Qatari researchers found that bifacial 2P horizontal single-axis tracking PV systems in desert conditions produced up to 13.5% more electricity than fixed-tilt systems over long-term field testing in Qatar. The study also showed strong seasonal and technology-dependent performance, with tracker advantages varying with irradiance and weather conditions.
Researchers at Hamad Bin Khalifa University (HBKU) in Qatar compared the performance of bifacial, two-in-portrait (2P) horizontal PV systems with horizontal single-axis trackers (HSAT) against fixed-tilt systems under desert conditions in the Middle East and found that the bifacial arrays can generate up to 13.5% more electricity than their counterparts.
“This study assessed the impact of module technology, ground coverage ratio (GCR), string configuration, and environmental conditions on the energy yield,” corresponding author Maulid M. Kivambe told pv magazine.”With seven tracker rows, variable pitches, 34 strings, 13 commercial PV module variants, multiple placements relative to the torque‑tube and fixed-tilt string references, the testbed is among the largest HSAT research facilities globally.”
The 20-month field testing was conducted at HBKU’s Qatar Environment and Energy Research Institute (QEERI), where the horizontal single-axis tracking PV system is operated since 2020. The site features very high solar irradiation and is classified as a desert climate under the Köppen-Geiger-Photovoltaic system. The installation includes seven rows of SOLTEC-SF7 trackers with varying ground coverage ratios and multiple PV string configurations using 13 different module technologies. It employs astronomical single-axis tracking with asymmetric backtracking to reduce shading and optimize energy yield.
Module rear-side temperatures were monitored using embedded sensors, while multiple irradiance components such as plane-of-array irradiance (POA), global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI), and rear-side irradiance were measured using calibrated pyranometers and reference cells. A fixed-tilt system served as a benchmark, installed at a 22° south-facing tilt with similar string configurations and row spacing as the tracking system. Both systems operated on a natural gravel surface representative of desert conditions.
The tests showed that tracker-based system achieved annual average gains of 15.5% in plane-of-array irradiation and 13.5% in specific energy yield relative to the fixed-tilt configuration, with peak performance occurring in early July 2024, when daily energy yield gains reached approximately 36%.
However, the testing also demonstrated that tracker advantages were strongly seasonal, with benefits mainly from February to September under high direct irradiance conditions. From October to January, the fixed-tilt system was found to outperform the tracker-based array by up to 7.2% due to lower sun angles and reduced tracker effectiveness.
DC power analysis confirmed that the tracker-based system better captures early morning and evening irradiance in summer, while fixed tilt performs better around midday in winter. Under overcast conditions, performance differences diminished because diffuse irradiance dominates and is captured similarly by both systems.
Overall, the analysis showed that the tracker-based systems provide higher annual yields, but their advantage is highly dependent on solar geometry and weather conditions, with performance varying with irradiance composition.
“Among the evaluated technologies, silicon heterojunction (HJT) modules generated the highest overall energy yield, particularly under conditions of high irradiance and elevated ambient temperatures as expected, owing to their superior temperature coefficients and high bifaciality factors,” the scientists explained. “N-type PERT and high-efficiency bifacial PERC modules also demonstrated strong performance, indicating that high bifacial response can partially compensate for less favourable temperature coefficients.”
They also found that string layout relative to the torque tube exhibited minimal impact on energy yield, suggesting a high degree of layout flexibility for tracker-based systems in desert installations.
Their findings are available in the study “The Impact of Module Technology, Ground Coverage Ratio, and String Configuration on the Performance of Bifacial PV Systems on Horizontal Single-Axis Trackers in Desert Environments,” published in Renewable Energy.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
Popular content
Source link