O apelo por processos mais limpos em aspectos econômicos e ambientais são desafios na busca de metodologias que atinjam a sustentabilidade na produção dos mais diversos gêneros englobando conceitos que vão da minimização de resíduos a substituição de matrizes energéticas. Neste mesmo cenário, a demanda por óleos vegetais tem se intensificado em virtude do crescimento do mercado oleoquímico nos segmentos de biocombustíveis, alimentos, fármacos e cosméticos. Nas diversas nuances da sustentabilidade, a energia solar vem se destacando por representar uma fonte não poluente e praticamente inesgotável da Terra com grande potencial de aproveitamento. Este trabalho teve como objetivo principal estudar o uso da energia solar nos processos de lixiviação e destilação, associados à obtenção de óleos de amendoim, coco e baru. Na extração, o solvente é aquecido e percola as partículas do material contido no interior de um leito fixo. Foram utilizados nos experimentos dois modelos de concentradores solares para o aquecimento do solvente etanol hidratado combustível, sendo um de formato cilíndrico-parabólico e outro de geometria biangular de doze lados. Para os testes, foram variadas as vazões de alimentação do solvente em 15, 25 e 35 mL/min, sendo a de 25 mL/min que apresentou melhor hidrodinâmica em todas as extrações. O protótipo biangular alcançou uma eficiência 15,34% maior que o primeiro na extração do óleo de amendoim, quando comparado o rendimento com o Soxhlet. Para as extrações com o coco e o baru foram empregues duas granulometrias diferentes em cada e o concentrador biangular atingiu eficiência de 70,88% e 89,24%, respectivamente para a menor granulometria avaliada. A destilação solar foi utilizada na recuperação do solvente resultante da miscela. Os testes em batelada revelaram como sendo 0,16 cm a altura ideal para melhor taxa de evaporação. Tal valor permitiu projetar um modelo de alimentação continua para que o destilador operasse sempre próximo a faixa de altura calculada. Nos processos em batelada e continuo, a destilação alcançou respectivamente 84,2% e 75,58% de rendimento na coleta de destilado e, em contrapartida, 26,86 % e 44,22% de eficiência térmica. Foram obtidos dados do INMET para analisar a influência das condições meteorológicas. / The requirement for cleaner processes in economic and environmental aspects are challenges in the search for methodologies that achieve sustainability in the production of the most diverse genres, encompassing concepts ranging from waste minimization to substitution of energy matrices. In this same scenario, the demand for vegetable oils has intensified due to the growth of the oleochemical market in the biofuel, food, pharmaceutical and cosmetic segments. In the various nuances of sustainability, solar energy has stood out because it represents a nonpolluting and virtually inexhaustible source of the Earth with great potential of use. The main objective of this work was to study the use of solar energy in the leaching and distillation processes associated with obtaining peanut, coconut and baru oils. Upon extraction, the solvent is heated and percolates the particles of the material contained within a fixed bed. Two models of solar concentrators for the heating of the hydrous ethanol fuel solvent were used, one of parabolic-cylindrical shape and the other of twelve-sided biangular geometry. For the tests, the solvent feed rates were varied at 15, 25 and 35 mL/min, with 25 mL/min that presented better hydrodynamics at all extractions. The biangular prototype achieved a 15.34% greater efficiency than the first one in the extraction of the peanut oil, when compared the yield with the Soxhlet. For the extraction with the coconut and the baru two different granulometries were used in each one and the biangular concentrator reached efficiency of 70.88% and 89.24%, respectively, for the smaller granulometry evaluated. Solar distillation was used to recover the solvent resulting from miscella. The batch tests revealed to be 0.16 cm the ideal height for better evaporation rate. This value allowed the design of a continuous feed model so that the distiller always operated near the calculated height range. In the batch and continuous processes, distillation reached 84.2% and 75.58%, respectively, in the distillate collection and, in contrast, 26.86% and 44.22% of thermal efficiency. INMET data were obtained to analyze the influence of meteorological conditions. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

This thesis presents and demonstrates procedures to model and optimize the collector field of a parabolic trough solar thermal power plant. The collector field of such a plant is universally organized into parallel loops of solar collectors. Heat transfer fluid returning from the energy conversion plant is heated to a moderately high temperature in the field. Typically fluid enters a collector loop around 270 °C and leaves at 380 °C. The fluid is then returned to the plant to generate steam. In the first part of this thesis, the collector field and the energy conversion system of a typical parabolic trough solar thermal power plant are modeled. The model is compared with actual performance data and is enhanced and verified as necessary. Originally, the collectors in the plants under consideration were provided with evacuated tube receivers of the highest feasible efficiency without much regard for cost effectiveness. In practice, these receivers have failed at an unexpected rate and need replacement. It is unlikely that a very expensive evacuated tube receiver is now the most cost effective for every location in a collector loop. In particular, a receiver optimized for 270 °C operation may not be optimal at 380 °C. For example, a relatively inexpensive receiver with a flat black absorber and no vacuum may be more cost effective in the lower temperature segments of a loop. In the second part of this thesis, a procedure for the optimum deployment of collectors is developed and demonstrated. The results of this research should be directly applicable to the refurbishment and upgrading of several of the largest solar energy plants in the world.

