Energia Solar - ES
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- Aquecimento ambiente com energia solarPublication . Mendes, J. Farinha
- Assegurar a qualidade em sistemas solares térmicos: certificação de sistemas solares e seus componentesPublication . Carvalho, Maria JoãoAs aplicações de sistemas solares térmicos são múltiplas. Na gama das baixas e médias temperaturas as aplicações mais comuns são aquecimento de piscinas, preparação de Água Quente Sanitária, Aquecimento ou Arrefecimento Ambiente. Estes sistemas podem ainda ser utilizados na indústria, quer para a preparação de água quente de processo ou aquecimento de outros fluidos térmicos para processos que requerem temperaturas mais elevadas. Em qualquer aplicação pretende-se que o sistema solar térmico tenha um tempo de vida suficientemente largo que permita rentabilizar o investimento inicial. Para esse efeito será necessário assegurar a qualidade do sistema de modo a garantir o comportamento térmico do sistema e reduzir os custos de manutenção ao longo do seu tempo de vida. Neste artigo apresentamos o actual estado da Certificação de Colectores e Sistemas Solares pré-fabricados1. Fazemos primeiro uma introdução ao processo de elaboração das actuais normas de produto. Em seguida descrevemos o actual estado do sistema de certificação.Terminamos apresentando os trabalhos em curso para a melhoria de normas e esquema de certificação nos sistemas solares térmicos e seus componentes.
- Assessment of dye distribution in sensitized solar cells by microprobe techniquesPublication . Barreiros, M. Alexandra; Corregidor, V.; Alves, L. C.; Guimarães, Fernanda; Mascarenhas, João; Torres, Erica; Brites, Maria JoãoDye sensitized solar cells (DSCs) have received considerable attention once this technology offers economic and environmental advantages over conventional photovoltaic (PV) devices. The PV performance of a DSC relies on the characteristics of its photoanode, which typically consists of a nanocrystalline porous TiO2 film, enabled with a large adsorptive surface area. Dye molecules that capture photons from light during device operation are attached to the film nanoparticles. The effective loading of the dye in the TiO2 electrode is of paramount relevance for controlling and optimizing solar cell parameters. Relatively few methods are known today for quantitative evaluation of the total dye adsorbed on the film. In this context, microprobe techniques come out as suitable tools to evaluate the dye surface distribution and depth profile in sensitized films. Electron Probe Microanalysis (EPMA) and Ion Beam Analytical (IBA) techniques using a micro-ion beam were used to quantify and to study the distribution of the Ru organometallic dye in TiO2 films, making use of the different penetration depth and beam sizes of each technique. Different 1D nanostructured TiO2 films were prepared, morphologically characterized by SEM, sensitized and analyzed by the referred techniques. Dye load evaluation in different TiO2 films by three different techniques (PIXE, RBS and EPMA/WDS) provided similar results of Ru/Ti mass fraction ratio. Moreover, it was possible to assess dye surface distribution and its depth profile, by means of Ru signal, and to visualize the dye distribution in sample cross-section through X-ray mapping by EPMA/EDS. PIXE maps of Ru and Ti indicated an homogeneous surface distribution. The assessment of Ru depth profile by RBS showed that some films have homogeneous Ru depth distribution while others present different Ru concentration in the top layer (2 lm thickness). These results are consistent with the EPMA/EDS maps obtained.
- Biomarkers of exposure to metal dust in exhaled breath condensate: methodology optimizationPublication . Félix, P. M.; Franco, C.; Barreiros, M. Alexandra; Batista, B.; Bernardes, S.; Garcia, S. M.; Almeida, A. B.; Almeida, S. M.; Wolterbeek, H. Th.; Pinheiro, TeresaIn occupational assessments where workers are exposed to metal dust, the liquid condensate of exhaled breath (EBC) may provide unique indication of pulmonary exposure. The main goal of this study was to demonstrate the quality of EBC to biological monitoring of human exposure. A pilot study was performed in a group of metal dust–exposed workers and a group of nonexposed individuals working in offices. Only metal dust–exposed workers were followed along the working week to determine the best time of collection. Metal analyses were performed with inductively coupled plasma mass spectrometry (ICP-MS). Analytical methodology was tested using an EBC sample pool for several occupationally exposed metals: potassium, chromium, manganese, copper, zinc, strontium, cadmium, antimony, and lead. Metal contents in EBC of exposed workers were higher than controls at the beginning of the shift and remained augmented throughout the working week. The results obtained support the establishment of EBC as an indicator of pulmonary exposure to metals.
- CdTe nano-structures for photovoltaic devicesPublication . Corregidor, V.; Alves, L. C.; Franco, N.; Barreiros, M. Alexandra; Sochinskii, N. V.; Alves, E.CdTe nano-structures with diameter of ∼100 nm and variable length (200–600 nm) were fabricated on glass substrates covered with conductive buffer layers such as NiCr, ZAO (ZnO:Al2O3 + Ta2O5) or TiPd alloys. The fabrication process consisted of the starting vapour deposition of metal catalyst dropped layer followed by the isothermal catalyst-prompted vapour growth of CdTe nano-structured layer of controllable shape and surface filling. The effect of buffer layers on the crystallographic orientation and thickness of CdTe nano-structured layers is investigated by means of IBA techniques, SEM and X-ray diffraction. It was shown that the formed CdTe nano-layers have a cubic structure, mainly oriented towards the [1 1 1] crystallographic direction, except for those grown on ZAO layer where the X-ray diffraction signal is very weak to be associated to any crystallographic form. The RBS spectra recorded on different areas of each sample type showed an almost constant thickness and SEM images revealed an homogeneous and dense distribution of the structures. It was also possible to study the first stage of the nano-structures grown on the Bi2Te3 seeds.
