Increased energy production of First Solar horizontal single-axis tracking PV systems without backtracking

Backtracking (“BT”) is a shade avoidance algorithm for single-axis horizontal tracker PV systems which has historically been regarded as superior to all other tracking algorithms. Because their internal electrical structure does not create a large shading penalty, First Solar modules have the option of not backtracking (also termed “Truetracking” or “TT”) while most c-Si modules do not. Experiments on multiple PV systems presented in this paper show that TT yields 1.7%-2.5% higher annual energy than BT with First Solar modules. First Solar and independent third parties have shown that PVSyst, the industry standard PV prediction tool, over-predicts energy for systems in BT mode due to an incorrect assumption about diffuse shading. Additionally, other publically available PV prediction tools have limitations that prevent them from accurately predicting tracking PV system performance. First Solar has developed its own PV system energy prediction tool, ISIS, which appropriately accounts for diffuse shading and other differences between BT and TT. ISIS predicts more energy for First Solar systems in TT mode. Consequently, the default tracking configuration for First Solar utility scale systems is TT.