High Vapor Transport Deposition: A Novel Process to Develop Cu2ZnSn(SxSe1–x)4 Thin Film Solar Cells

Kesterite thin film solar cells are known to be a promising cost-effective solution because they are based on earth-abundant and environmental compounds. However, it is known that their best efficiency (12.6%) has not been improved since 2013, meanwhile other thin-film solar cells have demonstrated that their performance has been enhanced continuously. The main drawbacks to explain this situation is the narrow process window of this compound and simultaneously, the high composition and thermal control needed to avoid intrinsic defects in the p-type layer. The high vapor transport deposition process has not been explored yet by kesterite thin film solar cell developers. Herein, we present the results obtained using a design of a new vacuum deposition method similar to close space sublimation, which reported excellent results in CdTe. The main advantages of this novel process are: 1) to achieve a high deposition rate; 2) to be able to deposit precursor materials and to carry out the sulfur-selenization in the same process chamber, avoiding the two steps used in the sequential process; 3) to provide a high accuracy in the chemical composition control; and 4) simple design using commercial components to facilitate its scalability for large production

Angular Dependence of Photonic Crystal Coupled to Photovoltaic Solar Cell

Photonic crystals have the advantage of minimizing thermal losses from solar cells, reflecting the solar radiation that is not absorbed by the photovoltaic device. To optimize this optical response, photonic crystals are designed considering the relative position of the Bragg peak and the bandgap of the solar cell, under normal incident irradiation conditions. The aim of this research article was to determine experimentally the optical limits of a solar cell coupled to a photonic crystal acting as beam splitter. For that purpose, the photovoltaic system was characterized under indoor and outdoor conditions; angular dependence of the irradiation source was determined in each case, and both results were compared with good agreement. Moreover, other parameters such as irradiation spectrum and polarization of the light were investigated. The main conclusion is that photovoltaic performance is highly affected by the Bragg peak shifting and the profile is distorted, due to the angular dependence with the sun. These experimental limits must be considered at the early design stage to avoid performance losses

Fitness, body composition, and metabolic risk scores in children and adolescents: the UP&DOWN study

We aimed to analyse the longitudinal association between physical fitness (PF) and body composition (BC) with a metabolic risk score (Met4) in children and adolescents and to elucidate whether the association between PF and Met4 differs when using relativized or absolute fitness variables. A total of 188 children (86 females) and 195 adolescents (97 females) were included. Cardiorespiratory fitness (CRF) was determined by the 20-m shuttle run test, and muscular fitness (MF) was determined by hand grip and standing long jump tests. Height and weight were measured, and the body mass index (Kg/ m2) was calculated. Triceps and subscapular skinfolds were assessed to compute body fat percentage. Met4 was computed from systolic blood pressure, triglycerides, high-density lipoprotein cholesterol, and glucose levels. Relative CRF was longitudinally and negatively associated with Met4 in female children (β = −0.031, p = 0.025), while absolute CRF was positively associated with Met4 in male children and adolescents (β = 0.000, p < 0.05). Relative upper and lower-body MF were longitudinally and negatively associated with Met4 in female adolescents (β = −1.347, β = −0.005, p < 0.05), while absolute lower-body MF was positively associated with Met4 in male children (β = 0.000, p = 0.019). BC was longitudinally and positively associated with Met4 in male children (β-ranging from 0.011 to 0.055, all p < 0.05) and male adolescents (β-ranging from 0.011 to 0.046, all p < 0.05). Conclusion: BC is more strongly associated with Met4 than PF in children and adolescents. An optimal body weight status should be considered the main objective of health-promoting programs at childhood and adolescence. Furthermore, the way of expressing the fitness variables determines the direction of the association with Met4.CRUE-CSICNational Plan for Research, Development, and Innovation (R + D + i) from the Spanish Ministry of Science and Innovation DEP 201021662-C04-00 DEP 2010-21662-C04-01 DEP 2010-21662-C04-02 DEP 2010-21662-C04-03 DEP 2010-21662-C04-0

Influence of Degradation Processes in Lead–Acid Batteries on the Technoeconomic Analysis of Photovoltaic Systems

Most technoeconomic feasibility studies of photovoltaic (PV) systems with batteries are mainly focused on the load demand, PV system profiles, total system costs, electricity price, and the remuneration rate. Nevertheless, most do not emphasise the influence degradation process such as corrosion, sulphation, stratification, active material seeding, and gassing on battery lifetime, efficiency, and capacity. In this paper, it is analysed the influence of the degradation processes in lead–acid batteries on the technoeconomic analysis of PV systems with and without battery. Results show that Net Present Value (NPV), Payback Period (PBP), and Discounted PayBack Period (DPBP) have a heavy dependence on the assumptions about the value of the battery performance parameters according to its degradation processes. Results show NPV differences in the range from −307% to 740%, PBP differences in the range from 9% to 188%, and DPBP differences in the range from 0% to 211%

The social value of education: between subjectivity and objectivity. Theoretical and methodological considerations for evaluation

En este artículo se presenta una reflexión acerca del valor social de la educación (VSE) como constructo a evaluar. Se presenta una definición del constructo VSE, que se identifica como la utilidad que tiene la educación para el bienestar personal y social. Desde esta perspectiva, en el VSE se diferencian dos tipos de acercamiento: el VSE-Objetivo (que hace referencia a la utilidad objetiva medida a través de indicadores estadísticos referidos a diversos factores que involucran la educación), y el VSE-Subjetivo (que se define como la percepción que tienen las personas acerca de la utilidad de la educación tanto para el desarrollo personal como social). Se aportan reflexiones acerca del VSE en relación a la justicia social. Se justifican los motivos del interés que puede tener el VSE y se presenta una referencia acerca de posibles indicadores e instrumentos para su evaluaciónDesarrollado en el marco del proyecto M-AVACO, financiado por el MICINN (España). Referencia del proyecto: EDU2009-13485

