3,405 research outputs found
APLICACIÓN DE FOTOCATÁLISIS SOLAR A PH NEUTRO PARA LA ELIMINACIÓN DE CONTAMINANTES QUÍMICOS Y BIOLÓGICOS
No full textLos estudios realizados en esta Tesis Doctoral se han centrado en la aplicación de los Procesos de Oxidación Avanzada (AOPs) en condiciones próximas a la neutralidad para la eliminación de contaminantes químicos (contaminantes emergentes) y biológicos (larvas de mejillón cebra) en aguas naturales, mediante aplicación de procesos de fotocatálisis solar heterogénea con TiO2 y foto-Fenton solar a pH neutro.
Los tratamientos de oxidación aplicados a los contaminantes emergentes se han realizado en simulador solar y en planta piloto y su degradación se ha seguido empleando diversas técnicas analíticas ccomo UHPLC, GC-MS, espectroscopía UV-IR (COD, DQO); además se ha realizado un estudio de la evolución de la toxicidad (Vibrio fischeri) durante cada proceso.
Los estudios con TiO2 en simulador solar consiguen eliminar la totalidad de los contaminantes en menos de 240 minutos, observándose un aumento de la toxicidad del 50% a los 120 minutos de tratamiento, que prácticamente desaparece al final del proceso; cunado el proceso se escala a planta piloto se aprecia una ralentización en todas las degradaciones justificada por la diferencia entre los espectros (solar y simulador solar) en la región de 280-300nm.
Del estudio destaca el hecho de que el rendimiento de las reacciones foto-Fenton en medio neutro es aceptable para su aplicación y está muy influenciado por la concentración inicial de los contamiantes y de ácidos húmicos presentes en el medio, ya que se contraponen su función de estabilización del hierro en disolución, el posible efecto de filtro interno y la acción como atrapador de especies activas. Por otra parte, los ensayos toxicológicos muestran fluctuaciones con el tiempo de tratamiento debido a la generación de intermedios de reacción tóxicos, habiéndose identificado los principales mediante GC-MS. Se ha realizado además un estudio mecanístico sobre la participación del radical hidroxilo en el proceso, siendo menor en medio neutro que en medio ácido. El agua de sBernabeu García, A. (2012). APLICACIÓN DE FOTOCATÁLISIS SOLAR A PH NEUTRO PARA LA ELIMINACIÓN DE CONTAMINANTES QUÍMICOS Y BIOLÓGICOS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17739Palanci
Numerical Simulation of III-V Solar Cells Using D-AMPS
No full textNumerical simulation of devices plays a crucial role in their design, performance prediction, and comprehension of the fundamental phenomena ruling their operation. Here, we present results obtained using the code D-AMPS-1D, that was conveniently modified to consider the particularities of III-V solar cell devices. This work, that is a continuation of a previous paper regarding solar cells for space applications, is focused on solar cells structures than find application for terrestrial use under concentrated solar illumination. The devices were fabricated at the Solar Energy Institute of the Technical University of Madrid (UPM). The first simulations results on InGaP cells are presented. The influence of band offsets and band bending at the window-emitter interface on the quantum efficiency was studied. A remarkable match of the experimental quantum efficiency was obtained. Finally, numerical simulation of single junction n-p InGaP-Ge solar cells was performed
Reliability evaluation of III-V concentrator solar cells
No full textConcentrator solar cells have been proposed as an interesting way of reducing the cost of photovoltaic electricity. However, in order to compete with conventional solar modules it is necessary not only to reduce costs but also to evaluate and increase the present reliability. Concentrator solar cells work at higher temperature, solar radiation and current stress than conventional solar cells and a carefully reliability analysis is needed. In this paper a reliability analysis procedure, that is being developed, is presented
Análise experimental de um sistema solar com concentrador cilindro parabólico
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2013Neste trabalho foi realizado um estudo experimental de um coletor solar cilindro parabólico, com 4m de comprimento e 3m de largura, operando em Florianópolis, Santa Catarina. O projeto e construção do coletor também foram realizados durante este trabalho. O fluido de trabalho utilizado foi água destilada, com vazões variando de 0,05 kg/s a 0,3 kg/s. A temperatura de operação variou entre a temperatura ambiente, 25°C, até 150°C e a pressão dos testes foi mantida entre 4 e 6 bar. O concentrador cilindro parabólico é equipado com elementos absorvedores com recobrimento seletivo e isolamento térmico evacuado. O diâmetro interno dos elementos absorvedores, por onde escoa a água é de 67 mm, semelhante ao utilizado em centrais solares de grande porte. Dados de radiação solar global e direta foram realizados durante os testes e confrontados com os resultados das medições realizadas no coletor. Com isso obteve-se os parâmetros de rendimento global e ótico do coletor. Foram realizados também testes de perdas térmicas para se obter um coeficiente global de perdas de calor e assim o rendimento térmico. Abstract: At the present work, an experimental analysis of a parabolic trough solar collector, which is 4m long and 3m wide, was carried out at the city of Florianópolis, Santa Catarina, Brazil. In this work the project and the assembly of the collector were entirely done. Tests were carried out with water as the working fluid. The water mass flow rate ranged from 0,05 kg/s to 0,3kg/s. The temperature of operation ranged between the ambient temperature, 25°C, until 150°C, and the pressure was maintained between 4 and 6 bar. The parabolic trough collector is equipped with heat collector element recovered with selective coating and with vacuum for thermal insulation. The inner diameter of the heat collector element, where the water flows, is 67mm, the same used in commercial scale solar power plants. Direct and global solar radiation was measured during the testes and confronted with the measurements in the collector. With these measurements the global and optical efficiencies of the collector was determined. To determine the thermal efficiency and to obtain a global heat loss coefficient, thermal losses tests were carried out
Advances in quantum dot intermediate band solar cells
