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PV Module

Electroluminescence:

Enlightening Defects

Michael Reutera, Liviu Stoicescub, Jürgen H. Wernera,b

a Steinbeiszentrum Photovoltaik, Stuttgart, Germany bInsitute for Photovoltaics, University of Stuttgart, Germany

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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

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Who we are…

Steinbeis-Transferzentrum

Angewandte Photovoltaik

und Dünnschichttechnik

Institut für Photovoltaik

Universität Stuttgart

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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

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Steinbeis Center Photovoltaics

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

Research and development for photovoltaics

Head Prof. Jürgen Werner

Turnover 200 000 €/year

[2] DE 102012107316.3

[3] DE 102010004439A1 [4] DE 2012000152

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Daylight Luminescence System

Schott EFG Sunpower IBC Monocrystalline Sanyo HIT Multicrystalline

[2] DE 102012107316.3

Electroluminescence

Photoluminescence

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+0.3%abs module efficiency by white ribbons

Principle of total internal reflection reduces shading

Efficiency gain Δη = +0.3%abs.

Low cost efficiency boost in PV modules

β

ΦTIR

incoming ray

gain:

53%

loss: 47%

white ribbon

Measurement

14.7

14.8

14.9

15.0

15.1

reference

ribbons

4 white3 white2 white

abs.

abs.

mo

du

le e

ffic

ien

cy h

(%

)

dfinger

= 2.22 mm

Dhabs.

Flat ribbon

incoming ray loss: 100%

[3] DE 102010004439A1

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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!

1 cm 1 cm

Front side Back side

[4] DE 2012000152

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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

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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

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Module Failure Modes

Hot spots

Delamination Browning

Potential induced degradation (PID)

Mikrocracks, broken cells,

Finger interruptions

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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

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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

Optical characterization methods

UV - Fluorescence Thermography Luminescence

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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

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Daylight Luminescence System

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

Photoshop merger of false color DaySy images on top of PV system image

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Service Availability

Measure when YOU want: 100% Availability Day and Night

0 100 700 700 100 0

Daytime Irradiance in W/m²

Thermography

DaySy - PL

DaySy – Self Powered EL

DaySy – EL with Power Generator

Night -EL Night -EL

DaySy EL of installed Module 8 MP Dark-Box EL MPP Thermography

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DaySy – Self Powered EL Modulation

Dark Box EL @ 10 A DaySy EL

2 - 6 Generator-Strings

DaySy Box

DaySy box modulates the generator strings in order to create EL image

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DaySy – Photoluminescence (PL)

Dark Box EL @ 0.1 A DaySy PL

DaySy Box

DaySy box modulates the module under test in order to create PL image

No generator strings necessary

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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

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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

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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

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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

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4 Modules at once

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

640x512 320x256

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1 Module

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

640x512 320x256

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Close Up

Microcracks and broken fingers visible in both resolutions

320x256 is sufficient

640x512 320x256

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Measurement time: DaySy - EL

73 W/m²

DaySy 1 sec 5 sec

10 sec 60 sec

Dark Box EL

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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

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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

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Disconnected module areas

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PID

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Ohmic losses

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Low light response

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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

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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

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Thanks for your attention

For furhter information on DaySy analysis please visit

our homepage www.solarzentrum-stuttgart.com