John Wohlgemuth - Academia.edu (original) (raw)
Papers by John Wohlgemuth
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send oomments regarding this burden estimate or any other aspect of this oollection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson
JPL Block tests especially Block V helped improve the reliability and durability of PV modules. Q... more JPL Block tests especially Block V helped improve the reliability and durability of PV modules. Qualification tests reduce infant mortality, cannot validate warranty service lifetime but may be used to provide comparative information. The International PV Module Quality Assurance Task Force was established in 2011 to improve PV lifetime predictions. The QA Task Force has created Task Groups for 1. Manufacturing Consistency, 2.Thermal and mechanical fatigue and vibration, 3. Humidity, temperature, and voltage, 4. Diodes, shading and reverse bias, 5. UV, temperature and humidity, 6. Communication of PV QA ratings to the community, 7. Snow and Wind Loading, 8. Thin-film PV, 9. CPV and 10. Connectors and Junction Boxes. Task Group 8 Thin-film PV formed in 2012 has identified important failure modes in the following areas: Corrosion, Semiconductor junction degradation, Interconnection degradation, Delamination, Diodes and shading, Glass breakage and special issues for flexible packages. This group is compiling observed failure modes and has decided that the existing task groups 2, 3, 4, and 7 covered the requisite essential accelerated tests in those areas and has assigned volunteers to them. Group 8 created subgroups to define the acceleration tests in Semiconductor Junction Degradation, Monolithic Interconnection, Micro-delamination, Shading and Flexible Packages. Subgroups are holding conference calls, creating a bibliography and are compiling cell and module data. Please join as volunteers and participate actively.
Efforts to fabricate high efficiency, ultrathin coplanar back contact cells are described. Includ... more Efforts to fabricate high efficiency, ultrathin coplanar back contact cells are described. Included is a description of design considerations, cell fabrication, and theoretical and experimental analyses of loss mechanisms. The results of these efforts has been the fabrication of a 11.8% AM0 efficient, 50 micron cell when measured at 25 C. Design and process changes required to increase the efficiency
Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002.
... and reclamation from used slurry; wa-ter-based slurries; multiple wire use; multiple mounting... more ... and reclamation from used slurry; wa-ter-based slurries; multiple wire use; multiple mounting tables on older-generation saws; and diamond ... Rheological studies conducted by Moving Die Rheometer (MDR) as presented in Figure 6, below, indicate that within the first 2.5 ...
Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference, 1988
In order to optimize production processes used to make solar cells, it is helpful to have experim... more In order to optimize production processes used to make solar cells, it is helpful to have experimental access to the effects of the process by measuring parameters more fundamental than those derived from the current-voltage characteristics of finished devices. The authors have developed a set of nine small cells which can be made on a single substrate using the same
Reliability of Photovoltaic Cells, Modules, Components, and Systems VI, 2013
19th IEEE …, 1987
Impurities in the crucible used to case polycrystalline silicon lead to a reduction in the bulk l... more Impurities in the crucible used to case polycrystalline silicon lead to a reduction in the bulk lifetime of the silicon adjacent to the crucible. This effect by plots of cell short-circuit current and diffusion length as a function of distance from the side of the ingot. Lower values obtained near the outer edge result in lower overall cell efficiencies and
2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017
Investors would like to be confident that a PV plant will work as promised before investing large... more Investors would like to be confident that a PV plant will work as promised before investing large sums of money. Data showing that PV modules can withstand thousands of hours of accelerated testing are a comfort, but are not sufficient to characterize the economic useful life (EUL) of the whole PV system. An inability to be confident of every aspect of the system can motivate less favorable contract terms. In the end, a winning partnership is obtained when a carefully engineered, durable design is married with a robust quality management system and the marriage is extended across all parts of the value chain. However, this marriage is challenging because of the conventional cultural divide between design engineers and quality management specialists. International standards are being developed to facilitate this partnership and include technology-specific requirements in the quality management systems used for component manufacture and system design, construction and operation.JRC.C.2-Energy Efficiency and Renewable
One would hope that PV modules are designed for survival in the outdoors. However, it appears tha... more One would hope that PV modules are designed for survival in the outdoors. However, it appears that some module types are really designed to pass the qualification (IEC 61216/61646) and safety (IEC 61730 and UL 1703) tests. While this has resulted in an overall increase in module reliability and a reduction in infant mortality, it may not result in the most cost-effective solution for long-term reliability and minimum power degradation. This paper will provide several examples of module types and even solar cells designed to pass the tests that do not result in good cost-effective long-term solutions for outdoor performance. This presentation is meant to stimulate a discussion about how to remedy this situation and improve the overall PV industry.
Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference, 2005.
Hot spot heating occurs when a module's operating current exceeds the reduced short circuit c... more Hot spot heating occurs when a module's operating current exceeds the reduced short circuit current of a shadowed or faulty cell or group of cells within the module. In order to determine whether a crystalline silicon module is adequately protected against hot spots, two hot spot test have been developed and utilized as a part of IEC 61215 "Crystalline silicon terrestrial photovoltaic (PV) modules - Design qualification and type approval" and as part of UL 1703 "UL Standard for Safety for Flat-Plate Photovoltaic Modules and Panels". Each of these tests has some problems. Working Group 2 of IEC Technical Committee 82 on photovoltaics is developing a revised hot spot test as a modification to IEC 61215. Major features of the revision include 1) a new way of identifying low and high shunt cells by measuring a set of IV curves for a module with each cell shadowed in turn, 2) selection and testing of 3 low shunt cells and one high shunt cell, 3) providing modified procedures to determine the worst case shadowing for the selected cells and 4) testing of the low shunt cells for 1 hour and of the high shunt cell for a longer time (still to be determined).
: This work on nonreflective vertical-junction silicon solar cells has resulted in high conversio... more : This work on nonreflective vertical-junction silicon solar cells has resulted in high conversion efficiency radiation resistant solar cells. New techniques of oxidation growth and the use of photolothography enable the use of an orientation dependent etch to produce grooves 5-10 microns wide and over 100 microns deep. These silicon wafers have been processed into solar cells with all of the processes performed at temperatures compatible with producing high efficiency solar cells. A theoretical calculation of the generated current for the vertical junction structure was performed. It indicates the decreased dependence on carrier diffusion length and, therefore, the reduced effect of radiation damage on collection efficiency for vertical junction solar cells. Vertical junction solar cells 2 cm x 2 cm in size have been fabricated with AMO conversion efficiencies greater than 13%. These cells have shown superior radiation resistance. (Author)
L’invention concerne un systeme de toiture a cellule solaire integree composee de bandes de group... more L’invention concerne un systeme de toiture a cellule solaire integree composee de bandes de groupes de cellules solaires. Chaque bande se compose d‘une longueur d’un substrat d’un materiau flexible etanche a l’eau. Une premiere couche de materiau de liaison est enduite sur le substrat sur lequel se trouve un groupe de cellules photovoltaiques (PV) precâblees. Une seconde couche de materiau de liaison est appliquee et une feuille de feuille rigide individuelle est appliquee sur la seconde couche au-dessus de chaque groupe de cellules PV. On applique ensuite de la chaleur et du vide pour faire fondre les materiaux de liaison, pour ainsi relier les groupes de cellules PV et la feuille de verre sur le substrat pour constituer des groupes de cellules solaires espacees sur celui-ci. On peut ensuite replier la bande en accordeon a des fins de manipulation.
ABSTRACT: This paper discusses how BP Solar utilizes long term module exposure data, field return... more ABSTRACT: This paper discusses how BP Solar utilizes long term module exposure data, field return data and accelerated stress tests to determine module lifetimes, expected failure rates and to identify failure mechanisms. A small number of modules have been deployed outdoors for long time periods with periodic measurements of performance in order to establish degradation rates. Field returns are reviewed for both overall return rates and to identify the failure mechanism that caused the return. Accelerated stress tests are utilized to evaluate commercial products and all new materials, processes and designs against known failure mechanisms. In order to ensure the 25 year warranty offered on most crystalline silicon products, BP Solar has designed an extended accelerated test sequence. This paper presents results of this test sequence as applied to BP Solar modules as well as to modules from nine other PV manufacturers.
This presentation describes fatigue experiments and discusses dynamic mechanical loading for Cu r... more This presentation describes fatigue experiments and discusses dynamic mechanical loading for Cu ribbon interconnects.
In commercial production, Solarex's baseline multicrystalline solar cells are 130 cm2 in area... more In commercial production, Solarex's baseline multicrystalline solar cells are 130 cm2 in area with an average efficiency of approximately 13%. One of the goals of Solarex's Photovoltaic Ma Technology (PVMaT) program (sponsored the development of a cost effective cell process to achieve an average cell efficiency of 15% on large area substrates. In this paper the details of the efforts to scale up the area of the cells from 130 cm2 to 230 cm2 and the details of the development of an integrated high cell process sequence are reported.
