dinesh soundararajan applied project presentation
TRANSCRIPT
![Page 1: Dinesh Soundararajan Applied Project Presentation](https://reader033.vdocument.in/reader033/viewer/2022052606/5885fbe61a28ab0a3f8b48f3/html5/thumbnails/1.jpg)
Non-Destructive and Destructive Evaluation of Field Aged Photovoltaic Module
Dinesh SoundararajanASU Photovoltaic Reliability Laboratory (ASU-PRL)
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• Introduction• Methodology
– Non Destructive Methods• Result
– Destructive Methods• Result
• Conclusion
Slide 2
Outline
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Introduction• Solder bond failure is one of key degradation issues
• Solder bond degradation leads to higher series resistance (Rs) at metal circuit
• The power directly depends on Fill Factor (FF) which in turn is affected by series resistance (Rs)
• Destructive and Non Destructive Tests were conducted on 23Y ARCO Solar M65 module of 30 cells exposed in Xoxocotla, Mexico (Hot-Humid)
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Methodology
• Solder bond degradation is analyzed through Non-Destructive and Destructive methods.• Destructive methods enables cell level analysis • Non Destructive Methods:
– IV & DIV Curve Tests – IR & EL Tests– Reflectance Test (Cell level)
• Destructive Methods: - DIV Curve Test (Cell level)- IR Test (Cell level)
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Non-Destructive MethodsIV Curve Test• IV Curve Test is the most basic test to determine the
performance of a PV module Normalized IV Curve (STC – 1000 W/m2 / 25⁰C / 1.5 AM)
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Slide 6
DIV Curve Test
• The dark IV test is done in a dark chamber at ambient temperature of 25 C ⁰• DC voltage is increased in steps until 1.25 times Voc is reached
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DIV Curve Test
0 5 10 15 20 250 5 10 15 20 250.0001
0.001
0.01
0.1
1
10
0
0.2
0.4
0.6
0.8
1
1.2Dark IV Curve
Semi-Log
Linear
Voltage (V)
Sem
i-Log
Cur
rent
(A)
Line
ar C
urre
nt (A
)
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Result: Performance Analysis
Isc (A) Voc (V) Imp (A) Vmp (V) FF (%) Rs (Ω) Pm (W)
Rated
at STC
3.25 18.00 2.95 14.60 73.00 0.64 43.00
Normalized
to STC
1.79 15.78 1.08 8.56 32.70 5.23 9.3
Percentage
change
- 44.92% - 12.33% - 63.38% - 41.37% - 55.21% + 717.19% - 78.37%
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Result: Performance Analysis
Imp Vmp FF Rs Pm
-200.00%
-100.00%
0.00%
100.00%
200.00%
300.00%
400.00%
500.00%
600.00%
700.00%
800.00%
- 63.38%- 41.37% - 55.21%
+ 717.19%
- 78.37%
Percentage change between rated and tested value
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IR Image Analysis
• The IR image of the module shows the presence of various hot spots in the module mostly along the solder bonds
Ambient - 28⁰C
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EL Image Analysis
• EL image shows poor contact or inactive regions as dark lines, areas.
• Completely dark cells are dead cells.
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Reflectance Analysis• Reflectance is caused by browning and delamination.• 82% of cells between median to worst reflectance value – Edge
cells
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Result – Reflectance analysis• Edge cells reflected the light 33.6% more than Non-Edge Cells
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Delamination - Image processing (MatLab)
• The gray area are the delamination of encapsulant due to moisture penetration
• It increases the reflectance rate• Delamination in edge cells is much higher than non-
edge cells
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Destructive Methods
• Analyzing the performance at the cell level we could determine the causes and thus the extent of degradation more accurately
• Cell location based analysis helps in focusing on the often over looked areas for reliability issues
• Destructive tests enable analysis at cell level
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Preparation for Destructive Testing
• Backsheet is cut in a specific area with access to solder ribbons in small squares using a single edge blade
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Preparation for Destructive Testing Contd..
• It is then heated using an air heat gun to break the adhesive bonds between the backsheet and the cell encapsulant
• The backsheet (made of three layers) is removed
• Then the encapsulant is also removed exposing the ribbons
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Preparation for Destructive Testing Contd..
• Finally the positive ribbon beneath the cell and the negative ribbon beneath the adjacent cell is soldered to the ribbon leads
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Cell level IR Test
• Cell level IR Test is done in dark room to capture resistive heating alone
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Result – Cell level IR Test
• Tcenter < Tedge < Tsolder in almost every cell of the module • The series resistance of solder increases due to moisture
induced degradation.
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Cell level DIV Curve Test
• It is done using a cell level DIV tester integrated with a solar simulator
• Through cell level DIV tests the series resistance Rs, shunt resistance Rsh and Fill Factor FF (%) of each cell are found
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Result – Cell level DIV Tests
• Non-Edge cells has 1.7% lower series resistance, 31% higher shunt resistance, 7% higher FillFactor than edge cells
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Result – FF Vs Rsh Vs Rs Vs Tedge, solder, center
• Fill Factor FF dropped with increasing Tcenter, Tedge and Tsolder and importantly dropped drastically with slight increase of series resistance Rs but FF increased with increasing shunt resistance Rsh.
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Conclusion
Test module - 23 years aged Arco M65 moduleSite - Xoxocotla, Mexico (Hot-Humid) • 717.19% increase in series resistance (Rs), 73.8% drop in
maximum power (Pmax) which is -3%/year• Very high power loss is due to harsh Hot-Humid climate at
Xoxocotla, Mexico• 33.6% higher reflectance in edge cells than non-edge cells• 1.7% lower Series resistance (Rs) in non-edge cells than
edge-cells• Degradation is due to moisture penetration through the
insulation along frame and permeation through backsheet.