AGCS Expert Days 2013 Photovoltaics Long Term Reliability and ...

AGCS Expert Days 2013 Photovoltaics Long Term Reliability and Typical Error Patterns BEC-Engineering GmbH - Dipl. Ing. (FH) Christian Vodermayer

07.11.2013

AGCS Expert Days 2013 - Photovoltaics Long Term Reliability and Typical Error Patterns

engineering and technical advisor company with R&D department and own testfield

Independent

Innovative

engineers, physicians and software developers from project development to applied research and development

© BEC-Engineering GmbH 2013

Multidisciplinary

Experienced

in cooperation with Allianz Center for Technology (AZT)

services and solutions for photovoltaic systems and renewable energies

successfully completed since 2006 services for more than 850 PV projects worldwide correlating with a total volume of more than 1.750 MWp

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Headquarter Poing • Engineering • Performance Prediction & Validation • Field Measurement • Analysis & Simulation Branch Frabertsham • Lab & Field Measurement • Research & Development • Green Building & Energy Management

successfully realized services for more than 850 PV projects worldwide with a total volume of more than 1.750 MWp

Benefits of photovoltaics

Technical advantages

Commercial advantages

Social & environmental advantages

Direct conversion from sunlight to electrical power

Solid yield expertises for financial calculation

Minimal CO2 emission

No moving parts, low maintenance cost

More than 20 years of operational experience

Minimal environmental risks (e.g. noise, air pollution)

No fuel required

High reliability

Very low social risk (acceptance and society)

Solid predictability - short and longterm for grid integration

Low power production price per kWh (grid parity given for some southern european countries)

Easy dismantling and recycling

Scalable – from small residential installation up to multi MWp power plant



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Relevance of photovoltaics in Germany •

The 2012 cumulative installed capacity of 32.4 GWp is distributed on 1.3 million PV plants from 0.05kWp up to 80MWp

•

In 2012 Germans PV power plants produced 28 TWh which equals 5.3 percent net of electrical energy consumption (4.3 percent gross)

•

On sunny days the power produced by the installed capacity covers short time 30-40 percent of total demand Wind (green) and photovoltaic (yellow) power production per month 2012 in germany

SOURCE: Frauenhofer ISE

Photovoltaic and wind are excellent complementary energy sources © BEC-Engineering GmbH 2013


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Example utility scale PV power plant

SOURCE: JOHANN BUNTE Bauunternehmung GmbH & Co. KG

50 MWp PV power plant in Northern Germany with 300.000 m² area, produces around 47.000 MWh / year



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PV market volume – what happend in the past (2000 – 2012)

EUROPE (-25 %) APAC (+83 %) China (+100 %) Americans (+70 %) MEA (+240 %)

SOURCE: EPIA

More than 102.000 MWp worldwide installed at the end of 2012 © BEC-Engineering GmbH 2013


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Prognosis for the next years

Estimated global PV market volume until 2017

SOURCE: EPIA

Bloomberg New Energy Finance estimates worldwide 36,7 Gigawatt new installations for 2013 © BEC-Engineering GmbH 2013


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Photovoltaic systems demonstrate excellent longterm reliability if you prevent…


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Project planning and engineering mistakes

•

Selection of wrong materials and / or components

•

Poor product quality and design

•

Faulty installation

•

Inadequate protection concepts against enviromental risks e.g. fire, hail, snow loading, storm, lightning, overvoltage, damage from animals, theft, vandalism, flood, landslide

•

Faulty operation

•

Poor maintenance AGCS Expert Days 2013 - Photovoltaics Long Term Reliability and Typical Error Patterns

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German claim statistics based on insurance information

SOURCE: GDV

Overvoltage is the most dominating claim reason of all fundamental damages © BEC-Engineering GmbH 2013


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Block diagram of a utility scale PV system

Module

String

Superstring

Inverter station


Wechselrichter Transformer station

Public grid connection


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Classification of common error patterns Reason for errors

Classification of risks

Involved components / systems

NatCat (e. g. hail, snow, storm)

Short-term or long-term risks

PV modules

Climate factors (e.g. temperature, radiation)

Probability of damage

Protection system (e.g. overvoltage, lightning)

Type of installation (e.g. on roof, free field)

Level of possible damage

Security system (e.g. theft, fire)

