AET and HALT. Accelerated Environmental Stress Testing in the PV World. Dr. David P. Dumbleton Senior Consultant

Transcription

1 AET and HALT Accelerated Environmental Stress Testing in the PV World Dr. David P. Dumbleton Senior Consultant

2 Prediction is very difficult, especially if it s about the future - Niels Bohr The Nobel Prize in Physics 1922 Creator of the Bohr Atomic Model

3 Content What characterizes an environmental durability test method? What is the difference between the IEC test program and weathering testing? A proposed testing methodology to simulate ageing of PV modules in an accelerated way.

4 The Environment There are many different kinds of environment Different environment durability tests If the environment is earth s surface Weathering test

5 The Science of Weathering Combined efforts of several disciplines to Understand, Measure, Predict, Simulate, and Accelerate The property changes of Materials, Parts, and Products That occur due to the combined impact of Primary and Secondary Weather factors.

6 Multi-disciplinary Approach Physics Chemistry Biology Mathematics Material Testing Photo Chemistry Erythema Research Numerical Environmental Simulation Sensor Technology Reaction Kinetics Photo Biology DOE - Design of Experiments Meteorology Polymer Chemistry Statistics Conservation Service Life Prediction - SLP Radiometry FMEA, FMECA Corrosion Protection

7 Characteristic failure modes Cracking Rusting Delamination V. Quaschning, TU Berlin, Alterungserscheinungen bei Photovoltaikmodulen, Langzeiterfahrung einer PV- Testanlage an der TU-Berlin, 14th Symposium on PV Solar Energy, Bad Staffelstein, March 1999

8 Problem solved? Materials, design, processing & construction techniques in traditional metal framed field-aged Si modules are largely different from currently manufactured products. Lessons learned from wafer Si technologies don t automatically transfer to thin film technologies, especially other semiconductors. Lessons learned from traditional wafer Si modules don t necessarily apply to other form factors such as BIPV or flexible products.

9 Primary Weather Factors

10 Secondary Weather Factors

11 Heat / Cold Temperature changes, shock Mechanical factors, e.g. abrasion by sand, dust, hail, Solar Radiation Water: Air humidity, Rain, Condensation, Snow, Ice Man-made and natural air pollutants, e.g. NO x, SO x, soot, dust, NH 3 Salt water, mist acid rain Oxygen, O 3 Biological factors, e.g. mildew, algae, bird s droppings, Ageing (microscopic) Property change (macroscopic): Function, appearance (Premature) Failure

12 Expectations from a Weathering Test Method Accelerated To get answers as quickly as possible Realistic (correlating) Same stress factors and failure modes as in real life Relevant Same chemical degradation mechanisms as in real life Precise Acceptable repeatability and reproducibility Comprehensive All relevant failure mechanisms are reproduced

13 Major Objectives of Weathering Testing To save time To reduce risk

14 Weathering - The Status Industries: automotive, plastics, coatings, pharma, textile, building materials, cosmetics, food, paints, furniture, aerospace, military, glazing, electric/electronics, etc. 1 Weathering Test Methods available Dedicated standards developing committees Many 3 Test programs in place Everywhere 4 Technology and Instrumentation Available and operating 5 Technical and scientific expertise Excellent, > 50 years 6 Industry data and experience Vast, 90 years

15 Weathering - The Status Industries: PV, Solar thermal, CPV, CST 1 Weathering Test Methods available None 2 Dedicated standards developing committees A few, just starting 3 Test programs in place None; IEC is not a weathering test 4 Technology and Instrumentation Available, with limitations 5 Technical and scientific expertise Limited, a few years 6 Industry data and experience Very limited

16 The premise The PV modules economics of PV is based on modules performing reliably for 25+ years. Weather durability performance data is needed: for product development decisions to avoid catastrophic failure to determine and support warranty to provide assurance to financial stakeholders

17 The problem Outdoor testing is a must, but it takes much too long to be of much use as a decision maker. We clearly can not wait 25 years or even a significant fraction of 25 years to introduce a new product. Therefore we must develop and utilize accelerated tests to qualify these new products. Source:

18 Complexity of SLP for modules We define what we mean by a 30-year module life and the testing protocol that we believe is involved in achieving such a prediction. However, we do not believe that a universal test (or series of tests) will allow for such a prediction to be made. We can test for a lot of things, but we believe it is impossible to provide a 30-year certification for any arbitrary photovoltaic (PV) module submitted for test. Based on known failure mechanisms, we can use AET s to estimate TTF for what we determine to be the most damaging failure modes relative to system-energy output. Unfortunately, appropriate values for acceleration factors in testing will depend on many variables and TTF will depend on the environmental stresses at the location of use. The development of a universal 30-year pass/fail certification for all PV module types cannot be expected. Module 30 Year Life : What Does it Mean and Is it Predictable/Achievable? T. J. McMahon, G. J. Jorgensen, and R. L. Hulstrom, National Renewable Energy Laboratory, Golden, CO D. L. King and M. A. Quintana, Sandia National Laboratories, Albuquerque, NM; NCPV Product Review Meeting, April 16-19,2000, Denver CO

19 IEC design qualification tests e.g. IEC 61215, IEC 61646

20 Comments on HALT HALT does not attempt to simulate the field environment- only seeks to find design and process flaws by any means possible. Intent is to determine failure modes, NOT demonstrate that a product meets specified requirements. Not meant to determine reliability but to improve it. Test environments are not directly related to real life and may be controversial. Time-dependent failure modes may not be revealed. Difficult to do on complex structures because of complex loading FMVT (failure mode verification testing).» - Gregg Hobbs, originator of HALT & HASS tests

21 IEC tests vs. long term environmental durability tests Atlas 25 plus Life Testing Screening

22 An empirical approach... Based on known PV degradation Fundamental weathering testing Experience of other industries An accelerated weather aging protocol, not a service life predictor Takes advantage of technology from weathering and reliability testing Independent of PV technology Complements IEC-type qual testing Acknowledges basic limitations & constraints

23 Synergy in weather elements Heat, Solar Radiation and Moisture act in synergy producing effects they don t alone. They can t be accelerated at the same rate, if at all.

24 Weather & climate cycles Heat, Solar Radiation and Moisture are delivered in both short term (daily) and longer term (seasonal) cycles, not in steady-state conditions.

25 Weather & climate delivery Nature doesn t change weather and climate delivery based on your product. Neither do weathering tests.

26 Empirical: Black Box approach The empirical view is not from the perspective of the module, but rather from the way that nature delivers the stresses.

27 Conclusions Lacking definitive long term aging data for Multiple modules of the same type Same manufacturer, design and materials; same processing; same exposures Multiple modules of different technologies for current designs, materials, processing Detailed knowledge of all failure modes Acceleration factors Models of simultaneous/sequential mechanisms Performance in multiple varied climates

28 Conclusions A weathering durability assessment Based on simultaneous stress delivery closer to nature Relatively independent of device specifics Based on climate-derived stress profiles Offering some reasonable degree of acceleration Based on experiences in other industries... Appears logical and of value For research & product development To support warranty and performance claims Provides independent 3 rd party data for financial stakeholders

29 Atlas 25 PLUS Durability Test Program

30 Atlas 25 PLUS is a method to simulate environmental ageing of PV modules in an accelerated way

31 Questions? Thank you for your attention!

32 For questions or a copy of this presentation ddumbleton@atlasmts.com or contact us at info@atlas-mts.com David Dumbleton Atlas Material Testing Technology LLC 2010 Atlas Material Testing Technology LLC