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This work presented an experimental investigation on the use of a bio-composite as an insulating material in building. During the past few years, many projects have tried to create new composites with a high insulating properties, essentially thermal, which plays an important role in buildings energy efficiency (Chikhi et al. in Energy Build 66:267–273, 2013).

This work presented an experimental investigation on the use of a bio-composite as an insulating material in building. During the past few years, many projects have tried to create new composites with a high insulating properties, essentially thermal, which plays an important role in buildings energy efficiency (Chikhi et al. in Energy Build 66:267–273, 2013).

The present work focuses on the study of the thermophysical properties of low porous insulation materials. In peculiar, we investigate the pore structure of composite materials and cements by thermal method. This method, adapted for fragile materials, is based on an existing model which allows the determination of pore size distribution. Firstly, the existing analytical model is presented. The thermal conductivity is modeled by assimilating the studied medium to N fluid phases and one solid phase in series / parallel. Secondly, some extensions to this model are proposed. In particular, we show that in the case of a single pore size, it is possible to obtain a finer pore size distribution by means of a normal law. We also show for the first time that the normalization of the thermal conductivity is an interesting way to study the pore size distribution of a material without knowing the overall porosity rate (which strongly depends on the method used). Furthermore, this model and its extensions have been successfully applied to different kinds of materials (plant fiber composites and cements). Fibers reinforced composites have one class of pores around 30 – 60 lm. Chemical treatments do not affect this pore size. Cements show a macroporosity (around 20 lm) which is often underestimated.

The present work focuses on the study of the thermophysical properties of low porous insulation materials. In peculiar, we investigate the pore structure of composite materials and cements by thermal method. This method, adapted for fragile materials, is based on an existing model which allows the determination of pore size distribution. Firstly, the existing analytical model is presented. The thermal conductivity is modeled by assimilating the studied medium to N fluid phases and one solid phase in series / parallel. Secondly, some extensions to this model are proposed. In particular, we show that in the case of a single pore size, it is possible to obtain a finer pore size distribution by means of a normal law. We also show for the first time that the normalization of the thermal conductivity is an interesting way to study the pore size distribution of a material without knowing the overall porosity rate (which strongly depends on the method used). Furthermore, this model and its extensions have been successfully applied to different kinds of materials (plant fiber composites and cements). Fibers reinforced composites have one class of pores around 30 – 60 lm. Chemical treatments do not affect this pore size. Cements show a macroporosity (around 20 lm) which is often underestimated.

Photovoltaic systems belong to the green energy dynamics which is an ambitious program based on energy efficiency and sustainable development. In this study, the impact of the aging of a photovoltaic module is investigated on the electrical performance of a grid-connected system. A photovoltaic conversion chain with MPPT (Maximum Power Point Tracking) control and LC (Inductor-Capacitor) filter is modeled and dimensioned according to the grid constraints. A method of hybridation detection of the MPPT coupling long-time aging evolution and short-time determination is proposed. Aging laws for the electrical and optical degradations of the photovoltaic module are introduced for the long-time evolution. Results display the lowering of the maximal power point with a rate of 1%/year and a slight augmentation of the THD over time even though it remains inferior to the IEEE standard STD 19-1992 maximum value of 5% for a usage of 20 years. Moreover, an equivalent scheme for the additional electrical resistance engendered by the aging of the photovoltaic module regarding other resistances of the photovoltaic system is given. Finally, the elevation of this resistance by 12.8% in 20 years may have non-negligible consequences on the power production of a large-scale installation.

Photovoltaic systems belong to the green energy dynamics which is an ambitious program based on energy efficiency and sustainable development. In this study, the impact of the aging of a photovoltaic module is investigated on the electrical performance of a grid-connected system. A photovoltaic conversion chain with MPPT (Maximum Power Point Tracking) control and LC (Inductor-Capacitor) filter is modeled and dimensioned according to the grid constraints. A method of hybridation detection of the MPPT coupling long-time aging evolution and short-time determination is proposed. Aging laws for the electrical and optical degradations of the photovoltaic module are introduced for the long-time evolution. Results display the lowering of the maximal power point with a rate of 1%/year and a slight augmentation of the THD over time even though it remains inferior to the IEEE standard STD 19-1992 maximum value of 5% for a usage of 20 years. Moreover, an equivalent scheme for the additional electrical resistance engendered by the aging of the photovoltaic module regarding other resistances of the photovoltaic system is given. Finally, the elevation of this resistance by 12.8% in 20 years may have non-negligible consequences on the power production of a large-scale installation.

