the IEA PVPS Task 13 report, bifacial, single-axis tracked systems show a 16% reduction in levelized electricity cost (LCOE) compared to monofacial fixed-tilt systems, with an increase of up to 35% in energy yield. The report confirms that bifacial tracking systems currently dominate the utility-scale PV market, with bifacial cells used in more than 90% of modules sold and more than 60% of the market share for PV systems using single-axis trackers.
The additive nature of tracker and bifacial gains – typically 15-20% from tracking and 2-10% from bifacial technology – results in a compelling cost-performance proposition. This makes bifacial tracking systems the most cost-effective option in approximately 90% of global regions.
Challenges
Despite their advantages, bifacial tracking systems face several technical and logistical challenges. The IEA PVPS Task 13 report identifies key areas of concern:
Complexity of system design: The ambidextrous nature of bifacial modules complicates system design. Minimizing shadows from the tracker itself and optimizing ground reflection are crucial to maximizing efficiency.
Response to extreme weather: Tracker systems must adapt to severe weather conditions, such as high winds, hail, snow and flooding. Advanced trackers now include sensors and weather forecasts to adjust module positions and limit damage. However, the effectiveness of these systems can vary. For example, while automated responses to hail are becoming more common, many systems still lack robust strategies for extreme conditions, which can lead to significant damage if failure occurs.
Performance Modeling: Accurate performance modeling remains a challenge. The blind model comparison of the IEA’s PVPS Task 13 report revealed differences of up to 100% in backside irradiance predictions between different models, highlighting the need for improved validation datasets and modeling techniques.
Albedo improvement: Improving energy yield through albedo optimization with reflective materials is promising, but is limited by the durability of these materials. Current research focuses on strategic placement and longevity to make albedo enhancement a viable practice.
Market development and trends
Bifacial PV tracking systems, in which bifacial modules are mounted on movable racks that track the sun, dominate the utility-scale PV market worldwide. Today, more than 90% of modules sold use bifacial cells, and more than 60% of the market share for PV systems uses single-axis trackers. The financial benefits of these systems are significant, with typical tracker gains of 15-20% and bifacial gains of 2-10% being additive.
Bifacial tracking market development is influenced by several factors, including design considerations, terrain topology and steel prices. Supply chain issues and the importance of reliable delivery schedules are critical. Using local providers can help offset costs and reduce carbon emissions associated with transportation.
Companies are also focusing on specific market sectors, such as dual applications for AgriPV, deployment on non-agricultural or otherwise unusable land and highly sloping sites. These diverse perspectives on land use and value shape the strategies and investments in two-way tracking systems.
IEA PVPS Task 13 obtained data from interviews with 16 tracker companies, which accounted for more than 87% of the global market share between 2012 and 2021, and a review of the 2022 Wood Mackenzie Global Solar PV Tracker report. Key findings include that 70% of these companies have been active for at least ten years, that approximately 50% sell trackers in more than 20 countries and that more than 80% sell in more than 10 countries.
Performance modeling and yield assessment
IEA PVPS Task 13 conducted a blind PV performance modeling study to compare different modeling tools and their performance predictions for different system design parameters. Participants were asked to simulate a set of six imaginary PV systems for which system design and weather data were provided. This study aims to compare predictive models and ensure accurate assessments of system performance and yield. The results can be found in the recent report.
Future perspective
The future of bifacial tracking looks promising, and continued progress is expected to lead to wider adoption. Improvements in module efficiency, tracker technology and system integration will improve the performance and reliability of these systems. As more data becomes available, predictive models will become more accurate, allowing designs to be optimized and energy yields to be maximized.
IEA PVPS Task 13 aims to support the solar industry in overcoming challenges and realizing the full potential of bifacial tracking through ongoing research, international collaboration and dissemination of research results.
This article is part of a monthly column from the IEA PVPS programme. It was contributed by IEA PVPS Task 13 – Reliability and Performance of PV Systems.
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