Interaction between components (e.g. contact corrision, PID)

Safety risks

Mounting system

Component design

Risks of yield loss

Cabeling (DC + AC)

Bad component quality

Risks to loss warranty

Monitoring system

Engineering (e.g. protection systems)

Secondary risks

Inverter

Transport

Internal or external damage source

Grid connection (transformer station)

Construction

Manifestation of possible damage

Infrastructure (e.g. drainage)

O&M © BEC-Engineering GmbH 2013


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Excerpt of common error patterns Natural catastrophes

Engineering errors

Transport, construction and O&M errors

Examples with focus on PV module based errors

PV module with hail damage

Poor system design

PV module with transport damage

PV module with encapsulation error

PV module with snow load

Poor lightning & overvoltage protection design

PV module with handling damage

PV module with defective bypass diodes

Storm

Poor static evaluation of mounting system

PV system with poor DC cabeling

PV module with poor solar cells

Flood

Poor cable sizing

Mounting systems with installation errors

PV module with poor solder joints

Landslide

Poor shading analysis

Inadequate Operation & Management

PV module with potential induced degradation (PID)

Lightning

Poor protection system design (e.g. for inverter, transformer station)

Poor PV module installation

PV module (initial) stabilisation problems

Fire

Poor infrastructure design

Poor monitoring system installation

PV module with longterm degradation



Bold examples explaind in presentation

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Excerpt of common error pattern



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Typical error pattern – PV module with hail damage

© BEC-Engineering GmbH


EL picture shows small cracks, caused by production, transport, installation or hail

Cracks which are caused with higher possiblity through hail (no damaged glass)

Reasons and factors

cell thickness and PV module design, orientation and quality of installation of PV modules


Hail caused glass break of PV module

PV Module

Comment

If no glass break exists, detailed examination of EL pictures are necessary to select between hail and other reasons


Short Risk Assessment

Power degradation due broken cells now or in the future, insulation errors

Influenced Components


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Typical error pattern – PV module with snow load


Free field PV generator in the summer in Southern Germany


Free field PV generator in the winter in Southern Germany


PV modules, mounting system, cabeling

Comment

2006 was in Germany an extreme snow situation


Reasons and factors

Climate conditions, wrong system design / installation



PV module with defective frame caused by snow loading

Damaged components like PV modules, safety risks due to insulation errors, yield loss through snow based shading


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Typical error pattern – PV module soiling



Edge soiling even with high tilt angel (self cleaning doesn't work)

Typical soiling of a PV module

Reasons and factors

Bad O&M, PV module type and installation, special soiling conditions

Moss already shades the lower cell row


PV module, PV generator

Comment

Average measured PV module power loss due to soiling in Europe is two percent (more as 400 measurements done)




Yield loss, hotspots, defective bypass diodes, insulation errors


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Typical error pattern - wrong system design

Power in W

Component selection and interconnection of PV modules and inverter for safe and economic operation at all local climate conditions •

PV generator voltage and current level has fit to inverter input

•

PV generator DC power has fit to inverter input power

power limitation

time DC Power AC Power SOURCE: Dr. Bruno Burger, FhG ISE, Staffelstein 2005

Reasons and factors

Wrong engineering, local climate factors (radiation, temperature)

Inverter, Modules, Cabeling

Comment

Exact climate conditions and behaviour of PV module + AC inverter + tracker characteristics must be known!



Safety aspects like overvoltage, yield losses due power limitation accelerated aging of inverter pos.



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Typical error pattern – poor lightning and overvoltage protection design


Grounding connection with wrong material



Wrong installation of lightning protection

Reasons and factors


Complete PV system including grid connection

Comment

Besides the PV system itself also the building for roof systems is under risk (e.g. overvoltage, fire, electric shock). Frequently protection systems are complete missing!


