Veröffentlichungen
2018 |
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F. Haase, J. Käsewieter, S. R. Nabavi, E. Jansen, R. Rolfes, and M. Köntges IEEE Journal of Photovoltaics 8 (6), 1510-1524, (2018), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: Crack, mechanical loading, photovoltaic (PV) module, Silicon solar cell @article{Haase2018c,
title = {Fracture Probability, Crack Patterns, and Crack Widths of Multicrystalline Silicon Solar Cells in PV Modules During Mechanical Loading}, author = {F Haase and J Käsewieter and S R Nabavi and E Jansen and R Rolfes and M Köntges}, doi = {10.1109/JPHOTOV.2018.2871338}, issn = {2156-3381}, year = {2018}, date = {2018-11-01}, journal = {IEEE Journal of Photovoltaics}, volume = {8}, number = {6}, pages = {1510-1524}, abstract = {We experimentally analyze the position and opening behavior of cracks in multicrystalline silicon solar cells laminated in standard-sized frameless modules during mechanical loading in a 4-line-bending setup. The results of the experiment are reproduced by simulations for a standard module. These simulations open the opportunity to simulate also complex load situations. Cell interconnect ribbons have big influence to which critically extended module can be bended until a crack appears. Modules with cell interconnect ribbons that are parallel to the bending axis can be bended four times less until cell cracking than modules with cell interconnect ribbons oriented perpendicular to the bending axis and two times less compared with a module without cell interconnect ribbons. Small edge cracks parallel to the bending axis and cross cracks at the busbar decrease the critical bending in the module by a factor of four compared to small edge cracks perpendicular to the bending axis and crack-free cells. The presence of the backsheet decreases the crack width during mechanical loading by 30% compared to a module without a backsheet. In the standard module, the crack width of a single crack is 3.4 μm at loads comparable to the IEC 61215 5400 Pa test.}, keywords = {Crack, mechanical loading, photovoltaic (PV) module, Silicon solar cell}, pubstate = {published}, tppubtype = {article} } We experimentally analyze the position and opening behavior of cracks in multicrystalline silicon solar cells laminated in standard-sized frameless modules during mechanical loading in a 4-line-bending setup. The results of the experiment are reproduced by simulations for a standard module. These simulations open the opportunity to simulate also complex load situations. Cell interconnect ribbons have big influence to which critically extended module can be bended until a crack appears. Modules with cell interconnect ribbons that are parallel to the bending axis can be bended four times less until cell cracking than modules with cell interconnect ribbons oriented perpendicular to the bending axis and two times less compared with a module without cell interconnect ribbons. Small edge cracks parallel to the bending axis and cross cracks at the busbar decrease the critical bending in the module by a factor of four compared to small edge cracks perpendicular to the bending axis and crack-free cells. The presence of the backsheet decreases the crack width during mechanical loading by 30% compared to a module without a backsheet. In the standard module, the crack width of a single crack is 3.4 μm at loads comparable to the IEC 61215 5400 Pa test.
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2017 |
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H. Schulte-Huxel, R. Witteck, H. Holst, M. R. Vogt, S. Blankemeyer, D. Hinken, T. Brendemühl, T. Dullweber, K. Bothe, M. Köntges, and R. Brendel IEEE Journal of Photovoltaics 7 (1), 25-31, (2017), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: cell interconnection, Current measurement, loss analysis, Optical interconnections, Optical losses, passivated emitter and rear cell (PERC), photovoltaic (PV) module, Photovoltaic cells, Photovoltaic systems, ray tracing, Resistance, Silicon solar cell, Standards @article{Schulte-Huxel2016,
title = {High-efficiency modules with passivated emitter and rear solar cells an analysis of electrical and optical losses*}, author = {H Schulte-Huxel and R Witteck and H Holst and M R Vogt and S Blankemeyer and D Hinken and T Brendemühl and T Dullweber and K Bothe and M Köntges and R Brendel}, doi = {10.1109/JPHOTOV.2016.2614121}, issn = {2156-3381}, year = {2017}, date = {2017-01-01}, journal = {IEEE Journal of Photovoltaics}, volume = {7}, number = {1}, pages = {25-31}, abstract = {We process a photovoltaic (PV) module with 120 half passivated emitter and rear cells that exhibits an independently confirmed power of 303.2 W and a module efficiency of 20.2% (aperture area). The cells are optimized for operation within the module. We enhance light harvesting from the inactive spacing between the cells and the cell interconnect ribbons. Additionally, we reduce the inactive area to below 3% of the aperture module area. The impact of these measures is analyzed by ray-tracing simulations of the module. Using a numerical model, we analyze and predict the module performance based on the individual cell measurements and the optical simulations. We determine the power loss due to series interconnection of the solar cells to be 1.5%. This is compensated by a gain in current of 1.8% caused by the change of the optical environment of the cells in the module. We achieve a good agreement between simulations and experiments, both showing no cell-to-module power loss.