Abstract

A two-axis tracking scheme designed for <250x concentration realized by a single-axis mechanical tracker and a translation stage is discussed. The translation stage is used for adjusting positions for seasonal sun movement. It has two-dimensional x-y tracking instead of horizontal movement x-only. This tracking method is compatible with planar waveguide solar concentrators. A prototype system with 50x concentration shows >75% optical efficiency throughout the year in simulation and >65% efficiency experimentally. This efficiency can be further improved by the use of anti-reflection layers and a larger waveguide refractive index.

© 2014 Optical Society of America

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References

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  1. J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18(2), 1122–1133 (2010).
    [Crossref] [PubMed]
  2. J. H. Karp, E. J. Tremblay, J. M. Hallas, and J. E. Ford, “Orthogonal and secondary concentration in planar micro-optic solar collectors,” Opt. Express 19(S4Suppl 4), A673–A685 (2011).
    [Crossref] [PubMed]
  3. D. Moore, G. Schmidt, and B. Unger, “Concentrated photovoltaics stepped planar light guide,” in International Optical Design Conference, OSA Technical Digest (Optical Society of America, 2010), paper JMB46P.
    [Crossref]
  4. O. Selimoglu and R. Turan, “Exploration of the horizontally staggered light guides for high concentration CPV applications,” Opt. Express 20(17), 19137–19147 (2012).
    [Crossref] [PubMed]
  5. Y. Liu, R. Huang, and C. Madsen, “A lens-to-channel waveguide solar concentrator,” in Renewable Energy and the Environment, OSA Technical Digest (Optical Society of America, 2013), paper RT3D.1.
  6. Y. Liu, R. Huang, and C. K. Madsen, “Design of a Lens-To-Channel Waveguide System as a Solar Concentrator Structure,” Opt. Express 22(S2Suppl 2), A198–A204 (2014).
    [Crossref] [PubMed]
  7. W. C. Shieh and G. D. Su, “Compact solar concentrator designed by minilens and slab waveguide,” Proc. SPIE 8108, 81080H (2011).
    [Crossref]
  8. S. C. Chu, H. Y. Wu, and H. H. Lin, “Planar lightguide solar concentrator,” Proc. SPIE 8438, 843810 (2012).
    [Crossref]
  9. J. H. Karp and J. E. Ford, “Planar micro-optic solar concentration using multiple imaging lenses into a common slab waveguide,” Proc. SPIE 7407, 74070D (2009).
    [Crossref]
  10. K. Arizono, R. Amano, Y. Okuda, and I. Fujieda, “A concentrator photovoltaic system based on branched planar waveguides,” in SPIE Solar Energy + Technology (International Society for Optics and Photonics, 2012), pp. 84680K.
  11. K. A. Baker, J. H. Karp, E. J. Tremblay, J. M. Hallas, and J. E. Ford, “Reactive self-tracking solar concentrators: concept, design, and initial materials characterization,” Appl. Opt. 51(8), 1086–1094 (2012).
    [Crossref] [PubMed]
  12. V. Zagolla, E. Tremblay, and C. Moser, “Efficiency of a micro-bubble reflector based, self-adaptive waveguide solar concentrator,” Proc. SPIE 8620, 862010 (2013).
    [Crossref]
  13. V. Zagolla, E. Tremblay, and C. Moser, “Light induced fluidic waveguide coupling,” Opt. Express 20(S6), A924–A931 (2012).
    [Crossref]
  14. E. Tremblay, D. Loterie, and C. Moser, “Thermal phase change actuator for self-tracking solar concentration,” Opt. Express 20(S6), A964–A976 (2012).
    [Crossref]
  15. V. Zagolla, E. Tremblay, and C. Moser, “Proof of principle demonstration of a self-tracking concentrator,” Opt. Express 22(S2Suppl 2), A498–A510 (2014).
    [Crossref] [PubMed]
  16. J. M. Hallas, K. A. Baker, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Two-axis solar tracking accomplished through small lateral translations,” Appl. Opt. 51(25), 6117–6124 (2012).
    [Crossref] [PubMed]
  17. W. T. Welford and R. Winston, The Optics of Nonimaging Concentrators (Academic Press, Inc., 1978), Chap. 2.

