From Event: SPIE Optical Engineering + Applications, 2017
In solar tower power plants, factors such as tracking accuracy, facets misalignment and surface shape errors of concentrating heliostats are of prime importance on the efficiency of the system. At industrial scale, one critical issue is the time and effort required to adjust the different mirrors of the faceted heliostats, which could take several months using current techniques. Thus, methods enabling quick adjustment of a field with a huge number of heliostats are essential for the rise of solar tower technology. In this communication is described a new method for heliostat characterization that makes use of four cameras located near the solar receiver and simultaneously recording images of the sun reflected by the optical surfaces. From knowledge of a measured sun profile, data processing of the acquired images allows reconstructing the slope and shape errors of the heliostats, including tracking and canting errors. The mathematical basis of this shape reconstruction process is explained comprehensively. Numerical simulations demonstrate that the measurement accuracy of this “backward-gazing method” is compliant with the requirements of solar concentrating optics. Finally, we present our first experimental results obtained at the THEMIS experimental solar tower plant in Targasonne, France.
Mathieu Coquand, Cyril Caliot, and François Hénault, "Tracking and shape errors measurement of concentrating heliostats," Proc. SPIE 10379, Nonimaging Optics: Efficient Design for Illumination and Solar Concentration XIV, 103790N (Presented at SPIE Optical Engineering + Applications: August 07, 2017; Published: 7 September 2017); https://doi.org/10.1117/12.2272791.
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