Desarrollo de nanomateriales 2d metálicos para nanofluidos con aplicación en energía solar de concentración

The cost-effective optimisation of renewable power generation systems is a must in the present context of a global climate crisis and a growing demand for reliable, affordable and clean power supply. Reliability is a challenging issue for renewable technologies like photovoltaics, which produces electricity under ceaseless solar irradiation and therefore suffers of daily intermittency. The integration of concentrated solar power plants in hybrid power blocks has been proposed as a solution for this intermittency by taking advantage of thermal energy storage to maintain production and compensate the supply. A limitation for this solution is the low solar-to-thermal energy conversion due to the poor thermophysical properties of the typical heat transfer fluid flowing through solar collectors. The use of nanofluids as has been proposed to improve this conversion. This thesis aims to provide knowledge and understanding of the Physical Chemistry of nanofluids, with particular attention to features and processes that determine their stability and heat transfer and storage capabilities. Here Pd nanoplate-containing aromatic oil-based nanofluids have been prepared and characterised through different techniques to assess their applicability as volumetric absorbers and heat transfer fluids in parabolic trough collectors of concentrating solar power plants. A significant contribution from this thesis refers to the influence of the structure and dynamics of solid-liquid interfaces on the physical properties of nanofluids on the basis of simulations at the density functional theory and molecular dynamics levels-of-theory. The findings presented are expected to have both practical and fundamental implications on future research.La optimización del rendimiento de los sistemas de producción eléctrica renovable es una necesidad en el contexto actual, caracterizado por una crisis climática global y una creciente demanda por un suministro eléctrico fiable, rentable y limpio. La fiabilidad es un tema desafiante para algunas tecnologías renovables como la fotovoltaica, que producen electricidad únicamente bajo irradiación solar incesante y sufre, por tanto, de intermitencia diaria. La inclusión de plantas de energía solar de concentración en bloques híbridos de potencia constituye una prometedora solución para esta intermitencia, por aprovechamiento del almacenamiento térmico de energía para mantener la producción y compensar el suministro. Una limitación de esta solución es la baja eficiencia de la conversión solar-térmica por las deficientes propiedades termofísicas del fluido de transferencia de calor que circula a través de los colectores solares. Se propone el uso de nanofluidos para mejorar la eficiencia de conversión. Esta tesis pretende aportar conocimiento y comprensión sobre la Química Física de los nanofluidos, con particular atención a todos aquellos aspectos y procesos que determinan su estabilidad y aptitud para la transferencia y almacenamiento de calor. Se han preparado nanofluidos con nanoplates de Pd en un aceite aromático y se han caracterizado mediante diferentes técnicas para evaluar su aplicabilidad como absorbedores volumétricos y fluidos transferentes de calor en colectores cilindro-parabólicos de plantas de energía solar de concentración. Una contribución significativa de esta tesis se refiere a la influencia de la estructura y dinámica de la interfase sólido-líquido en las propiedades físicas de los nanofluidos, en base a simulaciones desarrolladas en el contexto de la Teoría del Funcional de la Densidad y de la Dinámica Molecular. Se espera que los hallazgos que aquí se presentan tengan implicaciones prácticas y fundamentales en investigaciones futuras

Tunnelling and swelling in triassic sulphate-bearing rocks: part II: case studies from Jura Mountains

Part II of this series of paper deals with the phenomenology of swelling in tunnels from Jura Mountains (Switzerland) excavated through the Gipskeuper and the Anhydritgruppe. The main features of expansions observed in the presented case studies are summarized and the performance of resisting and yielding support systems is compared. Evidences presented in this series of papers indicate that the transformation of anhydrite into gypsum is not a reasonable explanation for long-term expansive phenomena occurring in sulphate-bearing rocks. It is suggested that these phenomena are strongly related to rock degradation due to both tunneling induced drainage towards the bottom of excavations and tunneling induced ventilation

