A comparison of hole-filling methods in 3D

This paper presents a review of the most relevant current techniques that deal with hole-filling in 3D models. Contrary to earlier reports, which approach mesh repairing in a sparse and global manner, the objective of this review is twofold. First, a specific and comprehensive review of hole-filling techniques (as a relevant part in the field of mesh repairing) is carried out. We present a brief summary of each technique with attention paid to its algorithmic essence, main contributions and limitations. Second, a solid comparison between 34 methods is established. To do this, we define 19 possible meaningful features and properties that can be found in a generic hole-filling process. Then, we use these features to assess the virtues and deficiencies of the method and to build comparative tables. The purpose of this review is to make a comparative hole-filling state-of-the-art available to researchers, showing pros and cons in a common framework.• Ministerio de Economía y Competitividad: Proyecto DPI2013-43344-R (I+D+i) • Gobierno de Castilla-La Mancha: Proyecto PEII-2014-017-PpeerReviewe

Thermo-economic and sensitivity analysis of a central tower hybrid Brayton solar power plant

[EN]A hybrid central tower thermo-solar plant working with a gas turbine is simulated by means of an in-house developed model and software. The model considers the integration of all plant subsystems. The calculation of the heliostat solar field efficiency includes the main losses factors as blocking, shadowing, attenuation, interception, and cosine effect. The simulation considers a Brayton cycle for the power unit with irreversibilities in the compressor and turbine, and pressure drops in the heat absorption and extraction processes. A combustion chamber burning natural gas ensures an approximately constant power output. The model is flexible and precise. At the same time it is fast enough to perform sensitivity studies on the efficiency of any subsystem and the overall plant. Thus, it allows for performing a thermo-economic analysis of the plant checking the influence of the main plant design parameters. The focal objective is to analyze the importance on the levelized cost of electricity (LCoE) of the key plant design parameters. The direct influence of parameters from the heliostat field and receiver (as tower height, distance to the first row of heliostats, heliostats size, receiver size and heat losses, etc.) on final LCoE is surveyed. Similarly, parameters from the turbine as pressure ratio, turbine inlet temperature, influence of recuperation and others, are also analyzed. The dimensions of the plant are taken from SOLUGAS prototype near Seville, Spain, although another location with quite different solar conditions in Spain is also considered. LCoE values predicted are about 158 USD/MWh. The analysis concludes that among several parameters surveyed, two of them are key in LCoE predicted values: turbine inlet temperature and solar receiver aperture size.Junta de Castilla y León of Spain (project SA017P17

Towards a Sustainable Future through Renewable Energies at Secondary School: An Educational Proposal

[EN]A compilation of innovative educational activities to work on concepts related to the production of electrical energy is presented. To approach the real-life secondary education curriculum, they are grouped to be performed during a week denominated Renewable Energy Week: an educational proposal aimed to promote the respect for the environment through the insight on Sustainable Development Goals (SDG) and renewable energy sources. The students would build and perform low-cost experiments so as to deeply understand the essence of energetic transformations, as well as electricity generation. Learning by discovery, collaborative learning and experimentation, are the methodological pillars that characterize Renewable Energy Week, since they have been proven to be efficient methodologies to promote students’ learning. Innovative techniques for pupils evaluation are employed, including a rubric, Socrative application and a set of sheets regarding experiments. Through this educational proposal, the students are expected to achieve a deep understanding of some key concepts related to electricity and awaken their interest in scientific subjects, making them conscious of the transition to sustainable development that our planet urgently requires. At the same time, this project offers to teachers a series of experiments and innovative activities to work on the SDG in Physics, Chemistry and Technology subjects.University of Salamanca through Innovation and teaching improvement project ID 2019/16

Thermo-economic study of hybrid parabolic dish solar power plants in different regions of Spain