Photovoltaic cells are considered as one of the most critical components in photovoltaic systems for they convert the sunlight photons into electricity. However defects on the surface of the photovoltaic cells have a detrimental effect on them. Thus, research focuses on one hand on the degradation caused by the cracks namely on their impacts on the efficiency of photovoltaic modules and on the other hand on the techniques which are used to spot them. The main objective of this review is to inquire on the impact of the microcracks on the electrical performance of silicon solar cells and to list the mostused detection techniques of cracks.

Photovoltaic cells are considered as one of the most critical components in photovoltaic systems for they convert the sunlight photons into electricity. However defects on the surface of the photovoltaic cells have a detrimental effect on them. Thus, research focuses on one hand on the degradation caused by the cracks namely on their impacts on the efficiency of photovoltaic modules and on the other hand on the techniques which are used to spot them. The main objective of this review is to inquire on the impact of the microcracks on the electrical performance of silicon solar cells and to list the mostused detection techniques of cracks.

Ce projet vise à déterminer la faisabilité technique de l’introduction de déchets de palmier à l’état brut et après traitement chimique dans du ciment afin d’élaborer un nouvel éco-composite de construction qui soit léger, bon isolant thermique et acoustique. Dans les composites, l’augmentation de la fraction massique de fibres induit une diminution progressive de la conductivité et la diffusivité thermique et s’accompagne d’une perte des propriétés mécaniques et d’une diminution de la densité. Le dégraissage des fibres améliore les propriétés mécaniques, les composites obtenus sont moins fragiles que ceux obtenus à partir de fibres brutes.

The use of thermal energy storage composite materials allows passive cooling and heating in buildings, yielding substantial energy savings. The purpose of this study is to develop and test a new phase change material (PCM) composite by loading expanded perlite (EP) with paraffin (RT27) to form plaster composites. The leakage tests allowed to unfold the optimal RT27 loading rate. To avoid paraffin leakage out of the composite structure, a waterproof product, Sikalatex® (SL), was used to coat the RT27/EP composite before mixing it with plaster. Thermal properties of RT27/EP/SL integrated in plaster were assessed. The effect of aluminum powder insertion on enhancing the composite thermal properties, was investigated. Paraffin loading rate was 60% by direct impregnation. FTIR analyses proved that the produced composites showed a good chemical compatibility between different components. DSC analyses revealed that composites have suitable energy storage capacities of 51.57 ± 0.01 and 49.95 ±0.15 kJ.kg-1 for RT27/EP/SL and RT/EP/SL/Al, respectively. These composites are suitable for indoor temperature regulation. Thermal cycling tests showed a good thermal stability of plaster PCM composite. Thermal conductivity of plaster composite containing 50% wt of RT27/EP/SL/Al composite was increased by 80% and 68% at 12°C and 40°C respectively compared with the aluminum free composite.

The use of thermal energy storage composite materials allows passive cooling and heating in buildings, yielding substantial energy savings. The purpose of this study is to develop and test a new phase change material (PCM) composite by loading expanded perlite (EP) with paraffin (RT27) to form plaster composites. The leakage tests allowed to unfold the optimal RT27 loading rate. To avoid paraffin leakage out of the composite structure, a waterproof product, Sikalatex® (SL), was used to coat the RT27/EP composite before mixing it with plaster. Thermal properties of RT27/EP/SL integrated in plaster were assessed. The effect of aluminum powder insertion on enhancing the composite thermal properties, was investigated. Paraffin loading rate was 60% by direct impregnation. FTIR analyses proved that the produced composites showed a good chemical compatibility between different components. DSC analyses revealed that composites have suitable energy storage capacities of 51.57 ± 0.01 and 49.95 ±0.15 kJ.kg-1 for RT27/EP/SL and RT/EP/SL/Al, respectively. These composites are suitable for indoor temperature regulation. Thermal cycling tests showed a good thermal stability of plaster PCM composite. Thermal conductivity of plaster composite containing 50% wt of RT27/EP/SL/Al composite was increased by 80% and 68% at 12°C and 40°C respectively compared with the aluminum free composite.