Bad Engineering


Lightning protection causes shading of PV generator

damage risk for complete PV system caused by lightning and fire, safety risks


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Typical error pattern – PV module with transport damage



Inadequate handling and transportation of PV modules on a track

EL picture of PV module before correct transportation

Reasons and factors

Bad module quality, wrong module handling during transport and construction


PV modules

Comment

Pre- and post shipment inspections are important



EL picture of PV module after correct transportation – power loss from -3 percent



Short and long term yield losses. Damage could increase during years

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Typical error pattern – PV module with handling damage


PV module backsheet scratch

Reasons and factors


EL image of PV module shows obvious scratch

Not experienced and professional working construction team

PV module

Comment

Site supervision during construction phase can significantly decrease the risk of handling damages



PV module degradation through entering of humidity, insulation error, safety risk due to electrical shock



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Typical error pattern – PV systems with poor DC cabeling



Damage of DC cabeling by wrong installation handling

Insufficient plugged DC connector

Reasons and factors

Wrong engineering, bad installation and O&M


Cabeling, complete system

Comment

DC cabeling errors can be fixed without special effort




Fire caused by inadequate DC cabeling

Safety aspects like electric shock, yield loss, electrical arc, fire, component failure


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Typical error pattern – PV systems with poor DC cabeling



Wasps‘nest at cable tube

DC cable with UV and wind damage

Reasons and factors

Wrong engineering, bad installation and O&M

Damage of cable through wasps


Cabeling, complete system

Comment

You have to consider also risks like bugs entrance through open cable ducts




Saftey aspects like electric shock, yield loss, electrical arc, fire, component failure


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Typical error pattern – mounting system with installation errors


Wrong material combination on post of mounting system

SOURCE: AZT


Insufficient torque at screw

Reasons and factors

Engineering errors, unprofessional construction team

Post too short – no stable construction


PV Modules, Cables

Comment

Site supervision during construction phase can significantly decrease the risk of installation damages




Lack of stability, PV module damage, saftey risk

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Typical error pattern - inadequate Operation & Management

SOURCE: AZT

SOURCE: AZT

Fire hazard due to faulty operational management (missing cutting grass)

Reasons and factors

PV module damage due to inadequate maintenance work (cutting grass and module cleaning)


Primarily modules, cables and mounting system

Comment

e.g. cleaning periodically required in southern europe countries – risk of damage due to cleaning procedure


Unprofessional O&M supplier


Safety aspects like fire, electrical shock, component damage, yield loss


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Typical error pattern – PV module with encapsulation error

Picture shows small abnormality on the left bottom corner

EL image shows inactive area on the bottom

Reasons and factors

Wrong module design and manufracturing


PV module

Comment

Long therm behaviour of the phenomenon is under investigation



Infrared Image confirms the inactive area

Power degradation, PV module breakdown, hot spots, insulation errors


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Typical error pattern – PV module with defective bypass diode



PV module connection box shows deformation due to overheated bypass diodes

Image of open connection box shows the defective bypass diode

Reasons and factors

IR image highlights bypass diode temperatures above 80 degree


PV module

Comment

Replacement of bypass diodes is possible for the most PV modules with low costs


Wrong product design or production, shading over longer time, overvoltage




Yield loss, PV module damage, insulation errors

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Typical error pattern – PV module with poor solar cells


IR image of PV generator with hot cells and other thermal phenomenons

Reasons and factors


PV module on the BEC testfield with single hot cell (temperature delta 9 k)

Bad cell and PV module quality, aging effects, transport and installation errors, NatCat


PV Modules,

Comment

There is no possibility up to now to repair PV modules with bad solar cells





IV curve of left PV module shows -12 percent less output power

PV module and generator related yield loss, PV module breakdown, risk of hot spots

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Typical error pattern – PV module with poor solder joint

Visual image shows burned joint and delamination




IR image from module left shows hot spot with temperatures about 80 degree!

Production error, strong thermal and mechanical stress


PV module, PV generator

Comment

There is no possibility up to now to repair PV modules with this type of error


Reasons and factors

Burned EVA foil above connection box



Power degradation, module breakdown, insulation errors, electrical arc, fire

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Typical error pattern – PV module with potential induced degradation (PID)



PV module array shows suspect thermal signature due to PID Reasons and factors

Power loss distribution of the PV modules in string depending on potential to ground Wrong module and system design, special climate factors (humidity, temperature)

PV modules

Comment

PID is through an negative applied voltage reversible for some module technologies



Yield loss and depending from the technology and installation & climate complete PV module break down



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Open circuit voltage @STC

Typical error pattern – PV module (initial) stabilisation problems

Datasheet value +10%

• Modul LK1 ▪ Modul LK2 ▶ Modul LK3

Datasheet value © BEC-Engineering GmbH

17 month exposure time

Increase of PV module open ciruit voltave above datasheet value Reasons and factors

PV module initial output power stabilization requires certain operation time (more than 5 percent initial degradation) Wrong product design / engineering,climate factors (Radiation, Temperature),


Modules, complete system

Comment

Exact PV module behaviour must be known for accurate system design!