A review of expansive phenomena in Wagenburg North Tunnel

The paper deals on tunnelling and swelling in anhydritic-gypsiferous claystones. The geology of the Gipskeuper in Baden-Württemberg (Germany) and the phenomenology of expansions in Wagenburg North tunnel are described. Consistent swelling triggering events, mechanisms and exhaustion causes were identified using a thermo-hydro-chemo-mechanical theoretical analysis. It is suggested that long-term swelling in tunnels excavated through anhydritic-gypsiferous claystones is a result of solvent-way gypsum crystal growth due to ventilation induced groundwater evaporation and rock drying; an opposite concept to the usual consequences of drying in argillaceous materials, which causes shrinkage strains

Tunnelling and swelling in triassic sulphate–bearing rocks: part I: case studies from Baden–Württemberg

Cases of swelling in tunnels excavated through Triassic sulphate-bearing rocks from the Gipskeuper and the Anhydritgruppe are presented and discussed in this series of papers in order to gain a better understanding of the expansive phenomena in these materials and to identify the most relevant ones. Part I deals with main features of swelling in tunnels and alternative supports designs for their control an mitigation, as well as with the phenomenology of swelling in tunnels from Baden-Württemberg (Germany) excavated through the Gipskeuper

Probing the thermal resistance of solid-liquid interfaces in nanofluids with molecular dynamics

The significance of interfacial thermal resistance in the thermal conductivity of nanofluids is not well understood, in part because of the absence of measurements of this quantity. Here, we study the interfacial thermal resistance for metal-oil nanofluids of interest as heat transfer fluids for concentrating solar power, using density functional theory and molecular dynamics simulations. Insights on the role of chemical interactions in determining the interfacial thermal resistance are revealed. The results presented here showcase a general picture in which the stronger the chemical interactions between species at the interface, the lower the associated interfacial thermal resistance. The implications toward nanofluid design are discussed. We show that, for this important family of metal-oil nanofluids, the interfacial thermal resistance values are low enough so that it is possible to afford a reduction in particle size, minimizing stability and rheological issues while still offering enhancement in the effective thermal conductivity with respect to the base fluid.40 página

Diseño de un sistema de gestión de seguridad y salud en el trabajo, bajo la norma ISO 45001:2018 en la empresa ACP Ltda. Automatización Control y Potencia

El presente proyecto se enfocó al diseño de un SG-SST bajo la norma ISO 45001 versión 2018 en la empresa ACP LTDA. el cual le va a permitir a la empresa gestionar adecuadamente los riesgos y oportunidades de SST y mejorar el desempeño, prevenir lesiones y deterioro de la salud de los trabajadores relacionado con las actividades que desarrollan y brindar espacios de trabajo saludables seguros”. “El proyecto se parametrizó en tres fases fundamentales: un diagnóstico de la empresa basado en una guía ISO 45001, el análisis del contexto de la organización basado en la planeación estratégica y el diseño de SG-SST de acuerdo a los criterios establecidos en la Norma ISO 45001”. “Dentro del cumplimiento de las fases del proyecto se diseñaron los documentos exigidos en cada uno de los numerales de la norma ISO 45001 y se establecieron las directrices de cumplimiento de cada uno de los numerales. Como evidencia de lo anterior, se diseñó la política de SST de ACP LTDA, se diseñaron los perfiles de cargos, se elaboraron las matrices de identificación de peligros y valoración de riesgos, se diseñó el plan de emergencias y se establecieron los procedimientos, programas, formatos, planes y herramientas necesarias para dar cumplimiento los requisitos legales y la norma ISO 45001”. “El proyecto se apoya en un estudio descriptivo, se recabó información de los empleados para evaluar las deficiencias actuales de la empresa y se identificaron oportunidades de mejora mediante un método analítico. Al esbozar todos los requisitos exigidos por la norma en los capítulos: contexto de la organización, liderazgo, planificación, apoyo, operación, evaluación del desempeño y mejora, el proyecto condujo al diseño de un SG-SST para la empresa ACPLTDA”.Universidad Libre Seccional Barranquilla -- Facultad de Ingeniería -- Programa de Ingeniería Industria

