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Effects of Degradation on Solar

Photovoltaic Systems

Katherine A. Kim, Pradeep S. Shenoy, and Philip T. Krein ECE Department

University of Illinois at Urbana-Champaign

Power Affiliates Program Meeting May 4, 2012

• “Go Green” – Reduce carbon emissions – Utilize renewable energy

• Lower electricity cost • Tax Benefits

Motivation

2

Customer Perspective

• Installation Costs – Equipment – Labor

• Warranty (25 years) • Maintenance

– Upkeep – Part replacement

• Payback time

Engineering Perspective

• Efficiency • Reliability • Fault-tolerance

Solar PV Considerations

3

Maximize System W/$

Weakness = Mismatch

Enemies

1. Dust accumulation 2. Partial shading

3. Degradation

If PV was a Superhero…

4

[http://www.applied-solar.info]

PV Mismatch

5

Each Panel Series String

(with bypass diode)

PV Mismatch

6

Wde HiPerforma™ 245 W - 240 W

Vd SuperPoly 285 W - 290 W

PV Cell Binning

7

Vd 275 W - 280 W

[Images: http://am.suntech-power.com/]

• Laborious • Adds Cost

Huge effort to reduce mismatch

PV Cell Binning

8

Wde HiPerforma™ Vd Vd SuperPoly

• Mean, μ – decreases over time – 1 to 0.5% per year (Si)

• Standard Deviation, σ – increases over time – More studies required

PV Degradation Model

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[3] Vazquez and Stolle

[http://www.poweredbysearch.com/canadian-seo]

Variation Effects on String Power

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Variation Effects on String Power

11

CV =𝜎𝜇

Cascaded Architecture Differential Architecture

Overcoming Mismatch

12

Cascaded Architecture Differential Architecture

Overcoming Mismatch

13

• Panel level control

• Converters – Process 100% power – Rated for panel

• Higher Cost

• Panel level control

• Converters – Process fraction of power – Rated less than panel

• Lower Cost

Increased power at Lower cost Increased W/$

• PV System Design Goal: Maximize watt per dollar (W/$)

• PV mismatch greatly reduces output power • Cell binning reduces mismatch within panel • Degradation over time

– Mean power decreases – Standard deviation increases

• Differential Power processing – Overcome string variation losses – Higher efficiency, lower cost than cascaded

Summary

14

1. J. Poortmans, et al., “Linking nanotechnology to gigawatts: Creating building blocks for smart PV modules,” Progress in Photovoltaics: Research and Appl., vol. 19, no. 7, pp. 772–780, 2011.

2. S. Poshtkouhi. A. Biswas, and O. Trescases, "DC-DC converter for high granularity, sub-string MPPT in photovoltaic applications using a virtual-parallel connection," in Proc. IEEE Applied Power Electron. Conf. Expo., pp.86-92, Feb. 2012.

3. M. Vazquez and I. Rey-Stolle, “Photovoltaic module reliability model based on field degradation studies,” Progress in Photovoltaics: Research and Appl., vol. 16, no. 5, pp. 419–433, 2008.

4. D. C. Jordan and S. R. Kurtz. “Photovoltaic degradation rates—an analytical review,” Progress in Photovoltaics: Research and Appl., Oct. 2011.

5. A.M. Reis, et al., "Comparison of PV module performance before and after 11-years of field exposure," in Proc. of Photovoltaic Specialists Conf., pp. 1432- 1435, May 2002.

6. P. Sanchez-Friera, et al., “Analysis of degradation mechanisms of crystalline silicon PV modules after 12 years of operation in Southern Europe,” Progress in Photovoltaics: Research and Appl., vol. 19, no. 6, pp. 658–666, 2011.

7. G. R. Walker and P. C. Sernia, “Cascaded DC-DC converter connection of photovoltaic modules,” IEEE Trans. Power Electron., vol. 19, no. 4, pp. 1130-1139, July 2004.

8. P. S. Shenoy, B. Johnson, P. T. Krein, "Differential power processing architecture for increased energy production and reliability of photovoltaic systems," in Proc. IEEE Applied Power Electron. Conf. Expo., pp.1987-1994, Feb. 2012.

Selected References

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Acknowledgments

• Advanced Research Projects Agency-Energy (ARPA-E) The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000217. The information, data, or work presented herein was funded in part by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

• Grainger Center for Electric Machinery and Electromechanics (CEME)

• National Science Foundation (NSF) through the Graduate Research Fellowship Program

• Colleagues in the Power and Energy Systems Group

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Questions?

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Photo by Helen Hwang