2014 (2)

2013 (1)

V. Zagolla, E. Tremblay, and C. Moser, “Efficiency of a micro-bubble reflector based, self-adaptive waveguide solar concentrator,” Proc. SPIE 8620, 862010 (2013).
[Crossref]

2012 (6)

2011 (2)

2010 (1)

2009 (1)

J. H. Karp and J. E. Ford, “Planar micro-optic solar concentration using multiple imaging lenses into a common slab waveguide,” Proc. SPIE 7407, 74070D (2009).
[Crossref]

Baker, K. A.

Chu, S. C.

S. C. Chu, H. Y. Wu, and H. H. Lin, “Planar lightguide solar concentrator,” Proc. SPIE 8438, 843810 (2012).
[Crossref]

Ford, J. E.

Hallas, J. M.

Huang, R.

Karp, J. H.

Lin, H. H.

S. C. Chu, H. Y. Wu, and H. H. Lin, “Planar lightguide solar concentrator,” Proc. SPIE 8438, 843810 (2012).
[Crossref]

Liu, Y.

Loterie, D.

Madsen, C. K.

Moser, C.

Selimoglu, O.

Shieh, W. C.

W. C. Shieh and G. D. Su, “Compact solar concentrator designed by minilens and slab waveguide,” Proc. SPIE 8108, 81080H (2011).
[Crossref]

Su, G. D.

W. C. Shieh and G. D. Su, “Compact solar concentrator designed by minilens and slab waveguide,” Proc. SPIE 8108, 81080H (2011).
[Crossref]

Tremblay, E.

Tremblay, E. J.

Turan, R.

Wu, H. Y.

S. C. Chu, H. Y. Wu, and H. H. Lin, “Planar lightguide solar concentrator,” Proc. SPIE 8438, 843810 (2012).
[Crossref]

Zagolla, V.

Appl. Opt. (2)

Opt. Express (7)

Proc. SPIE (4)

W. C. Shieh and G. D. Su, “Compact solar concentrator designed by minilens and slab waveguide,” Proc. SPIE 8108, 81080H (2011).
[Crossref]

S. C. Chu, H. Y. Wu, and H. H. Lin, “Planar lightguide solar concentrator,” Proc. SPIE 8438, 843810 (2012).
[Crossref]

J. H. Karp and J. E. Ford, “Planar micro-optic solar concentration using multiple imaging lenses into a common slab waveguide,” Proc. SPIE 7407, 74070D (2009).
[Crossref]

V. Zagolla, E. Tremblay, and C. Moser, “Efficiency of a micro-bubble reflector based, self-adaptive waveguide solar concentrator,” Proc. SPIE 8620, 862010 (2013).
[Crossref]

Other (4)

W. T. Welford and R. Winston, The Optics of Nonimaging Concentrators (Academic Press, Inc., 1978), Chap. 2.

K. Arizono, R. Amano, Y. Okuda, and I. Fujieda, “A concentrator photovoltaic system based on branched planar waveguides,” in SPIE Solar Energy + Technology (International Society for Optics and Photonics, 2012), pp. 84680K.

Y. Liu, R. Huang, and C. Madsen, “A lens-to-channel waveguide solar concentrator,” in Renewable Energy and the Environment, OSA Technical Digest (Optical Society of America, 2013), paper RT3D.1.

