Evolution and Classification of Solar Tracking Systems: From Fixed-Mount to Dual-Axis Configurations

The energy delivered by a photovoltaic (PV) panel depends on how closely its surface stays perpendicular to the incident solar beam. Solar trackers address this, but published energy-gain figures vary widely (about 10–100% across reviews, and 22–56% in a 2020 review), and many historical and technical statements are repeated without primary sources. This review addresses that inconsistency for readers who must choose or design a tracker. Following a documented search protocol, it (i) traces PV and tracker development against verified sources, (ii) defines the azimuth, zenith/elevation and tilt conventions and the two incompatible azimuth conventions in use, (iii) classifies trackers by degrees of freedom, drive and control strategy, and (iv) synthesises reported gains from reviews and field studies. Field studies in the set report dual-axis gains of 30.8–37.2% over fixed mounts, and single-axis gains of 10–24%, with wide variation in baseline, duration and climate; the extra gain of dual-axis over single-axis is only a few percentage points in the most comparable study. Control strategy, land use and parasitic energy consumption affect the net benefit as much as the number of axes. The review closes with recommendations for standardised reporting and states where its findings are useful