Experimental Benchmark for the 3D wind tunnel testing of torsional aeroelastic instabilities in single-axis solar trackers

Wind-excited torsional oscillation of photovoltaic single-axis solar trackers constitutes a class of complex fluid-structure interaction phenomena, involving torsional galloping, torsional divergence, 1DOF flutter, VIV and buffeting. The highest potential for structural damage corresponds to torsional aero-elastic instability, which develops when wind speed exceeds a critical value that, for a given tracker, depends on tilt. Current engineering standards do not offer reliable criteria to yield safe operation conditions, therefore each case requires specific wind tunnel testing. Since data reported in the literature are scarce and scattered, from both industry and academia there is a growing need to define a Benchmark as a reference to compare results and validate methodologies of different studies. This paper proposes a tracker model with 3D aeroelastic characteristics, both torsion and bending, appropriate for wind tunnel testing, including geometry, mounting details, experimental methodology and critical velocity criterion. Tracker units built according to this model were tested in two different wind tunnels (at Polytechnic University of Madrid and University of Oviedo), and the respective measurements show good agreement. The reported results include stability maps with comparison to literature data, an evaluation of the phenomena identified, and the effects of the tracker relative position in a row.