}, keywords = {cell interconnection, Current measurement, loss analysis, Optical interconnections, Optical losses, passivated emitter and rear cell (PERC), photovoltaic (PV) module, Photovoltaic cells, Photovoltaic systems, ray tracing, Resistance, Silicon solar cell, Standards}, pubstate = {published}, tppubtype = {article} } We process a photovoltaic (PV) module with 120 half passivated emitter and rear cells that exhibits an independently confirmed power of 303.2 W and a module efficiency of 20.2% (aperture area). The cells are optimized for operation within the module. We enhance light harvesting from the inactive spacing between the cells and the cell interconnect ribbons. Additionally, we reduce the inactive area to below 3% of the aperture module area. The impact of these measures is analyzed by ray-tracing simulations of the module. Using a numerical model, we analyze and predict the module performance based on the individual cell measurements and the optical simulations. We determine the power loss due to series interconnection of the solar cells to be 1.5%. This is compensated by a gain in current of 1.8% caused by the change of the optical environment of the cells in the module. We achieve a good agreement between simulations and experiments, both showing no cell-to-module power loss.
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M. R. Vogt, H. Schulte-Huxel, M. Offer, S. Blankemeyer, R. Witteck, M. Köntges, K. Bothe, and R. Brendel IEEE Journal of Photovoltaics 7 (1), 44-50, (2017), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: Glass, Mathematical model, Nominal operating cell temperature (NOCT), operating temperature, passivated emitter rear cell (PERC), photovoltaic (PV) module, Photovoltaic cells, PV module thermal properties, ray tracing, silicon, Temperature measurement, Temperature sensors, Thermal conductivity @article{Vogt2017b,
title = {Reduced module operating temperature and increased yield of modules with PERC instead of Al-BSF solar cells}, author = {M R Vogt and H Schulte-Huxel and M Offer and S Blankemeyer and R Witteck and M Köntges and K Bothe and R Brendel}, doi = {10.1109/JPHOTOV.2016.2616191}, issn = {2156-3381}, year = {2017}, date = {2017-01-01}, journal = {IEEE Journal of Photovoltaics}, volume = {7}, number = {1}, pages = {44-50}, abstract = {We demonstrate a reduced operating temperature of modules made from passivated emitter rear cells (PERCs) compared with modules made from cells featuring an unpassivated fullarea screen-printed aluminum rear side metallization aluminum back surface field (Al-BSF). Measurements on specific test modules fabricated from p-type silicon PERC and Al-BSF solar cells reveal a 4 °C lower operating temperature for the PERC module under 1400 W/m2 halogen illumination, if no temperature control is applied. For detailed analysis of the temperature effect, we perform a 3-D ray tracing analysis in the spectral range from 300 to 2500 nm to determine the radiative heat sources in a photovoltaic (PV) module. We combine these heat sources with a 1-D finite element method model solving the coupled system of semiconductor, thermal conduction, convection, and radiation equations for module temperature and power output. The simulations reveal that the origin of the reduced temperature of the PERC modules is a higher efficiency, as well as a higher reflectivity, of the cells rear side mirror. This reduces the parasitic absorptions in the rear metallization and increases the reflection for wavelengths above 1000 nm. This operating temperature difference is simulated to be linear in intensity. The slope depends on the spectral distribution of the incoming light. Under 1000 W/m2 in AM1.5G, our simulations reveal that the operating temperature difference is about 1.7 °C. The operating temperature can be lowered another 3.2 °C, if all parasitic absorption for wavelengths longer than 1200 nm can be prevented. Standard testing conditions applying a temperature control to the module do not show this effect of enhanced performance of the PERC modules. Yield calculations for systems in the field will thus systematically underestimate their electrical power output unless the inherently lower operating temperature of PERC modules is taken into account.