Research Papers

Advanced Dual-Axis Backtracking Improves Output While Reducing Project Costs—Technology That Produces the Best Project Internal Rate of Return in the Solar Industry

[+] Author and Article Information
Kenneth W. Oosting

Founder and CEO
e-mail: Kenneth.oosting@inspiredtech-usa.com

Dustin Keele

Inspired Solar Technologies, Inc.,
5736 Lonetree Boulevard,
Rocklin, CA 95765

Contributed by the Solar Energy Division of ASME for publication in the Journal of Solar Energy Engineering. Manuscript received June 9, 2012; final manuscript received December 21, 2012; published online March 22, 2013. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 135(2), 021017 (Apr 08, 2013) (13 pages) Paper No: SOL-12-1152; doi: 10.1115/1.4023439 History: Received June 09, 2012; Revised December 21, 2012

This paper reviews the results of 3 years of research and development in optimizing solar project internal rate of return (IRR) through various solar mounting strategies, including fixed-mount, single-axis, and dual-axis tracking. Various tracking algorithms are explored. The results of the research show that shadowing from adjacent photovoltaic (PV) arrays, as well as horizon clouds, significantly impact power output in traditional mounting architectures, but that innovative tracking algorithms and array shape can reduce the negative impact of shadowing. These innovations produce greater power output while reducing project costs and substantially increasing project IRR.

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Fabozzi, F., and Grant, J., 2000, Value Based Metrics: Foundations and Practice, Frank J. Fabozzi Associates, New Hope, PA.
Western Regional Climate Center, 2013, “Average Number of Cloudy Days,” http:// www.wrcc.dri.edu/htmlfiles/westcomp.ovc.html
Cess, R. D., Zhang, M. H., Minnis, P., Corsetti, L., Dutton, E. G., Forgan, B. W., Garber, D. P., Gates, W. L., Hack, J. J., Harrison, E. F., Jing, X., Kiehi, J. T., Long, C. N., Morcrette, J.-J., Potter, G. L., Ramanathan, V., Subasilar, B., Whitlock, C. H., Young, D. F., and Zhou, Y., 1995, “Absorption of Solar Radiation by Clouds: Observations Versus Models,” Science, 267, pp. 496–499. [CrossRef] [PubMed]
Appleyard, D., 2011, “PV Trackers Seek Their Place in the Sun,” Renewable Energy World.com, http://www.renewableenergyworld.com/rea/news/article/2011/10/pv-trackers-seek-their-place-in-the-sun
Panico, D., Garvison, P., Wenger, H., and Shugar, D., 1991, “Backtracking: A Novel Strategy for Tracking PV Systems,” Conference Record of the Twenty Second IEEE Photovoltaic Specialists Conference, Las Vegas, NV, October 7–11, pp. 668–673 [CrossRef].
Pfister, G., McKenzie, R. L., Liley, J. B., Thomas, A., Forgan, B. W., and Long, C. N., 2003, “Cloud Coverage Based on All-Sky Imaging and Its Impact on Surface Solar Irradiance,” J. Appl. Meteorol. Climatol., 42(10), pp. 1421–1434. [CrossRef]
Bartky, C. E., 1965, “Theoretical Estimates of Cloud Reflection and Transmission in the Infrared,” Appl. Opt., 4(7), pp. 847–851. [CrossRef]
Lorenzo, E., Narvarte, L., and Muñoz, J., 2011, “Tracking and Back-Tracking,” Prog. Photovoltaics, 19, pp. 747–753. [CrossRef]
Haugen, F., 2009, Basic Dynamics and Control, TechTeach, Skien, Norway.
Oosting, K., and Dickerson, S. L., 1988, “Simulation of a High-Speed Lightweight Arm,” Proceedings of IEEE International Conference on Robotics and Automation, Philadelphia, PA, April 24–29, pp. 494–496. [CrossRef]
Rao, K. R., 2011, Energy and Power Generation Handbook: Established and Emerging Technologies, ASME Press, New York.
Utsa, M. A., Akyazi, O., and Altas, I. H., 2011, “Design and Performance of Solar Tracking System With Fuzzy Logic Controller Used Different Membership Functions,” 7th IEEE International Conference on Electrical and Electronics Engineering (ELECO), Bursa, Turkey, December 1–4, pp. II-381–II-385.
Camacho, E. F., Berenguel, M., Rubio, F., and Martinez, D., 2012, Control of Solar Energy Systems, Springer-Verlag, London.
Armstrong, S., and Hurley, W. G., 2005, “Investigating the Effectiveness of Maximum Power Point Tracking for a Solar System,” IEEE 36th Power Electronics Specialists Conference (PESC'05), Recife, Brazil, June 16, pp. 204–209. [CrossRef]


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Fig. 1

Horizon clouds and horizon features

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Chart 1

Relative electrical output of mounting technologies

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Fig. 2

Advanced dual-axis backtracking amplifies panel efficiency improvements

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Fig. 3

Nonbacktracking mode energy is the double integral represented by the volume under the surface within the confines of the cylinder. Backtracking mode energy is the double integral represented by the volume under the surface but outside the cylinder. The cylinder is the boundary where the sun reaches 45 deg elevation.

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Fig. 4

Large circular test array on dual-axis tracker

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Chart 3

Relative metal content of technologies

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Fig. 5

Field optimization backtracking angle power output value/land use costs

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Fig. 6

Top view of trackers in horizontal/stow position

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Fig. 7

Mechanical advantage of backtracking

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Fig. 8

Nonbacktracking actuator load

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Fig. 9

Backtracking actuator load

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Fig. 10

Live test structures

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Fig. 11

Percent efficiency of photon flux for competing mounting systems

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Fig. 12

Percent efficiency of photon flux for competing mounting systems with shading

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Chart 4

Case study key metrics

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Chart 5

Alternate case study key metrics

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Chart 6

Estimated value contribution from select portable features of advanced dual-axis backtracking

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Chart 7

Estimated relative value contribution from integrated features of advanced dual-axis backtracking




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