Tracking and shape errors measurement of concentrating heliostats
Mathieu Coquand Cyril Caliot François Hénault
Outline 1)General Introduction / Context 2)Backward-Gazing Method 3)Numerical Simulations 4)Experiments and Preliminary Results 5)Conclusion and Outlooks
2
Different types of CSP Plants
3
Why must we characterize the concentrators Immediate applications • Decrease the necessary time to adjust thousands of reflective facets • Identify damaged facets, to be repaired or replaced More prospective applications • To evaluate and optimize prototypes • To predict performance • To analyze mechanical stress, and the influence of the wind and gravity • A better control of the heliostat tracking is necessary for the development of pointing strategies 4
Different types of errors Facet alignment error (canting error) Heliostat tracking error
Local surface errors (low or mid-spatial frequency)
5
Method’s Description
Images of the reflection of the sun on the heliostat are taken from different points of view. By knowing the sun profile, it is possible to reconstruct the optical errors of the mirrors. 6
Slope Errors Equations
=
Wavefront reconstruction from the four images
1 2
Wavefront to surface slopes transform matrix
7
Proceedings Iij(P) − Images of the sun reflected by the heliostat
WFE slopes
Reference WFE slopes
∂W ( P ) ∂x and ∂W ( P ) ∂y
∂WR ( P ) ∂x and ∂WR ( P ) ∂y
reconstructed from images
Y X slopes WFE reconstruction Eqs. 4,
Subtraction
-
Z O
9 and15
Y slopes
Y
X slopes WFE slopes to surface slopes Eqs. 16 matrix
Southwell algorithm
Z O
Warp algorithm
Y slopes Reconstructed heliostat surface
Heliostat surface slopes
WFE slopes corrected from aberrations
8
Numerical Simulations Heliostat and sun models
Each facet is misaligned by ±1 mrad around the azimuth and altitude axes
10% focus mismatch - Focal length 200 m - Distance to target 180 m
(
B (ε ) = B0 exp − ε ε 0
4
)
a) Dimensions of the simulated heliostat in mm b) Super-Gaussian sun profile with parameter ξ = 4 9
Numerical Simulations WFE and slopes Reconstruction Errors
Experiments at THEMIS power plant Targasonne – France (Pyrenees Mountains)
A 5th camera is used to calibrating the sun profile during images acquisition
12
Experiments Acquisitions and Treatments
Raw images
″Rectangularized″ images 13
Experiments - Preliminary Results Wavefront slopes along X
Wavefront slopes along Y
Simulated slopes 14
Conclusion and Outlooks • A four cameras backward-gazing method to characterize solar concentrators has been described • Numerical simulations have been performed to validate the method, and to demonstrate that its accuracy is compliant with the requirement for concentrating surfaces in solar power plants • An experiment has been set-up in THEMIS solar power plant. The method already works in WFE sensing mode, but: • Image processing has highlighted the difficulty to superimpose the images (“registration”) • The validation of the method in surface shape sensing mode is in progress
15
Possible extension to freeform optics metrology Observed source object OS
lation to calculate the 3-D coordinates related to the sensor coordinate system ... [S0091-3286(00)02701-X] ... multiple points is imaged under different viewing angles, ... value images, the optical properties of the object, and the ... lens distort
11.4 Observers and Viewing Conditions. The test panel was constituted by eight female and nine male observers with normal vision and various degrees of.
Then we discuss the advantages and drawbacks of the different methods depending on the intended usage of the. MTF and why Jang and Allebach's method ...
Source: CGGC, based on company annual reports, individual interviews, and ..... delay in extending the renewable energy investment tax credits and the U.S..
Cardiac chambers and major vessels were segmented using shape-constrained de- formable models while the left atrial appendage (LAA) was extracted using ...
i=1, 2, with n1+n2=n, dn(x, y)=Fn(dn1(x1, y1), dn2(x2, y2)) ...... There are some advantages in ... try[ing] to catch the extent of inequality in some objective sense...
âVagueness and Language Useâ. Jean-Roch LAUPER. International .... The British Journal for the Philosophy of. Science 19(4): 281-299. TAYLOR, John R.
Point laser light at a tracer particle travelling with a fluid, and the scattered .... oscillates at a frequency proportional to the volume flow rate of the main jet flow.
... (M. Marcoux). Chemical Engineering Science 65 (2010) 5092â5104 .... at any moment, the flux N1 is given by its one-dimensional,. Bath temperature.
trated in the right image in figure 1, the vertical texture direction is remarkably .... from human's perception view. We proposed a mea- ... Lecture Notes in Ar-.
Jan 19, 2009 - The Curve sketching option allows you to draw and refine a curve in the ... You can iterate by drawing as many sketches as you want; the curve ...
In some test-books, the word pound-feet is used to represent ... has potential energy that is equal to the work ... to two simple problems. The power indicated is ...
the projection angle and the focal point location of a ... proximation and a rational function, respectively, to ... represents an arbitrary point on the object, B indi-.
May 8, 2009 - for high-speed photography [81â83]. The objects in rapid periodic ..... This project was supported by the National Natural Science. Foundation of China (No. ..... /http://web.mit.edu/museum/exhibits/S. [81] Asundi AK, Sajan MR.
medial surface. The method applied on MRI data, is based ... INTRODUCTION. Human cortical ..... Proceedings of Medical Imaging, Image Processing, 1996,.
Nov 2, 2005 - To quantify the errors in the qubit we use the concept of FIDELITY. ... Computingâ A. M. Steane, Reports on Progress in Physics, vol 61,.
Nov 4, 2015 - the first-order solution (accounting for uncertainties). However, .... Foundation Lectures (New Haven: Yale University Press). Davison, T. M. ...
The coupler used a design-rule-based transformation .... â18 dB, and coupling is â28 dB or bet- ter across the ... The following electron microscope photos show ...
Analysis of Pointing Errors Reveals Properties of Data. Representations and Coordinate Transformations Within the. Central Nervous System. J. McIntyre.
