Sandwich shield subjected to bird impact: Use of surrogate models for influencing parameter analysis and shield behaviour understanding

In this work, the behaviour of a sandwich shield subjected to a 1.82 kg bird impact at 175 m/s is studied using a finite element model. The most influential design parameters (6) are varied and their effects on the shield behaviour and on the target protection are assessed. First, we try to establish an engineer's visualization by varying parameters 2 by 2 using three 5-levels full-factorial designs of experiments (DOE). These three 2D DOE enable us to visualize precisely the different effects of each parameter. Then a full sensitivity analysis (6D) is performed using a Latin Hypercube sampling, to assess the possible interactions between parameters. Surrogate models are constructed using the Gaussian Process framework to follow the variation of the outputs in the 6D design space. These surrogate models are finally studied using two statistical methods: the Sobol’ method and the Morris method. The methodology developed in this study enables to improve the understanding of the behaviour of a shield under a soft body impact, as a first step towards a shield design tool

Influence of Solder Pads to PERC Solar Cells for Module Integration

AbstractThe majority of screen printed solar cells has silver pads at the rear side to enable soldering for the module manufacturing. The pads increase the recombination at the silicon/metal interface due to the absence of a back surface field (BSF) at the solder pads. This reduces the efficiency of full-area Al-BSF solar cells. For passivated emitter and rear cells (PERC), a large area fraction of the rear side is covered with the passivation layer. When using specially designed Ag pastes for the rear side of PERC cells, the passivation of this layer is maintained, and the rear recombination is reduced.A comparison of solar cells with and without solder pads confirms that there is no loss in solar cell performance, both cell types achieve an efficiency of 19.6%. We investigate the influence of solder pads to PERC solar cells by calculating the effective rear surface recombination. The calculations confirm that there is a loss in open circuit voltage of less than 2mV due to the solder pads.A 54-cell PERC PV module is manufactured. The cell-to-module loss reveals that the module process is still to be optimized. Comparable modules made from 9 solar cells lost less than 1% relative in all J-V parameters after a 1000h damp-heat test

Barrier properties of hybrid structures - Application to solar cells encapsulation

Les matériaux utilisés pour diverses applications en électronique organique ou photovoltaïque denouvelle génération subissent des dégruvent être encapsulés à l’aide de matériaux barrière àl’oxygène et à l’eau. Pour l’encapsulation des cellules photovoltaïques organiadations sous les effets conjugués de l’eau et de l’oxygène. Afinde limiter cette dégradation, ces dispositifs peques, les perméabilités àl’eau (WVTR) et à l’oxygène (OTR) de l’encapsulant ne doivent pas excéder 10-3 g.m-2.j-1 et 10-3cm3.m-2.j-1 respectivement.L’objectif de ce travail de thèse est l’étude et l’élaboration par voie humide d’une structuremulticouche hybride organique/inorganique flexible, transparente et barrière aux gaz ainsi que lacompréhension des mécanismes permettant de limiter la diffusion des gaz au travers de cette structure.Dans un premier temps, le travail de thèse a été consacré à la réalisation d’une couche mince d’oxydede silicium sur substrat polymère à partir d’un précurseur inorganique : le perhydropolysilazane(PHPS). Différentes voies de conversion du précurseur ont été étudiées et comparées. Lesperméabilités à l’eau et à l’oxygène des meilleures couches déposées sur substrat polymère sont del’ordre de 0,1 g.m-2.j-1 et 0,1 cm3.m-2.j-1 respectivement. Ces valeurs sont comparables à cellesobtenues pour des dépôts réalisés par voie plasma.Des structures multicouches hybrides ont été réalisées en intercalant des couches de polymère entredes couches d’oxyde de silicium afin de décorréler les défauts des couches denses. Cela a permisd’atteindre des perméabilités inférieures ou égales à 10-2 g.m-2.j-1 à l’eau et de l’ordre de 10-3 cm3.m-2.j-1 à l’oxygène.Les performances au cours du temps sous irradiation de cellules solaires encapsulées ont étécomparées. L’encapsulation avec le meilleur matériau barrière développé confère une stabilitéremarquable aux cellules.Cette étude a ainsi permis de montrer les structures barrières élaborées par voie liquide constituent unealternative de choix pour l’encapsulation à grande échelle de cellules photovoltaïques.Materials used in organic electronic devices or new generation photovoltaics undergo degradation byoxygen and water. In order to prevent their degradation, the devices should be encapsulated withmaterials showing a low permeability to oxygen and water vapor. For organic solar cellsencapsulation, material permeability to water (WVTR) and oxygen (OTR) should not exceed 10-3 g.m-2.d-1 and 10-3 cm3.m-2.d-1 respectively. The aim of this work is to study and develop a solutionprocessed,flexible, transparent and gas-barrier multilayer inorganic/organic hybrid structure, and tounderstand the mechanisms involved in diffusion limitation through these barriers.Firstly, this work has been dedicated to the realization on a polymer substrate of a thin silicon oxidelayer from an inorganic precursor: the perhydropolysilazane (PHPS). Different precursor conversionpaths have been studied and compared. The best barrier layers on polymer substrate have shownoxygen and water permeabilities of about 0,1 g.m-2.d-1 and 0,1 cm3.m-2.d-1 respectively. This result iscomparable to the permeability of plasma deposited layers.Multilayer hybrid structures have been realized by introducing a polymer layer between inorganiclayers in order to decorrelate the thin layer defects. This achieved permeabilities below 10-2 g.m-2.d-1for water and 10-3 cm3.m-2.d-1 for oxygen.The photovoltaic performances of encapsulated organic solar cells under illumination have beencompared over time. Encapsulation with the best barrier material developed during this work resultedin good device stability.This study has shown that entirely solution-processed barrier materials are a promising option for largescale organic solar cells encapsulation

