Dr. John H. Wohlgemuth Profile

Dr. John H. Wohlgemuth

at National Renewable Energy Lab

SPIE Involvement:

Editor | Author | Instructor

Proceedings Article | 26 September 2016 Presentation + Paper

Investigation of a wedge adhesion test for edge seals

Michael Kempe, John Wohlgemuth, David Miller, Lori Postak, Dennis Booth, Nancy Phillips

Proceedings Volume 9938, 993803 (2016) https://doi.org/10.1117/12.2239161

KEYWORDS: Photovoltaics, Glasses, Humidity, Ultraviolet radiation, Solar cells, Adhesives, Calcium, Polymers, Visualization, Opacity

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Many photovoltaic (PV) technologies have been found to be sensitive to moisture that diffuses into a PV package. Even with the use of impermeable frontsheets and backsheets, moisture can penetrate from the edges of a module. To limit this moisture ingress pathway from occurring, manufacturers often use a low permeability polyisobutylene (PIB) based edge seal filled with desiccant to further restrict moisture ingress. Moisture ingress studies have shown that these materials are capable of blocking moisture for the 25-year life of a module; but to do so, they must remain well-adhered and free of cracks. This work focuses on adapting the Boeing Wedge test for use with edge seals laminated using glass substrates as part of a strategy to assess the long-term durability of edge seals. The advantage of this method is that it duplicates the residual stresses and strains that a glass/glass module may have when the lamination process results in some residual glass bending that puts the perimeter in tension. Additionally, this method allows one to simultaneously expose the material to thermal stress, humidity, mechanical stress, and ultraviolet radiation. The disadvantage of this method generally is that we are limited by the fracture toughness of the glass substrates that the edge seal is adhered to. However, the low toughness of typical uncrosslinked or sparsely crosslinked PIB makes them suitable for this technique. We present data obtained during the development of the wedge test for use with PV edge seal materials. This includes development of the measuring techniques and evaluation of the test method with relevant materials. We find consistent data within a given experiment, along with the theoretical independence of fracture toughness measurements with wedge thickness. This indicates that the test methodology is reproducible. However, even though individual experimental sets are consistent, the reproducibility between experimental sets is poor. We believe this may be due to inconsistencies in sample history, sample batch, or small changes in sample preparation/assembly from one month to the next. Because the fracture strength of typical edge seal materials is so low, they cannot be relied upon for mechanical strength. A small stress or strain on the edge seal is capable of promoting delamination or tearing causing the edge seal to fail. Because of this, edge seals are very dependent on the processing and construction parameters in the full size PV module such that any long term evaluation of their durability must be conducted on full size modules to be accurate.

SPIE Journal Paper | 17 December 2015

Survey of potential-induced degradation in thin-film modules

Peter Hacke, Kent Terwilliger, Stephen Glick, Greg Perrin, John Wohlgemuth, Sarah Kurtz, Keith Showalter, John Sherwin, Eric Schneller, Stephen Barkaszi, Ryan Smith

JPE, Vol. 5, Issue 01, 053083, (December 2015) https://doi.org/10.1117/12.10.1117/1.JPE.5.053083

KEYWORDS: Copper indium gallium selenide, Thin films, Corrosion, Transparent conductors, Resistance, Humidity, Glasses, Sodium, Environmental sensing, Electroluminescence

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Proceedings Article | 23 September 2015 Paper

Development of a resistivity standard for polymeric materials used in photovoltaic modules

Michael Kempe, David Miller, Dylan Nobles, Keiichiro Sakurai, John Tucker, Jayesh Bokria, Tsuyoshi Shioda, Kumar Nanjundiah, Toshio Yoshihara, Jeff Birchmier, Oihana Zubillaga, John Wohlgemuth

Proceedings Volume 9563, 956302 (2015) https://doi.org/10.1117/12.2189662

KEYWORDS: Polymers, Standards development, Photovoltaics, Humidity, Electrodes, Positron emission tomography, Solar cells, Diamond, Time metrology, Ions

