Results 1 - 10 of 18
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[en] With the advancement of synthesis methods, boron nitride nanotubes seem to become increasingly valuable in fundamental physical research and find applications in a number of forms, from dyed neutron-absorbing fabrics to high-temperature catalysts and photovoltaic devices.
[en] The cost reductions and the environmental benefits aligned with global concerns about climate change have made solar photovoltaic technology the most installed source of energy in the power sector worldwide. Brazil has the largest know reserves of silicon in the world. Therefore, there is a huge potential for developing a national technology for purifying and manufacturing silicon wafers within an increasingly competitive and efficient photovoltaic industry. The IPEN initiative of investigating the production of metallic silicon and metallurgical route purification required a characterization of samples in different stages of production from quartz to wafer and understanding the characterization methods for silicon wafers taking into account the main defect mechanisms such as light-induced degradation. Metallic silicon is produced in IPEN via magnesio-thermal reduction through acid leaching to form a metallurgical grade silicon with relatively low impurities. One more acid leaching step resulted in a specific ultra-metallurgical grade silicon. The same acid leaching was processed in a commercially available Brazilian-made metallurgical grade silicon produced via carbothermal reduction. All samples impurities was measured by ICP-OES. The result is a material with ultra-metallurgical grade silicon content with excess of B and P. While wafer characterization was studied, an extensive investigation was taken on LeTID, which causes remain unknown, at Institute for Energy Technology, Norway. Neighboring high performance mc-Si p-type wafers were tested in different firing process conditions. The effects was investigated in terms of defects activation and a corresponding lifetime degradation and recovery at illuminated annealing. A sample with almost fully suppressed LeTID is shown. A new method have been proposed to separate Boron Oxygen-Light Induced Degradation effects of LeTID, enabling to measure even where it was thought to be fully suppressed. New models for LeTID defect formation and suppression are proposed. Both silicon purification and light-induced degradation characterization in mc-Si studies shows a wide range of research on new production routes that may require tailored processes of crystallization and solar cell manufacturing such as gettering and firing. (author)
[en] High potential spinel oxide based lithium nickel manganese oxide (4.7 V vs. Li, 147 mAh/g), LiNi0.5Mn1.5O4 (LNMO) material was up scaled to 30 g through sol gel auto-combustion process. The powders calcined at 800 °C for 8 hrs exhibited highly crystalline structure with disordered (Fd3m) phase and developed truncated octahedral structure as characterized by XRD and FESEM
[en] The present dissertation aimed at estimating the photovoltaic (PV) generation potential at the Pici Campus of the Federal University of Ceara (UFC). Data collected during the period of one year - September 2016 to August 2017 - were evaluated on a photovoltaic (PV) distributed generation (DG) connected to the distribution network of the Pici Campus/UFC and the irradiation in the vicinity of the PV DG. Representative day charts were plotted for each month in the sample period. The annual average irradiance (Igmês m), average electricity generation (Gmês m), average PV capacity factor (FCmed) and PV efficiency (eFV) for the study region were of 5.21 kWh/m²/day, 7.55 kWh/day (0.7754kWh/m²/day), 20.98% and 14.94%, respectively. The equivalence in the reduction of CO2 provided by the PV DG (ECO2) in the LEA in the period studied was 255.64 kgCO2/year. The analysis of the PV potential of the Pici Campus was done with a focus on the ceilings of the buildings of the Technology Center (CT-UFC), Science Center (CC-UFC), Agricultural Science Center (CCA-UFC), Institute of Culture and Art/University Restaurant (ICA-UFC/RU-UFC) and University Library (BU-UFC), which are separated into five sets of areas that have a PV generation potential of 2.67 GWh/year, 4.80 GWh/year, 1.97 GWh/year, 2.25 GWh/year and 0.55 GWh/year respectively, totaling a PV potential of 12.25 GWh/year, with a total installed capacity of 6.67 MWp. For case 1, cost of PV DG in the Pici Campus based on the Investment of the Federal Institute of Ceara (IFCE), the investment for the implementation of the PV DG system (CFV) is R $ 29,262,587.57. For Case 2, cost of PV DG in the Pici Campus based on the Investment in the solar park of Nova Olinda, Piaui the required investment is R $ 20,400,732.78. The amount of the invoice for the Campus do Pici in this period was R $ 8,330,313.61. The consumption of electric energy was 14.33 GWh, with 1.19 GWh consumed in peak time (HP) and 13.14 GWh consumed in the off-peak time HFP. The average Gmês m of the Pici Campus is able to offset R $ 5,047,425.79 (93.29%) of the value of energy consumption in the HFP. The return period of the PV DG PRIFV) investment installed in the Pici Campus is from four to six years. (author)