A promising and novel solar concentrator design has been thoroughly investigated and optimised. A prototype concentrator based on this novel geometry was validated using ray tracing techniques. This ray tracing demonstrated the comparative performance of this novel concentrator in regards to equivalent parabolic dishes. The effect of mirror surface normal errors on performance was established using Monte-Carlo based ray tracing code, which agreed well with the optical performance of this prototype which was determined experimentally. A need for low-cost solar cookers to replace bio-mass worldwide was identified, and the concentrator design was then developed as a low-cost solar oven. Despite existing in some number, no current design is able to achieve high performance at low-cost. An industrial partner, Dytecna, was initially involved in the process of this development of the system as a solar cooker. In support of a field trial for the solar cooker developed with Dytecna, a detailed thermal model of the oven was developed. A low-cost lightmeter was constructed and calibrated in order to measure the direct normal irradiance during the field trial in Italy. Laboratory work provided baseline results for the heating of various thermal masses in the oven. The Italian field trials provided a wealth of feedback into the design of the system and many valuable results. The solar cooker was able to bring 0.75L of water to the boil in 33 minutes with an average heat throughput of 203W. Important benchmark results and practical experience of several competing receiver materials was obtained; further lab testing provided more accurate measurements of the receivers' performances. The experiences of the Italian field trial were fed back into the design of a subsequent prototype, intended for a much larger field trial in Tanzania. Improvements in the hotplate, receiver material, and the oven were all incorporated into the design. Additionally, the structure of the solar cooker was redesigned to incorporate a low-cost wooden construction. Supporting work was conducted for the month long trial in which 8 solar cookers would be distributed to families in Tanzania. The field trial in Tanzania provided a wealth of user feedback into the design. At the same time the new solar cooker exceeded previously established performances in Italy. The new design was able to provide an average of 246W of heat to 1kg of water, which was brought to boiling point in 25 minutes. This represents a heating efficiency of 66% compared to the incident solar flux on the hotplate. In response to findings during the Tanzanian trials, further laboratory work was conducted into establishing the reflectivities of low-cost candidate mirror materials. Throughout all phases of the project the design of the solar cooker was refined and improved with the goal of a solar cooker design that could reach price-point, performance, and usability standards which would ensure market success.

Made available in DSpace on 2014-12-17T14:57:38Z (GMT). No. of bitstreams: 1 CarlosAlbertoPQLF.pdf: 2273640 bytes, checksum: a4f60a823eb1d55227bb74c387319cef (MD5) Previous issue date: 2007-05-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / A model of a solar oven with a reflective surface composed of two mirror segments is presented, constituting a two semi-parabolic surfaces made of fiberglass, applied on a ceramic mold, intended to be used in residential and commercial cooking. The reflective surface of the semi-parable is obtained with the use of multiple plain segments of 2 mm wide mirrors. The semi-parabolic structure has visible movements that are comparable to that of the sun. The technical details of the manufacturing and assembling processes will be presented with an analysis of the viability of thermal, economic, and materials of such prototype. This prototype has important social implications and primordial aspects, which combats the ecological damages caused by the wide-scale use of firewood during cooking. It has been demonstrated that the solar oven has the capacity to cook simultaneous two meals distinct for a family of four / Apresenta-se um modelo de fog?o solar ? concentra??o composto por dois segmentos espelhados, constituindo duas semi-par?bolas, obtidas atrav?s da utiliza??o de fibra de vidro, aplicada sobre um molde cer?mico, destinado ao cozimento de alimentos para fins residenciais, urbanos e rurais. O espelhamento das semi-par?bolas foi obtido atrav?s da utiliza??o de m?ltiplos segmentos planos de espelho de 2 mm de espessura. A estrutura das semi-par?bolas tem mobilidade de movimentos para a corre??o do movimento aparente do sol. Ser?o apresentados detalhes t?cnicos dos processos de fabrica??o e montagem e uma an?lise das viabilidades, t?rmica, econ?mica e de materiais de tal prot?tipo, que tem uma conota??o social importante e um aspecto primordial, que ? o combate a danos ecol?gicos proporcionados pela utiliza??o, ainda em larga escala, da lenha para o cozimento dos alimentos. Comprovou-se que ? poss?vel o cozimento simult?neo de alimentos de duas refei??es distintas para uma fam?lia de quatro pessoas

