53. Modal Analysis and Dynamic Monitoring of a Concentrating Solar Heliostat

Heliostats are structures that track the sun and reflect sunlight to a centrally located receiver on top of a tower to produce heat for electricity generation. Commercial power towers can consist of thousands of heliostats that are subject to wind-induced loads, vibration, and gravity-induced sag. This paper presents modal tests of a heliostat located at the National Solar Thermal Test Facility (NSTTF) at Sandia National Labs in Albuquerque, New Mexico. The heliostat was instrumented with 22 accelerometers, 4 strain gauges, and 3 wind anemometers to examine manually and wind-induced vibrations of the structure. Data acquisition software was developed to provide real-time monitoring of the wind velocity, heliostat strain, mode shapes, and natural frequencies which will be used to validate finite element models of the heliostat. The ability to test and monitor full-scale heliostats under dynamic wind loads will provide a new level of characterization and understanding compared to previous tests that utilized scaled models in wind-tunnel tests. Also, the development of validated structural dynamics models will enable improved designs to mitigate the impacts of dynamic wind loads on structural fatigue and optical performance.