[en] While recalling important dates of the evolution of legislation regarding energy self-consumption, this guide presents the legal context and some basic generalities of collective self-consumption, briefly discusses the evolution of the regulatory framework. Then, it defines some key points for a successful self-consumption: to ensure the project technical feasibility, to organise the project with the different actors, the use of a convention with the distribution network manager, the definition of coefficients of distribution of production among consumers, the definition of the tax regime. An example is briefly evoked
[en] This research thesis reports the development of a 25 kW plasma pilot aimed at the purification of silicon of metallurgical grade in order to obtain a material complying with requirements of the photovoltaic industry. The author first reports the design and development of a high power plasma applicator able to comply with technical requirements while analysing energy efficiencies. The process has been adapted to the processing of large ingots (4 cm) in order to define heat and matter transfers on silicon samples to allow an extrapolation of the process at the industrial scale. Two types of materials have then been envisaged: massive and powder. Phenomena of matter and heat transfer between plasma and particle have been modelled while taking chemical reactions in boundary layer into account. In order to validate the model, the author addressed the inverse case of ultra-fine powder (Si3N4 and TiN) synthesis which corresponds to reactions in plasma phase between the vapour coming from the particle and the nitrogen coming from the plasma. This analysis allows the validation of the model and of the powder processing approach in the case of perfectly certified material.
[fr]Cette etude a porte sur la mise au point d'un pilote plasma 25 kW destine a purifier du silicium de qualite metallurgique en vue d'obtenir un materiau repondant au cahier des charges de l'industrie photovoltaique. La premiere partie de cette etude a consiste a realiser et developper un applicateur plasma de haute puissance (25-100 kW) capable de repondre aux imperatifs techniques tout en analysant les rendements energetiques susceptibles d'etre obtenus selon les differentes configurations d'exploitation. Le choix des conditions optimales de rendement ont ete effectuees en tenant compte de la composition du plasma adaptee au traitement du materiau (n ou p). A cette fin, nous avons experimente l'adaptation du procedeau traitement de lingots de grande taille (4 cm) afin de definir les transferts de chaleurs et de matiere sur des echantillons de silicium permettant une extrapolation du procede a l'echelle industrielle. A ces bilans energie et matiere, nous avons joint la qualification des silicium recycles type n ou p afin de souligner la composition optimale du plasma dans les deux cas de figure. La deuxieme partie de cette etude imposait d'envisager deux types de materiaux: le materiau massif et le materiau en poudre. C'est la raison pour laquelle nous avons etudie de facon tres precise les obligations techniques qui naissent de la manipulation des poudres. Pour mener a bien ce travail, il etait indispensable de modeliser les phenomenes de transfert de matiere et de chaleur plasma-particule, ce qui nous a conduit a developper un modele qui tient compte des reactions chimiques en couche limite. Cette etape a constitue une phase capitale de notre memoire puisqu'elle permet desormais d'aborder la chimie et de mieux comprendre les phenomenes de decomposition et de purification sous plasma. Pour conclure et verifier ce modele, nous avons traite le cas inverse de la synthese de poudres ultrafines (Si3N4 et TIN) traduisant les reactions en phase plasma entre la vapeur provenant de la particule et l'azote du plasma. Cette analyse permet alors de valider le modele et la demarche de traitement de poudre dans le cas d'un materiau parfaitement qualifie. (auteur)
