Researchers at the National Taiwan University of Science and Technology have developed new adjustable reflector systems for increasing the performance of vertical bifacial PV arrays.
“The system is capable of automatically modifying both tilt angle and effective length on an hourly basis, based on real-time solar altitude and wind speed data,” the scientists explained, noting that their attempt to use this technology in PV applications is not the first one ever conducted at the research level. “This adaptive configuration enhances solar irradiance capture and ensures structural safety throughout daily and seasonal variations.”
The research team utilized the so-called Taguchi method, which is intended to minimize the variation in a process through robust design of experiments even against uncontrollable environmental factors, to identify the key parameter interactions and performance trends of the reflector-equipped PV systems.
The experimental setting included photovoltaic modules, adjustable reflectors, inverters, an anemometer to measure wind speed, a pyranometer for solar radiation, a power controller, and a data logger.
The bifacial modules were mounted vertically with an east–west orientation, while the reflectors were tilted at an angle equal to half of the solar altitude angle relative to the horizontal plane. With this configuration, the reflected sunlight strikes the solar panel surface perpendicularly, which the scientists said maximizes the amount of reflected irradiance received by the panel.
“For example, when the solar altitude angle is 30°, the optimal reflector angle is approximately 15°; when the altitude angle is 45°, the reflector should be set to around 22.5°,” they also explained. “Taguchi optimization was further used to evaluate and determine the most effective combination of parameters, including reflector width, distance from the panel, material type, and tracking mechanism.”
They also used the Analysis of Variance (ANOVA) statistical tool to identify if the observed differences among factor levels are significant and assess the influence of each factor on the response variable. Furthermore, they utilized the TRNSYS model to conduct a comparative analysis between the experimental results and the simulation outputs.
The testing showed that the best system configuration can be achieved with aluminum reflectors, both front and back reflector angles set to half the solar altitude, reflector areas larger than the module surface, and an azimuth angle of 110°. This reportedly improves the efficiency by approximately 11% over a standard bifacial system without reflectors, and by 3.19% over non-optimized reflector systems.
“The optimized system achieved a total power gain of 71.32% compared to a baseline system without reflectors, and a 3.19% improvement over unoptimized reflector configurations, demonstrating substantial year-round performance benefits,” said the researchers. “The integrated use of TRNSYS simulation and the Taguchi method provides a robust framework for future design and optimization of reflector-enhanced PV systems.”
Looking forward, the academics said they want to test the system in real PV systems and other geographies.
Their findings can be found in the study “Performance improvement of vertically installed bifacial solar panels with adjustable reflectors optimized using the Taguchi method,” published in Energy Nexus.
Recently, researchers at the University of Twente in the Netherlands have investigated how free-space luminescent solar concentrators (FSLSCs) could be used to enhance bifacial PV module performance in vertical PV installations and have found that electricity production could be increased by up to 60% during the winter.
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Mirrors cost more than PV per area nowadays. Nice try 20 years ago. Dumb idea nowadays.