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Cylindrical and Flat Solar Collector Geometries: Theory and Experiment

Optical Society of America's (OSA's) RENEWABLE ENERGY AND THE ENVIRONMENT Conference, 11 November - 15 November 2012, Hotel Pullman Eindhoven Cocagne, Eindhoven, Netherlands,
TITLE: Cylindrical and Flat Solar Collector Geometries: Theory and Experiment
AUTHORS/INSTITUTIONS: J. Koshel, , Photon Engineering LLC, Tucson, AZ;
J. Koshel, College of Optical Sciences, University of Arizona, Tucson, AZ;
G. Smestad, , Solar Energy Materials and Solar Cells, San Jose, CA;
D. Shull, P. Stephens, T. Healy, Electrical Engineering Department, Santa Clara University, Santa CLara, CA; KEYWORDS: Other areas of optics: Solar energy, nonimaging optical systems, geometrical optics, Etendué.
http://www.osa.org/meetings/optics_and_photonics_congresses/renewable_energy_and_the_environment/

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Cylindrical and Flat Solar Collector Geometries: Theory and Experiment

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  2. 2. O%,'.&D(J.%* U  !"#$%&'$()#*2.#)'*(/##*,DT/2*D2/* ,5$%VW#1*!O0-*,/(5%.#.@"3* R  4')(X$%@*%.,*'/YD$'/&* R  6)2/*.H*1.D%J%@=*(..#$%@=*)%&* (#/)%$%@* R  !O0-*Z*?Q[*/($/%,* R  ]$%&*#.)&2*'/&D(/&* R  G.^*'..H*8/%/,')J.%* U  -$@%$W()%,*1/&$)*(.L/')@/*.H*,5/* ,/(5%.#.@"3* R  F.^*&./2*$,*^.'X_* R  C./2*$,*^.'X*^/##_* R  ]/*)'/*%.,*$%,/'/2,/&*$%*,5/* 8.#$J(2*`1D(5a* ?*>B*S.L/1T/'*?Q>?* Photo by Greg P. Smestad
  3. 3. P.JL)J.%* U  b/c/'*D%&/'2,)%&*,5/* ("#$%&'$()#*,DT/*,/(5%.#.@"3* R  ]5),*$2*,5/*,5/.'"*T/5$%&* 8/'H.'1)%(/_* R  C./2*$,*^.'X*T/c/'*,5)%*%.%V ,')(X$%@*d),*8)%/#2_* R  !)%*2.e^)'/*1.&/#$%@*T/* D2/&*,.*)((D'),/*&/,/'1$%/* 8/'H.'1)%(/_* R  !)%*,5/*,/(5%.#.@"*T/* $18'.L/&_* U  6&D()J.%)#*,..#*H.'* D%&/'@')&D),/*2,D&/%,2*),* -)%,)*!#)')*K%$L/'2$,"* B*>B*S.L/1T/'*?Q>?* Photos by Greg P. Smestad
  4. 4. q dDB D6 !5)')(,/'$2J(2*.H*!"#$%&'$()#*4DT/*A)%/#2* U  4DT/*&$)1/,/'*f*!g*f*??*11* U  4DT/*28)($%@*f*"*f*?!g*f*EE*11* U  4DT/VT)(X8#)%/*2/8)')J.%*f*!#*f*>:h!g*f*BB*11* U  !/##*&$)1/,/'*f*!$*f*>h*11* U  4DT/*G/%@,5*f*%*f*>QQQ*11* U  M'')"*f*&'()*+*f*EQ* E*>B*S.L/1T/'*?Q>?* Direct sunlight Glass Tubes Index-Matching Fluid CIGS
  5. 5. !9:.;<$ b)2/&*.%*,5/*'/2/)'(5*.H*/L)(D),/&*,DT/2* h*>B*S.L/1T/'*?Q>?*
  6. 6. C'$L$%@*9/)2.%*H.'*!"#$%&'$()#*4DT/2* g*>B*S.L/1T/'*?Q>?* ! -8 -6 -4 -2 0 2 4 6 8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 d/D6= 1 d/D6= 2 d/D6= inf Solar Hour ED/E0 Equinox Tilt = Latitude Replicated: D. C. Beekley and G. R. Mather, Jr., “Analysis and experimental tests of a high-performance evacuated tubular collector,” DOE/NASA CR-150874, 1978. Manuscript Freely obtained at: http://ntrs.nasa.gov/archive/nasa/ casi.ntrs.nasa.gov/19790008199_1979008199.pdf
