Researchers at the Nanjing University of Science and Technology in China have designed a ventilated building-integrated photovoltaic system (VL-BIPV) that they claim may represent an optimal solution for rooftops with limited load capacity of less than 15 kg/m2.
“The VL-BIPV system adds only 6 kg/m² of load when applied on rooftops, effectively addressing the challenges faced by conventional modules,” the research's corresponding author, Chenglong Luo, told pv magazine. “Additionally, compared to conventional rooftop PV systems, the VL-BIPV system features a ventilation channel that effectively reduces the temperature of the PV modules in hot environments, thereby mitigating the impact of high temperatures on their normal operation.”
In the paper “Performance prediction of ventilated building-integrated photovoltaic system with lightweight flexible crystalline silicon module based on experimental fitting method,” published in Renewable Energy, Luo and his colleagues also explained that under the modules used for the VL-BIPV system there is an airflow channel that reduces its operating temperature.
The proposed system went through a series of experimental tests and simulations and its performance was compared to that of a conventional rooftop PV system without any cooling. Both systems were located at a university building in Nanjing and had a tilt angle of 26 degrees.
“During the test, the solar radiation intensity was 908.05 W/m2, and the ambient temperature was 33.73 C,” the academics said. “It can be observed that the short-circuit current of the VL-BIPV system was slightly higher by 0.08 A compared to that of the conventional system, while the open-circuit voltage of the VL-BIPV system was 0.98 V higher.”
The test indicated that the VL-BIPV system achieved a 6.52% increase in annual power generation compared to the conventional system, with an overall PV efficiency of approximately 1.07 times higher. “The VL-BIPV system achieved a PV efficiency ranging from 18.91% to 19.29%, averaging at 19.06%, while the conventional system achieved a PV efficiency ranging from 17.19% to 17.59%, averaging at 17.36%,” the researchers further explained.
The analysis also showed that, over the 25-year operational lifespan of both systems, the power generation of the VL-BIPV system is 28.67 kWh/W, which exceeds that of the conventional system by about 1.78 kWh/W. “Additionally, the highest average and maximum cell temperatures in the VL-BIPV system during the year are 58.39 C and 64.74 C, respectively, both lower than the conventional system’s peak at 68.34 C,” the group said.
More details about system costs and commercial maturity were not provided in the study.
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