LIDAR for heliostat optical error assessment

Little, Charles Q.; Small, Daniel E.; Yellowhair, Julius E.

doi:10.1063/5.0087691

Cited by 4 publications

(2 citation statements)

References 2 publications

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“…Many methods have been developed for heliostat metrology, generally in two categories: (1) methods that use diffuse targets, and (2) methods that use specular reflection from the mirrors (which we refer to as deflectometry). Methods relying on diffuse (non-specular) targets include laser tracking, 5,6 3D photogrammetry, 7,8 and radar. 9 These methods measure target positions in 3D, from which surface slopes are estimated.…”

Section: Introductionmentioning

confidence: 99%

Grating-embedded mirrors for heliostat tracking error metrology

Wisniewski,

Arnold,

Kim

et al. 2023

Advances in Solar Energy: Heliostat Systems Design, Implementation, and Operation

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Concentrated solar power (CSP) plants need to monitor the surface slope error of thousands of heliostats with sub-milliradian accuracy. We present grating embedded mirrors (GEMs) and the accompanying Diffractive Auto-Stigmatic Hartmann Camera (DASHCam) metrology system for measuring heliostat surface slopes. GEMs have multiple phase diffraction gratings written within a glass mirror substrate using an ultrafast laser. The gratings direct a small fraction of incident light to non-specular directions, which the DASHCam senses from a virtual center of curvature to measure the facet slopes at each grating location. Our results show, in a laboratory environment, 24 µrad RMS measurement repeatability and 47 µrad RMS accuracy, with single-shot image capture. GEMs and DASHCam are a compact, accurate, and high-speed heliostat slope error metrology system that is robust to the harsh environmental conditions at CSP plants.

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Section: Introductionmentioning

confidence: 99%

Grating-embedded mirrors for heliostat tracking error metrology

Wisniewski,

Arnold,

Kim

et al. 2023

Advances in Solar Energy: Heliostat Systems Design, Implementation, and Operation

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“…Effective and efficient field inspection technology for CSP plant is necessary for various applications such as efficient control, maintenance, and repair. Currently the inspection of CSP systems relies on conventional imaging techniques [1], deflectometry [2], flux mapping [3], machine vision [4], and LIDAR scanning [5]. These state-of-art heliostat inspection technologies have different limitations in terms of accuracy, speed, complexity, or cost.…”

Section: Introductionmentioning

confidence: 99%

Toward Autonomous Field Inspection of CSP Collectors With a Polarimetric Imaging Drone

Tian,

Desai,

Bai

et al. 2023

SolarPACES Conf Proc

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We developed a polarimetric imaging drone to perform field inspections of heliostats and carried out field tests at Sandia’s National Solar Thermal Test Facility (NSTTF). The preliminary results show that Degree of Linear Polarization (DOLP) and Angle of Polarization (AOP) images greatly enhanced the edge detection results compared with the conventional visible images, supporting fast and accurate detection of heliostat mirror edges and cracks. The system holds the promise to enable future automated detection of heliostats optical errors and mirror defects.

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Laboratory Demonstration of Grating Embedded Mirrors for Single-Shot Heliostat Optical Metrology

Wisniewski,

Arnold,

Kim

et al. 2024

Journal of Solar Energy Engineering

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Concentrated solar power (CSP) plants need to monitor the surface slope error of thousands of heliostats with sub-milliradian accuracy. Large numbers of heliostats installed in harsh environments means that measurement speed and durability are key design considerations for metrology systems. We present a compact, accurate, and high-speed heliostat slope error metrology system that is robust to the harsh environmental conditions at CSP plants. The system is composed of (1) Grating Embedded Mirrors (GEMs), which have multiple phase diffraction gratings written within a glass mirror substrate, and (2) a compact optical system, the Diffractive Auto-Stigmatic Hartmann Camera (DASHCam). Using focused ultrafast laser pulses, we write phase gratings within float glass mirror facets without damaging the reflective coating. The gratings direct a small fraction of incident light to non-specular directions, which the DASHCam senses from a virtual center of curvature to measure the facet slopes at each grating patch. In a CSP plant, each heliostat facet would be a GEM, and the DASHCam would rapidly measure slope and canting errors during heliostat manufacturing, installation, or operation. We fabricated 0.1 meter-diameter GEMs, built a prototype DASHCam system. Our results show, in a laboratory environment, 24 μrad RMS measurement repeatability and 47 μrad RMS accuracy, with single-shot image capture. The combination of GEMs and DASHCam is a promising metrology approach that could lead to improved optical accuracy of heliostats throughout their life cycle. This work serves as a proof of principle for this system.

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LIDAR for heliostat optical error assessment

Cited by 4 publications

References 2 publications

Grating-embedded mirrors for heliostat tracking error metrology

Grating-embedded mirrors for heliostat tracking error metrology

Toward Autonomous Field Inspection of CSP Collectors With a Polarimetric Imaging Drone

Laboratory Demonstration of Grating Embedded Mirrors for Single-Shot Heliostat Optical Metrology

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