CALIBRATION AND ANALYSIS OF HELIOSTATS

Transcription

1 Hornberg Castle in the Black Forest, Germany May 15-16, 2013 CALIBRATION AND ANALYSIS OF HELIOSTATS R. Monterreal CIEMAT-PSA Unidad de Sistemas Solares de Concentración

2 HELIOSTAT Components: Facets, support structure, drives, control, pedestal Functional features: Concentrating solar radiation (imaging) It is able to stop the reflected solar on a target along the day It belongs to a heliostat field 2

3 HELIOSTAT (kinds) T-Type Stretched membrane Linear focus 3

4 HELIOSTAT (sizes) Small 16 m 2 Medium 40 m 2 Big 140 m 2 Very big 200 m 2 4

5 HELIOSTAT (qualification) What does heliostat qualification mean? Remember heliostat functional features: Imaging capacity Aiming capacity Heliostat qualification find out a merit number or quality number for both functional features: Imaging capacity quality number: Optical quality (slope-error, beam dispersion error, beam quality) Aiming capacity quality number: Tracking quality (tracking error) 5

6 HELIOSTAT (qualification\test facility) Heliostat Testing Platform at PSA 12mx12m white lambertian Target 6

7 HELIOSTAT (qualification\tools) Hardware: Measuring system Software: Image Pro Plus, Matlab 7

8 HELIOSTAT (qualification\diagram) The heliostat qualification process (tracking and optics): Calibration? Test campaign Analysis (or evaluation) TRK and Optical Quality 8

9 HELIOSTAT CALIBRATION: SUN-TRACKING 9

10 CALIBRATION: SUN-TRACKING MOVEMENT 3 things working together: Canonical sun-tracking movement Daily sun-tracking movement Offsets 10

11 CALIBRATION: SUN-TRACKING MOVEMENT\Preliminary things Heliostat painted to avoid possible Influence from optics Check image quality on target 11

12 CALIBRATION: SUN-TRACKING MOVEMENT\Preliminary things Check availability of maximum XY coordinates on target 12

13 CALIBRATION: SUN-TRACKING MOVEMENT Canonical sun-tracking movement Daily sun-tracking movement Offsets What does it mean? Heliostat movement on target as a result of the internal programming to follow the set-point What do we search? Relevant parameters for a proper description 13

14 CALIBRATION: CANONICAL SUN-TRACKING MOVEMENT 14

15 CALIBRATION: CANONICAL AIMING MOVEMENT stop start stop start t t o DB (Dead Band) DBo Expected pattern Experimental pattern Relevant parameters: t, Db dt -> daily energy saving 15

16 CALIBRATION: CANONICAL AIMING MOVEMENT Possible error sources: Programming mistake Bad encoder reading wrong ratio bit/angle Others (electronic noise, ) 16

17 CALIBRATION: SUN-TRACKING MOVEMENT Canonical sun-tracking movement Daily sun-tracking movement Offsets What does it mean? Systematic error source(s) influence. It means Daily drift is present (red line) What do we search? Relevant parameters for a proper description 17

18 CALIBRATION - DAILY TRACKING MOVEMENT sunset sunset sunrise sunrise XY Corr = 0.80 XY Corr = Corr(X,t) = 0.86 Corr(X, t) = 0.58 Corr(X,t) = Corr(X, t) =

19 CALIBRATION - DAILY TRACKING MOVEMENT XY Corr = 0.80 XY Corr = Corr(Y,t) = 0.96 Corr(Y,t) =

20 CALIBRATION: DAILY TRACKING MOVEMENT Possible error sources: Drive out of plumb Wrong LAT and LONG Bad encoder reading wrong ratio bit/angle Sun position errors Time error Others 20

21 CALIBRATION: OFFSETS Canonical sun-traking movement Daily sun-traking movement Offsets What does it mean? What do we search? 21

22 CALIBRATION: OFFSETS Real aiming point Offs_Az X Offs_EL Expected aiming point 22

23 CALIBRATION OFFSET CORRECTION X Y 23

24 CALIBRATION: OFFSETS CORRECTION Possible error sources: Bad encoder reading wrong ratio bit/angle Wrong reference angles (Az, EL) Time error Others 24

25 CALIBRATION: SUN-TRACKING MOVEMENT SUMMARY ISSUE Relevant numbers values Effects 1 Canonical movement DB DB o, t t o Fits with programming pattern 2 Daily movement corr(xy) 0, corr(x, t) 0, corr(y, t) 0 no daily drift 3 Offsets X 0, Y 0 no offset 25

26 HELIOSTAT CALIBRATION: OPTICS 26

27 OPTICAL CALIBRATION WHAT DOES CANTING MEAN? Heliostat mounting at PSA Heliostat mounted at PSA 27

28 OPTICAL CALIBRATION WHAT DOES CANTING MEAN? OPTICAL CALIBRATION CANTING means optical alignment Heliostat after mounting (before facets alignment) Heliostat after mounting (after facet alignment) 28

