IMPROVING THE EFFICIENCY OF A PHOTOVOLTAIC SYSTEM BY INCORPORATING TRACKING SYSTEM AND MPPT: A REVIEW <s> By the use of equations <s> A new very simple, reliable solar tracker is described. The solar tracker is based on a new arrangement of auxiliary bifacial solar cell connected directly to D.C. motor. Auxiliary solar cells (panels) can both sense and provide energy for tracking. <s> BIB001 </s> IMPROVING THE EFFICIENCY OF A PHOTOVOLTAIC SYSTEM BY INCORPORATING TRACKING SYSTEM AND MPPT: A REVIEW <s> By the use of equations <s> The most general form of solar tracking formulae of an arbitrarily oriented heliostat toward an arbitrarily located target on the Earth is presented. With this complete solution, the used azimuth-elevation, spinning-elevation tracking formula, etc., are the special cases of it. Therefore, more application may be sought out for many individual cases in solar engineering. The new form of tracking solution could bring changes in the geometry and structure of the design of heliostat to meet various requirements. <s> BIB002 </s> IMPROVING THE EFFICIENCY OF A PHOTOVOLTAIC SYSTEM BY INCORPORATING TRACKING SYSTEM AND MPPT: A REVIEW <s> By the use of equations <s> In this study, a novel high accurate offline sensorless dual-axis solar tracker is proposed that can be widely used in photovoltaic systems and solar concentrators. The offline estimated data extracted from solar map equations are used by the tracker to find the sun direction where the maximum value of solar energy is captured. The solar tracker has been built, and it is experimentally verified that 19.1%–30.2% more solar energy can be captured depending on the seasons by utilizing the tracker. The contribution of this work is that the proposed offline sensorless dual-axis solar tracker not only has a very simple structure with a fabrication cost much less than sensor based solar trackers but also high accurately tracks the sun direction with a very small tracking error of only 0.43° which is less than the other sensorless and sensor based dual-axis solar trackers reported in the literature excluding the sensor based dual-axis solar trackers equipped with expensive sensors mounted on high accurate mechanical carriers. Furthermore, unlike all sensor based solar trackers, since the technique is offline, the proposed tracker does not use any feedback signal, and thus, its operation is independent from external disturbances and weather conditions such as cloudy sky. <s> BIB003
Formulas that describe the position of the sun at different latitudes have been framed for azimuth and elevation angles BIB002 . The solar tracking formulas of the azimuth-elevation method with θ H as the elevation angle and ρ H as the azimuth angle are given in equations (1) and BIB001 . Fig 3 shows the orientation of the solar panel after it has been rotated. (1) BIB001 where (3) ϕ is the rotation angle about zenith from north towards east. λ is the altitude angle of target relative to the earth's surface. Φ is the local latitude δ is the declination angle of the sun ω is the solar hour angle. Chen, Lim and Lim BIB002 presented a most general form of solar tracking formula for a heliostat that is arbitrarily oriented towards an arbitrarily located target. The previous existing tracking equations include the azimuth-elevation tracking formulae and the further developed spinning-elevation sun tracking formula. The authors derived a general form of sun tracking formula from which the previously existing tracking methods can be extracted as special conditions. An offline sensorless dual-axis solar tracker was designed by Fathabaldi BIB003 for photovoltaic systems and solar concentrators. The data required for tracking were extracted from solar map equations. The proposed system was cost effective as it did not require any feedback signal or sensor. The operation was independent from external disturbances and weather conditions. An increase of about 20% was observed in the absorbed solar energy and the tracking error of the system was found to be 0.43°.