QDs haben aufgrund ihrer einzigartigen optischen und elektronischen Eigenschaften erhebliche Aufmerksamkeit erregt und sind vielseitige Materialien für verschiedene Anwendungen. T-QDs, wie AIS/ZnS, haben aufgrund ihrer geringeren Toxizität, Umweltverträglichkeit und einstellbaren optischen Eigenschaften an Bedeutung gewonnen. Diese Arbeit konzentriert sich auf die MW-Synthese von AIS/ZnS-QDs und untersucht den Einfluss von Syntheseparametern auf ihre optischen Eigenschaften sowie deren nachfolgende Anwendung in LSCs. Die Synthese kombiniert einen zweistufigen Erhitzungsansatz mit MW, was eine präzise Kontrolle über die QD-Zusammensetzung, Liganden und die chemische Zerfallsreihenfolge ermöglicht. Die Studie untersucht die Variation der Ag:In:S:Zn-Verhältnisse und den Einfluss von vier verschiedenen Liganden auf die optischen Eigenschaften. Die Ergebnisse bestätigen die Vielseitigkeit dieser QDs bei der Herstellung wasserlöslicher, hochphotolumineszierender Materialien. Die AIS/ZnS-QDs werden weiterhin als Materialien für LSCs genutzt, um erneuerbare Energie in BIPV-Systemen zu nutzen. Die Studie erforscht die Integration dieser QDs in eine Polymermatrix für LSCs und betont die Effizienz der Synthese. Zwei Syntheseansätze, ein zweistufiges Erhitzungsverfahren und die MW-Synthese mit Thiol-Liganden, erzeugen QDs, die in Toluol dispergierbar sind. Die resultierenden lumineszierenden Platten, integriert in LSC-Geräte, zeigen eine hohe PL QY (>60%). Die optischen Verluste werden für verschiedene Ligandenkombinationen verglichen, wobei überlegene Ergebnisse für MPA-OLA/OA-capped QDs beobachtet werden. Die LSC-Geräte, gekoppelt mit Si-Solarzellen unter einem Sonnensimulator, zeigen OPE-Werte von 3,8 ± 0,2% und 3,5 ± 0,2% für GSH-OLA/OA bzw. MPA-OLA/OA AIS/ZnS-QDs, und QOE-Werte von 24,1 ± 0,4% und 27,4 ± 0,4%. Die erreichte Leistung, gepaart mit der einfachen, wasserbasierten Synthese und den guten optischen Eigenschaften, unterstreicht das Potenzial von AIS/ZnS-QDs als LSCs. / QDs gained significant attention for their unique optical and electronic properties, making them versatile materials for various applications. t-QDs, such as AIS/ZnS, gained prominence due to their lower toxicity, eco-friendly nature, and tunable optical characteristics. This thesis focuses on the MW-assisted synthesis of AIS/ZnS QDs, exploring the impact of synthesis parameters on their optical properties and subsequent application as LSCs. The synthesis methodology combines a two-step heating approach with MW assistance, allowing for precise control over QD composition, ligands, and chemical decomposition order. The study investigates the variation of Ag:In:S:Zn ratios and the influence of four different ligands on optical properties. The results confirm the versatility of these QDs in producing water-soluble, highly photoluminescent materials with PL QY of 60-65% and long PL decay. The synthesized AIS/ZnS QDs are further utilized as materials for LSCs, aiming to harness renewable energy in building-integrated photovoltaic systems. The study explores the integration of these QDs into a polymer matrix for LSCs, emphasizing the efficiency of the synthesis method. Two synthesis approaches, a two-step heating method and MW-assisted synthesis with thiol ligands, yield QDs dispersible in organic solvents. The resulting luminescent slabs, integrated into LSC devices, exhibit high PLQY (>60%). Optical losses due to reabsorption and matrix effects are compared for different ligand combinations, with superior results observed for MPA-OLA/OA-capped QDs. The LSC devices coupled with Si-solar cells under a solar simulator demonstrate OPE values of 3.8 ± 0.2% and 3.5 ± 0.2% for GSH-OLA/OA and MPA-OLA/OA AIS/ZnS QDs, respectively, and QOE values of 24.1 ± 0.4% and 27.4 ± 0.4%. The achieved device performance, among the highest reported, coupled with the simplicity of the water-based synthesis and the excellent optical properties, underscores the potential of AIS/ZnS QDs as LSCs.