Safety aspects e.g. overvoltage and overcurrent, damage of components, yield losses

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Typical error pattern – PV module with longterm degradation



Strong variation in degradation behavior with stabilization for identical thin film PV modules

Reasons and factors

Long term degradation of crystalline silicon based PV module arrays showing constant degradation without sign of stabilization

Wrong Design, production errors, operation errors


PV modules

Comment

There are fundamental differences in PV module degradation mechanism depending on the technology



Yield loss up to breakdown from significant parts of the complete PV power plant


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Portfolio for Photovoltaics - Cooperation AZT and BEC



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Portfolio for Photovoltaics - Cooperation AZT and BEC

The interdisciplinary collaboration between experienced experts from AZT and BEC ensures that our customers benefit from our: -

excellent know-how in system technology, components and performance,

combined with an -

extensive expertise in analysis, evaluation and failure prevention strategies.

We are your specialists when it comes to the warranty and the long-term reliability of your PV power plant performance and investment.



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Numbers in relation to longerm reliabilty of existing PV systems



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Results from field inspection of 30 MWp PV power plant capacity

Examples from string power measurements for multiple systems with in sum about 30MWp lining out different reasons for resulting yield loss: Fault

Resulting average yield loss and range

Module breakage and cabling issues Inverter operation issues Low performing modules Total yield loss

1,1 % (0,5 - 2 %) 2 % (0,5 - 3 %) 3 % (2 % - 9 %) 5,1 % (3 – 14 %)

All findings above were not detected by experienced EPC’s in charge of O&M relying common monitoring systems



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Detailed examination of 252 PV modules with more than 15 years of operation

Different type of cell cracks •

In the 90th usual solar cells had arround 300-400 μm thickness. Based on common theory solars cells of today (~150-200 μm) should be less sensitive for micro cracks

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Around 40 percent of all analysed PV modules show at least one cell with a crack. Todays PV module on average show significantly more micro cracks

Delamination •

Different intensive delamination, especially on busbars

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In sum 216 pieces (86 percent) are affected

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Direct correlation between power and delamination not confirmed yet



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Detailed examination of 252 PV modules with more than 15 years of operation

Results of the power measurement •

On average all PV modules show -10 percent deviation of nominal power after 15 years and more

•

Deviation from nominal power showed variation during the production years 0,00%

Deviation from nominal pwer

-2,00% -4,00% -6,00% -8,00% -10,00% -12,00% -14,00% -16,00% -18,00% -20,00% 94-09


94-13

94-24

94-30

94-36 94-39 95-09 95-13 95-22 95-26 Production year and calender week

95-49

96-33


97-20

97-21

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Detailed examination of 252 PV modules with more than 15 years of operation Results of the power measurement •

Around 55 percent show a negative power deviation of less than 10 percent

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Two PV modules have inactive cell strings this causes power loss of more than 25 percent

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Two PV modules showed complete breakdown

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Only 5 PV modules could be claimed due to a power loss of more than 20 percent Percentages of PV modules 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Deviation from nominal power

0%

-5%

-10%

-15%

-20%

-25%

-30% © BEC-Engineering GmbH 2013


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Conclusion…

• PV has an excellent reliability about 20 years and more if the component design, engineering, transport, construction and also O&M is well done

• The displayed examples show different error patterns and reasons which require specific expertise and experience in Pre- and Postloss phase for evaluation and root cause analysis

• The relevance of photovoltaic power generation will grow for insurer with the increasing share on total power generation over the coming years

• Consulting and engineering services support in the project involved companies and institutions is important to achieve an economic and safe investment



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BEC takes the closer look.



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BEC-Engineering GmbH Bahnhofstr. 1 85586 Poing Germany Phone: Fax: E-mail: Web:


+49 8121 884567 0 +49 8121 884567 88 [email protected] www.bec-engineering.de


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