This document provides a summary of a research project on modeling the degradation of solar photovoltaic modules over time. It examines modules installed at two solar power plants in India - a 1 MW plant on an ash dyke and a 1 MW canal top plant. Testing showed canal top modules had lower temperatures and higher performance. The project developed loss models and found polycrystalline modules degraded 1.73-3.89% annually at one plant and 0.17-1.95% at the other. Regular cleaning can avoid a 1.61% efficiency loss from soiling. The models matched simulated results within a few percent.

1. Internal Guide:
Prof. M. Natarajan
VIT University, Vellore,TN
External Guide:
Dr. Sagar Agravat
Scientist-C, GERMI, Gujarat

2.  Introduction
 Literature review
 Methodology
 Work Done
 Results & Discussion
 Verification
 Conclusion
 References

3. Scope:
Impact on energy generation due to degradation of
solar PV modules installed at Solar PV power plant
since the date of installation till the present date and
develop a reliability model for future solar PV plant
installations.

4. » Degradation Study of PV modules installed at solar PV
power plant
» Comparison between performance of ground mounted
& canal top mounted modules
» Development of Loss Models
» Reliability Evaluation of Solar PV Power Plant based on
Loss Models developed

5. » On global survey of degradation rate, it was
analyzed that mono-crystalline technology has
undergone minimum range of degradation while
the rate of degradation for polycrystalline
technology varied in a wide range
» Outdoor Testing along with Data Acquisition
System were the most reliable analysis
methodology
» Several models for evaluating degradation were
reported.
» Faulty PV identification and dynamic thermal
model to evaluate instantaneous thermal effect
on performance were remarkable.

6.  GTPS 1MW Solar PV
Power Plant
» Technology: Multi-Tech
» Located above closed
(filled) ash dyke of
GSECL's Gandhinagar
Thermal Power Station
» Latitude: 23°16' N
» Longitude: 72°40' E
» Operating since: Aug‘11
 1 MW Narmada Canal
Top Solar PV Power
Plant
» Technology: Poly-
crystalline
» Located above
Narmada river canal at
Sanand, Gujarat
» Latitude: 23°05' N
» Longitude: 72°18' E
» Operating since: Aug‘11

7. 1 MW Narmada Canal Top Solar PV Power Plant
GTPS 1MW Solar PV Power Plant

8. Parameter GTPS
Module
Technology
Poly-crystalline CIGS
[Copper Indium
Gallium
Selenide]
A-Si
[Amorphous-Si]
Mono-crystalline CdTe
[Cadmium
Telluride]
Capacity of each
PV module (Watt)
240 235 95 107 250 85
Total no. of each
PV module
2088 432 1056 924 405 1170
Total DC Capacity
(Watt)
500400 101520 100320 98868 101250 99450
Type of Inverter Central String
Capacity Of
Inverter (kW)
500 7
Total no. of
Inverter
1 75
Total Capacity of
Inverter (kW)
1025

9. Parameter Narmada Canal Top Plant
Module Technology
Poly-crystalline
Capacity of each PV
module (Watt)
275 280 285
Total no. of each PV
module
1056 2480 80
Total DC Capacity
(Watt)
290400 694400 22800
Type of Inverter Central
Capacity Of Inverter
(kW)
220
Total no. of Inverter 4
Total Capacity of
Inverter (kW)
880

10. PV Modules
Polycrystalline-2088, 240Wp
DC Junction Box
Central Inverter
Transformer
HT Bus-bar
HT PanelHT Panel Transformer
PV Modules
I. Poly-crystalline-432, 235Wp
II. Mono-crystalline-405, 250Wp
III. Thin Film
a. A-Si-924, 107Wp
b. CdTe-1170, 85Wp
c. CIGS-1056, 95Wp
String Inverter
Power Distribution Box
Low Voltage Distribution Box
Transmission
Tower
11KV AC

13. 1. Degradation of Modules
Outdoor Testing using sun simulator along with Data
Acquisition System

14. 1 set of reading takes place at:
i. 15 minute duration
ii. Equal radiation
iii. Equal wind speed
iv. Equal cloud casting
v. Equal ambient temperature
 4 modules were tested for
each set of readings
 Canal Top (CT) reference &
Ground Mounted (GM)
reference modules were tested
at every set periodic
assessment of performance
 Readings for GM Test & CT Test
modules were taken from
different modules mounted
respectively
 Readings from CT Test & GM
Test modules intimidated the
overall performance trend of
plant
2. Comparison of ground mounted & canal top
mounted modules:

15. Calculation of In-plane Radiation
Incident Angle Modifier (IAM) Factor
Effect in Module Temperature
% Variation in Efficiency due to change in Temperature
Power Calculation for 1 module
% of Power loss due to DC & Cable Loss
% of Power Loss due Conversion Losses

17. y = 0.0661x2 - 0.2796x + 41.41
R² = 0.0761
y = 0.05x2 + 0.59x + 47.26
R² = 0.7328
30.0
35.0
40.0
45.0
50.0
55.0
0 1 2 3 4 5 6 7
Temperature(°C)
Set Number
Temperature Difference between Canal Top & Ground Mounted Reference Modules
CT ref
GM ref
Poly. (CT ref)
Poly. (GM ref)
Average difference is 10°C
y = 0.1393x2 - 0.9321x + 41.3
R² = 0.1875
y = 0.2643x2 - 1.4729x + 50.38
R² = 0.5757
30.0
35.0
40.0
45.0
50.0
55.0
0 1 2 3 4 5 6 7
Temperature(°C)
Set Number
Temperature Difference between Canal Top & Ground Mounted Temp
CT test
GM test
Poly. (CT test)
Poly. (GM test)
Average difference is 10°C

18. y = -0.1559x + 40.89
R² = 0.5133
y = -0.0298x + 44.233
R² = 0.1736
35.00
36.00
37.00
38.00
39.00
40.00
41.00
42.00
43.00
44.00
45.00
0 2 4 6 8 10 12 14
OCVoltage(V)
Set Number
Canal Top & Ground Mounted Open Circuit Voltage Difference
GM Voc
CT Voc
Linear (GM Voc)
Linear (CT Voc)
Average difference is 4V

19. y = 0.0786x2 - 0.6046x + 35.086
R² = 0.8393
y = 0.033x2 - 0.1521x + 33.973
R² = 0.3403
33.4
33.6
33.8
34
34.2
34.4
34.6
34.8
0 1 2 3 4 5 6 7
VoltageatMaximumPower(Vmpp)
Set Number
CT Vmpp
GM Vmpp
Poly. (CT Vmpp)
Poly. (GM Vmpp)
Maximum Voltage difference between Canal Top & Ground Mounted Reference Modules

20. y = 0.0147x2 - 0.2762x + 15.384
R² = 0.36
y = 0.0266x2 - 0.4447x + 16.212
R² = 0.8392
13
13.5
14
14.5
15
15.5
16
16.5
0 2 4 6 8 10 12 14
Efficiency(%)
Set Number
Canal Top & Ground Mounted Efficiency Difference
GM Efficiency
CT Efficiency
Poly. (GM Efficiency)
Poly. (CT Efficiency)

21. 40.0
42.0
44.0
46.0
48.0
50.0
52.0
10.00
12.00
14.00
16.00
18.00
set 1 set 2 set 3 set 4 set 5 set 6
Temperature(°C)
Efficiency(%)
Set Number
Effect on Efficiency due to Temperature (Test) Efficiency
Temperature

22. 20.0
25.0
30.0
35.0
40.0
45.0
10.00
15.00
20.00
set 1 set 2 set 3 set 4 set 5 set 6
Temperature(°C)
Efficiency(%)
Set Number
Canal Top: Effect of Temperature (Test) on Efficiency
Efficiency
Temperature

23. 100.00
120.00
140.00
160.00
180.00
200.00
220.00
240.00
260.00
280.00
300.00
860
870
880
890
900
910
920
930
1 2 3 4 5 6 7 8 9 10 11 12 13
Power(W)
Radiation(Wm-2)
Set Number
Canal Top Power vs Radiation CT Radiation
CT Power
255.00
260.00
265.00
270.00
275.00
280.00
850
860
870
880
890
900
910
920
930
1 2 3 4 5 6 7 8 9 10 11 12 13
Power(W)
Radiation(Wm-2)
Set Number
Ground Mounted Power vs Radiation GM Radiation
GM Power

24. y = 279.24x-0.014
R² = 0.4325
y = 250.17x0.0596
R² = 0.6779
230.00
240.00
250.00
260.00
270.00
280.00
290.00
0 1 2 3 4 5 6 7
P
o
w
e
r
Set Number
Canal Top & Ground Mounted Power CT ref
GM ref