- A certificação de qualidade em sistemas solares para aquecimento de águaPublication . Costa, J. Cruz; Carvalho, Maria João; Mendes, J. Farinha; Prates, Manuel João LopesTendo em atenção a política nacional para o desenvolvimento do mercado da Energia Solar Térmica, motivada pela necessidade de uma maior utilização das Energias Endógenas (Resolução do Conselho de Ministros nº154/2001 de 27 de Setembro), descreve-se a situação actual na área dos Equipamentos Solares para Aquecimento de Água, no que diz respeito à Certificação de Produtos e à Certificação de Pessoas, como medidas necessárias para a Garantia de Qualidade nesta área.
- Characterization and electrochemical behaviour of nanostructured calcium samarium manganite electrodes fabricated by RF-Magnetron SputteringPublication . Barrocas, B.; Sério, S.; Rovisco, A.; Nunes, Y.; de Sá, A.I.; Pereira, M. I. da Silva; Jorge, M. E. MeloCa1-xSmxMnO3(0 . x . 0.4) films were successfully fabricated on Indium Tin Oxide (ITO) coated quartzglass substrates by radio frequency magnetron sputtering technique (RF- magnetron sputtering) fromcompacted nanosized powder targets, and subsequent annealing at 800.C in air, for 6 h. X-ray diffrac-tion shows a pure typical perovskite phase for x . 0.1. Scanning electron microscopy and atomic forcemicroscopy revealed that the films surface is dense, with low roughness, depending on the Sm content, even though a few cracks were observed. Crystallite size was found to decrease with the Sm content. Theelectrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The oxide electrode fs capacitance was estimated using both techniques and the corresponding roughness factors evaluated. The values obtained from the two methods show a good agreement. A com-parison between the voltammetric data and those referred in the literature allowed finding out that theredox reaction occurring at the electrode surface involves the pair Mn4+/Mn3+. EIS measurements con-firm the voltammetric data and they also give additional information about the film porosity and the charge transfer resistance. This last parameter is associated with the oxidation and reduction of the pairMn3+/Mn4+and after normalized by the roughness factor shows an increase with samarium content.
- Chemical Activities, a(H) and a(X), of Constituents in H2X Type Gas Molecules (X = O or S) at Arbitrary Degree of DissociationPublication . Shohoji, NobumitsuChemical activities, a(X) and a(H), of constituents, X and H, in H2X type gas molecules (X = S or O) were evaluated as functions of temperature T and extent α of dissociation adapting a thermodynamic analysis procedure developed by Katsura for interpreting enhanced a(N) and a(H) in NH3 gas molecules with suppressed α by flowing. Present analysis results showed that both H2S and H2O gas molecules are chemically rather inert even at comparatively low α unlike nitrogen-family tri-hydrides XH3 that were proved to yield high chemical activity of each constituent in a state being away from thermodynamic equilibrium. The parameter α referring to the extent of dissociation of HnX type gas molecules appears to be a significant parameter in evaluating the chemical activities, a(X) and a(H), in the HnX gas molecules that are remained non-dissociated.
- Como vai o autoconsumo em Portugal?Publication . Joyce, AHá cerca de um ano (outubro de 2014) foi publicada a legislação que regula o chamado Autoconsumo de Energia Eléctrica em Portugal (Decreto-Lei nº 153/2014 de 20 de outubro) pelo que se poderá colocar a questão: "Como vai o Autoconsumo em Portugal?" .Efetivamente a saída desta legislação era, há muito esperada pelo mercado, nomeadamente do fotovoltaico, que nela viu a possibilidade de relançar uma atividade económica que teve impulso dinâmico, quando em 2007 foi criado o regime da microgeração e posteriormente o da minigeração, mas que, devido à crise económica e financeira praticamente paralisou.
- Computational model of a Calcium-looping fluidized bed calcination reactor with imposed concentrated solar irradiancePublication . Rodrigues, Diogo; Rivero, Mayra Alvarez; Pinheiro, Carla I.C.; Cardoso, João P.; Mendes, Luís FilipeABSTRACT: The Calcium-looping process is a promising option for thermochemical energy storage in concentrating solar power plants. A crucial element of this process is the solar calcination reactor, where the endothermic reaction of CaCO3 calcination occurs with formation of CaO and CO2. The solar energy that is chemically stored in the reaction products can be retrieved by the exothermic reaction of CaO carbonation when needed. In this article, a new computational model is developed for the solar calcination reactor in this Calcium-looping process. The calcination reaction takes place in the riser of a continuous circulating fluidized bed that corresponds to an absorber tube exposed to concentrated solar radiation, which allows the reaction chamber to be indirectly heated. A core-annulus heat transfer model and a modified version of the Kunii-Levenspiel fluid dynamics model are used. In contrast to previous models found in the literature, the change in the mass flow rate of the species and in the density of the phases due to the reaction is considered. Simulation studies are performed with a fixed and imposed concentrated solar irradiance on the reactor wall, which varies in both the axial and angular directions. Wall conduction in the angular direction is also considered. The results show that nearly complete calcination can be achieved with a reactor of 4 m of height. A sensitivity analysis with respect to the model parameters and inlet conditions shows that the calcination conversion is mostly affected by the solids mass flow rate and the bed temperature at the inlet.