Quality Assurance and Production Optimization
for PV Module Production
-Killing two Birds with one Stone
1.
PICON Solar introduction
2.
The quality issue
3.
Examples for the costs of not doing quality assurance
and quality management
Outline
and quality management
4.
How QA and QM automatically results in production
optimization
PICON Solar – worldwide consulting at the crossing point where technology and client´s features translate into unique strategy.
Services: i. quality assurance, bankability issues ii. production optimization
iii. technology and process development iv. strategic business development
About PICON Solar
iv. custom-made studies on technologies and products
Typical clients: We have no typical clients!
Financial institutions as well as government institutions. Module and component producers, raw material suppliers
as well as equipment manufacturers.
About PICON Solar
Dr. Ilka Luck
2008 Founding of PICON Solar as managing partner
2007 – 2008 Managing director of Global Solar Energy Deutschland GmbH 2006 Co-founding partner of PI Berlin among other companies in the
renewable energy sector, „business angel“
2001 – 2006 Founder and managing director of Sulfurcell Solartechnik GmbH,
today Soltecture
Dr. Steffen Schuler
since 2011 Principal Consultantwith PICON Solar
2007 – 2011 Head of Technology, Global Solar Energy Deutschland 2006 – 2007 Team Leader Product Engineering for Fab-Cluster
Technology Transfer, Qimonda AG, Dresden
2003 –2006 Product Engineer for DRAM Component Yield
Enhancement, Infineon Technologies / Qimonda AG, Dresden
2002 – 2003 Post Doctoral Researcher, Hahn-Meitner-Institut Berlin,
The Quality Issue
• PV, especially c-Si based PV used to be considered a well established technology coming with the corresponding long-term stability. More and more PV plants show a life time of 20 years and beyond.
• When the German EEG and other subsidies triggered the tremendous demand for PV modules availability was all that mattered.
• Industrial productions often run by companies that have not yet accumulated long-term experience with PV module reliability superseded the former manufactures.
• The need for profit, later the enormous cost pressure introduces new materials and processes – no long-term experience available and with IEC standards insufficient for life time projections.
long-term experience available and with IEC standards insufficient for life time projections.
• Failures in the field occur – some completely new, some long thought overcome.
• Investors, financing and insuring institutions have become concerned about the safety of their project profitability.
The quality issue is back!
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Yellowing – a failure long thought gone
• yellowing appeared within months afterinstallation coming with significant power degradation.
• the use of uncertified material turned out to be the origin of this failure.
• violation of product warranty! Replacement costs as high as 450 k€ per MWp.
• power warranty to be violated within 2 – 4 years after installation
years after installation
• financial loss for PV plant owner per MWp as high as 25.000 €* in year 2 alone that will further accumulate!
Degradation will not stop at 90 % of the initial power after 2 years!
* Assuming 0,45 €/Wp, 1000 MWh/MWp, FIT 0,25 €ct/kWh
Consequences
Investor:
substantial financial loss
How to ensure Module Quality
Check before installation(e.g. PI´s quality test-packages, PI China´s pre-shipment checks, PICON´s factory inspections)!
Advantages: • you get what you pay for (power at STC)
• first impression of potential module performance (EL, PID, Peel, Weak Light, sometimes LID and Hot-Spot)
Disadvantage: • probe size often not of statistical relevance
• long term stability not addressed due to lack of time (long-term climate chamber testing, UV)
(long-term climate chamber testing, UV)
Better have the module manufacturer check for quality as well!
→Quality assurance and quality management in PV module production
Manufacturers´ comment: Too expensive! Are you aware of the cost pressure out there? People don´t pay for quality.
Sadly right in the past years. However, it is changing. But is QA and QM really too expensive?
Inexact power determination
within error margin of measurement • Manufacturer C is perfectly fine*.
Satisfying customer expectations and not over delivering.
• Manufacturer A is losing** almost 50 k€
due to downgrading of 1 % production volume and almost 140 k€by not upgrading 3 % of production volume.
• Manufacturer B underperforms. He
loses** 1.6 Mio €due to downgrading and loses** 1.6 Mio €due to downgrading and weakening his reputation.
• Manufacturer D is clearly not in control of his process which does not help his
reputation. He loses 936 k€due to down-grading and almost 1.3 Mio €by not up-grading.
