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

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

2 engineering and technical advisor company with R&D department and own testfield Independent Innovative services and solutions for photovoltaic systems and renewable energies engineers, physicians and software developers from project development to applied research and development Multidisciplinary Experienced successfully completed since 2006 services for more than 850 PV projects worldwide correlating with a total volume of more than MWp in cooperation with Allianz Center for Technology (AZT)

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

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

5 Benefits of photovoltaics Technical advantages Direct conversion from sunlight to electrical power No moving parts, low maintenance cost No fuel required Solid predictability - short and longterm for grid integration Commercial advantages Solid yield expertises for financial calculation More than 20 years of operational experience High reliability Low power production price per kwh (grid parity given for some southern european countries) Social & environmental advantages Minimal CO2 emission Minimal environmental risks (e.g. noise, air pollution) Very low social risk (acceptance and society) Easy dismantling and recycling Scalable from small residential installation up to multi MWp power plant 5

6 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 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 6

7 Example utility scale PV power plant SOURCE: JOHANN BUNTE Bauunternehmung GmbH & Co. KG 50 MWp PV power plant in Northern Germany with m² area, produces around MWh / year 7

8 PV market volume what happend in the past ( ) EUROPE (-25 %) APAC (+83 %) China (+100 %) Americans (+70 %) MEA (+240 %) SOURCE: EPIA More than MWp worldwide installed at the end of

9 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

10 Photovoltaic systems demonstrate excellent longterm reliability if you prevent 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 10

11 German claim statistics based on insurance information SOURCE: GDV Overvoltage is the most dominating claim reason of all fundamental damages 11

12 Block diagram of a utility scale PV system Module String Superstring Inverter station Wechselrichter Transformer station Public grid connection 12

13 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) Type of installation (e.g. on roof, free field) Interaction between components (e.g. contact corrision, PID) Probability of damage Level of possible damage Safety risks Protection system (e.g. overvoltage, lightning) Security system (e.g. theft, fire) 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) Transport Construction Secondary risks Internal or external damage source Manifestation of possible damage Inverter Grid connection (transformer station) Infrastructure (e.g. drainage) O&M 2013 AGCS Expert Days Photovoltaics Long Term Reliability and Typical Error Patterns 13

14 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 PV module with snow load Poor system design Poor lightning & overvoltage protection design PV module with transport damage PV module with handling damage PV module with encapsulation error PV module with defective bypass diodes Bold examples explaind in presentation 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 14

15 Excerpt of common error pattern 15

16 Typical error pattern PV module with hail damage EL picture shows small cracks, caused by production, transport, installation or hail Cracks which are caused with higher possiblity through hail (no damaged glass) Hail caused glass break of PV module Influenced Components PV Module Reasons and factors cell thickness and PV module design, orientation and quality of installation of PV modules Short Risk Assessment Power degradation due broken cells now or in the future, insulation errors Comment If no glass break exists, detailed examination of EL pictures are necessary to select between hail and other reasons 16

17 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 module with defective frame caused by snow loading Influenced Components PV modules, mounting system, cabeling Reasons and factors Climate conditions, wrong system design / installation Short Risk Assessment Damaged components like PV modules, safety risks due to insulation errors, yield loss through snow based shading Comment 2006 was in Germany an extreme snow situation 17

18 Typical error pattern PV module soiling Typical soiling of a PV module Edge soiling even with high tilt angel (self cleaning doesn't work) Moss already shades the lower cell row Influenced Components PV module, PV generator Reasons and factors Bad O&M, PV module type and installation, special soiling conditions Short Risk Assessment Yield loss, hotspots, defective bypass diodes, insulation errors Comment Average measured PV module power loss due to soiling in Europe is two percent (more as 400 measurements done) 18

19 Power in W Typical error pattern - wrong system design 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 DC Power AC Power time SOURCE: Dr. Bruno Burger, FhG ISE, Staffelstein 2005 Influenced Components Inverter, Modules, Cabeling Reasons and factors Wrong engineering, local climate factors (radiation, temperature) Short Risk Assessment Safety aspects like overvoltage, yield losses due power limitation accelerated aging of inverter pos. Comment Exact climate conditions and behaviour of PV module + AC inverter + tracker characteristics must be known! 19

20 Typical error pattern poor lightning and overvoltage protection design Grounding connection with wrong material Wrong installation of lightning protection Lightning protection causes shading of PV generator Influenced Components Comment Complete PV system including grid connection Reasons and factors Bad Engineering Short Risk Assessment damage risk for complete PV system caused by lightning and fire, safety risks 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! 20

21 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 EL picture of PV module after correct transportation power loss from -3 percent Influenced Components PV modules Reasons and factors Bad module quality, wrong module handling during transport and construction Short Risk Assessment Short and long term yield losses. Damage could increase during years Comment Pre- and post shipment inspections are important 21

22 Typical error pattern PV module with handling damage PV module backsheet scratch EL image of PV module shows obvious scratch Influenced Components PV module Reasons and factors Not experienced and professional working construction team Short Risk Assessment PV module degradation through entering of humidity, insulation error, safety risk due to electrical shock Comment Site supervision during construction phase can significantly decrease the risk of handling damages 22

23 Typical error pattern PV systems with poor DC cabeling Damage of DC cabeling by wrong installation handling Insufficient plugged DC connector Fire caused by inadequate DC cabeling Influenced Components Cabeling, complete system Reasons and factors Wrong engineering, bad installation and O&M Short Risk Assessment Safety aspects like electric shock, yield loss, electrical arc, fire, component failure Comment DC cabeling errors can be fixed without special effort 23