25. y = -1.0946x2 + 13.214x + 237.67
R² = 0.736
245.00
250.00
255.00
260.00
265.00
270.00
275.00
280.00
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Power(W)
Set Number
Dust Accumulation
Output Power
Poly. (Output Power)

26. » Mono-crystalline modules: 2.16-2.95% per year
» CdTe modules:0.48-2.92% per year
» A-Si modules: 9.85-11.16% per year
» Poly-crystalline modules:
 GTPS: 1.73-3.89 % per year
 Narmada Canal Top Plant: 0.17-1.95 % per year
 Canal top mounted modules had an all time lower
temperature than ground mounted modules thereby
had higher open circuit voltage and efficiency
 Soiling reduces power output by: 24-25.6 W
efficiency by :1.08-1.61%

27.  Calculation of In-plane Radiation: 523.527 Wm-2
 Error: 0.05461-0.13181%
 Incident Angle Modifier (IAM) Factor: 0.942 to 0.411
 % Drop in Module Temperature due to Wind: 9.821%
 Variation in Efficiency due to change in Temperature: 0.54%
 Power Calculation for 1 module:
Poly-crystalline: 96.97 W, Mono-crystalline: 108.48 W, A-Si: 42.4 W, CdTe:
38.46 W, CIGS: 41.81 W
 Total power output:
Poly-crystalline: 244364.4 W, mono-crystalline: 43934.4 W, A-Si: 39177.6 W,
CdTe: 40786.2 W, CIGS: 44151.36 W
 Ohmic loss: 0.5576%-1.8958%. The ohmic losses were observed to be
more at higher values of irradiance.
 Conversion loss: 0.17%-4.50%. At times of inverter failure, conversion
losses were as high as 19.36%.
 Inverter efficiency: At an average, the efficiency of inverter was in the
range of 96.97-98.43%

28. The loss parameters obtained closely match with
that of simulated results with an average
deviation of
 2% for IAM Factor
 3.78% for power loss due to temperature
 0.22% for ohmic loss
 0.07% for inverter efficiency
VERIFICATION:

30. 0
20000
40000
60000
80000
100000
120000
140000
160000
180000
Energy(kWh)
Month
Simulated and Real Time Generation
2013 simulated
2013 real time
2014 simulated
2014 real time

31.  Average rate of degradation: nearly 1%
GTPS: 2.81% NCT: 1.06%
 Expected plant performance:
GTPS Ash-dyke Plant: up to 2037
Narmada Canal Top Plant: up to 2048
 Regular cleaning is required to avoid power and
efficiency loss by nearly 25W and 1.61 %
respectively for each module
 The model developed and results obtained for
losses nearly matches with theoretical simulation

32. 1. Mukadam K, Chenlo F, Rebollo L, Matas A, Zarauza L, Valera P, Garcia P. Three years of operation
and experience of the 1 MW photovoltaic plant. Proceedings of the 14th European Photovoltaic
Solar Energy Conference, Barcelona, Spain, 1997; 705–708.
2. Alonso-Abella M, Chenlo F, Vela N, Chamberlain J, Arroyo R, Alonso Martínez FJ. Toledo PV plant
1MWp—10 years of operation.Proceedings of the 20th European Photovoltaic Solar Energy
Conference, Barcelona, Spain, 2005; 2454–2457.
3. Marion B, del Cueto J, McNutt P, Rose D. Performance summary for the first solar CdTe 1-kW
system, NREL/CP-520-30942, Lakewood, CO, USA, October 2001.
4. Multi-pronged analysis of degradation rates of photovoltaic modules and arrays deployed in
Florida; K. O. Davis1*, S. R. Kurtz2, D. C. Jordan2, J. H. Wohlgemuth2 and N. Sorloaica-Hickman1
5. Realini A. Mean time before failure of photovoltaic modules, Federal Office for Education and
Science, Final report BBW 99.0579, June 2003.
6. Realini A, Burá E, Cereghetti N, Chianese D, Rezzonico S, Sample T, Ossenbrink H. Study of a 20
year old PV plant (MTBF project).Proceedings of the 17th European Photovoltaic Solar Energy
Conference, Munich, Germany, 2001; 447–450.
7. Marion B, Adelstein J. Long-term performance of the SERF PV systems. Proceedings of the NCPV
and Solar Programme Review Meeting, Denver, 24–26 March 2003; 199–201. NREL/CD-520-
33586.
8. Carr AJ, Pryor TL. A comparison of the performance of different PV module types in temperate
climates.SolarEnergy2004; 76:285–94.

