The output of solar photovoltaic (PV) cells is strongly dependent on the abundance of solar radiation. However, electrical performance of PV cells is affected by their operating temperatures, and that high temperatures lead to decreases in efficiency of a PV module. Thus, to maximize the performance of a PV system, a number of technologies such as sun tracking and active cooling systems have been developed and implemented in practice. The objective of a sun tracking system is to minimize the angle of incidence between solar rays and PV modules, in order to maximize power production. However, changing the tilt angle also affects convective cooling, and thus should be taken into account when optimizing the tilt angle. By increasing the convective heat transfer (e.g. natural, forced, mixed), the operating temperatures could be decreased significantly without an active cooling system, thus increasing PV efficiency and power production. This paper aims to quantify the effects of natural and mixed convection cooling for fixed angled solar PV modules. A case study is performed for a test PV module located at the California State University, Los Angeles, in Los Angeles, California. The plate consisted of 1.651 m long by 0.991 m wide was constructed to mimic a solar module. The plate will be free to rotate to vary the tilt angle, while at different wind speeds .This paper will focus on developing a tool to optimize the tilt angle, considering convective cooling and historical solar data. Several published sources were used to develop heat transfer correlations for mixed convection of inclined plates. These published source conducted numerical simulations and experiments to validate their results. The experiments consist of a heated plate with varying the tilt angle relative to the wind, mimicking that of a PV module. The results from this paper, as well as other well-established convection correlations are used to predict the performance of the PV module at various tilt angles, wind speeds, wind direction, and lastly azimuth angle. The results will  be presented in three case studies; the first on will focus on a PV panel that is in a fixed position, while the wind speed and wind direction. The second case study will present have a changing tilt angle as well as the wind speed and direction. The last case study will also change the azimuth angle of the PV panel as well as the other variables mentioned before. The results show that convection has effect on PV performance, by increasing the cooling load on the PV panel, thus leading to higher power output and efficiency. Furthermore, the results showed that the optimal tilt angle was not affected by convection and that the optimal tilt angle remained around 26° to 28°. Wind direction was also shown to have minimal effects on the performance of the PV panel and thus did not affect the optimal tilt angle as well.


Quantifying the Effects of Convective Heat Transfer on Photovoltaic Performance and Optimal Tilt Angle

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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