  7. 7. =>&#,2$(+$?65>+-&>,*5$!@A#1$ 4,*B#&$(+$?65>+-&>,*5$!@A#1$ O'')&$)%(/*9)J.*.%*!"#$%&'$()#*4DT/2* i*>B*S.L/1T/'*?Q>?* ED/E0 ER/E0ED = irradiance on tilted cylindrical tubes from direct sunlight ER = irradiance on tilted cylindrical tubes from backplane scatter E0 = irradiance on flat panel normal to direct sunlight E = irradiance on horizontal flat panel from direct sunlight Solar Hour Solar Hour Latitude = 40° Tilt = 28° d = 2D6 http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790008199_1979008199.pdf Latitude = 40° Tilt = 28° White-Panel Backplane d = 2D6
  8. 8. -8 -6 -4 -2 0 2 4 6 8 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 !.18)'$2.%3*!"#$%&'$()#*M'')"*j*+#),*A)%/#* k*>B*S.L/1T/'*?Q>?* 0.5(ED+ER)/E0orE/E0 Solar Hour Flat Panel Cylindrical Tubes The theory indicates flat panels should be better around noon, while the tubes are better in early and late hours http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790008199_1979008199.pdf 1.0 - 0
  9. 9. :C%:;DE:F!$ P/)2D'/1/%,2*)%&*(.18)'$2.%2*,.*,5/.'"* l*>B*S.L/1T/'*?Q>?*
  10. 10. 45/"*G..X*G$X/*+#),*A)%/#2m* Greater than the critical angle Photo by Greg P. Smestad >B*S.L/1T/'*?Q>?* >Q*
  11. 11. m)%&*45/"*G..X*G$X/*b#$%&2* Less than the critical angle Photos by Greg P. Smestad Tubes Shadows >B*S.L/1T/'*?Q>?* >>*
  12. 12. 6&@/V9)"*0/.1/,'"*.H*!"#$%&'$()#*4DT/2* >?*>B*S.L/1T/'*?Q>?* Cylindrical Tubes Performance Region Critical or Acceptance Angle qa qa Flat Panel Performance Region Flat Panel Performance Region
  13. 13. P/)2D'/&*On*!D'L/2*H.'*-.#)'*A)%/#2* >B*S.L/1T/'*?Q>?* >B*
  14. 14. !.18)'$%@*An*P.&D#/*A.^/'* First glance: cylindrical tube panel (Solyndra) performs better than flat panel (Solar Frontier) Second glance: we need to normalize for differences in solar cell active area Third glance: there is the characteristic kink in the curve due to critical angle phenomenon Electrical 3 September 2012 Latitude = 37.3492° Longitude = -121.9381° Altitude = 20 m White-Panel Backplane >B*S.L/1T/'*?Q>?* >E*
  15. 15. S.,*-.*+)2,3*O,*$2*A.^/'*C/%2$,"* First glance: flat panel (Solar Frontier) performs better than cylindrical tube panel (Solyndra) Second glance: we are gaining some power from the open regions in the panel, but not doubling Third glance: the kink is still there due to critical angle phenomenon Electrical 3 September 2012 Latitude = 37.3492° Longitude = -121.9381° Altitude = 20 m White-Panel Backplane >B*S.L/1T/'*?Q>?* >h*
  16. 16. :G/#&>)#+2*5H$:5#,2&>,*5$ %(I#&$=#+1>26$ !"#(&6H$D&&*->*+,#$;*0($ !.18)'$2.%*.H*45/.'"*)%&*678/'$1/%,*Electrical >B*S.L/1T/'*?Q>?* >g*
  17. 17. !"#$%&'$()#*4DT/*M'')"*!.18)'$2.%*,.*45/.'"* 28 October 2012 (AM1.5 Conditions) Latitude = 37.3492° Longitude = -121.9381° Altitude = 20 m Black Velvet Backplane >B*S.L/1T/'*?Q>?* >i* 45/.'"3*&$'/(,*.%*("#$%&'$()#*,DT/2* ED/E0 Solar Hour Latitude = 40° d = 2D6
  18. 18. 4.J!KL;:$E.=:MDFN$ n)#$&)J.%*)%&*.8J1$N)J.%* >k*>B*S.L/1T/'*?Q>?*
