Mostrando artículos por etiqueta: 2019 publication
Solar pyrolysis of agave and tomato pruning wastes: Insights of the effect of pyrolysis operation parameters on the physicochemical properties of biochar
Alejandro Ayala-Cortés, Camilo Alberto Arancibia-Bulnes, Heidi Isabel Villafán-Vidales, Diego Ramón Lobato-Peralta, Diana Cristina Martínez-Casillas, and Ana Karina Cuentas-Gallegos
Abstract
Agave angustifolia leaves and tomato pruning biomasses were processed into carbon materials by solar pyrolysis. The influence of temperature and heating rate was studied in the physicochemical properties of the obtained biochars. The characterization techniques include elemental analyses (CHONS), physisorption to determine surface area by BET and DFT models, and capacitance values were determined by cyclic voltammetry as the electrochemical technique. It was found that for both biomasses, temperatures below 900°C are beneficial because more homogeneous and porous structures are obtained. The highest values of capacitance and surface area were obtained for tomato carbons at 450 and 600 °C, respectively. REFEREN
Solar Irradiation over a Flat Surface with Different Tracking Strategies
Adriana E. Gonzalez-Cabrera, David Riveros-Rosas, Héctor Estevez, Anayeli Ramirez, Mauro G. Valdes, Camilo A. Arancibia-Bulnes and Luis F. Zarzalejo
Abstract
The importance of solar tracking systems lies in the need to optimize the amount of solar radiation on solar collectors of different types. In this work, the monthly mean daily irradiation was analyzed on a flat surface of unitary area, under different tracking schemes of the Sun, by means of the use of a numerical model. For this purpose, solarimetric data was obtained from some stations of the new Mexican Solarimetric Network, the solar irradiance incident on a flat horizontal plate was calculated. Also, the movement of some tracking systems was carried out in steps with different time intervals in order to compare it with their respective continuous movement. It was found that stepped movements report yearly incident solar irradiation values above 98% respect to continuous movement in the widest interval.
Solar Irradiation over a Flat Surface with Different Tracking Strategies
Comments to “A simple method to achieve a uniform flux distribution in a multi-faceted point focus concentrator”
Lúar Moreno-Álvarez, Andrés Amat-Castrillón
Abstract
We have found the flux homogenization technique described in the paper published in volume 93, pages 115–124 (august 2016), does not provide homogenized fluxes in all out-of-focus distances of the solar receiver, but only above a certain transition distance, and that some of the numerical analysis procedures used in that document should be revised or complemented to achieve better reproducibility of the results. In addition, we also note that some statements and conclusions in that document are mistaken or formulated incorrectly, so it is necessary their correction.
Synthesis and characterization of tantalum carbide nanoparticles using concentrated solar energy
Yannely Carvajal-Campos, Laura Ceballos-Mendivil, Francisco Baldenebro-López, Carlos Pérez-Rábago, Claudio A Estrada
Abstract
Tantalum carbide (TaC) nanoparticles were synthesized using the IER-UNAM (HoSIER) solar furnace, which reduces polluting gas emissions and dependence on fossil fuels through the use of concentrated solar energy. TaC synthesis was performed through a carbothermal reduction method from Ta/O/C complex, using tantalum pentachloride (TaCl5) and synthesized phenolic resin as sources of tantalum and carbon, respectively, at a temperature of 1200 °C, in a reaction time of 30 min, under argon atmosphere. A solar reactor equipped with a quartz window was used, designed to work in controlled atmospheres. Complex Ta/O/C bonds and thermal decomposition were analyzed by FT-IR and TG/DSC, respectively, while the structure and morphology of TaC were analyzed by XRD, TEM, and SEM techniques. Results showed a TaC with a cubic crystalline structure, a low amount of Ta2O5 and a near-spherical …
Synthesis and characterization of tantalum carbide nanoparticles using concentrated solar energy
A lab-scale rotary kiln for thermal treatment of particulate materials under high concentrated solar radiation: Experimental assessment and transient numerical modeling
Alessandro Gallo, Elisa Alonso, Carlos Pérez-Rábago, Edward Fuentealba, María Isabel Roldán
Abstract
Rotary kilns are worldwide used for industrial processes that involve thermal treatments of particulate materials. However, a great amount of fossil fuels is employed in such processes. As alternative, solar rotary kilns are considered for this application due to their versatility and potential to substitute traditional fossil-fuel driven devices. In order to boost the development of this technology, efforts have to be focused on the control of the particle temperature during the treatment. In this context, a lab-scale rotary kiln was built and tested using a 7-kWe high-flux solar simulator at University of Antofagasta. It was conceived to treat particulate materials of different nature and it is able to reach temperatures higher than 800 °C under different operation strategies. Silicon carbide was selected for initial tests because it is inert, endures high temperatures (up to 1600 °C) and it has been proposed as thermal storage vector in several researches on concentrated solar power. In a first stage, the empty kiln was preheated up to about 800 °C, reaching a steady state in less than three hours and with a power of approximately 370 W entering the kiln cavity. Afterwards, 43 g of silicon carbide were introduced in the furnace and the system was heated again up to a second steady state above 800 °C. In this stage, particles showed a fast increment of their temperature and exceeded 700 °C in less than three minutes after loading. A one-dimensional transient numerical model was also developed to perform the thermal analysis of the kiln and the estimation of both the particle temperature and the system efficiency. Numerical results showed good agreement with experimental data and thermal losses could be quantified in detail. Therefore, the model was also used to predict the thermal behavior of a solar rotary kiln working in batch mode..
Effect of non-uniform concentrated solar flux on direct steam generation in vertical pipes of solar tower receivers
V.M.Maytorena, J.F.Hinojosa
Abstract
The purpose of this work is to analyze the effect of non-uniform concentrated solar radiation on direct steam generation in a vertical tube of solar tower receiver. The modified RPI model was used for the conditions of critical heat flux coupled to a Eulerian two fluid model. The mathematical model was solved with CFD software. The results were validated with experimental data reported in the literature and a parametric study was carried out to determinate the effect of non-uniform concentrated solar radiation, on the steam quality, the volumetric fraction, enthalpies and temperatures of liquid and steam. Non-uniform concentrated solar fluxes favor generation of steam but produce conditions that may influence the structural durability of DSG receivers, like high axial temperature gradients and zones with temperatures above the melting temperature of stainless steel.
Thermal analysis of a finned receiver for a central tower solar system
A Piña-Ortiz, JF Hinojosa, RA Pérez-Enciso, VM Maytorena, RA Calleja, CA Estrada
Abstract
In this study, a thermal analysis of a finned receiver prototype for a thermosolar tower system is presented. The experimental system consists of parallelepiped aluminum enclosure of 1.2 m high, 1.23 m wide and 0.1 m depth. At the interior, 1232 cylindrical fins with a diameter of 0.0095 m (3/8”) and 0.09 m length increases the heat transfer area up to 225%. The vertical wall receives the incoming solar concentrated radiation from a group of heliostats whilst at the interior a constant flow of water removes the absorbed energy. Experimental temperature profiles were obtained at different heights and depths and a comparison was made with numerical results obtained with the use of commercial CFD software. It was found that the maximum thermal efficiency of the receiver was 94.4 %, decreasing as the radiative flux increases.
Thermal analysis of a finned receiver for a central tower solar system