Some experience in an improvement cycle in classroom to teach Thermodynamics

En este artículo se comparten las experiencias de aplicar un Ciclo de Mejora en el Aula ciclo(CIMA) durante la asignatura de Termodinámica en el Grado de Ingeniería de las Tecnologías Industriales de la Universidad de Sevilla. El objetivo ha sido invertir la metodología aplicada para centrar la atención en los alumnos, generando situaciones que les involucren en la clase. Se trata así de evitar la “clase magistral” y que los alumnos consigan un mayor aprendizaje y a largo plazo (Beard y Hartley, 1984). Se ha planteado un nuevo modelo metodológico aplicando un aprendizaje basado en problemas.A session for the improvement in teaching has been achieved to implement new methodologies in the Thermodinamics subject, which is included in the Bachelor Degree for Industrial Engineering at the University of Seville. The main objective of this project has consisted in flipping the traditional “master class” to transfer the main role of the classroom to the students. It is expected that this alternative teaching methodology will let students get a better understanding of the concepts in the long-term (Beard and Hartley, 1984). More precisely, the proposed model is focussed on the learning procedure based on problems

On split Leibniz algebras

Con intención de acometer la estructura de álgebras de Leibniz arbitrarias (sin restricciones ni en su dimensión ni en su cuerpo base), definimos las álgebras de Leibniz split como la generalización natural de las álgebras de Lie split. Desarrollando técnicas de conexiones de raíces para estas álgebras, mostramso que son suma de una subespacio de una subálgebra abeliana e ideales bien definidos, tales que estos ideales tienen producto nulo cuando se multiplican dos distintos. En caso de que una álgebra de Leibniz split sea de longitud máxima caracterizamos su simplicidad en términos de conexiones de raíces

Mitigating energy poverty: Potential contributions of combining PV and building thermal mass storage in low-income households

The issue of energy poverty has devastating implications for the society, and it has been aggravated in the past years due to the economic crisis and the increase of energy prices. Among the most affected are those with low incomes and living in inefficient buildings. Unfortunately, the bitter reality is that sometimes this part of the population are facing the next question: Heating, or eating? The declining prices of distributed energy technologies such as photovoltaics provides an opportunity for positive social change. Although their use does not address energy poverty directly, substantial contributions may be made. Measurements of indoor temperatures in a social housing district of southern Spain in 2017 have revealed the unbearable temperatures that the occupants have to endure, both in summer and winter. Using this district as a case study, the present work aims to evaluate the benefits of exploiting its rooftop PV potential to cover part of the electricity consumption of the district (reducing the energy bills), and use the surplus electricity to supply power for the heat pumps in the district. Optimal alternatives regarding maximum PV production, maximum self-sufficiency ratio and minimum investment costs have been found, considering as well different options when sharing the available electricity surplus to improve the thermal comfort of the occupants. As far as the authors know, no previous study has followed an approach aimed at energy poverty alleviation such as the one presented in this work. The results show that using the surplus electricity to heat or cool the whole dwellings would improve the thermal comfort of the occupants in average up to 11% in winter and 26% in summer. If all the PV generation was used or more buildings in the area were employed to install PV modules, improvements up to 33% in winter and 67% in summer could be obtained, reducing at the same time the thermal comfort differences among the dwellings of the district

Background questionnaires of PISA: a study of the assessment indicators

The PISA assessment system has generated and continues to generate intense debate about its structure and usefulness. This article focuses on the context questionnaires as a way to analyze and understand the results properly. The objectives are to analyze the background indicators used in the different editions of the PISA tests, used in different studies and the results of these studies. An overview of the model used is provided to ensure that these indicators are no longer something that accompanies the performance test to reach their true meaning: jointly analyze the performance along with the variables that may be influencing the results. As methodology is used document analysis of publications related to PISA and results, as well as a semantic analysis of scientific work that has generated PISA. The results show that some indicators have remained throughout the various editions of PISA, while others have changed. The translation of a stable model in editions from PISA 2015 in which the most relevant items are included will undoubtedly facilitate the study of results at vertical and horizontal level. Thus, the importance of PISA context questionnaires established to properly understand their results and the need for more complex studies of multilevel or nested that normally used, generally based on descriptive statistics and / or percentagesThe PISA assessment system has generated and continues to generate intense debate about its structure and usefulness. This article focuses on the context questionnaires as a way to analyze and understand the results properly. The objectives are to analyze the context indicators used in the different editions of the PISA tests, used in different studies and the results of these studies. An overview of the model used is provided to ensure that these indicators are no longer something that accompanies the performance test to reach their true meaning: jointly analyze the performance along with the variables that may be influencing the results. As methodology is used document analysis of publications related to PISA and results, as well as a semantic analysis of scientific work that has generated PISA. The results show that some indicators have remained throughout the various editions of PISA, while others have changed. The translation of a stable model in editions from PISA 2015 in which the most relevant items are included will undoubtedly facilitate the study of results at vertical and horizontal level. Thus, the importance of PISA context questionnaires established to properly understand their results and the need for more complex studies of multilevel or nested that normally used, generally based on descriptive statistics and / or percentages