No full textSeveral groups have reported on intermediate band solar cells (IBSC) fabricated with InAs/GaAs quantum dots (QD) which exhibit quantum efficiencies (QE) for sub-bandgap photon energies. However, this QE is produced by the absorption of photons only through valence band (VB) to intermediate band (IB) transitions. The absorption of photons of that energy in IB to conduction band (CB) transitions is weak and is usually replaced by carrier escape. This mechanism is incompatible with the preservation of the output voltage, and therefore, it cannot lead to the high efficiencies predicted by the IBSC model. In this work, we discuss the contribution of thermal and tunneling mechanisms to IB-CB carrier escape in current QD-IBSCs. It is experimentally demonstrated that in QD-IBSC prototypes where tunnel escape has been eliminated, the sub-bandgap QE is suppressed at sufficiently low temperatures, and when this occurs, the only limit for the open-circuit voltage (VOC) is the fundamental semiconductor bandgap, as stated by the IBSC theoretical model
Valoración de colectores solares térmicos planos de vacío para la producción de frío
No full textLos objetivos a cumplir son: - Revisión bibliográfica sobre el estado actual de la tecnología de energía solar térmica de baja temperatura y sus aplicaciones para la producción de frío.- Análisis de los datos experimentales de los colectores planos de vacío y de la máquina de absorción YAZAKI WFC-10. - Adaptación de un modelo de una instalación de frío solar (planta solar y máquina de absorción) empleando el calor procedente de los colectores solares planos y analizando la influencia de la superficie solar y volumen del tanque de almacenamiento. - Realización de un estudio económico y medioambiental de la instalación.Ingeniería Técnica en Mecánic
Parameters and method to evaluate the solar reflectance properties of reflector materials for concentrating solar power technology - Official SolarPACES reflectance guideline verstion 2.5
No full textThe goal of this document is to serve as guidance on the relevant parameters and measurement possibilities to reliably evaluate the reflectance quality of a solar reflector material. It is a tool on how to obtain and provide the necessary data on reflectance properties, so that the material in question can be adequately evaluated for its destined application or be compared with other materials. It does not serve as guidance on how to use these data in simulations, ray-tracing, evaluation of efficiency in different collector systems etc. Commercial instruments or validated laboratory prototypes may be employed to measure the here defined parameters, as long as they fulfil the here mentioned requirements. This guideline describes on one hand the parameters and values that should ideally be measured for a complete and adequate reflector characterization. Since the technology to fulfil the ideal case is not yet available, the guideline defines on the other hand the minimum required parameters that are necessary for a useful evaluation and that can be acquired today
Raising the Efficiency Limit of the GaAs-based Intermediate Band Solar Cell Through the Implementation of a Mololithic Tandem with an AlGaAs top Cell.
No full textThe high efficiency limit of the intermediate band solar cell (IBSC) corresponds to the case of using as intermediate band (IB) host material a semiconductor with gap in the range of 2 eV. Traditional photovoltaic materials, such as Si and GaAs, are not appropriate to produce IB devices because their gaps are too narrow. To overcome this problem, we propose the implementation of a multi-junction device consisting of an IBSC combined with a single gap cell. We calculate the efficiency limits using the detailed balance model and conclude that they are very high (> 60% under maximum concentration) for any fundamental bandgap from 0.7 to 3.6 eV in the IBSC inserted in the tandem. In particular, the two-terminal tandem of a GaAs-based IBSC current matched to an optimized AlGaAs top cell has an efficiency limit as high as 64%
Passive sorting of asteroid material using solar radiation pressure
No full textUnderstanding dust dynamics in asteroid environments is key for future science missions to asteroids and, in the long-term, also for asteroid exploitation. This paper proposes a novel way of manipulating asteroid material by means of solar radiation pressure (SRP). We envisage a method for passively sorting material as a function of its grain size where SRP is used as a passive in-situ ‘mass spec-trometer’. The analysis shows that this novel method allows an effective sorting of regolith material. This has immediate applications for sample return, and in-situ resource utilisation to separate different regolith particle sizes
Energetic Comparison of Linear Fresnel and Parabolic Trough Collector Systems
No full textWithin the last years, Linear Fresnel (LF) collector systems have been developed as a technical alternative to parabolic trough collector (PT) systems. In the past, LF systems focused on low- and medium temperature applications. Nowadays, LF systems equipped with vacuum receivers can be operated at the same temperatures as PT systems. Papers about the technical and economical comparison of specific PT and LF systems have already been published, [1-3]. However, the present paper focuses on the systematic differences in optical and thermodynamic performance and the impact on the economic figures
In a first step the optical performance of typical PT and LF solar fields has been examined, showing the differences during the course of the day and annually. Furthermore, the thermodynamic performance, depending on the operating temperature, has been compared.
In a second step, the annual electricity yield of typical PT and LF plants are examined. Solar Salt has been chosen as heat transfer fluid. Both systems utilize the same power block and storage type. Solar field size, storage capacity, and power block electrical power are variable, while all examined configurations achieve the same annual electricity yield. As expected for molten salt systems, both systems are the most cost-effective with large storage capacities. The lower thermodynamic performance of the LF system requires a larger solar field and lower specific costs in order to be competitive. Assuming specific PT field costs of 300 €/m² aperture, the break-even costs of the LF system with Solar Salt range between 202 and 235 €/m², depending on the site and storage capacity.
Keywords: linear Fresnel, parabolic trough
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