Counteraction: Continuous referencing and calibration of sun simulator.
* assuming a -0% / +5% sorting
Inprecisely cured EVA
range of recommended EVA gel contents • Manufacturer B and D are obviously not
in control of their lamination process. EPCs are likely to stop PV power plant projects facing such results.
Expected loss: 450 k€per planned MWp as modules will not be sold plus handling and transportation.
• Overcuring compared to EVA gel content eats up precious equipment time. An eats up precious equipment time. An additional 5 – 10 % gel content needs easily 1 – 2 min additional curing. Adjusting cycle time* accordingly will
increase capacity by 7 % (14 %)or spare every 14th (7th) shift.
Counteraction: Close monitoring of lamination process and EVA gel content determination procedure.
Inadequate long-term DH stability
• Performance of manufacturer C (purple) isimpressive, that of manufacturer A (green) just fine enough.
• The dramatic drop in performance puts a slight question mark behind manufacturer B (yellow).
• For modules from manufacturer E (pink) the probability of failing after 10 years in the field is very high. The investor faces a loss of 50 %
today´s minimum requirement for DH stability
is very high. The investor faces a loss of 50 % of the expected turn-over of 20 years
(2.5 Mio € / MWp). The manufacturer faces 450 k€ per MWp replacement costs plus handling and transport.
• But what is wrong with manufacturer D (blue)? One module performs just fine, the other fails after 2000 h DH. Unstable
production process, different materials, outsourced production?
Counteraction: thorough material qualification, tight production monitoring, no outsourcing.
Microcracks and broken cells
The client´s point of view:• Modules with broken cells are usually not accepted by clients as they imply poor craftsmanship in module production. Financial loss: no sales at all
• Clients typically only accept modules with a very low number of microcracks as they do not know which microcrack will evolve into a safety hazard or power loss.
Financial loss: no sales at all.
The manufacturer´s point of view: The manufacturer´s point of view:
• Typically internal pass criteria for number of broken cells and microcracks exist for PV modules.
• A module that does not pass the final inspection does cost the manufacturer 0,5 €/Wp or 120 €/module.
• A cell that does not pass incoming goods control does cost the manufacturer 0,38 €/Wp or 1,6 €/cell.
• The earlier a failure is detected the less expensive it is!
Counteraction: incoming goods inspection, continuous quality assurance in production.
We have seen that QA and QM involves at least the check for non-conforming materials and processes, monitoring and tightening of process parameters and long-term reliability testing.
We have also shown that these activities result in increase of yield, through-put and turnover.
And this is basically what production optimization is all about. And tools to do so already exists. They have been developed e. g. in the automotive and semiconductor industry and can be easily adapted for the use in solar:
• Non conforming material or product disposition by MRB (Material Review Board)
• Process distribution can be tightened by e.g. L6S methods (Lean Six Sigma)
Production optimization as a result of QA and QM
• Process change requests and their roll-out needs to be reviewed and documented by PCRB (Process Change Review Board)
• Standardized problem solving processes (like 8D)
• Introduction of accelerated ageing conditions with acceleration factors beyond DH like HAST (Highly Accelerated Lifetime Testing) to allow short feedback cycles in case of material, process or product changes
• With more tools available (e. g. DoE, SPC, CP/Cpk)
• Prerequisite: Production optimization starts with a well developed MES (Manufacturing Execution System) and an appropriate data base storing process for Key Input/output Variables (KIV/KOV), materials (batches), process revisions, operators, equipment, maintenance, etc.
Conclusion
• Failures long thought overcome also include broken cells, microcracks and finger interruptions apart from yellowing.
• New phenomena have evolved.
• We have derived the financial losses for investors and manufacturers for yellowing, inexact STC
determination, insufficiently cured EVA, inadequate long-term DH stability and broken cells /microcracks. They can amount to more than a million Euro.
• Counteraction to prevent these quality issues to occur are standard quality assurance and quality management tools.
management tools.
Their costs may amount to several ten thousand Euro, hardly more than 10 % of the above mentioned financial losses without counteractions.
• Costs for QA and QM are easily financed by the savings due to avoided failures and additional production capacities. They are not too high!
• QA and QM automatically result in production optimization with its increased yield, through-put and turnover. The tools are available and ready for adaptation!