The present work focuses on the study of the thermophysical properties of Posidonia Oceanica natural fibers in order to investigate the potential of their use as loose-fill thermal insulation material in the Mediterranean construction. 24 samples were prepared. Bulk densities were varied from 17 kg m-3 to 155 kg m-3. Chemical alkali treatments with various conditions were applied to these fibers. The influence of treatments and of density on morphological and thermophysical properties of samples was evaluated. The surfaces were examined by using scanning electron microscopic. The thermal measurements were performed with the Hot Disk thermal constants analyzer. Results have shown that thermal conductivity decrease when density decreases until an optimum. After that, it increases as the density is reduced. Furthermore, regarding thermal conductivity, it was found out that the effect of chemical treatment is not significant mainly at the low densities. A very slight improvement was found at high densities with treated fibers, mainly the treatment that consists of immerging fibers twice in 2% sodium hydroxide solution during 2 h at 80 °C. Higher mass heat capacity was observed with this same treatment. Additionally, it was revealed in this study that Posidonia-Oceanica fibers have thermal conductivity and thermal diffusivity close to conventional insulation materials and higher mass heat capacity that reached 2533 J kg-1 K-1.

Though gallium arsenide (GaAs) solar cells are proven to be relatively stable in space working conditions, they are prone to the effects of aging, which deteriorate their characteristics. The lifetime of solar cells is restricted by the degree of radiation damage that they receive. This important factor affects the performance of solar cells in practical applications. The aim of this article is to investigate by numerical simulation on the influence of aging on the main characteristics of GaAs solar cells in the space. Degradations of the electrical characteristics are simulated for over a period of 15 years. The atmosphere (AM0) conversion efficiency decreases with time from 19.08% for the unirradiated cells to 10.38% in 15 years of the mission in space. Even with low doses of particle irradiation, the performance is significantly reduced subsequent to usage over the period of 15 years of the mission in space. Numerical simulation results also reveal that the short-circuit current, the open-circuit voltage, and the conversion efficiency decline gradually with time. Moreover, the calculated evolutions are in good agreement with the measured behaviors of GaAs-based solar cells embedded in geostationary satellites during the Navigation Technology Satellite 2 (NTS-2), the Engineering Test Satellite V (ETS-V), and the NAVigation Satellite Timing And Ranging (NAVSTAR) missions, which substantiate the introduced aging law accounting for both the cumulated doses of particles and the different electron and hole traps in the structure.

Though gallium arsenide (GaAs) solar cells are proven to be relatively stable in space working conditions, they are prone to the effects of aging, which deteriorate their characteristics. The lifetime of solar cells is restricted by the degree of radiation damage that they receive. This important factor affects the performance of solar cells in practical applications. The aim of this article is to investigate by numerical simulation on the influence of aging on the main characteristics of GaAs solar cells in the space. Degradations of the electrical characteristics are simulated for over a period of 15 years. The atmosphere (AM0) conversion efficiency decreases with time from 19.08% for the unirradiated cells to 10.38% in 15 years of the mission in space. Even with low doses of particle irradiation, the performance is significantly reduced subsequent to usage over the period of 15 years of the mission in space. Numerical simulation results also reveal that the short-circuit current, the open-circuit voltage, and the conversion efficiency decline gradually with time. Moreover, the calculated evolutions are in good agreement with the measured behaviors of GaAs-based solar cells embedded in geostationary satellites during the Navigation Technology Satellite 2 (NTS-2), the Engineering Test Satellite V (ETS-V), and the NAVigation Satellite Timing And Ranging (NAVSTAR) missions, which substantiate the introduced aging law accounting for both the cumulated doses of particles and the different electron and hole traps in the structure.

To optimize de-icers use in winter on roads and airports, some sustainable solutions were promoted in a global project entitled “Roads of the Future”. PCM into pavements were then considered to rely on the released enthalpy to delay the occurrence of black ice or snow accumulation. Coupling a spectroscopic monitoring of the PCM behavior and thermography on pavement surface indicated a significant delay between the phase change and the thermal manifestation of the released energy. Considering an accurate description of PCM according to cooling weather phenomena, these elements might provide valuable information for numerical models.

