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Wind loads on single-axis and double-axis solar PV tracking systems

Single-axis and double-axis tracking systems may be subjected to wind dynamic effects such as buffeting forces resulting from the wakes of upstream rows. Thus dynamic am­pli­fi­cation of the mode shapes may occur below or at typical design wind speeds if the vortex shedding frequency matches the natural frequency of the structure. Structural damping of the tracking system acts to mitigate the structure’s response.

There are two ways to handle trackers.

A) Time domain analysis:
From the wind tunnel testing pressure-time-series cor­res­pon­ding to global structural load effects such as lift forces, drag forces, hinge moment or bending mo­ments can be identified. These pressure-time-series may be fed into structural analysis soft­ware to calculate peak stresses or displacements, foundation loads etc. due to resonant effects.

B) Frequency domain analysis:
A structural modal analysis has to be conducted first. The results of the modal analysis (mode shapes, natural frequencies, critical damping, mass distribution, stiffness) have to be provided to I.F.I. for calculation of equivalent static load dis­tributions. This analysis has the advantage of being in a format that struc­tural engineers are used to work with. Furthermore, equivalent static wind loads can be easily combined with other loads such as snow or earthquake by applying the combination rules of wind loading codes such as ASCE 7-10.