PV MODULE RELIABILITY AND QUALITY TESTING

PV MODULE RELIABILITY AND QUALITY TESTING TestLab PV Modules Daniel Philipp Fraunhofer Institute for Solar Energy Systems ISE 18.06.2015 PV Investors Day www.ise.fraunhofer.de

AGENDA n Introduction n Technological risk factors and failure experience n Strengths and weaknesses of established quality standards n Testing methods n Electroluminescence imaging n Cell breakage due to thermo-mechanical stress n Potential induced degradation (PID) n Summary 2

Fraunhofer ISE Fields of Activity Fotos n Solar Thermal Technology n Energy Efficient Buildings n Hydrogen Technology n Energy System Technology n Photovoltaics 3

TestLab PV Modules Failure Research and Testing Service n Failure analyses n Identification of root causes and relevant stress factors n Failure prevention Accredited Testing Laboratory for: - IEC 61215 - IEC 61730-1/2 4 - IEC 61646

Technical Risks with focus on module reliability Risk factors! Market pressure PV industry à Innovations to save costs / increase efficiency à Might lead to save QA / QC effort! More challenging installation climates (desert, tropical) Learning effects from increasing long term experience with PV application Improved Testing methods à Type testing acc. to standards à Qualtty control measures 5

Experience on Serial Failures Serial Failures Company Year Severety Potential Induced Degradation 1 Sunpower 2006 Medium Potential Induced Degradation 2 Multiple 2007 - today Overheating due to cell cracks Multiple 2008 - today Medium Critical Strong back-sheet browning Multiple 2008 Medium Delamination Shell Solar 2013 Critical Overheating due to interconnction corrosion BP-Solar 2009 Critical J-box overheating Multiple 2010-today Critical Light induced degradation on PERC cells Multiple 2014 6

Experience on Serial Failures Serial Failures Company Year Severety Potential Induced Degradation 1 Sunpower 2006 Medium Potential Induced Degradation 2 Multiple 2007 - today Overheating due to cell cracks Multiple 2008 - today Medium Critical Strong back-sheet browning Multiple 2008 Medium Delamination Shell Solar 2013 Critical Overheating due to interconnction corrosion BP-Solar 2009 Critical J-box overheating Multiple 2010-today Critical Light induced degradation on PERC cells Multiple 2014 7

Module Testing Strengths and weaknesses of standards n IEC 61215 n IEC 61646 n IEC 61730 1/2 à c-si PV Modules à Thinfilm modules à Safety standard for PV modules 8

Certification acc. to IEC 61215 Full Testings Scope PreCond (LID) - Visual Inspection - Power - Insulation - Leakage Current TC, NOCT, low irrad. UV (15 kwh/m²) Temp.-Cycling 200 cycles Outdoor Exposure Temp.-Cycling 50 Damp Heat Bypass Diode Humidity Freeze Mech. Load Hail Hot Spot Termination Visual Inspection - Power - Insulation - Leakage Current 9

Certification acc. to IEC 61215 Statistical Failure Rates During Certification Failure Rate per Test in % 20 15 10 5 0 15.1 14.8 14.4 12.3 5.7 2.4 1.4 1 0.2 HF HS ML DH TC200 TC50 OE HL UV About 30 % of all module types fail in at least one test Stress Test (HF): Humidity Freeze, (HS): Hot Spot, (ML): Mechanical Load, (DH): Damp Heat, (TC200/50): Thermal Cycling, (OE): Outdoor Exposure, (HL): Hail Test, (UV): UV Test 10

Certification acc. to IEC 61215 and IEC 61730 Strength and Weaknesses Strengths: n The only binding testing schemes which assure minimum quality and safety requirements n Independency n Consistency of materials and components covered Weaknesses n Test done once on few modules n Important degradation factors not sufficiently covered: n High ground potential (PID) n UV irradiation n Combined appearance of stress factors 11

Module Testing Electroluminescence imaging n Manufacturers: In-line quality control n Testing Labs: To evaluate test results n Buyers: Set acceptance criteria micro cracks inactive cell areas grid finger interruptions 12

Module Testing Electroluminescence imaging n Manufacturers: In-line quality control n Testing Labs: To evaluate test results n Buyers: Set acceptance criteria micro cracks Example: max 3 cells / module max 5 cracks in total inactive cell areas Example: max 1 cell / module max 15 % cell area grid finger interruptions Example: max 3 cells / module 13

Module Testing Thermal Cycling Test from IEC 61215 200 Cycles -40 ß à 85 Celsius Pass criterion from certification: max. 5 % power reduction No visible defects Electrical insulation OK 14

Module Testing Thermal Cycling Test from IEC 61215 Before Thermal Cycling 200 After PASS! 15

Module Testing Thermal Cycling Test Statistics: Cell-crack formation and power after Thermal Cycling Additional cracks rel. power loss rel. frequency [%] 22 20 18 16 14 12 10 8 6 4 2 0 0 10 20 30 40 50 60 70 additional micro cracks after 200 cycles after 400 cycles More than 50 % of modules have less than 3 additional cell cracks! rel. frequency [%] 30 25 20 15 10 5 after 200 cycles of thermal cycling after 400 cycles of thermal cycling IEC- fail-level 0-10 -9-8 -7-6 -5-4 -3-2 -1 0 1 2 3 rel. power loss [%] 16

Module Testing Thermal Cycling Test from IEC 61215 Before Thermal Cycling 200 After PASS! 17

Module Testing Potential Induced Degradation + inverter PVstring - 18 PID: System Potential to grid ground leads to power degradation on susceptive Neg. ground potential c-si PV modules

Module Testing Potential Induced Degradation PID Laboratory Test 0% PID Test -83,3 % n Draft for standardised test procedure: n -1000 Volts cell to frame n Climate chamber: n 60 Celsius n 85 % relative humidity Module is rated PID sensitive if powerloss < 5% Number of tested modules 60 55 50 45 40 35 30 25 20 15 10 5 0-100 % - 80 % - 60 % - 40 % - 20 % 0 % Relative Power Loss due to PID Indoor Test 19

Summary n Please learn from experiance on failures! n Testing methodogies have improved n International standards ensure basic quality n Tests beyond standards recomended n For better type design tests n To contol quality 20

Thank-you for your attention! Fraunhofer Institute for Solar Energy Systems ISE Daniel Philipp www.ise.fraunhofer.de daniel.philipp@ise.fraunhofer.de 21

Module Testing Electroluminescence imaging n EL inspection became state of the art as inline- measurement: (before / after lamination) n Buyers of modules define acceptance criterions micro cracks Example: max 3 cells / module max 5 cracks in total inactive cell areas Example: max 1 cell / module max 15 % cell area grid finger interruptions Example: max 3 cells / module 22