On 18/19 January 2018 a wind incident caused the failure of many PV trackers at the Mafraq solar field. sbp has been engaged by ACWA Power to perform a root cause analysis (RCA) for the failed PV trackers. The root cause of the failure was found to be torsional flutter. In addition, it was found that the used wind tunnel test did not provide dynamic amplification factors. Due to the initial assumptions of too low design wind load, the resistance of main components like the main beam and its corresponding clamps was not sufficient.
Therefore, it was necessary to modify these components in the redesign done by Nclave. In the redesign, perimeter and interior trackers were handled differently. The initial perimeter trackers were split in two redesigned perimeter trackers. Thus, the eigenfrequency was increased and the drive load was decreased. The main beam section of the interior trackers was changed to provide sufficient torque resistance and the quantity of dampers has been doubled. Intensive wind tunnel studies were conducted to prove that the redesigned trackers are stable against flutter. The design of the clamps has been enhanced in all trackers. New drives have been designed for the interior trackers while the original drives have been reused for the shortened perimeter trackers. Nevertheless, NCLAVE showed that some of the tracker components had enough resistance and they have been reused in the redesign such as the posts and the purlins.
The scope of sbp during the redesign phase was technical consulting of ACWA and guiding the design team of NCLAVE and ET Solutions to prevent errors like the ones that caused the failure of the initial Mafraq PV tracker.