}, keywords = {Glass, Mathematical model, Nominal operating cell temperature (NOCT), operating temperature, passivated emitter rear cell (PERC), photovoltaic (PV) module, Photovoltaic cells, PV module thermal properties, ray tracing, silicon, Temperature measurement, Temperature sensors, Thermal conductivity}, pubstate = {published}, tppubtype = {article} } We demonstrate a reduced operating temperature of modules made from passivated emitter rear cells (PERCs) compared with modules made from cells featuring an unpassivated fullarea screen-printed aluminum rear side metallization aluminum back surface field (Al-BSF). Measurements on specific test modules fabricated from p-type silicon PERC and Al-BSF solar cells reveal a 4 °C lower operating temperature for the PERC module under 1400 W/m2 halogen illumination, if no temperature control is applied. For detailed analysis of the temperature effect, we perform a 3-D ray tracing analysis in the spectral range from 300 to 2500 nm to determine the radiative heat sources in a photovoltaic (PV) module. We combine these heat sources with a 1-D finite element method model solving the coupled system of semiconductor, thermal conduction, convection, and radiation equations for module temperature and power output. The simulations reveal that the origin of the reduced temperature of the PERC modules is a higher efficiency, as well as a higher reflectivity, of the cells rear side mirror. This reduces the parasitic absorptions in the rear metallization and increases the reflection for wavelengths above 1000 nm. This operating temperature difference is simulated to be linear in intensity. The slope depends on the spectral distribution of the incoming light. Under 1000 W/m2 in AM1.5G, our simulations reveal that the operating temperature difference is about 1.7 °C. The operating temperature can be lowered another 3.2 °C, if all parasitic absorption for wavelengths longer than 1200 nm can be prevented. Standard testing conditions applying a temperature control to the module do not show this effect of enhanced performance of the PERC modules. Yield calculations for systems in the field will thus systematically underestimate their electrical power output unless the inherently lower operating temperature of PERC modules is taken into account.
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2016 |
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J. Käsewieter, F. Haase, and M. Köntges Model of cracked solar cell metallization leading to permanent module power loss Artikel IEEE Journal of Photovoltaics 6 (1), 28, (2016). Abstract | Links | BibTeX | Schlagwörter: Bridge circuits, Cell metallization, crack degradation, Electrical resistance measurement, Fatigue, fatigue model, metallization, photovoltaic (PV) module, Photovoltaic cells, power loss, Resistance, silicon @article{Käsewieter2016,
title = {Model of cracked solar cell metallization leading to permanent module power loss}, author = {J Käsewieter and F Haase and M Köntges}, doi = {10.1109/JPHOTOV.2015.2487829}, year = {2016}, date = {2016-01-01}, journal = {IEEE Journal of Photovoltaics}, volume = {6}, number = {1}, pages = {28}, abstract = {We measure the progression of resistances of cell cracks in laminated multicrystalline silicon solar cells and study the impact of the crack width and the number of loading cycles. The resistance of the front fingers increases by a factor larger than 1000 during loading. The resistance increase always recovers to its initial value of 0.2 Ω under unloaded conditions. This holds for up to 105 bending cycles. In contrast, the rear resistance of the aluminum paste shows a fatigue behavior. During the first 100 bending cycles, the unloaded rear resistance increases continuously from 0.03 to 2 Ω. Afterwards, it starts to scatter in the range of 0.1 Ω to more than 4000 Ω after 103 cycles. The rear resistance of a sample without rear encapsulation degrades 24 000 times slower compared with an encapsulated sample. After 105 cycles, the rear resistance is still less than 0.2 Ω. We introduce a model for the development of the crack resistance, which qualitatively explains the measured resistance values.}, keywords = {Bridge circuits, Cell metallization, crack degradation, Electrical resistance measurement, Fatigue, fatigue model, metallization, photovoltaic (PV) module, Photovoltaic cells, power loss, Resistance, silicon}, pubstate = {published}, tppubtype = {article} } We measure the progression of resistances of cell cracks in laminated multicrystalline silicon solar cells and study the impact of the crack width and the number of loading cycles. The resistance of the front fingers increases by a factor larger than 1000 during loading. The resistance increase always recovers to its initial value of 0.2 Ω under unloaded conditions. This holds for up to 105 bending cycles. In contrast, the rear resistance of the aluminum paste shows a fatigue behavior. During the first 100 bending cycles, the unloaded rear resistance increases continuously from 0.03 to 2 Ω. Afterwards, it starts to scatter in the range of 0.1 Ω to more than 4000 Ω after 103 cycles. The rear resistance of a sample without rear encapsulation degrades 24 000 times slower compared with an encapsulated sample. After 105 cycles, the rear resistance is still less than 0.2 Ω. We introduce a model for the development of the crack resistance, which qualitatively explains the measured resistance values.