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Proceedings Article | 8 October 2014 Paper

A review of manufacturing metrology for improved reliability of silicon photovoltaic modules

Kristopher Davis, Joseph Walters, Eric Schneller, Hubert Seigneur, R. Paul Brooker, Giuseppe Scardera, Marianne Rodgers, Nahid Mohajeri, Narendra Shiradkar, Neelkanth Dhere, John Wohlgemuth, Andrew Rudack, Winston Schoenfeld

Proceedings Volume 9179, 91790Y (2014) https://doi.org/10.1117/12.2063781

KEYWORDS: Manufacturing, Reliability, Metrology, Silicon, Semiconducting wafers, Photovoltaics, Crystals, Solar cells, Diodes, Silicon solar cells

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Proceedings Article | 8 October 2014 Paper

Research, test, and development activities performed by junction box bypass diode task force # 4

Vivek Gade, Narendra Shiradkar, Paul Robusto, Kent Whitfield, John Wohlgemuth, Yasunori Uchida, Neelkanth Dhere

Proceedings Volume 9179, 91790H (2014) https://doi.org/10.1117/12.2062195

KEYWORDS: Diodes, Solar cells, Manufacturing, Temperature metrology, Reliability, Standards development, Failure analysis, Resistance, Photovoltaics, Renewable energy

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Proceedings Article | 6 October 2014 Open Access

International PV QA Task Force's proposed comparative rating system for PV modules

John Wohlgemuth, Sarah Kurtz

Proceedings Volume 9179, 917902 (2014) https://doi.org/10.1117/12.2067927

KEYWORDS: Solar cells, Climatology, Ultraviolet radiation, Photovoltaics, Humidity, Corrosion, Manufacturing, Laser sintering, Standards development, Diodes

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Proceedings Article | 24 September 2013 Paper

Examination of an optical transmittance test for photovoltaic encapsulation materials

David Miller, Jaione Bengoechea, Jayesh Bokria, Michael Köhl, Nick Powell, Michael Smith, Michael White, Helen Rose Wilson, John Wohlgemuth

Proceedings Volume 8825, 882509 (2013) https://doi.org/10.1117/12.2024372

KEYWORDS: Transmittance, Silica, Photovoltaics, Ultraviolet radiation, Polymers, Glasses, Spectrophotometry, Solar cells, Standards development, Integrating spheres

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Proceedings Article | 24 September 2013 Paper

Predicting PV module service life

John Wohlgemuth, Sarah Kurtz, Tony Sample, Masaaki Yamamichi

Proceedings Volume 8825, 882503 (2013) https://doi.org/10.1117/12.2027754

KEYWORDS: Solar cells, Ultraviolet radiation, Diodes, Photovoltaics, Humidity, Manufacturing, Thin films, Climatology, Reliability, Standards development

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SPIE Journal Paper | 17 December 2012 Open Access

Special Section Guest Editorial: Guest Editorial: Special Section on Reliability of Photovoltaic Cells, Modules, Components, and Systems

Neelkanth Dhere, John Wohlgemuth, Kevin Lynn

JPE, Vol. 2, Issue 1, 022099, (December 2012) https://doi.org/10.1117/12.10.1117/1.JPE.2.022099

KEYWORDS: Solar cells, Reliability, Photovoltaics, Manufacturing, Solar energy systems, Solar energy, Switches, Data modeling, Roads, Renewable energy

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Proceedings Article | 16 October 2012 Paper

Examination of a junction-box adhesion test for use in photovoltaic module qualification

David Miller, John Wohlgemuth

Proceedings Volume 8472, 84720M (2012) https://doi.org/10.1117/12.929793

KEYWORDS: Silicon, Adhesives, Foam, Glasses, Positron emission tomography, Photovoltaics, Manufacturing, Solar cells, Tin, Interfaces

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Proceedings Article | 16 October 2012 Paper