[EN]Small-scale hybrid parabolic dish Concentrated Solar Power (CSP) systems coupled to a micro-gas turbine are a promising option to obtain electrical energy in a distributed manner. During the day, solar energy is used to produce electricity and the absence of sunlight can be overcome with the combustion of a fossil or renewable fuel. This study presents the technical feasibility and thermo-economic model of a hybridized power plant in different regions of Spain, considering the local climatic conditions. The implemented model aims to provide a realistic view of the behaviour of the system, using a reduced number of selected parameters with a clear physical meaning. The irreversibilities taking place in all subsystems (solar part, combustion chamber, micro-gas turbine, and the corresponding heat exchangers) have been considered in the model, developed in Mathematica® language. The model considers the instant solar irradiance and ambient temperature dynamically, providing an estimation of the power output, the associated fuel consumption, and the most relevant pollutant emissions (CO2, CH4 and NO2) linked to combustion, for hybrid and combustion only operating modes at selected geographical locations in Spain. The considered power output ranges between 7 to 30 kWe which is achieved by varying the design specifications. The levelized cost of electricity (LCoE) indicator is estimated as a function of investment, interest rate, maintenance and fuel consumption actual costs in Spain. The electricity costs from hybrid parabolic dish are between 22% and 27% lower compared to pure combustion power plant, while specific fuel consumption and therefore CO2 emissions can be reduced up to 33%. This model shows the potential of hybrid solar dishes to become cost-competitive against non-renewable ones from the point of view of electricity costs and significant reduction in gas emission levels in regions with high solar radiation and low water resources.Junta de Castilla y Leó

Micro Gas Turbine and Solar Parabolic Dish for distributed generation

[EN]A thermodynamic model for a Brayton-like microturbine in combination with a solar parabolic dish is analyzed in order to evaluate its efficiency under any ambient condition. The thermodynamic cycle is a recuperative Brayton cycle with internal irreversibilities in the recuperator, compressor and turbine and external losses associated to the heat transfers in the solar receiver, the combustion chamber, and the environment. All the irreversibilities have been taken into account in the model with home-software elaborated using Mathematicaâ. The model validation is done by comparison with results provided by Semprini et al. [1]. An analysis of hybrid and sunless performance is carried out for four different microturbine power outlets (30, 23, 15 and 7 kWe) and for four days of the year (corresponding to each season). The greenhouse emissions are also calculated for both off-design performance and for the four power output levels

Solar Volumetric Receiver Coupled to a Parabolic Dish: Heat Transfer and Thermal Efficiency Analysis

[EN]Concentrated Solar Power plants are commonly recognized as one of the most attractive options within carbon free power generation technologies because their high efficiency and also because implementation of hybridization and/or storage is feasible. In this work a small-scale system focused on distributed production, in the range of kWe (5kWe to 30kWe), is modeled. A parabolic dish collects direct solar power towards a receiver located at its focus. There, the heat transfer fluid increases its temperature for thermal storage or for directly producing electricity at the power block. Thus, this is a crucial component in CSP systems since it greatly influences global efficiency. There is a trade-off in the energy balance within the thermal receiver, since the higher the temperatures it achieves, the higher the radiation losses could be. In this work, a heat transfer analysis for an air volumetric receiver coupled to a parabolic dish is carried out. The solar receiver is modeled under steady-state conditions using a detailed set of equations. The model considers the main losses by convection, conduction and radiation at the glass window and the surrounding insulator. The temperatures and heat transfers along the different receiver zones are computed with a built from scratch in-house code programmed in Mathematica®. The thermal efficiency mainly depends on the incoming solar irradiance at the glass window, the receiver geometry and the type of materials considered, as well as on the ambient temperature. It is expected that this model (precise but not too expensive from the computational viewpoint) could help to identify the main bottlenecks

Modeling a solar pressurized volumetric receiver integrated in a parabolic dish: Off-design heat transfers, temperatures, and efficiencies

[EN]Concentrated solar power plants are commonly recognized as one of the most attractive options within carbonfree power generation technologies because of their high efficiency and feasible hybridization and/or storage implementation. In this work, a complete heat transfer analysis for an air volumetric receiver coupled to a parabolic dish focused on distributed generation (in the range of kWe) is carried out. It includes most relevant heat losses. Dish collector optical efficiency is computed by means of a ray-tracing software while the thermal performance of the solar receiver is modeled under steady-state conditions using a comprehensive set of equations with a clear physical origin and meaning. Detailed information on the temperatures and heat transfers along the different inner and outer receiver zones are computed with a built from scratch inhouse code programmed in Mathematica®. The model considers the main losses from convection, conduction and radiation and through the surrounding insulator. The resulting thermal efficiency mainly depends on the incoming solar irradiance at the glass window, the receiver geometry and the type of materials considered, as well as on the ambient temperature. Explicit numerical results are given at two locations under different meteorological conditions. Optical efficiencies reach values of about 84%. For irradiance values around 800– 900 W/m2, at the receiver outlet, air can reach temperatures of about 1200 K and receiver thermal efficiency is over 80%. It is expected that this model (precise but not too expensive from the computational viewpoint) could help to identify the main efficiency bottlenecks, paving the way for optimization when designing this type of concentrated solar plants through further coupling with a power block, as Brayton or other cycles