33. 9. McNutt P, Adelstein J, Sekulic W. Performance evaluation of a 1.5-kW a-Si PV array using the PVUSA
power rating method at NREL's outdoor test facility, 2005 DOE Solar Energy Technologies Program
Review Meeting, Denver, CO, USA, NREL/CP-520-38971, November 2005.
10. Adelstein J, Sekulic W. Small PV systems performance evaluation at NREL's outdoor test facility
using the PVUSA power rating method, 2005 DOE Solar Energy Technologies Program Review Meeting,
Denver, CO, USA, NREL/CP-520-39135, November2005.
11. Akamoto S, Oshiro T. Dominant degradation of crystalline silicon photovoltaic modules
manufactures in 1990 20th EPSEC 2005.
12. Dunlop ED, Halton D. The performance of crystalline silicon photovoltaic solar modules after 22
years of continuous outdoor exposure. Progress in Photovoltaics Research and Applications 2006;
14:53–64.
13. Raghuraman B, Lakshman V, Kuitche J, ShislerW, Tamizh Mani G, Kapoor H. An overview of SMUD’s
outdoor photovoltaic test program at Arizona State University. IEEE; 2006.
14. Foster RE, Gómez Rocha LM, Gupta VP, Sánchez-Juárez A, Cruz JO, Rosas JC. Field testing of CdTe PV
modules in Mexico.Proceedings of the 35th American Solar Energy Society Annual Solar Conference,
Denver, CO, USA, 2006.
15. Hedström J, Palmblad L. Performance of old PV modules: measurement of 25 years old crystalline
silicon modules, Elforsk Rapport 06:71, October 2006.
16. Guastella S. Assessment of PV plant performance in Italy. Proceedings of the 22nd European
Photovoltaic Solar Energy Conference, Milan, Italy, 2007; 2884–2888.
17. Rüther R, Knob P, Beyer HG, Dacoregio MM, Montenegro AA. High performance ratios of a double-
junction a-Si BIPV grid-connected installation after five years of continuous operation in Brazil.
Proceedings of the 3rd World Conference on PV Energy Conversion, Osaka, Japan, 2003; 2169–2172.

34. 18. Rüther R, Dacoregio M, Salamoni I, Knob P, Bussemas U. Performance of the first grid-connected,
BIPV installation in Brazil over eight years of continuous operation. Proceedings of the 21st European
Photovoltaic Solar Energy Conference, Dresden, Germany, 2006; 2761–2764.
19. Apicella F, Giglio V, Pellegrino M, Ferlito S, Tanikawa F, Okamoto Y, Thin film modules: long term
operational experience in Mediterranean climate. Proceedings of the 23rd European Photovoltaic
Solar Energy Conference, Valencia, Spain, 2008;3422–3425. DOI: 10.4229/23rdEUPVSEC2008-
5BV.2.21.
20. Case study of two different photovoltaic technologies; Kristopher Davis, H. Moaveni
21. Quintana MA, King DL, Hosking FM, Kratochvil JA, Johnson RW, Hansen BR, Dhere NG, Pandit MB.
Diagnostic analysis of silicon photovoltaic modules after 20-year field exposure. Proceedings of the
28th PV Specialists Conference, Anchorage, AK, USA, 2000; 1420–1423. DOI:
10.1109/PVSC.2000.916159
22. Reis AM, Coleman NT, Marshall MW, Lehman PA, Chamberlin, CE. Comparison of PV module
performance before and after 11-years of field exposure. Proceedings of the 29th PV Specialists
Conference, New Orleans, LA, USA, 2002; 1432–1435.
23. Saleh IM, Abouhdima I, Gantrari MB. Performance of thirty years standalone photovoltaic system.
Proceedings of the 24th European Photovoltaic Solar Energy Conference, Hamburg, Germany, 2009;
3995–3998. DOI: 10.4229/24thEUPVSEC2009-5DO.7.6.
24. Adelstein J, Sekulic B. Performance and reliability of a 1-kW amorphous silicon photovoltaic roofing
system. Proceedings of the 31st PV Specialists Conference, Lake Buena Vista, FL, USA, 2005; 1627–
1630. DOI: 10.1109/PVSC.2005.1488457.

