Scientists from the Vellore Institute of Technology in India have investigated the influence of tilt angle on energy generation in bifacial PV systems deployed on white-painted ground surfaces.
“We demonstrated the optimal tilt angle for maximizing energy production from bifacial PV modules, taking into account both direct and reflected irradiance,” the research’s corresponding author, Suprava Chakraborty, told pv magazine. “Our research underscores the significant role of ground reflectance, particularly when using white-painted surfaces, in enhancing the performance of bifacial PV modules.”
The analysis was conducted by continuously adjusting the tilt angle of a 440 W bifacial monocrystalline PERC panel provided by Indian manufacturer Loom Solar Pvt. Ltd. and deployed on the roof of the research institute from 0 to 90 degrees during sunny days in February of this year, with measurements being taken at one-hour intervals between 9:00 a.m. and 5:00 p.m.
“Eight distinct inclination angles were chosen, ranging from 0° (horizontal) to 90° (vertical),” the academics explained. “These extreme positions offer distinct rear-side light exposure conditions, enabling a thorough examination of their influence on power generation.”
The different tilt angles were 0, 13, 25, 30, 35, 40, 45, and 90 degrees. “Literature surveys have consistently demonstrated that within the 30-degree to 60-degree tilt range, bifacial PV modules positioned at 30 degrees consistently outperform those at 60,” they added.
The group utilized a high-precision I-V tracer to measure the I-V curves of the panel and a radiation sensor to measure the solar irradiance incident on both the front and rear sides of the panel. An infrared thermal imaging camera was used for panel temperature measurements.
The analysis showed that the maximum daily average power generation was achieved when the module was titled at 30 degrees, which resulted in a power output of 316.85 W and a bifacial irradiation ratio ranging from 0.20 to 0.40. It also showed that daily average power exhibited a progressive increase from 0 degrees to 30 degrees, followed by a decline to a minimum of 148.51 W at 90 degrees. “Interestingly, the irradiation ratio displayed the opposite trend, increasing from 0.32 to 0.96 at 90 degrees,” the scientists observed.
“These findings suggest that while overall irradiation reaching the module increases with tilt angle, optimal power generation is achieved at a 30 tilt due to a balance between front and rear irradiance,” Chakraborty stated. “Power output from the PV module exhibited minimal change for tilt angles ranging from 13 degrees to 45 degrees in this experimental setup, when accounting for a 5 % measurement uncertainty.”
The research team presented its findings in the study “Tilt angle optimization for bifacial PV module: Balancing direct and reflected irradiance on white painted ground surfaces,” published in Applied Energy.
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Would the latitude of the Vellore Institute of Technology test facility not be a factor in the calculation as well as the time of year?