Heliostat geometrical characterization by UAV-assisted, close-range photogrammetry

An innovative approach for the characterization of the mirror geometry of Concentrating Solar Thermal (CST) plants is presented in this article. The approach takes advantage of the current advances in the commercial unmanned aerial vehicle (UAV) technology to perform airborne, close-range photogrammetry for accurate characterization of the mirror's geometry. To improve spatial resolution and, thus, reconstruction performance, the approach involves a projector for projecting a feature-rich image on the surface of the mirror to be characterized. A UAV flying on a predetermined flight path is used to capture overlapping snapshots of the projected image using its on-board high definition digital camera. By the use of photogrammetry tools, the snapshots are stitched together and processed accordingly to reconstruct the surface of the reflector. Although the approach was tested and validated experimentally by characterizing the mirror surface of a single-facet heliostat, the developed method can also be applied for the characterization of any type of solar concentrating mirror geometry.