35. 25. Pietruszko SM, Fetlinski B, Bialecki M. Analysis of the performance of grid connected photovoltaic
system. Proceedings of the 34th IEEE PV Specialist Conference, Philadelphia, PA, USA, 2009; 48–51. DOI:
10.1109/PVSC.2009.5411757.
26. Vignola F, Krumsick J, Mavromatakis F, Walwyn R. Measuring degradation of photovoltaic module
performance in the field.Proceedings of the 38th American Solar Energy Society Annual Solar
Conference, Buffalo, NY, USA, 2009
27. Dhere NG, Pethe SA, Kaul A. Photovoltaic module reliability studies at the Florida Solar Energy
Center. Reliability Physics Symposium (IRPS) 2010; 306–311. DOI: 10.1109/IRPS.2010.5488813.
28. Dhere NG, Pethe SA, Kaul A. PV module reliability and durability studies at the FSEC PV Materials
Lab, NREL PV Module Reliability Workshop, Golden, CO, USA, February
2010,http://www1.eere.energy.gov/solar/pv_module_reliability_workshop_2010.html
29. Musikowski HD, Styczynski AZ. Analysis of the operational behavior and long-term performance of a
CIS PV system. Proceedings of the 25th European Photovoltaic Solar Energy Conference, Valencia, Spain,
2010; 3942–3946. DOI: 10.4229/25thEUPVSEC2010-4DO.11.4.
30. Sastry O S, Sriparn S, Shil S K, Pant P C, Kumar R, Kumar A, et al. Performance analysis of the field
exposed single crystalline silicon module. Solar Energy Material and Solar cells2010; 94:1463–8.
31. Sanchez-Friera P, Piliougine M, Pelaez J, Carretero J, Sidrach de Cardona M. Analysis of degradation
mechanisms of crystalline silicon PV modules after 12 years of operation in Southern Europe. Progress in
Photovoltaics: Research and Application 2011
32. Jordan DC, Kurtz SR. Thin-film reliability trends toward improved stability. Proceedings of the 37th
PV Specialists Conference, Seattle, WA, USA, 2011.
33. George Makrides, Bastian Zinsser, Markus Schubert, George E. Georghiou; Performance loss rate of
twelve photovoltaic technologies under field conditions using statistical techniques; Department of
Electrical and Computer Engineering, University of Cyprus, Institute for Photovoltaic-University of
Stuttgart, Germany.

36. 34. Vikrant Sharma, O.S. Sastry , Arun Kumar, Birinchi Bora, S.S. Chandel; Degradation analysis of a-Si,
(HIT) hetero-junction intrinsic thin layer silicon and m-C-Si solar photovoltaic technologies under outdoor
conditions.
35. M. Torres-Ramírez, G. Nofuentes, J.P. Silva, S. Silvestre, J.V. Munoz; Study on analytical modeling
approaches to the performance of thin film PV modules in sunny inland climates.
36. Yihua Hua, Bin Gao b,⇑, Xueguan Song c, Gui Yun Tian b, Kongjing Li c, Xiangning He; Photovoltaic fault
detection using a parameter based model.
37. J.-P. Charles, F. Hannane, H. El-Mossaoui, A. Zegaoui, T.V. Nguyen, P. Petit, M. Aillerie; Faulty PV panel
identification using the Design of Experiments (DoE) method.
38. Tao Ma, Hongxing Yang, Lin Lu; Development of a model to simulate the performance characteristics
of crystalline silicon photovoltaic modules/strings/arrays.
39. Diego Torres Lobera, Seppo Valkealahti; Dynamic thermal model of solar PV systems under varying
climatic conditions.
40. L.M. Ayompe, A. Duffy, S.J. McCormack, M. Conlon; Validated real-time energy models for small-scale
grid-connected PV-systems.
41. Thomas Huld, Gabi Friesen, Artur Skoczek, Robert P. Kenny, Tony Sample, Michael Field a, Ewan D.
Dunlop; A power-rating model for crystalline silicon PV modules.
42. Manuel Va´zquez and Ignacio Rey-Stolle; Photovoltaic Module Reliability Model Based on Field
Degradation Studies.
43. K.H. Lam, J. Close, W. Durisch; Modeling and degradation study on a copper indium diselenide module.