Propriétés barrières de structures hybrides. Application à l'encapsulation des cellules solaires

Les matériaux utilisés pour diverses applications en électronique organique ou photovoltaïque denouvelle génération subissent des dégruvent être encapsulés à l aide de matériaux barrière àl oxygène et à l eau. Pour l encapsulation des cellules photovoltaïques organiadations sous les effets conjugués de l eau et de l oxygène. Afinde limiter cette dégradation, ces dispositifs peques, les perméabilités àl eau (WVTR) et à l oxygène (OTR) de l encapsulant ne doivent pas excéder 10-3 g.m-2.j-1 et 10-3cm3.m-2.j-1 respectivement.L objectif de ce travail de thèse est l étude et l élaboration par voie humide d une structuremulticouche hybride organique/inorganique flexible, transparente et barrière aux gaz ainsi que lacompréhension des mécanismes permettant de limiter la diffusion des gaz au travers de cette structure.Dans un premier temps, le travail de thèse a été consacré à la réalisation d une couche mince d oxydede silicium sur substrat polymère à partir d un précurseur inorganique : le perhydropolysilazane(PHPS). Différentes voies de conversion du précurseur ont été étudiées et comparées. Lesperméabilités à l eau et à l oxygène des meilleures couches déposées sur substrat polymère sont del ordre de 0,1 g.m-2.j-1 et 0,1 cm3.m-2.j-1 respectivement. Ces valeurs sont comparables à cellesobtenues pour des dépôts réalisés par voie plasma.Des structures multicouches hybrides ont été réalisées en intercalant des couches de polymère entredes couches d oxyde de silicium afin de décorréler les défauts des couches denses. Cela a permisd atteindre des perméabilités inférieures ou égales à 10-2 g.m-2.j-1 à l eau et de l ordre de 10-3 cm3.m-2.j-1 à l oxygène.Les performances au cours du temps sous irradiation de cellules solaires encapsulées ont étécomparées. L encapsulation avec le meilleur matériau barrière développé confère une stabilitéremarquable aux cellules.Cette étude a ainsi permis de montrer les structures barrières élaborées par voie liquide constituent unealternative de choix pour l encapsulation à grande échelle de cellules photovoltaïques.Materials used in organic electronic devices or new generation photovoltaics undergo degradation byoxygen and water. In order to prevent their degradation, the devices should be encapsulated withmaterials showing a low permeability to oxygen and water vapor. For organic solar cellsencapsulation, material permeability to water (WVTR) and oxygen (OTR) should not exceed 10-3 g.m-2.d-1 and 10-3 cm3.m-2.d-1 respectively. The aim of this work is to study and develop a solutionprocessed,flexible, transparent and gas-barrier multilayer inorganic/organic hybrid structure, and tounderstand the mechanisms involved in diffusion limitation through these barriers.Firstly, this work has been dedicated to the realization on a polymer substrate of a thin silicon oxidelayer from an inorganic precursor: the perhydropolysilazane (PHPS). Different precursor conversionpaths have been studied and compared. The best barrier layers on polymer substrate have shownoxygen and water permeabilities of about 0,1 g.m-2.d-1 and 0,1 cm3.m-2.d-1 respectively. This result iscomparable to the permeability of plasma deposited layers.Multilayer hybrid structures have been realized by introducing a polymer layer between inorganiclayers in order to decorrelate the thin layer defects. This achieved permeabilities below 10-2 g.m-2.d-1for water and 10-3 cm3.m-2.d-1 for oxygen.The photovoltaic performances of encapsulated organic solar cells under illumination have beencompared over time. Encapsulation with the best barrier material developed during this work resultedin good device stability.This study has shown that entirely solution-processed barrier materials are a promising option for largescale organic solar cells encapsulation.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Contact-free determination of ethylene vinyl acetate crosslinking in PV modules with fluorescence emission

