The information cont

2014 PV Module Reliability Workshop • Golden, Colorado • Feb

NREL is a national laboratory of the U. S. Department of Energy

and Renewable Energy, operated by the Alliance fo

Results of I-V Curves and Visual Inspection of PV Modules Deployed at TEP Solar Test Yard Peter McNu

David Miller, Blaise 

• IR images quickly detect problem• Visual inspection after IR image u

of problem

• Testing should be done by teams 

closely together

• Best procedure would be to scan 

camera, then take visual photos a

• Major visual defects included EVA 

marks, oozing adhesive, backshe

• Some modules show no signs of • Overall, after being deployed fro

found to be operating fairly well, their nameplate rating

• NREL is looking for other older PV 

• Contact: Peter McNutt | peter.mcn

• TEP Solar Test Yard PV Site Visit - 2013/2/05), David Miller, NREL, April 2013. • I-V Curves and Visual Inspection of 250 PV Modules Deployed over 2 Years in Tucson, Emily S. Kopp 

et al, University of Arizona, Tucson, 2012

• Development of a Visual Inspection Data Collection Tool for Evaluation of Fielded PV Module 

Condition, Corrine Packard et al, NREL, August 2012.

• PV SYSTEM REPORTS AT THE TEP SOLAR TEST YARD – available at 

http://uapv.physics.arizona.edu/pdfs/teptestyard_field_IVcurves.pdf

• Historic data for the TEP Solar Test Yard site is also available on the website 

http://uapv.physics.arizona.edu/dlpvdata.php

The authors would like to thank Adria Brook (U of AZ) and Randy Hunsberger (NREL), 

Work done under DOE Agreement # DE-AC36-08GO28308

• Solmetric PVA-600 PV analyzer• 600 Vdc and 20 Adc• Capacitive load• Operating temperature -00C to 500C• ~ $5000• Type K thermocouple • 1.00C resolution and accuracy• Range -1000C to 2000C

• Wireless connection to PVA-600• Field measurements include performance factor of 

PV modules or strings (measured / expected) 

• FLIR T440 IR camera• 320 x 240 pixel resolution• < 0.045 thermal sensitivity• Temperature range -200C to 12000C

• 7.5 to 13um spectral range• ~ $11,000

• Perform visual inspection 

(per Packard 2012 paper)

• Take IR images• Take photos• Take I-V traces 

I-V traces of 3 modules 

one “bad” & two “good

“bad” “good”

comparison of “bad” (56%) and “good” (88%) modu

• Crystalline Si Module• glass superstrate and 

polymeric backsheet

• Deployed 2006• String I-V performance 

ranged between 78% to 89% (measured 2 strings of 

9 modules – range was 58% to 89% in 2012 Kopp paper measuring 9 individual modules)

• Observed hot spots on 

2 out of 18 modules

• Crystalline Si • Deployed ~ 2003• Glass superstrate and 

polymeric backsheet

• All 16 modules have 

bubbles in backsheet 

• Discoloration pattern 

around j-box, parallel bus lines, and cell edges

• In 2014, measured values divided 

by nameplate ratings were 44% and 94% for 2 modules

• In 2012 Kopp paper, the rating 

ranged from 44% to 94% for 8 modules

• Module Nameplate Ratings:• Pmp = 180 W• Voc = 66.4V• Isc = 3.65A

• 65% of nameplate rating I-V trace –

9 module string

• String STC Nameplate Ratings (9 modules):• Pmp = 1521 W• Voc = 388 V• Isc = 5.46 A

• Module STC Nameplate Ratings:• Pmp = 170 W• Voc = 44 V• Isc = 5.4 A• Imp = 4.9 A• Vmp = 34.7 V

Manufacturer A

• The purpose of the PV Service Life Prediction project is to examine & report 

on how modules fielded 5 or more years are holding up 

• Testing performed January 13-16, 2014• NREL compared test results to 2012 testing performed by University of 

Tucson (Kopp, et. al.) as well as against STC nameplate ratings

• Details of module tests from three manufactures are presented• Present the common problems crystalline-silicon and thin-film modules exhibit

Crystalline-Silicon modules

most have glass superstrates and polymeric backsheets

(manufacturer)

D. 9 modules, deployed 2004 - 8 modules have typical EVA browning (1 recent 

replacement); All have loose j-box lids; Labels have fallen off all modules. Output (IV) of 3 modules ~ 82% of nameplate rating (see photo 1)

E. 10 modules, deployed ~ 2003 – 10 modules show no visible signs of defects. 

2 modules ~ 76% of nameplate. 

F. 8 modules, deployed ~ 2000) – all show typical EVA browning. No I-V taken.G. 15 modules, deployed 2009 - 1 module had burn mark on the back; all modules have 

frame adhesive oozing out of frames onto module front No I-V taken.

H. 9 modules, deployed 2003 – no visual defects. 2 modules ~ 72% of nameplate. I. 8 modules, deployed 2003 - All modules had some bubbles and ridges between cells in 

backsheet; EVA discoloration. 3 modules ~ 72% of nameplate. 

J. 20 modules, deployed 2000 - Typical (but not pronounced) EVA discoloration. 

3 modules ~ 69% of nameplate.

K. 72 glass-on-glass modules, deployed ~2001 - All have delamination above 

j-boxes; 6 modules have delamination in a corner or at an edge with subsequent corrosion of metallization. No I-V taken. (see photo 3)

Test Method Test Equipment

Tucson Electric Power Solar Test Yard

• Imp = 3.33A• Vmp = 54V

Manufacturer C

• Imp = 4.77 A• Vmp = 311 V

References

Conclusions

Manufacturer B

hot spot at j-box & 

2 rows of hot cells

Major Visual Observations

Thin-film modules

L. CIS, glass-on-glass, (deployed ~ 2003) – 2 of 20 modules removed (due to broken glass); 

Remaining modules had no visual defects. 2 modules ~ 76% of nameplate

M. CIGS, polymeric front & backsheet with discreet cells (deployed ~ 2003) - Some 

curling of substrate and delamination of superstrate. 1 module ~ 76% and 1 module ~ 55% of nameplate.

N. a-Si, glass/glass (deployed ~ 2004) - 1 of 150 had broken back glass; Corrosion around 

junction box contact feed through area on all modules; About 2/3rds of the modules had bar graph corrosion in lower corners. 4 module ~ 63% of nameplate. (see photo 2 )

Background

1. EVA browning –

Manu D

2. Bar-graph 

corrosion – Manu N

3. Delamination over 

j-box – Manu K

31 2