Examination of a size-change test for photovoltaic encapsulation materials

David Miller, Xiaohong Gu, Liang Ji, George Kelly, Nichole Nickel, Paul Norum, Tsuyoshi Shioda, Govindasamy Tamizhmani, John Wohlgemuth

Proceedings Volume 8472, 84720T (2012) https://doi.org/10.1117/12.929796

KEYWORDS: Aluminum, Glasses, Manufacturing, Standards development, Temperature metrology, Solar cells, Photography, Thermography, Photovoltaics, Solids

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Proceedings Article | 13 September 2011 Paper

Developing standards for PV packaging materials

John Wohlgemuth, Michael Kempe, David Miller, Sarah Kurtz

Proceedings Volume 8112, 81120A (2011) https://doi.org/10.1117/12.892794

KEYWORDS: Standards development, Photovoltaics, Solar cells, Safety, Polymers, Transmittance, Silicon, Thin films, Packaging, Manufacturing

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Proceedings Article | 20 August 2009 Paper

A semi-empirical method of predicting the lifetime of EVA encapsulant and polyester based backsheet materials

Zhiyong Xia, John Wohlgemuth, Daniel Cunningham

Proceedings Volume 7412, 74120B (2009) https://doi.org/10.1117/12.825472

KEYWORDS: Positron emission tomography, Polymers, Crystals, Solar cells, Humidity, Ultraviolet radiation, Temperature metrology, Reliability, Solar energy, Glasses

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Proceedings Article | 10 September 2008 Paper

Reliability of PV systems

John Wohlgemuth

Proceedings Volume 7048, 704802 (2008) https://doi.org/10.1117/12.795248

KEYWORDS: Photovoltaics, Reliability, Solar cells, Silicon, Crystals, Diodes, Humidity, Solar energy, Systems modeling

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Showing 5 of 14 publications

SPIE Conference Volume | 18 November 2016

Reliability of Photovoltaic Cells, Modules, Components, and Systems IX

SPIE Conference Volume | 14 October 2015

Reliability of Photovoltaic Cells, Modules, Components, and Systems VIII

SPIE Conference Volume | 4 November 2014

Reliability of Photovoltaic Cells, Modules, Components, and Systems VII

SPIE Conference Volume | 27 September 2013

Reliability of Photovoltaic Cells, Modules, Components, and Systems VI

SPIE Conference Volume | 1 November 2012

Reliability of Photovoltaic Cells, Modules, Components, and Systems V

Showing 5 of 9 publications

Conference Committee Involvement (9)

Reliability of Photovoltaic Cells, Modules, Components, and Systems IX

28 August 2016 | San Diego, California, United States

Reliability of Photovoltaic Cells, Modules, Components, and Systems VIII

9 August 2015 | San Diego, California, United States

Reliability of Photovoltaic Cells, Modules, Components, and Systems VII

20 August 2014 | San Diego, California, United States

Reliability of Photovoltaic Cells, Modules, Components, and Systems VI

27 August 2013 | San Diego, California, United States

Reliability of Photovoltaic Cells, Modules, Components, and Systems V

14 August 2012 | San Diego, California, United States

Showing 5 of 9 Conference Committees

Course Instructor

SC910: Design and Reliability of Photovoltaic Modules

Photovoltaic module design draws on knowledge from many disciplines: optical, electronic, mechanical and quality engineering. This course provides attendees with a basic working knowledge of photovoltaic (PV) module design and reliability. A brief summary of the Physics of Failure of Electronic Packages will be presented. The history of PV module field failures will be presented along with a description of how this field experience has been utilized to develop more reliable modules and accelerated stress tests to more rapidly evaluate module performance. The concept of qualification testing will be introduced with a discussion on its usefulness and limitations. Typical module configurations will be presented along with a discussion of the criteria utilized for component selection within these configurations. A number of examples based on commercial module construction will be used to illustrate these points. The long term reliability, degradation rates and lifetime for the present day commercial modules will be discussed.

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