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Abstract High energy consumption in the building sector appeals for the implementation and the improvement of innovative approaches with low-environmental impact. The development of eco-friendly composites as insulating materials in buildings provides practical solutions for reducing energy consumption. Different mass proportions (2.5%, 10%, and 20%) of untreated and chemically treated palm fibers were mixed with (cement, water and sand) so as to prepare novel composites. Composites were characterized by measuring water absorption, thermal conductivity, compressive strength and acoustic transmission. The results reveal that the incorporation of untreated and chemically treated date palm fibers reduces novel composites’ thermal conductivity and the mechanical resistance. Thermal measurements have proved that the loading of fibers in composites decreases the thermal conductivity from 1.38 W m−1 K−1 for the reference material to 0.31 W m−1 K−1 for composites with 5% of treated and untreated fibers. The acoustical insulation capacity of untreated palm fiber-reinforced composites (DPF) was the highest at 20% fiber content, whereas treated palm fiber-reinforced composites (TPF) had the highest sound insulation coefficient for fiber content lower than 10%. Compressive strength, thermal conductivity and density correlation showed that only chemically treated fiber-reinforced composites (TPF) are good candidates for thermal and acoustic building insulations.

Dans le cadre de la venue du Professeur Lin BORONG, Professeur invité de l’Université Paris-Est, le CERTES a organisé une demi-journée scientifique à l’IUT de Créteil-Vitry le 19 septembre de 14h à 17h30. L’évènement a été animé par Mahamadou ABDOU-TANKARI et Mustapha KARKRI, Maîtres de Conférences au CERTES. Ce séminaire a été l’occasion de nombreuses discussions et échanges sur les collaborations scientifiques entre les deux structures.

Lydia BOUROUIBA, Professeur au MIT (Massachussets Institute of Technology) a été accueillie au sein du CERTES les 5 et 6 septembre 2019.

Dans le cadre de son séjour au sein du CERTES, le Professeur Lin BORONG de l’Université de TSINGHUA (Chine), Professeur invité de l’Université Paris-Est, va animer une Master Class du 23 au 26 septembre 2019, chaque jour de de 14h à 17h30.

Le séminaire annuel des doctorants du CERTES s’est déroulé le mardi 9 octobre 2018 à l’IUT de Créteil-Vitry. Douze doctorants du laboratoire ont tout d’abord exposé leur sujet de thèse sous la forme d’une présentation « flash » de 180 secondes devant l’ensemble des membres du laboratoire. Les échanges se sont ensuite poursuivis lors d’une session « Poster ».

To optimize de-icers use in winter on roads and airports, some sustainable solutions were promoted in a global project entitled “Roads of the Future”. PCM into pavements were then considered to rely on the released enthalpy to delay the occurrence of black ice or snow accumulation. Coupling a spectroscopic monitoring of the PCM behavior and thermography on pavement surface indicated a significant delay between the phase change and the thermal manifestation of the released energy. Considering an accurate description of PCM according to cooling weather phenomena, these elements might provide valuable information for numerical models.

Abstract High energy consumption in the building sector appeals for the implementation and the improvement of innovative approaches with low-environmental impact. The development of eco-friendly composites as insulating materials in buildings provides practical solutions for reducing energy consumption. Different mass proportions (2.5%, 10%, and 20%) of untreated and chemically treated palm fibers were mixed with (cement, water and sand) so as to prepare novel composites. Composites were characterized by measuring water absorption, thermal conductivity, compressive strength and acoustic transmission. The results reveal that the incorporation of untreated and chemically treated date palm fibers reduces novel composites’ thermal conductivity and the mechanical resistance. Thermal measurements have proved that the loading of fibers in composites decreases the thermal conductivity from 1.38 W m−1 K−1 for the reference material to 0.31 W m−1 K−1 for composites with 5% of treated and untreated fibers. The acoustical insulation capacity of untreated palm fiber-reinforced composites (DPF) was the highest at 20% fiber content, whereas treated palm fiber-reinforced composites (TPF) had the highest sound insulation coefficient for fiber content lower than 10%. Compressive strength, thermal conductivity and density correlation showed that only chemically treated fiber-reinforced composites (TPF) are good candidates for thermal and acoustic building insulations.