D. Moore, G. Schmidt, and B. Unger, “Concentrated photovoltaics stepped planar light guide,” in International Optical Design Conference, OSA Technical Digest (Optical Society of America, 2010), paper JMB46P.
[Crossref]

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Figures (8)

Fig. 1
Fig. 1 (a) A side view and (b) a top view of the previously proposed lens-to-channel waveguide solar concentrator. A lens array concentrates incoming light onto the channel waveguides below. One end of each channel waveguide is angled by 45 ° , acting as the coupler to redirect light into the waveguides via total internal reflections. PV cells or other secondary optics are attached at the other end of the channel waveguides.
Fig. 2
Fig. 2 (a) A solar system is usually tilted at the angle of its latitude towards south (northern hemisphere) and therefore it sees symmetrical movement of the Sun throughout the year. (b) The sky dome seen by a solar system tilted as in (a). A single-axis tracker is used to rotate the whole structure daily from east to west (green line). As the Sun moves between the Cancer and the Capricorn (blue lines), the translation stage would adjust the relative position between the lens array and the waveguides to accommodate the ± 23.5 ° seasonal angle variation.
Fig. 3
Fig. 3 (a) Illustration of x-y and x-only movement of the translation stage using a lens-waveguide pair in XY plane (looking into the waveguide). When incident angle is large, field curvature and astigmatism become significant; focal points are not located in the same plane. If the relative movement is x-only, large spot size at oblique angles would lead to efficiency decrease. Therefore x-y movement is important to compensate for the increased spot size. (b) A brief 3D view of the proposed tracking scheme. Only chief rays are shown. At the Equinox, the lens array and the waveguides are aligned in all three dimensions. The system is placed so that the Sun travels in YZ plane at this time of the year. Departure from the Equinox, the single-axis mechanical tracker (x-axis in this figure) rotates the whole structure daily to ensure that the lens array and the channel waveguides are always aligned in z-direction. Relative movement by the translation stage happens only in x-axis and y-axis.
Fig. 4
Fig. 4 (a) The aberration-free lens focuses incoming light onto its paraxial image plane, from which we can estimate the maximum angle after the lens array. (b) A comparison between normal incidence and oblique incidence onto the coupler surface.
Fig. 5
Fig. 5 Plots of (a) incident angles on the coupler surface ψ i ; (b) reflection angles at sidewalls ψ s w ; and (c) reflection angles at the waveguide-substrate interface ψ s u b . Data points from different incident angles collapse to one curve in (c), indicating the oblique incidence has no impact on the y-axis reflection angle. Blue lines mark the acceptable angular range for TIRs.
Fig. 6
Fig. 6 (a) The simulation setup. The x-only detector plane is intentionally moved towards the lens to balance aberrations at large obliquities. (b) Spot radius plot using x-only and x-y tuning. They show huge difference (see Table 1) when incident angle is large. Four spot diagrams for 0 ° , 15.1 ° , 18.5 ° , and 21.3 ° fields are also shown. While x-y tuning suffers only comatic aberration, astigmatism is easily observed in the x-only scenario.
Fig. 7
Fig. 7 Plot of the projection factor cos θ , the estimated Fresnel reflection loss, the TIR coupling efficiency at the coupler η c o u p l i n g and the overall coupling efficiency η o v e r a l l .
Fig. 8
Fig. 8 (a) A schematic of the measurement setup. Incident angle is precisely controlled by the reflection mirror using a goniometer stage. (b) Comparison between simulation and experimental results for both x-y and x-only waveguide movement.

Tables (1)

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Table 1 Field angles and their corresponding spot sizes.

Equations (6)

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θ 1 = δ i arc tan [ 1 2 ( f / D ) ] < θ < θ 2 = δ i + arc tan [ 1 2 ( f / D ) ] ,
k i =k[ cos δ i sin δ i 0 sin δ i cos δ i 0 0 0 1 ][ sinγcosΩ cosγ sinγsinΩ ]( k x , k y , k z ).
ψ i =arccos( k y cosβ+ k z sinβ )> θ cc =arcsin( 1/ n w ).
k r =( k x , k y cos2β+ k z sin2β, k y sin2β k z cos2β )( k x0 , k y0 , k z0 ).
x-axis: ψ sw =| arccos k x k | θ cside =arcsin( 1 n w ),
y-axis: ψ sub =| arccos k y k | θ csub =arcsin( n s n w ),

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