Optical performance of inclined south–north axis three-positions tracked solar panels

In this work, the optical performance of solar panels with a new sun-tracking technique was theoretically investigated based on the proposed mathematical method and monthly horizontal radiation. The mechanism of the investigated sun-tracking is that the attitude angle of solar panels is daily adjusted three times at three fixed positions: eastward, southward, and westward in the morning, noon, and afternoon, respectively, by rotating solar panels about the inclined south–north axis (ISNA-3P sun-tracking). Calculation results showed that, for ISNA-3P tracked solar panels with a yearly fixed tilt-angle of the ISNA, the maximum annual collectible radiation on ISNA-3P tracked solar panels was about 93% of that on a solar panel with 2-axis sun-tracking; whereas for those with the ISNA being yearly adjusted four times at three fixed tilt-angles, it was about 96%. Results also indicated that the attempt to further increase the annual solar gain on ISNA-3P tracked solar panels by seasonally optimizing design of the sun-tracking system for maximizing solar gain in each of four seasons was not efficient, and thus not advisable in practical applications. Optimal parametric designs of such sun-tracking system for maximizing the annual solar gain on solar panels in different cases were also presented.

Research highlights
► The paper presented a new sun-tracking technique (ISNA-3P) for possible applications in PV generating systems.
► Algorithms to estimate daily collectible radiation on the fixed, 2-axis and ISNA-3P tracked solar panels were proposed based on solar geometry and monthly horizontal radiation.
► A detailed theoretical study on the optical performance of such tracked solar panels in terms of R3P-0 and R3P-2, the ratios of maximum annual solar gain to that on fixed and 2-axis tracked solar panels; optimal parameters affecting the optical performance of the systems were presented in the different cases.
► Results showed that such sun-tracking system was efficient to boost energy collection of non-concentrating solar panels.