July 2020
Cracks in silicon photovoltaic modules: a review
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.
Cracks in silicon photovoltaic modules: a review
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.
Etude des performances thermiques de matériaux à matrice cimentaire renforcés par des fibres de bois de palmier traitées
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.
Paraffin/ Expanded Perlite/Plaster as Thermal Energy Storage 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.
Paraffin/ Expanded Perlite/Plaster as Thermal Energy Storage 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.
Thermophysical characterization of Posidonia Oceanica marine fibers intended to be used as an insulation material in Mediterranean buildings
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.