Abstract

High-concentration solar-power optics require precise two-axis tracking. The planar micro-optic solar concentrator uses a lenslet array over a planar waveguide with small reflective facets at the focal point of each lenslet to couple incident light into the waveguide. The concentrator can use conventional tracking, tilting the entire assembly, but the system geometry also allows tracking by small lateral translation of the lenslet relative to the waveguide. Here, we experimentally demonstrate such microtracking with the existing concentrator optics and present optimized optical designs for systems with higher efficiency and angle range.

© 2012 Optical Society of America

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References

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  1. S. Kurtz, “Opportunities and challenges for development of a mature concentrating photovoltaic power industry,” NREL Tech. Rep. (2010).
  2. A. W. Bett and H. Lerchenmüller, “The FLATCON system from concentrix solar,” in Concentrator Photovoltaics, A. L. Luque and V. M. Andreev, eds. (Springer, 2007).
    [CrossRef]
  3. J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18, 1122–1133 (2010).
    [CrossRef]
  4. J. P. Morgan, “Light-guide solar panel and method of fabrication thereof,” U.S. patent 7,873,257 B2 (11June2008).
  5. S. Ghosh and D. S. Shultz, “Solar energy concentrator,” U.S. patent 7,672,549 B2 (2March2010).
  6. J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
    [CrossRef]
  7. F. Duerr, Y. Meuret, and H. Thienpont, “Tracking integration in concentrating photovoltaics using laterally moving optics,” Opt. Express 19, A207–A218 (2011).
    [CrossRef]
  8. J. M. Hallas, “Automated micro-tracking planar solar concentrators,” master’s thesis (University of California, San Diego, 2011).
  9. K. Baker, J. Karp, E. Tremblay, J. Hallas, and J. Ford, “Reactive self-tracking solar concentrators: concept, design, and initial materials characterization,” Appl. Opt. 51, 1086–1094 (2012).
  10. A. Rabl, Active Solar Collectors and Their Applications(Oxford University, 1985).
  11. D. Moore, G. R. Schmidt, and B. Unger, “Concentrated photovoltaic stepped planar light guide,” in International Optical Design Conference, OSA Technical Digest (CD) (Optical Society of America, 2010), paper JMB46P.
  12. B. L. Unger, “Dimpled planar lightguide solar concentrators,” Ph.D. dissertation (University of Rochester, 2010).

2012 (1)

2011 (1)

2010 (2)

J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18, 1122–1133 (2010).
[CrossRef]

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

Baker, K.

Bett, A. W.

A. W. Bett and H. Lerchenmüller, “The FLATCON system from concentrix solar,” in Concentrator Photovoltaics, A. L. Luque and V. M. Andreev, eds. (Springer, 2007).
[CrossRef]

Duerr, F.

Ford, J.

Ford, J. E.

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18, 1122–1133 (2010).
[CrossRef]

Ghosh, S.

S. Ghosh and D. S. Shultz, “Solar energy concentrator,” U.S. patent 7,672,549 B2 (2March2010).

Hallas, J.

Hallas, J. M.

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

J. M. Hallas, “Automated micro-tracking planar solar concentrators,” master’s thesis (University of California, San Diego, 2011).

Karp, J.

Karp, J. H.

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18, 1122–1133 (2010).
[CrossRef]

Kurtz, S.

S. Kurtz, “Opportunities and challenges for development of a mature concentrating photovoltaic power industry,” NREL Tech. Rep. (2010).

Lerchenmüller, H.

A. W. Bett and H. Lerchenmüller, “The FLATCON system from concentrix solar,” in Concentrator Photovoltaics, A. L. Luque and V. M. Andreev, eds. (Springer, 2007).
[CrossRef]

Meuret, Y.

Moore, D.

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

Morgan, J. P.

J. P. Morgan, “Light-guide solar panel and method of fabrication thereof,” U.S. patent 7,873,257 B2 (11June2008).

Rabl, A.

A. Rabl, Active Solar Collectors and Their Applications(Oxford University, 1985).

Schmidt, G. R.

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

Shultz, D. S.

S. Ghosh and D. S. Shultz, “Solar energy concentrator,” U.S. patent 7,672,549 B2 (2March2010).

Thienpont, H.

Tremblay, E.

Tremblay, E. J.

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

J. H. Karp, E. J. Tremblay, and J. E. Ford, “Planar micro-optic solar concentrator,” Opt. Express 18, 1122–1133 (2010).
[CrossRef]

Unger, B.

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

Unger, B. L.

B. L. Unger, “Dimpled planar lightguide solar concentrators,” Ph.D. dissertation (University of Rochester, 2010).

Appl. Opt. (1)

Opt. Express (2)

Proc. SPIE (1)

J. M. Hallas, J. H. Karp, E. J. Tremblay, and J. E. Ford, “Lateral translation micro-tracking of planar micro-optic solar concentrator,” in Proc. SPIE 7769, 776904 (2010).
[CrossRef]

Other (8)

J. M. Hallas, “Automated micro-tracking planar solar concentrators,” master’s thesis (University of California, San Diego, 2011).