29 OPTICAL CALIBRATION BAD CANTING EFFECT 29

30 OPTICAL CALIBRATION BAD CANTING EFFECT Some facets are out of focusing Where are their normal vectors? 30

31 OPTICAL CALIBRATION SEARCHING BAD CANTING CAUSES CESA Tower as a pinhole camera 31

32 OPTICAL CALIBRATION SEARCHING BAD CANTING CAUSES 32

33 OPTICAL CALIBRATION BAD CANTING CORRECTION Facets re-alignment with the CCD camera support (just overlap the peaks) 33

34 OPTICAL CALIBRATION CANTING CORRECTION FINISHED ALL IS DONE!! 34

35 PLEASE, REMAIN AT YOUR SEATS NOW IT IS TIME FOR HELIOSTAT ANALYSIS 35

36 HELIOSTAT (qualification\diagram) The heliostat qualification process (tracking and optics): Calibration Test campaign Analysis (or evaluation) TRK and Optical Quality 36

37 HELIOSTAT ANALYSIS \ TRACKING It is assumed a good TRK-calibration Next, sunrise to sunset TRK test Corr(X, Y) =

38 TRK ANALYSIS Corr(X, t) = 0.30 No drift! Corr(Y, t) =

39 TRK ANALYSIS SUNRISE TO SUNSET TEST STATISTICS OF XY POSITIONS ON TARGET Population.= 190 frames Max. STDEV (1) = 0.22 m. Min. STDEV (1). = 0.14 m Elipticity.... = 1.6 Elipticity angle... = 4.9 deg Correlación XY.. = 0.08 Time interval: 6:44 16:51 UT 0.14 m 0.22 m Corr(X, Y) =

40 TRK ANALYSIS: TRK-error () 0.14 m (1) 0.22 m (1) EL = 0.34 mrad Target AZ = 0.57 mrad heliostat 40

41 TRK ANALYSIS: TRK-error () 1 P(68%) 2 P(95%) Tracking-error (): It is defined as the standard deviation (1) of a normal probability distribution describing the angular deviations of the central ray reflected in the heliostat surface with regards to an ideal (error free) aiming point direction. Units: mrad. 41

42 TRK ANALYSIS: TRK-error () What TRK-error do we need for our solar tower plant? 1 TRK-error 1 is OK 2 TRK-error 2 is rejected Solar receiver 42

43 HELIOSTAT ANALYSIS \ OPTICS How this picture can be described? What is the corresponding picture from an ideal heliostat? These are the key points for unfolding heliostat optical quality 43

44 HELIOSTAT ANALYSIS \ OPTICS\ DESCRIPTION Image function f(x, y): Bidimensional discrete function which represents the digital image generated by a CCD camera in nxm order matrix format. f(x, y) central moments: p q pq ( x x) ( y y) f ( x, y) for p, q = 0, 1, 2... and x m m 10 ; 00 y dxdy m m In case of discrete function (digital picture): pq x y p q ( x x) ( y y) f ( x, y) 44

45 x y x y x y y x f y y x x y x f y y y x f x x ), ( ) )( ( ), ( ) ( ), ( ) ( ; ), ( ), ( cov ) var( ; ), ( ) var( ) var( ; ), ( ) var( y x f y x ar y y x f y x y x f x y x 45 ; ) var( ), ( cov ), ( cov ) var( y y x ar y x ar x C XY V V U U u e e V U ˆ ˆ, ) (, XY V U C EIG Our interest: p, q = 1, 2 HELIOSTAT ANALYSIS \ OPTICS\ DESCRIPTION

46 HELIOSTAT ANALYSIS \ OPTICS\ DESCRIPTION X Horizontal 1-radius (m): Picture standard deviation along X. information about picture expansion along horizontal target axis. Y Vertical 1-radius (m): Picture standard deviation along Y. information about picture expansion along vertical target axis. U Max. 1-radius (m): Picture standard deviation along U. information about picture expansion along eigen-axis U. V Min. 1-radius (m): Picture standard deviation along V. information about picture expansion along eigen-axis V. e = U / V Ellipticity (e, dimensionless): It gives us an idea about picture elongation Ellipticity direction (, deg): It is defined as the angle between XY and UV axis. It gives us an idea about picture rotation around {OT; X, Y}: 46

47 HELIOSTAT ANALYSIS \ OPTICS\IDEAL HELIOSTAT PICTURE SUNSHAPE FIAT-LUX code SINTHETIC PICTURE HELIOSTAT MODEL 47

48 HELIOSTAT ANALYSIS \ OPTICS\IDEAL HELIOSTAT PICTURE 48

49 HELIOSTAT ANALYSIS \ OPTICS\UNFOLDING OPTICAL QUALITY N N Who is responsible for bad Opt. Quality? Mirror slope-error is the very big responsible 49

50 HELIOSTAT ANALYSIS \ OPTICS\UNFOLDING OPTICAL QUALITY N N Slope-error (): It is defined as the standard deviation (1) of a normal probability distribution describing the deviation of the normal vector of the heliostat reflecting surface with regard to the one of an ideal reference surface, this means, free of optical errors. Units: mrad. 50

51 HELIOSTAT ANALYSIS \ OPTICS\UNFOLDING OPTICAL QUALITY 51

52 HELIOSTAT ANALYSIS \ OPTICS\UNFOLDING OPTICAL QUALITY 52

53 THANK YOU VERY MUCH 52