The degree of crosslinking of ethylene vinyl acetate (EVA) is a decisive factor for the photovoltaic (PV) modules reliability. Numerous chemical or physical methods may be applied to determine the extent of crosslinking reaction in the EVA material. The usual and most accurate ones are destructive as they require a sample of material from the module. In this work we present a contactless and non-destructive method for monitoring the crosslinking process of EVA based on fluorescence spectroscopy. We show the correlation of fluorescence emission intensity of EVA when submitted to UV light with its curing grade determined by a rheological method. This approach is of interest for in-line monitoring of the crosslinking during the lamination step and for quality control after production. © 2014 The Authors. Published by Elsevier Ltd

Isogeometric sizing and shape optimization of thin structures with a solid-shell approach

International audienceThis work explores the use of solid-shell elements in the the framework of isogeometric shape optimization of shells. The main difference of these elements with respect to pure shell ones is their volumetric nature which can provide recognized benefits to analyze, for example, structures with non-linear behaviors. From the design point of view, we show that this geometric representation of the thickness is also of great interest since it offers new possibilities: continuous sizing variations can be imposed by modifying the distance between the control points of the outer surfaces. In other words, shape and sizing optimization can be performed in an identical manner. Firstly, we carry out a range of numerical experiments in order to carefully compare the results with the commonly adopted technique based on the Kirchhoff-Love formulation. These studies reveal that both solid-shell and Kirchhoff-Love strategies lead to very similar optimal shapes. Then we apply a bi-step strategy to integrate shape and sizing optimization. We highlight the potential of the proposed approach on a stiffened cylinder where the cross-section along the stiffener is optimized leading to a final design with smooth thickness variations. Finally, we combine the benefits of both Kirchhoff-Love and solid-shell formulations by setting up a multi-model optimization process to efficiently design a roof

Structural properties of ultraviolet cured polysilazane gas barrier layers on polymer substrates

International audiencePerhydropolysilazane (PHPS) conversion to silica through high energy ultraviolet irradiation has been studied. Precursor conversion speed and structural properties of the UV cured PHPS have been investigated and showed that this conversion method is fast but that complete conversion into silica is not achieved in an oxygen depleted atmosphere for layer thicknesses higher than 30 nm, resulting in a composite structure with concentration gradients. We further show that Fourier transform infrared spectroscopy data allow investigating the local structure and composition over the depth of the obtained layers. Gas permeability of the thin UV cured PHPS layers deposited on polymers has been studied. We used a high sensitivity permeation measurement technique to determine water vapor and oxygen permeabilities of the barrier layers and show the correlation between helium, oxygen and water permeability of these materials. Oxygen and water vapor transmission rates of respectively 0.06 cm3/m2/day/bar and 0.2 g/m2/day have been obtained with layers deposited on a polymer substrate

Sandwich shield subjected to bird impact: Use of surrogate models for influencing parameter analysis and shield behaviour understanding

International audienceIn this work, the behaviour of a sandwich shield subjected to a 1.82 kg bird impact at 175 m/s is studied using a finite element model. The most influential design parameters (6) are varied and their effects on the shield behaviour and on the target protection are assessed. First, we try to establish an engineer's visualization by varying parameters 2 by 2 using three 5-levels full factorial designs of experiments (DOE). These three DOE enable us to visualize precisely the different effects of each parameter. Then a full sensitivity analysis (6D) is performed using a Latin Hypercube sampling, to assess the possible interactions between parameters. Surrogate models are constructed using the Gaussian Process framework to follow the variation of the outputs in the 6D design space. These surrogate models are finally studiedusing two statistical methods: the Sobol’ method and the Morris method. The methodology developed in this study enables to improve the understanding of the behaviour of a shield under a soft body impact, as a first step towards a shield design tool

Analyse Isogéométrique pour les problèmes d'Optimisation de Forme des Structures Coques

National audienceOn s’intéresse ici à l’optimisation de forme isogéométrique de coques. Le processus de résolution s’appuie sur une approche multi-modèles, rendue possible par les procédures de raffinement des fonctions NURBS qui conservent la géométrie. Des éléments massifs coques sont mis en place pour la simulation des structures élancées. L’extension de l’optimisation de forme des coques à ces éléments a pu être appliquée avec succès au cas simple d’un tube sous pression interne et semble constituer un outil pertinent pour l’optimisation de forme d’aérostructures