Aeroelastic instability mechanisms of single-axis solar trackers

Abstract

Single-axis solar trackers are currently the most commonly used racking system in utility scale solar photovoltaic (PV) plants. The last decade has seen significant advances in the understanding of single-axis tracker aerodynamics after significant failures have occurred due to aerodynamic instabilities. The current study focuses on the aeroelastic mechanisms causing these divergent instabilities. The analytical background as a function of static tilt angle is presented for the different instabilities. The role of aerodynamic stiffness and aerodynamic damping are examined through rigid sectional model testing and these results are used to perform numerical stability estimates using multiple theoretical approaches. These results are compared with aeroelastic model testing of a single-axis solar tracker over a wide range of static tilt angles. These analytical, numerical, and experimental approaches are used to assess the static tilt angles governed by stiffness-driven and damping-driven aerodynamic instabilities. The small size and light weight of single-axis trackers makes them more susceptible to turbulent gusts. This aspect has been addressed in the current study through the concept of the structurally averaged wind speed and the effective gust velocity factor. Comparison to the experimental results suggests that stiffness-driven torsional instability can respond quite rapidly to the passage of turbulent gusts.