2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), 2016
Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper... more Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper will present examples of various types of delaminations that have been observed in the field. It will then discuss the development of accelerated stress tests designed to duplicate those field failures and thus provide tools for avoiding them in the future.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send oomments regarding this burden estimate or any other aspect of this oollection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson
JPL Block tests especially Block V helped improve the reliability and durability of PV modules. Q... more JPL Block tests especially Block V helped improve the reliability and durability of PV modules. Qualification tests reduce infant mortality, cannot validate warranty service lifetime but may be used to provide comparative information. The International PV Module Quality Assurance Task Force was established in 2011 to improve PV lifetime predictions. The QA Task Force has created Task Groups for 1. Manufacturing Consistency, 2.Thermal and mechanical fatigue and vibration, 3. Humidity, temperature, and voltage, 4. Diodes, shading and reverse bias, 5. UV, temperature and humidity, 6. Communication of PV QA ratings to the community, 7. Snow and Wind Loading, 8. Thin-film PV, 9. CPV and 10. Connectors and Junction Boxes. Task Group 8 Thin-film PV formed in 2012 has identified important failure modes in the following areas: Corrosion, Semiconductor junction degradation, Interconnection degradation, Delamination, Diodes and shading, Glass breakage and special issues for flexible packages. This group is compiling observed failure modes and has decided that the existing task groups 2, 3, 4, and 7 covered the requisite essential accelerated tests in those areas and has assigned volunteers to them. Group 8 created subgroups to define the acceleration tests in Semiconductor Junction Degradation, Monolithic Interconnection, Micro-delamination, Shading and Flexible Packages. Subgroups are holding conference calls, creating a bibliography and are compiling cell and module data. Please join as volunteers and participate actively.
Efforts to fabricate high efficiency, ultrathin coplanar back contact cells are described. Includ... more Efforts to fabricate high efficiency, ultrathin coplanar back contact cells are described. Included is a description of design considerations, cell fabrication, and theoretical and experimental analyses of loss mechanisms. The results of these efforts has been the fabrication of a 11.8% AM0 efficient, 50 micron cell when measured at 25 C. Design and process changes required to increase the efficiency
Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002.
... and reclamation from used slurry; wa-ter-based slurries; multiple wire use; multiple mounting... more ... and reclamation from used slurry; wa-ter-based slurries; multiple wire use; multiple mounting tables on older-generation saws; and diamond ... Rheological studies conducted by Moving Die Rheometer (MDR) as presented in Figure 6, below, indicate that within the first 2.5 ...
Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference, 1988
In order to optimize production processes used to make solar cells, it is helpful to have experim... more In order to optimize production processes used to make solar cells, it is helpful to have experimental access to the effects of the process by measuring parameters more fundamental than those derived from the current-voltage characteristics of finished devices. The authors have developed a set of nine small cells which can be made on a single substrate using the same
Reliability of Photovoltaic Cells, Modules, Components, and Systems VI, 2013
19th IEEE …, 1987
Impurities in the crucible used to case polycrystalline silicon lead to a reduction in the bulk l... more Impurities in the crucible used to case polycrystalline silicon lead to a reduction in the bulk lifetime of the silicon adjacent to the crucible. This effect by plots of cell short-circuit current and diffusion length as a function of distance from the side of the ingot. Lower values obtained near the outer edge result in lower overall cell efficiencies and
2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017
Investors would like to be confident that a PV plant will work as promised before investing large... more Investors would like to be confident that a PV plant will work as promised before investing large sums of money. Data showing that PV modules can withstand thousands of hours of accelerated testing are a comfort, but are not sufficient to characterize the economic useful life (EUL) of the whole PV system. An inability to be confident of every aspect of the system can motivate less favorable contract terms. In the end, a winning partnership is obtained when a carefully engineered, durable design is married with a robust quality management system and the marriage is extended across all parts of the value chain. However, this marriage is challenging because of the conventional cultural divide between design engineers and quality management specialists. International standards are being developed to facilitate this partnership and include technology-specific requirements in the quality management systems used for component manufacture and system design, construction and operation.JRC.C.2-Energy Efficiency and Renewable
One would hope that PV modules are designed for survival in the outdoors. However, it appears tha... more One would hope that PV modules are designed for survival in the outdoors. However, it appears that some module types are really designed to pass the qualification (IEC 61216/61646) and safety (IEC 61730 and UL 1703) tests. While this has resulted in an overall increase in module reliability and a reduction in infant mortality, it may not result in the most cost-effective solution for long-term reliability and minimum power degradation. This paper will provide several examples of module types and even solar cells designed to pass the tests that do not result in good cost-effective long-term solutions for outdoor performance. This presentation is meant to stimulate a discussion about how to remedy this situation and improve the overall PV industry.
Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference, 2005.
Hot spot heating occurs when a module's operating current exceeds the reduced short circuit c... more Hot spot heating occurs when a module's operating current exceeds the reduced short circuit current of a shadowed or faulty cell or group of cells within the module. In order to determine whether a crystalline silicon module is adequately protected against hot spots, two hot spot test have been developed and utilized as a part of IEC 61215 "Crystalline silicon terrestrial photovoltaic (PV) modules - Design qualification and type approval" and as part of UL 1703 "UL Standard for Safety for Flat-Plate Photovoltaic Modules and Panels". Each of these tests has some problems. Working Group 2 of IEC Technical Committee 82 on photovoltaics is developing a revised hot spot test as a modification to IEC 61215. Major features of the revision include 1) a new way of identifying low and high shunt cells by measuring a set of IV curves for a module with each cell shadowed in turn, 2) selection and testing of 3 low shunt cells and one high shunt cell, 3) providing modified procedures to determine the worst case shadowing for the selected cells and 4) testing of the low shunt cells for 1 hour and of the high shunt cell for a longer time (still to be determined).
: This work on nonreflective vertical-junction silicon solar cells has resulted in high conversio... more : This work on nonreflective vertical-junction silicon solar cells has resulted in high conversion efficiency radiation resistant solar cells. New techniques of oxidation growth and the use of photolothography enable the use of an orientation dependent etch to produce grooves 5-10 microns wide and over 100 microns deep. These silicon wafers have been processed into solar cells with all of the processes performed at temperatures compatible with producing high efficiency solar cells. A theoretical calculation of the generated current for the vertical junction structure was performed. It indicates the decreased dependence on carrier diffusion length and, therefore, the reduced effect of radiation damage on collection efficiency for vertical junction solar cells. Vertical junction solar cells 2 cm x 2 cm in size have been fabricated with AMO conversion efficiencies greater than 13%. These cells have shown superior radiation resistance. (Author)
L’invention concerne un systeme de toiture a cellule solaire integree composee de bandes de group... more L’invention concerne un systeme de toiture a cellule solaire integree composee de bandes de groupes de cellules solaires. Chaque bande se compose d‘une longueur d’un substrat d’un materiau flexible etanche a l’eau. Une premiere couche de materiau de liaison est enduite sur le substrat sur lequel se trouve un groupe de cellules photovoltaiques (PV) precâblees. Une seconde couche de materiau de liaison est appliquee et une feuille de feuille rigide individuelle est appliquee sur la seconde couche au-dessus de chaque groupe de cellules PV. On applique ensuite de la chaleur et du vide pour faire fondre les materiaux de liaison, pour ainsi relier les groupes de cellules PV et la feuille de verre sur le substrat pour constituer des groupes de cellules solaires espacees sur celui-ci. On peut ensuite replier la bande en accordeon a des fins de manipulation.
ABSTRACT: This paper discusses how BP Solar utilizes long term module exposure data, field return... more ABSTRACT: This paper discusses how BP Solar utilizes long term module exposure data, field return data and accelerated stress tests to determine module lifetimes, expected failure rates and to identify failure mechanisms. A small number of modules have been deployed outdoors for long time periods with periodic measurements of performance in order to establish degradation rates. Field returns are reviewed for both overall return rates and to identify the failure mechanism that caused the return. Accelerated stress tests are utilized to evaluate commercial products and all new materials, processes and designs against known failure mechanisms. In order to ensure the 25 year warranty offered on most crystalline silicon products, BP Solar has designed an extended accelerated test sequence. This paper presents results of this test sequence as applied to BP Solar modules as well as to modules from nine other PV manufacturers.
This presentation describes fatigue experiments and discusses dynamic mechanical loading for Cu r... more This presentation describes fatigue experiments and discusses dynamic mechanical loading for Cu ribbon interconnects.
In commercial production, Solarex's baseline multicrystalline solar cells are 130 cm2 in area... more In commercial production, Solarex's baseline multicrystalline solar cells are 130 cm2 in area with an average efficiency of approximately 13%. One of the goals of Solarex's Photovoltaic Ma Technology (PVMaT) program (sponsored the development of a cost effective cell process to achieve an average cell efficiency of 15% on large area substrates. In this paper the details of the efforts to scale up the area of the cells from 130 cm2 to 230 cm2 and the details of the development of an integrated high cell process sequence are reported.
2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), 2016
Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper... more Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper will present examples of various types of delaminations that have been observed in the field. It will then discuss the development of accelerated stress tests designed to duplicate those field failures and thus provide tools for avoiding them in the future.