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Les caractéristiques des fluctuations des concentrations de polluants dans un environnement intérieur normalement occupé dépendent fortement de plusieurs paramètres, en particulier des occupants et de leurs activités et comportement, qui altèrent de manière considérable la nature statistique de leur variabilité temporelle. Ces fluctuations sont rarement disponibles et décrites dans la littérature. La mise à disposition de mesures en continu de la concentration en formaldéhyde et en particules (de 0,35 à 20 µm de diamètre) dans l’air d’un environnement de bureau et d’une maison expérimentale sur plusieurs mois avec un pas de temps fin (entre 1 min et 1 heure) a permis d’engager une réflexion sur la nature de ces fluctuations et leur prévisibilité. L’objectif de la thèse se décline en trois axes de recherche : (i) la caractérisation des fluctuations des concentrations des polluants cible ; (ii) la mise en évidence des sources de variabilité de ces fluctuations et (iii) la prévision des concentrations de ces polluants. Le premier axe concerne la détermination des caractéristiques communes partagées par les différents polluants. Le deuxième axe porte, à l’aide des approches par séparation aveugle des sources, sur l’estimation des déterminants des sources de variabilité. Le troisième axe est consacré à la prévision des fluctuations de concentration des polluants. L’analyse des séries temporelles pour ce type de données (hautes fréquences) doit prendre en compte l’échelle de temps sur laquelle évoluent plusieurs microstructures. Plusieurs outils ont été employés : l’analyse spectrale (dépendance à long terme par la mesure fractale et la statistique R/S), la mesure de l’oméga-prédictibilité, ainsi que la décomposition des séries en composantes latentes par STL (seasonal trend decomposition using Loess), SSA (singular spectrum analysis) et SBD (spectral band decomposition).L’identification des sources de variabilité de particules a été abordée par les méthodes de séparation aveugle des sources basées sur une factorisation matricielle en profils et contributions, sous contrainte statistique d’indépendance (ACI) ou de non-négativité (NNMF ou PMF). Les factorisations ont été appliquées à la matrice constituée des séries temporelles de différentes gammes de taille des particules. Certains profils ou contributions des sources ont pu été interprétés grâce aux variables exogènes “traceurs” de certaines sources (comme le CO2 indicateur de la présence de la source occupants).Concernant la prévision des concentrations de polluants, le choix des modèles a été basé sur la structure de la série temporelle, mise en évidence lors de l’étape de caractérisation. On constate de meilleures performances de prévisions sur la série ayant subi un prétraitement statistique de décomposition STL, SSA ou SBD. Plusieurs types de modèles stochastiques (linéaires ou non linéaires) ont été appliqués ensuite à ces composantes et le résultat final de la prévision est donné par leur combinaison. La caractéristique de non-linéarité qui apparaît sous forme de changements abrupts de concentration causée en grande partie par la manipulation des ouvrants et qui se greffe sur l’évolution régulière du système dynamique mérite un traitement spécial. Un nouveau type de modèles de prévision a été développé pour répondre aux exigences de la nature des données hautes fréquences présentant ce type de non linéarité. Ce modèle associe une étape de décomposition des séries en bandes spectrales (SBD) couplée avec une étape de modélisation par des modèles autorégressifs à seuil (TAR) ou par la dynamique du chaos : FFT-(TAR/Chaos).Les résultats montrent que le prétraitement par décomposition en bandes spectrales ou STL améliore sensiblement la prévision des concentrations de formaldéhyde et des particules fines jusqu’à un horizon de 10 heures pour le formaldéhyde (pas de temps 1 minute) et de 1 à 4 jours pour les particules selon leur taille (pas de temps horaire).

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Résumé – Ce travail porte sur la réalisation d’un benchmark de méthodes d’identification en vue de mesurer sur site la résistance thermique de parois de bâtiment par thermographie infrarouge active. Les mesures virtuelles sont générées à l’aide de différents Modèles Physiques Générateurs. Plusieurs méthodes d’estimation de paramètres sont comparées. Les résultats présentés se focalisent sur les parois ITI (Isolation Thermique par l’Intérieur) et montrent qu’une estimation satisfaisante de la résistance thermique de la paroi est possible dans de nombreux cas.