  19. 19. -.D'(/*-/,D83*S96G*-.#)'*P.&/#* 0 200 400 600 800 1000 1200 9/2/12 7:12 PM 9/3/12 12:00 AM 9/3/12 4:48 AM 9/3/12 9:36 AM 9/3/12 2:24 PM 9/3/12 7:12 PM 9/4/12 12:00 AM globalsolarradiation(W/m^2) Bird Bras Ryan-Stolzenbach >l*>B*S.L/1T/'*?Q>?* Site data and time info latitude in decimal degrees (positive in northern hemisphere) !"#!$%& longitude in decimal degrees (negative for western hemisphere) '(&(#%!)( ground surface elevation (m) 20.0 time zone in hours relative to GMT/UTC (PST= -8, MST= -7, CST= -6, EST= -5) -8 daylight savings time (no= 0, yes= 1) 1 start date to calculate solar position and radiation 3-Sep-12 start time 12:30 AM time step (hours) 0.5 number of days to calculate solar position and radiation 1 Bird model parameters barometric pressure (mb, sea level = 1013) 1013 ozone thickness of atmosphere (cm, typical 0.05 to 0.4 cm) 0.225 water vapor thickness of atmosphere (cm, typical 0.01 to 6.5 cm) 2 aerosol optical depth at 500 nm (typical 0.02 to 0.5) 0.26 aerosol optical depth at 380 nm (typical 0.1 to 0.5) 0.3 forward scattering of incoming radiation (typical 0.85) 0.85 surface albedo (typical 0.2 for land, 0.25 for vegetation, 0.9 for snow) 0.2 Bras model parameter Bras atmospheric turbidity factor (2=clear, 5=smoggy, default = 2) 2 Ryan-Stolzenbach model parameter Ryan-Stolzenbach atmospheric transmission factor (0.70-0.91, default 0.8) 0.8 Calculation of solar position based on NOAA's functions and clear-sky solar radiation based on Bird and Hulstrom's model, Bras model, and Ryan and Stolzenbach's model. On horizontal surface
  20. 20. -.e^)'/*0/.1/,'"*.H*-$%@#/*A)%/#* ?Q*>B*S.L/1T/'*?Q>?* Solar Spectrum = AM1.5 CIGS QE = NREL literature 3 September 2012 Latitude = 37.3492° Longitude = -121.9381° Altitude = 20 m White-Panel Backplane Solar noon results only shown on central tube Pe,tube (tracing) = 2.53 W Pe,array = 101.2 W
  21. 21. O=$8>1@*5>P*0(+$ Q=$?"*&2$ 9)"V4')($%@*9/2D#,2* ?>*>B*S.L/1T/'*?Q>?* Note: irradiance on back surface of tube Pe,tube = 2.53 W comparable to experiment 1.30 pm
  22. 22. P.&/#/&*6#/(,'$()#*A.^/'*0/%/')J.%* ??*>B*S.L/1T/'*?Q>?* Comparison of Solyndra cylindrical tube panel: experiment and ray trace model – good agreement. Variations due to solar source assumptions, such as atmospheric conditions Indicates that software ray- tracing model validates virtual design method. Electrical 3 September 2012 Latitude = 37.3492° Longitude = -121.9381° Altitude = 20 m White-Panel Backplane
  23. 23. o,/%&D/* U  +'/%(5*].'&3* R  n/'T3*/7,/%&/&* R  S.D%3*'/)(5* U  o,/%&D/*$2*)*@/.1/,'$(*H)(,.'3* U  O,*&/2('$T/2*,5/*dD7*8'.8)@)J.%*(5)')(,/'$2J(2*.H*)%*.8J()#*2"2,/13* ?B*>B*S.L/1T/'*?Q>?* !! "= aperture 2 cos ddAn s#E ( ) ,cosˆ, aperture !! "=# ddAL s$ar 2 aperture cos n L ddAL s ss E = !=" ## $ dAs q! dW! Arbitrary Source Radiance Lambertian Source Radiance Aperture
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