Computation of canting errors in heliostats by flux map fitting: experimental assessment.

Alberto Sánchez-González,Benjamin Grange,Cyril Caliot

doi:10.1364/oe.412116

Abstract

In solar tower plants, thousands of heliostats reflect sunlight into a central receiver. Heliostats consist of a subset of mirrors called facets that must be perfectly oriented (i.e., canted) to concentrate as much solar radiation as possible. This study presents and validates the so-called flux map fitting technique to detect and correct canting errors. The computed distributions were matched to a series of images through an optimization algorithm. According to the sensitivity analysis, three images spread along a single day provide sufficient information for the algorithm to succeed. Using this methodology, four heliostats at the THEMIS research facility were recanted, thereby substantially increasing the optical quality in three of them. The procedure to infer the heliostat aimpoint was assessed.

Highlights

The alignment of optical systems is crucial for proper operation
Alignment is required in imaging systems, such as telescopes [1,2], and in non-imaging systems, whose goal is to collect or concentrate light [3] rather than image formation. This is the case of concentrating solar power (CSP) systems, which concentrate solar radiation into a receiver [4]
By matching the computed flux maps to the measured ones, canting deviations were found in the modules of four heliostats at the THEMIS solar tower

Summary

Introduction

The importance of alignment is evident in reflecting systems involving mirrors. Alignment is required in imaging systems, such as telescopes [1,2], and in non-imaging systems, whose goal is to collect or concentrate light [3] rather than image formation. This is the case of concentrating solar power (CSP) systems, which concentrate solar radiation into a receiver [4]. Owing to solar beam divergence [6,7], heliostat mirror facets must be aligned to concentrate the maximum possible solar radiation

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Methods

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Conclusion