[en] This publication proposes, through descriptions of examples and evocations of researches and works, a detailed overview and illustrations of the role of chemistry in different sectors of energy. First in nuclear energy (in the fuel cycle, to address corrosion issues, in radiolysis), secondly in renewable energies (for solar photovoltaic energy, for the transformation of biomass into biofuels, for lithium-ion batteries, for the hydrogen technology, for fuel cells), thirdly analytical chemistry (application of its various techniques), and fourthly for the Environment (nuclear toxicology studies, processing for the valorisation of components, green chemistry)
[en] Micro-transfer printing (μTP) provides fast and precise assembly of micro-components from a variety of different source materials onto non-native target substrates such as glass, plastic, ceramic, and silicon. Retrievable micro-components are picked up by an elastomer stamp and printed onto the target substrate with yields exceeding 99.9%. Devices incorporating GaN, GaAs, InP, and other compound semiconductor materials are successfully integrated onto silicon and glass with fine precision to make highly integrated compound semiconductor micro-systems. (© 2020 Wiley‐VCH GmbH)
[en] Full text: The research about renewable energy sources has attracted attention since there is a high demand for clean energy around the world. In the case of solar energy, a prominent field is the investigation of multiferroic materials for applications in photovoltaic cells. In this scenario, KBiFe2O5 (KBFO) emerged as a strong candidate for such applications given mostly by its low bandgap energy. At room temperature, KBFO crystallizes in an orthorhombic structure and possesses interesting electronic properties making it suitable also for photovoltaic applications. Besides, it is reported that such structure transforms into a monoclinic one in very high temperatures and pressures. In this work, we obtained the monoclinic structure of KBFO at room temperatures and performed an analysis of the structural and vibrational properties of KBFO using Raman spectroscopy and Synchrotron X-ray powder diffraction (SXRPD) techniques under hydrostatic pressure variation. The study of Raman spectra obtained at high pressures revealed a first order phase transition in the material, characterized by a pressure hysteresis. Synchrotron X-ray powder diffraction (SXRPD) under varying pressure was employed to confirm such structural pressure-induced phase transition. An integrated evaluation of the results obtained by Raman and SXRPD techniques indicates that, possibly, the symmetry for the high-pressure crystalline phase belongs to the space group Pmmm. (author)
[en] Through presentations of different examples of actual and successful realisations combining agriculture and photovoltaic energy, this publication proposes a non-exhaustive overview of possible associations and sustainable solutions which are emerging at the crossroad of agricultural and energetic stakes. These examples more particularly concern photovoltaic farming greenhouses (for market gardening, horticulture, tree nurseries), dynamic photovoltaic shade-houses (viticulture, tree culture, market gardening), photovoltaic installations on farm buildings (storage, shelter), photovoltaic shade-houses (fish farming and other applications), ground photovoltaic plants (sheep breeding). Examples in over-seas agriculture are also presented
[fr]Ce document, qui presente des exemples tres divers de realisations concretes et benefiques du mariage entre agriculture et photovoltaique, se veut un panorama non-exhaustif des associations possibles et des solutions durables emergeant a la croisee des enjeux energetiques et agricoles. En effet, l'energie solaire photovoltaique s'impose dans le Monde comme l'une des energies majeures de ce siecle. En France, elle constitue l'une des composantes essentielles de la transition energetique dans laquelle est engage notre pays, comme l'a rappele l'adoption de la PPE revisee, qui fixe l'objectif ambitieux de 35,1 GW a 44 GW de capacites installees en 2028. Cette source d'energie renouvelable a la vertu de pouvoir etre deployee sur tout type de surface, au sol comme en toiture et sur de nombreux types de structures, en facade ou sur des ombrieres... Aussi, loin de s'apparenter a une artificialisation des sols, le solaire photovoltaique doit pouvoir continuer a prendre sa place de maniere raisonnee et raisonnable dans le monde agricole. De son cote, l'agriculture occupe une place economique et culturelle de premier plan en France. En effet, plus de la moitie de la superficie francaise est agricole (environ 30 millions d'hectares sur les 55 millions que compte le territoire continental), et notre pays est le premier pays agricole d'Europe en termes economiques. C'est donc tout naturellement que les acteurs du monde agricole et de la filiere photovoltaique se sont engages dans de multiples collaborations depuis plus de 10 ans maintenant, pour la realisation de projets photovoltaiques en milieu agricole