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Iec and Ieee Design Qualifications: an Analysis of Test Results Acquired over Nine Years
| Content Provider | Semantic Scholar |
|---|---|
| Author | Arends, Todd Kuitche, Joseph M. Shisler, W. Kang, Yi Tamizhmani, Govindasamy |
| Copyright Year | 2006 |
| Abstract | Bo Li, Todd Arends, Joseph Kuitche, William Shisler, Yi Kang, Govindasamy TamizhMani Arizona State University Photovoltaic Testing Laboratory (ASU-PTL) 7349 E. Unity Ave. Mesa, AZ 85212 USA Telephone: +1-480-727-1241, Fax: +1-775-314-6458, e-mail: manit@asu.edu ABSTRACT: The long term reliability of field deployed photovoltaic modules is dictated by four factors: (i) design quality, (ii) production quality, (iii) array/system configuration and (iv) actual combination of environmental conditions of the field. This paper discusses the design quality issues identified during the design qualification testing at ASU-PTL. The qualification testing does not, as anticipated, identify all the possible reliability issues in the actual field; however, it does identify the major/catastrophic design quality issues. ASU-PTL has been providing photovoltaic testing services since 1992 and has issued about 300 design qualification and type approval certificates. ASU-PTL received/continued its accreditation [per ISO17025 standard; formerly ISO Guide 25] in/since 1997 to provide testing services per IEC61215 (flat plate crystalline silicon), IEC61646 (flat plate thin film), IEEE1262 (flat plate crystalline silicon and thin film), UL 1703 (flat plate crystalline silicon and thin film) and IEEE1513 (concentrator) standards. These standards call for stress tests and non-stress tests before/after the stress tests. This paper presents an analysis on the design qualification test data, per IEC61215, IEC1646 and IEEE1262 standards, acquired between 1997 and 2005. During this period, about 1200 modules (87% c-Si and 13% thin-film technologies) have been subjected to over 8500 tests (including the performance tests). About 20% of these tests were stress tests and the other 80% were non-stress tests conducted before and after the stress tests. The results of all these tests were analyzed using, primarily, three approaches: (i) identify the percentage/order of failure rates for crystalline silicon technologies and thin-film technologies, (ii) identify the primary/potential reasons for these failures [viz. performance drop, major visual defect, dry/wet insulation breakdown], and (iii) finally, report the actual percent of power drop after the individual stress test. These data analyses indicate that the four of the highest failure rates, for c-Si technologies, were associated to damp-heat, thermal cycling (200 cycles), static load and bypass diode thermal stress tests. The primary reasons for failures in damp heat, thermal cycling static load and diode tests were performance drop beyond the maximum allowed limit of 5%, performance drop beyond the maximum allowed limit of 5%, module breakage and diode overheating beyond the maximum allowed junction temperature, respectively. The performance drop in damp heat and thermal cycling tests were primarily attributed to corrosion of cell components (due to moisture ingression) and differential thermal expansion of cell components (especially due to solder bonding and interconnect materials), respectively. The static load failure is attributed to inappropriate frame thickness, profile and/or design. The diode overheating was attributed to the use of underrated diodes. The highest failure rates, for thin-film technologies, were associated to damp-heat, outdoor exposure, static load and humidity-freeze stress tests. In conclusion, this investigation demonstrates that the accelerated stress tests used in the qualification testing and type approval programs do identify the major/potential design issues of photovoltaic modules. Keywords: Degradation, Performance, Qualification and Testing, Reliability 1 INTRODUCTION The long term energy production (or reliability and durability) of photovoltaic modules in the actual field conditions is as critical as the initial performance/power under standard test conditions (STC) because the consumers essentially pay for the energy production over 20-30 years, not just for the initial power. The long term reliability of field deployed photovoltaic modules is dictated by four factors: (i) design quality, (ii) production quality, (iii) array/system configuration and (iv) actual combination of environmental conditions of the field. The module design quality is dictated by various parameters including the physical, chemical, electrical, optical and mechanical properties of cell/construction materials, cell and circuit design processes and packaging processes. The production quality is dictated by the material procurement control and process control including the workmanship related to manual soldering and junction box attachment. The array/system configuration such as the resistance of inadequate cable size and mounting methods also influence, to a notable extent, the reliability of the modules. The design qualified and production quality controlled modules could still fail, though to a very less extent, in the actual field as they may experience different combination/extent of environmental conditions. This paper discusses the design quality issues identified during the design qualification testing at ASU-PTL. The design qualification testing is a set of well-defined accelerated stress tests [irradiation, environmental, mechanical and electrical] with strict pass/fail criteria1. The type, extent, limits and combination of these accelerated stress tests have been stipulated with two goals in mind: (i) accelerate the same failure mechanisms observed in the field without causing failures that do not occur in the filed, and (ii) induce these failure mechanisms in a reasonably short amount of time, say 70-120 days. The qualification testing does not, as anticipated, identify all the possible reliability issues in the actual field; however, it does identify the major/potential design quality issues. ASU-PTL has been providing photovoltaic testing services since 1992 and has issued about 300 design qualification and type approval certificates. These design qualification tests (and the corresponding type approval certificates) are |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://staff.aist.go.jp/k.otani/oitda/2078.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