Thermodynamic and Cost Analysis of a Solar Dish Power Plant in Spain Hybridized with a Micro-Gas Turbine

[EN]Small-scale hybrid parabolic dish concentrated solar power systems are a promising option to obtain distributed electricity. During the day, solar energy is used to produce electricity, and the absence of sunlight can be overwhelmed with fuel combustion. This study presents a thermo-economic survey for a hybridized power plant in different regions of Spain, considering the local climatic conditions. The developed model considers the instant solar irradiance and ambient temperature dynamically, providing an estimation of the power output, the associated fuel consumption, and the most relevant pollutant emissions linked to combustion. Hybrid and combustion-only operating modes at selected geographical locations in Spain (with different latitudes, mean solar irradiances, and meteorological conditions) are analyzed. The levelized cost of electricity indicator is estimated as a function of investment, interest rate, maintenance, and fuel consumption actual costs in Spain. Values of about 124 e/MWhe are feasible. Fuel consumption and emissions in hybrid operation can be reduced above 30% with respect to those of the same turbine working in a pure combustion mode. This model shows the potential of hybrid solar dishes to become cost-competitive against non-renewable technologies from the point of view of costs and reduction in gas emission levels in regions with high solar radiation and low water resources.University of Salamanca Grant Number PC-TCUE18-20-002, Junta de Castilla y León of Spain Grant Number SA017P17

Implicaciones cognitivas en la estimación psicofísica del sabor

Introducción: en la percepción sensorial del gusto, los conceptos de umbral absoluto (UA), los métodos psicofísicos para estimarlo y la influencia que ejerce el conocimiento previo sobre su percepción y reconocimiento son de difícil aprendizaje por su escaso estado de conciencia. Objetivo: evaluar los umbrales de detección de los cuatros sabores básicos en una muestra de jóvenes sanos, en condiciones de restricción de alimentos/no-restricción, y analizar la influencia del conocimiento previo de la astringencia para su detección-identificación. Método: se puso en contacto directo con las sustancias químicas de los sabores y de astringencia a 114 participantes con media de 20,03 años (DT = 5.45), el 75,4% mujeres, mediante una degustación teórica-práctica. Se aplicó un diseño de tratamiento invertido con las condiciones experimentales sobre restricción de alimentos y conocimiento de astringencia. Resultados: todos identificaron sus UA para los cuatro sabores básicos. El grupo con restricción fue significativamente más sensible (Tb = -3,305; p = 0,001) al dulce (UA = 2 g/l) que el grupo sin restricción (UA = 5 g/l). La detección-identificación de la astringencia resultó significativamente mayor (t = -13,323; p = 0,000) con información previa del nombre (79,31%) que sin esta información (19,64%), confundiéndola, o describiéndola, como sabor amargo (80,36%). Conclusiones: el aprendizaje del sabor se favorece cuando se realiza la medición psicofísica de los sentidos químicos junto a la formación de determinados conceptos teóricos sobre la percepción gustativa y denominación de sabores, al facilitar su proceso cognitivo posterior detección- identificación. También debe atenderse al proceso de homeostasis interna previa de los participantes por la variabilidad en los resultados de sus UA según las condiciones de hambre/saciedad anteriores a su estimación psicofísica.Introduction: in sensory perception of taste, it is difficult to learn the concepts of absolute threshold (AT), the psychophysical methods to estimate it and the influence exerted by prior knowledge on their perception and recognition, because they have little awareness. Objective: to assess absolute thresholds of four basic flavors in a sample of healthy young people, in conditions of food restriction/without restriction, and to analyze the influence of prior knowledge of astringency in its detection-identification. Methods: one hundred and fourteen participants with an average of 20.03 years old (SD = 5.45), 75.4% of them women, were put in direct contact with chemical substances of basic flavors and astringency through a theoretical-practical tasting. An inverted treatment design was applied with experimental conditions on food restriction and knowledge of astringency. Results: all identified their AT for basic flavors. The group with restriction was significantly more sensitive (Tb = -3.305, p = 0.001) to sweet (AU = 2 g/l) than the group without restriction (AU = 5 g/l). The detection-identification of astringency was significantly higher (t = -13.323, p = 0.000) with previous information of the name (79.31%) than without this information (19.64%), confusing or describing it as bitter taste (80.36). Conclusion: taste learning is facilitated with the performance of psychophysical measurements of chemical senses, together with training of certain theoretical concepts about taste perception and flavor denomination, because it facilitates the cognitive process for detection-identification. In addition, the process for the previous internal homeostasis of participants must be considered as their AU results vary according to the hunger/ satiety conditions prior to the psychophysical estimation