PV Module Electroluminescence: Enlightening Defects

PV Module Electroluminescence: Enlightening Defects Michael Reuter a, Liviu Stoicescu b, Jürgen H. Werner a,b a Steinbeiszentrum Photovoltaik, Stuttgart, Germany b Insitute for Photovoltaics, University of Stuttgart, Germany 1

Outline Who are we? Module failure modes Characterization methods New daylight luminescence DaySy Advantages How does it work? Throughput vs. resolution Defect images from real world Outlook 2

Who we are Steinbeis-Transferzentrum Angewandte Photovoltaik und Dünnschichttechnik Institut für Photovoltaik Universität Stuttgart 3

Institute for Photovoltaics, Uni Stuttgart Inventor of laser doped selective emitter Innovative laser processed IBC solar cells With h = 22 %! PV system analysis and monitoring since 2004 Stuttgart, Cyprus, Egypt Know-how chain: solar cell processing PV system Mobile electroluminescence inspection Daylight luminescence system: DaySy 4

Steinbeis Center Photovoltaics Research and development for photovoltaics Head Prof. Jürgen Werner Turnover 200 000 /year Hot topics Quality check: DaySy Daylight luminescence imaging of PV systems [2] White cell interconnections [3] Increased module efficiency by Dh = +0.3 % abs. Novel surface texture by metal assisted etching [4] Efficiency gain by Dh = +0.3 % abs [2] DE 102012107316.3 [3] DE 102010004439A1 [4] DE 2012000152 5

Daylight Luminescence System Electroluminescence Photoluminescence Schott EFG Sunpower IBC Monocrystalline Sanyo HIT Multicrystalline [2] DE 102012107316.3 6

+0.3% abs module efficiency by white ribbons module efficiency h (%) incoming ray loss: 100% 15.1 Measurement gain: 53% Flat ribbon incoming ray loss: 47% β white ribbon Φ TIR 15.0 14.9 14.8 14.7 Dh abs. abs. abs. reference d finger = 2.22 mm 2 white 3 white 4 white ribbons Principle of total internal reflection reduces shading Efficiency gain Δη = +0.3% abs. Low cost efficiency boost in PV modules [3] DE 102010004439A1 7

Novel surface texture for c-si Acidic texture requires saw damage Alkaline texture requires (100) surfaces Future cell concepts require single sided etch process Solution: Metal Assisted Etching batch & inline single side texture Gain: Dh = +0.4% abs in pilot production with 6000 cells/h! Front side Back side 1 cm 1 cm [4] DE 2012000152 8

Defects in PV-Modules Origin of the Defects Factory, transport, installation, service, aging Defects ripen PV System degrades! Which kind? Solar cell: Crack, PID, soldering, interconnections Material: Browning, delamination, glas, insulation Characterization I/V measurement Thermography Electroluminescence Photoluminescence UV-Flourescence 10

Module Failure Modes Delamination Mikrocracks, broken cells, Finger interruptions Browning Hot spots Potential induced degradation (PID) 11

Optical characterization methods UV - Fluorescence Thermography Luminescence UV - Fluorescence Thermography Luminescence Pro Cracks visible Power loss All defects Cost effective Cost effective Identification Con Night Irradiance Night Generator Generator Well aged cracks Identification Expensive 13

Daylight Luminescence System Photoshop merger of false color DaySy images on top of PV system image One System Five Use Cases Locate weak modules suffering from dead areas, broken cells or shunts Detect micro-cracks in close up images Identify potential induced degradation (PID) Reveal lifetime distribution via photoluminescence Complement thermography 15

Service Availability Measure when YOU want: 100% Availability Day and Night DaySy - PL DaySy Self Powered EL DaySy EL with Power Generator Night -EL Thermography Night -EL 0 100 700 700 100 0 Daytime Irradiance in W/m² DaySy EL of installed Module 8 MP Dark-Box EL MPP Thermography 16

good bad DaySy Self Powered EL Modulation DaySy EL Dark Box EL @ 10 A 2-6 Generator-Strings DaySy Box DaySy box modulates the generator strings in order to create EL image 17

good bad DaySy Photoluminescence (PL) DaySy PL Dark Box EL @ 0.1 A DaySy Box No generator strings necessary DaySy box modulates the module under test in order to create PL image 18

Measurement Procedure Connect Generator Modules/Strings Connect Measured Module/String Position Camera Measure Module String Complete? No Yes DaySy Box may be replaced with an appropriate inverter 20

System Impact In Situ measurement system impact One measurement string 2 6 generator strings Power loss only from the modulated strings Measurement time ca. 60 s/image 21

4 Modules at once 640x512 320x256 Both resolutions display major damage like damaged areas and groups of broken fingers On this scale well visible: Potential induced degradation (PID) and poor low light response 23

1 Module 640x512 320x256 Single broken fingers as well as micro-cracks visible in 640x512 Groups of broken fingers visible in 320x256 for single fingers & micro-cracks close up image necessary 24

Close Up 640x512 320x256 Microcracks and broken fingers visible in both resolutions 320x256 is sufficient 25

Measurement time: DaySy - EL Dark Box EL DaySy 1 sec 5 sec 10 sec 60 sec 73 W/m² 26

Resolution wrap up 320x256 Resolution is sufficient Start imaging multiple (4) Modules at once Dead areas; broken finger clusters; Interconnections; PID; poor low light response 1 kwp/image/minute 500 kwp/day For suspicious modules use close-up scans of 3x3 cells Image stitching and automation necessary Currently in 320x256 higher fps possible than 640x512 camera same result, cheaper sensor 640x512 excels at one module per image 27

Disconnected module areas 29

PID 30

Ohmic losses 31

Low light response 32

Outlook High throughput PV plant testing possible Available: Automated camera drones Thermography DaySy Daylight Luminescence Necessary: DaySy inverter integration Computer aided defect analysis and classification Standardization of acceptable damage 34

Thanks for your attention For furhter information on DaySy analysis please visit our homepage www.solarzentrum-stuttgart.com 35