Thermal performance of nanofluids based on tungsten disulphide nanosheets as heat transfer fluids in parabolic trough solar collectors

Nanofluids are considered as a new generation of heat transfer fluids since they exhibit thermophysical properties improvements compared with conventional heat transfer fluids. The high thermal conductivity of nano -fluids and even the isobaric specific heat enhancements over conventional liquids make these colloidal suspensions very attractive in many research areas, including solar energy. In this work, nanofluids based on tungsten disulphide (WS2) nanosheets have been prepared from the thermal oil currently used as heat transfer fluid in Concentrating Solar Power (CSP) plants. The high aspect ratio of WS2 bidimensional nanostructures provides high long-term colloidal stability to the nanofluids and facilitates heat transport. Cetyl-trimethylammonium bromide and polyethylene glycol have been used as surfactants to improve the exfoliation process and enhance the colloidal stability of the nanomaterial dispersions. Some properties such as density and viscosity of the base fluid have not been significantly altered by the presence of WS2 nanosheets in the base fluid. However, studies on the thermal properties of nanofluids have shown promising results with increases in thermal conductivity of up to 33% and heat transfer coefficient by 21% over the base fluid. Furthermore, it has been estimated that the overall efficiency of the CSP system could be improved by 31% by replacing the conventional thermal fluid with 2D-WS2-based nanofluids

Synthesis, Characterization and Photocatalytic Performance of Calcined ZnCr-Layered Double Hydroxides

The development of new materials for performing photocatalytic processes to remove contaminants is an interesting and important research line due to the ever-increasing number of contaminants on our planet. In this sense, we developed a layered double hydroxide material based on Zn and Cr, which was transformed into the corresponding oxide by heat treatment at 500 & DEG;C. Both materials were widely characterized for their elemental composition, and structural, morphological, optical and textural properties using several experimental techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy and physisorption techniques. In addition, the photocatalytic activity of both materials was analysed. The calcined one showed interesting photocatalytic activity in photodegradation tests using crystal violet dye. The operational parameters for the photocatalytic process using the calcined material were optimised, considering the pH, the initial concentration of the dye, the catalyst load, and the regeneration of the catalyst. The catalyst showed good photocatalytic activity, reaching a degradation of 100% in the optimised conditions and showing good performance after five photodegradation cycles.This research was funded by 2014-2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia, grant number FEDER-UCA18-107510

Stability and Thermal Properties Study of Metal Chalcogenide-Based Nanofluids for Concentrating Solar Power

Nanofluids are colloidal suspensions of nanomaterials in a fluid which exhibit enhanced thermophysical properties compared to conventional fluids. The addition of nanomaterials to a fluid can increase the thermal conductivity, isobaric-specific heat, diffusivity, and the convective heat transfer coefficient of the original fluid. For this reason, nanofluids have been studied over the last decades in many fields such as biomedicine, industrial cooling, nuclear reactors, and also in solar thermal applications. In this paper, we report the preparation and characterization of nanofluids based on one-dimensional MoS2 and WS2 nanosheets to improve the thermal properties of the heat transfer fluid currently used in concentrating solar plants (CSP). A comparative study of both types of nanofluids was performed for explaining the influence of nanostructure morphologies on nanofluid stability and thermal properties. The nanofluids prepared in this work present a high stability over time and thermal conductivity enhancements of up to 46% for MoS2-based nanofluid and up to 35% for WS2-based nanofluid. These results led to an increase in the efficiency of the solar collectors of 21.3% and 16.8% when the nanofluids based on MoS2 nanowires or WS2 nanosheets were used instead of the typical thermal oil

Estudio teórico de la estructura y la dinámica de un nanofluido con partículas de CuO

Resumen del proyecto de líneas prioritarias titulado "Estudio teórico de la estructura y la dinámica de un nanofluido con partículas de CuO" del IMEYMAT