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2013 |
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M. Köntges, S. Kajari-Schröder, and I. Kunze Crack Statistic for Wafer-Based Silicon Solar Cell Modules in the Field Measured by UV Fluorescence Artikel IEEE Journal of Photovoltaics 3 (1), 95-101, (2013). Links | BibTeX | Schlagwörter: Fluorescence (FL), Histograms, microcrack, Noise, photovoltaic (PV) module, Photovoltaic cells, Photovoltaic systems, Production, silicon, Strain @article{Köntges2013b,
title = {Crack Statistic for Wafer-Based Silicon Solar Cell Modules in the Field Measured by UV Fluorescence}, author = {M Köntges and S Kajari-Schröder and I Kunze}, doi = {10.1109/JPHOTOV.2012.2208941}, year = {2013}, date = {2013-01-01}, journal = {IEEE Journal of Photovoltaics}, volume = {3}, number = {1}, pages = {95-101}, keywords = {Fluorescence (FL), Histograms, microcrack, Noise, photovoltaic (PV) module, Photovoltaic cells, Photovoltaic systems, Production, silicon, Strain}, pubstate = {published}, tppubtype = {article} } |
2011 |
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U. Eitner, M. Pander, S. Kajari-Schröder, M. Köntges, and H. Altenbach Thermomechanics of PV Modules Including the Viscoelasticity of EVA Inproceedings WIP (Hrsg.): 26th European Photovoltaic Solar Energy Conference and Exhibition, 3267-3269, Hamburg, Germany, (2011), ISBN: 3-936338-27-2. Links | BibTeX | Schlagwörter: Encapsulation, Mechanics, photovoltaic (PV) module, reliability, Simulation @inproceedings{Eitner2011b,
title = {Thermomechanics of PV Modules Including the Viscoelasticity of EVA}, author = {U Eitner and M Pander and S Kajari-Schröder and M Köntges and H Altenbach}, editor = {WIP}, doi = {10.4229/26thEUPVSEC2011-4EO.3.1}, isbn = {3-936338-27-2}, year = {2011}, date = {2011-09-01}, booktitle = {26th European Photovoltaic Solar Energy Conference and Exhibition}, pages = {3267-3269}, address = {Hamburg, Germany}, keywords = {Encapsulation, Mechanics, photovoltaic (PV) module, reliability, Simulation}, pubstate = {published}, tppubtype = {inproceedings} } |
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M. Köntges, S. Kajari-Schröder, I. Kunze, and U. Jahn Crack Statistic of Crystalline Silicon Photovoltaic Modules Inproceedings WIP (Hrsg.): 26th European Photovoltaic Solar Energy Conference and Exhibition, 3290-3294, Hamburg, Germany, (2011), ISBN: 3-936338-27-2. Links | BibTeX | Schlagwörter: Electroluminescence, Lifetime, Micro Crack, photovoltaic (PV) module @inproceedings{Köntges2011,
title = {Crack Statistic of Crystalline Silicon Photovoltaic Modules}, author = {M Köntges and S Kajari-Schröder and I Kunze and U Jahn }, editor = {WIP}, doi = {10.4229/26thEUPVSEC2011-4EO.3.6}, isbn = {3-936338-27-2}, year = {2011}, date = {2011-09-01}, booktitle = {26th European Photovoltaic Solar Energy Conference and Exhibition}, pages = {3290-3294}, address = {Hamburg, Germany}, keywords = {Electroluminescence, Lifetime, Micro Crack, photovoltaic (PV) module}, pubstate = {published}, tppubtype = {inproceedings} } |