Field measurements of wind load effects in a photovoltaic single-axis tracker mounting rail
J. H. Koekemoer, Johann Bredell, Gerhard Venter, Josh Reinecke
Abstract
The demand for solar photovoltaic power installations has resulted in a highly competitive industry. Equipment suppliers are under pressure to reduce design margins for projects to be feasible. Single-axis trackers are widely used to increase yield and reduce the levelised cost of energy compared to fixed-tilt installations. Load coefficients on tracker arrays are usually quantified using model-scale studies conducted in atmospheric boundary layer wind tunnels. These dynamically sensitive structures have been known to suffer wind damage despite the use of modern design methods. Ongoing research into the support structure design is deemed important to ensure long-term reliability. The current study presents full-scale field data acquired over 109 days on an experimental one-in-portrait single-axis tracker facility located in the Western Cape, South Africa. The purpose of these measurements was to quantify wind load effects in two instrumented PV module mounting rails. Frequency domain data showed modal participation of both the torsional and bending modes of the torque tube. The effect of the bending mode was more pronounced for the rail furthest from a pile. Load coefficients calculated using experimental data were generally lower than those presented in ASCE 7-22. Fluctuating stresses at critical locations led to negligible fatigue damage. • Field measurements of wind load effects were taken on a single-axis tracker. • High wind speed events did not necessarily occur in the dominant wind direction. • Torsional and bending modes of the torque tube contributed to load effects. • Lower combined wind load coefficients were seen compared to design codes. • Fatigue damage was insignificant during the measurement period of 109 days.