24 Typical error pattern PV systems with poor DC cabeling DC cable with UV and wind damage Wasps nest at cable tube Damage of cable through wasps Influenced Components Cabeling, complete system Reasons and factors Wrong engineering, bad installation and O&M Short Risk Assessment Saftey aspects like electric shock, yield loss, electrical arc, fire, component failure Comment You have to consider also risks like bugs entrance through open cable ducts 24

25 Typical error pattern mounting system with installation errors Wrong material combination on post of mounting system Insufficient torque at screw SOURCE: AZT Post too short no stable construction Influenced Components PV Modules, Cables Reasons and factors Engineering errors, unprofessional construction team Short Risk Assessment Lack of stability, PV module damage, saftey risk Comment Site supervision during construction phase can significantly decrease the risk of installation damages 25

26 Typical error pattern - inadequate Operation & Management SOURCE: AZT Fire hazard due to faulty operational management (missing cutting grass) SOURCE: AZT PV module damage due to inadequate maintenance work (cutting grass and module cleaning) Influenced Components Primarily modules, cables and mounting system Reasons and factors Unprofessional O&M supplier Short Risk Assessment Safety aspects like fire, electrical shock, component damage, yield loss Comment e.g. cleaning periodically required in southern europe countries risk of damage due to cleaning procedure 26

27 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 Infrared Image confirms the inactive area Influenced Components PV module Reasons and factors Wrong module design and manufracturing Short Risk Assessment Power degradation, PV module breakdown, hot spots, insulation errors Comment Long therm behaviour of the phenomenon is under investigation 27

28 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 IR image highlights bypass diode temperatures above 80 degree Influenced Components PV module Reasons and factors Wrong product design or production, shading over longer time, overvoltage Short Risk Assessment Yield loss, PV module damage, insulation errors Comment Replacement of bypass diodes is possible for the most PV modules with low costs 28

29 Typical error pattern PV module with poor solar cells IR image of PV generator with hot cells and other thermal phenomenons PV module on the BEC testfield with single hot cell (temperature delta 9 k) IV curve of left PV module shows -12 percent less output power Influenced Components PV Modules, Reasons and factors Bad cell and PV module quality, aging effects, transport and installation errors, NatCat Short Risk Assessment PV module and generator related yield loss, PV module breakdown, risk of hot spots Comment There is no possibility up to now to repair PV modules with bad solar cells 29

30 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! Burned EVA foil above connection box Influenced Components PV module, PV generator Reasons and factors Production error, strong thermal and mechanical stress Short Risk Assessment Power degradation, module breakdown, insulation errors, electrical arc, fire Comment There is no possibility up to now to repair PV modules with this type of error 30

31 Typical error pattern PV module with potential induced degradation (PID) PV module array shows suspect thermal signature due to PID Power loss distribution of the PV modules in string depending on potential to ground Influenced Components PV modules Reasons and factors Wrong module and system design, special climate factors (humidity, temperature) Short Risk Assessment Yield loss and depending from the technology and installation & climate complete PV module break down Comment PID is through an negative applied voltage reversible for some module technologies 31

32 Open circuit Typical error pattern PV module (initial) stabilisation problems Datasheet value +10% Modul LK1 Modul LK2 Modul LK3 17 month exposure time Increase of PV module open ciruit voltave above datasheet value Datasheet value PV module initial output power stabilization requires certain operation time (more than 5 percent initial degradation) Influenced Components Modules, complete system Reasons and factors Wrong product design / engineering,climate factors (Radiation, Temperature), Short Risk Assessment Safety aspects e.g. overvoltage and overcurrent, damage of components, yield losses Comment Exact PV module behaviour must be known for accurate system design! 32

33 Typical error pattern PV module with longterm degradation Strong variation in degradation behavior with stabilization for identical thin film PV modules Long term degradation of crystalline silicon based PV module arrays showing constant degradation without sign of stabilization Influenced Components PV modules Reasons and factors Wrong Design, production errors, operation errors Short Risk Assessment Yield loss up to breakdown from significant parts of the complete PV power plant Comment There are fundamental differences in PV module degradation mechanism depending on the technology 33

34 Portfolio for Photovoltaics - Cooperation AZT and BEC 34

35 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. 35

36 Numbers in relation to longerm reliabilty of existing PV systems 36

37 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 1,1 % (0,5-2 %) 2 % (0,5-3 %) 3 % (2 % - 9 %) Total yield loss 5,1 % (3 14 %) All findings above were not detected by experienced EPC s in charge of O&M relying common monitoring systems 37

38 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 μm thickness. Based on common theory solars cells of today (~ μm) should be less sensitive for micro cracks 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 In sum 216 pieces (86 percent) are affected Direct correlation between power and delamination not confirmed yet 38

39 Deviation from nominal pwer 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% -2,00% -4,00% -6,00% -8,00% -10,00% -12,00% -14,00% -16,00% -18,00% -20,00% Production year and calender week 39

40 Deviation from nominal power 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 Two PV modules have inactive cell strings this causes power loss of more than 25 percent Two PV modules showed complete breakdown 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% 0% -5% -10% -15% -20% -25% -30% 40

41 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 relevance of photovoltaic power generation will grow for insurer with the increasing share on total power generation over the coming years 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 Consulting and engineering services support in the project involved companies and institutions is important to achieve an economic and safe investment 41

42 BEC takes the closer look. 42

43 BEC-Engineering GmbH Bahnhofstr Poing Germany Phone: Fax: info@bec-engineering.de Web: 43