J. P. Morgan, “Light-guide solar panel and method of fabrication thereof,” U.S. patent 7,873,257 B2 (11June2008).

S. Ghosh and D. S. Shultz, “Solar energy concentrator,” U.S. patent 7,672,549 B2 (2March2010).

S. Kurtz, “Opportunities and challenges for development of a mature concentrating photovoltaic power industry,” NREL Tech. Rep. (2010).

A. W. Bett and H. Lerchenmüller, “The FLATCON system from concentrix solar,” in Concentrator Photovoltaics, A. L. Luque and V. M. Andreev, eds. (Springer, 2007).
[CrossRef]

A. Rabl, Active Solar Collectors and Their Applications(Oxford University, 1985).

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

B. L. Unger, “Dimpled planar lightguide solar concentrators,” Ph.D. dissertation (University of Rochester, 2010).

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Figures (14)

Fig. 1.
Fig. 1.

Illustration of planar micro-optic solar concentrator operation. (a) Lenslets and microprisms direct sunlight into a slab waveguide with edge-mounted PV cells and (b) perspective view with one lenslet illuminated [3,6].

Fig. 2.
Fig. 2.

Normally incident light is focused by the lenses in the array onto reflective facets on the waveguide surface, which inject the light into guided modes (a) light that is tilted with respect to the concentrator is focused onto laterally shifted spots that miss the coupling features; (b) these spots can be recoupled by laterally translating the waveguide; and (c) lateral translation [8].

Fig. 3.
Fig. 3.

Plot of path and irradiance of Sun in San Diego over the course of a year. (Path data courtesy of University of Oregon, Solar Radiation Monitor Laboratory.)

Fig. 4.
Fig. 4.

Peak intensity of sunlight as a function of angle (a) over the course of three example days and (b) over the course of a full year for a fixed flat panel tilted at latitude in San Diego, California. (c) and (d) The same are shown for a one-dimensional (1D) mechanically tracked system tilted at latitude [9,10].

Fig. 5.
Fig. 5.

Ray-trace diagrams at discrete angles up to 35 deg using the wavelength spectrum of sunlight (left) and corresponding plots of encircled energy versus radius from centroid (right) for (a) the prototype singlet, (b) an optimized singlet, (c) a refractive doublet, and (d) a reflective lens. The dashed line at 30 μm corresponds to the radius of the coupling feature used in the prototype.

Fig. 6.
Fig. 6.

Optical coupling of light reflected from a 120 deg angled injection facet as a function of external incidence angle (including surface refraction, but not lens effects) for an F2 (n=1.62) waveguide with an air cladding. The vertical–horizontal coupling asymmetry seen in the lower graph results from light reflecting from the adjacent facet and emitting from the entrance aperture [9].

Fig. 7.
Fig. 7.

Optical efficiency as a function of angle for 128× geometric concentration for (a) the prototype, (b) the optimized singlet, (c) the optimized doublet, and (d) the reflective design.

Fig. 8.
Fig. 8.

Simulated optical efficiency versus geometric concentration using the three different lens designs with coupling feature width optimized at 128× concentration illuminated by on-axis sunlight.

Fig. 9.
Fig. 9.

Experimental setup, including the concentrator mounted onto an alignment stage and a rotation stage illuminated by an Xe arc lamp [8].

Fig. 10.
Fig. 10.

Normalized optical efficiency versus angle of incidence (a) perpendicular and (b) parallel to prism direction [6].

Fig. 11.
Fig. 11.

(a) Initial position of cams with lenses centered above injection elements, (b) demonstration of lateral motion with the pair of cams moving together for one axis of motion and the bottom cam providing the other axis, and (c) rotation is achieved by moving one of the two cams on the same side with respect to the other [6].

Fig. 12.
Fig. 12.

Frame and eccentric cams are made out of anodized aluminum coated in Teflon for low-friction contact with the lens array. A spring keeps the lens array in contact with the cams. (a) Top view with cover, (b) top view with cover removed, and (c) bottom view showing stepper motor mounting and worm drives [6].

Fig. 13.
Fig. 13.

Figure showing fabricated system. (a) Bottom view of partially assembled microtracking platform, (b) top view with attached solar cell, and (c) system without solar cell demonstrating bright output [8].

Fig. 14.
Fig. 14.

Plot of normalized optical efficiency versus time for an untracked system (red), a system that tracks the Sun using a hill-climbing algorithm (blue) and the expected response from the tracked system based on geometrical losses, intensity reduction, and off-axis performance of the system (green) [8].

Tables (1)

Tables Icon

Table 1. Annual Percentage of Energy Incident on Panel Collected for Simulated Lens Designs

Metrics