Ultrapurification of Silicon for Photovoltaic Applications

The recent explosive growth of Photovoltaics and the relative avidity for silicon of the predominant solar cell technology have resulted in a dramatic change of the polysilicon industry structure. While in the past the polysilicon was manufactured almost exclusively for the semiconductor industry, now more than half of the market is devoted to the solar industry. The different alternative routes to purify silicon for photovoltaic applications are presented in the paper, analysing their advantages and drawbacks. Emphasis is made on the CENTESIL initiative, a new private-public partnership venture promoting a pilot plant that is in an advanced state of construction. The goal is to allow the photovoltaic companies worldwide to count with an independent research centre to help them to establish their own polysilicon plant

Chemical Vapor Deposition Model of Polysilicon in a Trichlorosilane and Hydrogen System

The traditional polysilicon processes should be refined when addressing the low energy consumption requirement for the production of solar grade silicon. This paper addresses the fluid dynamic conditions required to deposit polysilicon in the traditional Siemens reactor. Analytical solutions for the deposition process are presented, providing information on maximizing the rate between the amount of polysilicon obtained and the energy consumed during the deposition process. The growth rate, deposition efficiency, and power-loss dependence on the gas velocity, the mixture of gas composition, the reactor pressure, and the surface temperature have been analyzed. The analytical solutions have been compared to experimental data and computational solutions presented in the literature. At atmospheric pressure, the molar fraction of hydrogen at the inlet should be adjusted to the range of 0.85–0.90, the gas inlet temperature should be raised within the interval of 673 and 773 K, and the gas velocity should reach the Reynolds number 800. The resultant growth rate will be between 6 and 6.5 _m min−1. Operation above atmospheric pressure is strongly recommended to achieve growth rates of 20 _m min−1 at 6 atm

Coffee and Caffeine Consumption for Human Health

The year 2019 has been prolific in terms of new evidence regarding the effects of coffee and caffeine consumption on diverse aspects of human functioning. This book collects 20 high-quality manuscripts published in Nutrients that include original investigation or systematic review studies of the effects of caffeine intake on human performance and health. The diversity of the articles published in this Special Issue highlights the extent of the effects of coffee and caffeine on human functioning, while underpinning the positive nature of most of these effects. This book will help with understanding why the natural sources of caffeine are so widely present in the nutrition behaviors of modern society

Radiation heat savings in polysilicon production: validation of results through a CVD laboratory prototype

This work aims at a deeper understanding of the energy loss phenomenon in polysilicon production reactors by the so-called Siemens process. Contributions to the energy consumption of the polysilicon deposition step are studied in this paper, focusing on the radiation heat loss phenomenon. A theoretical model for radiation heat loss calculations is experimentally validated with the help of a laboratory CVD prototype. Following the results of the model, relevant parameters that directly affect the amount of radiation heat losses are put forward. Numerical results of the model applied to a state-of-the-art industrial reactor show the influence of these parameters on energy consumption due to radiation per kilogram of silicon produced; the radiation heat loss can be reduced by 3.8% when the reactor inner wall radius is reduced from 0.78 to 0.70 m, by 25% when the wall emissivity is reduced from 0.5 to 0.3, and by 12% when the final rod diameter is increased from 12 to 15 cm

Relation between nonlinear refractive index and third-order susceptibility in absorbing media

Expressions relating complex third-order optical susceptibility (χ(3) = χR (3) + iχ I (3)) with nonlinear refractive index (n2) and nonlinear absorption coefficient (β) have been formulated that eliminate the commonly used approximation of a negligible linear absorption coefficient. The resulting equations do not show the conventional linear dependence of χR (3) with n2 and χI (3) with β. Nonlinear refraction and absorption result instead from the interplay between the real and imaginary parts of the first- and third-order susceptibilities of the material. This effect is illustrated in the case of a metal-dielectric nanocomposite for which n2 and β values were experimentally obtained by Z-scan measurements and for which the use of the new formulas for χR (3) and ≤ Ig(3) yield a large correction and a sign reversal for χI (3). © 2004 Optical Society of America.This work has been supported by the Ministerio de Ciencia y Tecnologı´a of Spain (DPI2002-00151, TIC2002- 03235). R. del Coso acknowledges the financial support of the Consejerı´a de Educacio´n de la Comunidad de Madrid and the European Social Fund (ESF).Peer Reviewe

Rotational versus glide technique in elite shot put: Trend analysis in the 21st century

Objective. The aim of this study was to analyse the trend in the use of rotational vs. glide shot-put techniques in World Championships in the last two decades and their association with shot-put performance. Methods. The technique used, and the throwing distance obtained by the finalists in the shot-put competitions (56 men and 55 women) in the World Championships between 2001 to 2019 were analysed. Results. In men, the use of the glide technique was less frequent than in women (30.6 vs. 87.7%; p < .01). In men, there has been a progressive reduction in the use of the glide technique (from 7 out of 10 shot putters in Paris in 2003 to 0 out of 12 shot putters in Doha in 2019). Although a similar tendency is observed in women athletes, the glide technique is still the principal style employed by women throwers (7 out of 12 women shot putters in Doha 2019). Throwing distance was similar between glide throwers and rotational shot putters in both men (20.66 ± 0.67 vs. 20.92 ± 0.88 m; d = 0.32; p = .128) and women athletes (18.85 ± 0.91 vs. 18.75 ± 0.71 m; d = 0.10; p = .753). In summary, the use of the rotational style in shot-put has increased in men athletes. A clear trend towards the use of the rotational technique is also present in women although the glide style is still the most prevalent. However, there are no differences in shot-put performance between techniques that justify the use of the rotational over the glide technique

Anti-Doping Knowledge of Students Undertaking Bachelor’s Degrees in Sports Sciences in Spain.

In Spain, students pursuing a career in athletic training, physical education, or scientific evaluation of sports enroll in a bachelor’s degree in sports sciences. This degree provides knowledge and skills in a broad array of sports settings and promotes research-based interdisciplinary knowledge. However, the student’s syllabus rarely includes specific academic training on anti-doping regulations or doping prevention. The purpose of this study was to assess the anti-doping knowledge of the students undertaking a bachelor’s degree in sports sciences in Spanish universities. One thousand two hundred and thirty-three bachelor students in sport science (907 males, 322 females, and 4 participants with non-binary sex) from 26 Spanish universities completed a validated questionnaire about general anti-doping knowledge. The questionnaire is an adapted version of the Play True Quiz of the World Anti-Doping Agency and contains 37 multiple-choice questions. The score obtained in the questionnaire was transformed into a 0–100-point scale. The questionnaire was distributed among students within each university by a faculty member and it was filled out online. Students obtained a score of 65.8 10.10 points (range = 32–92 points). There was an effect of the course in the score obtained (p < 0.001). Students of the first course (63.6 9.5 points) had lower scores than the remaining courses (p < 0.037) while the students of the fourth course obtained the highest scores (68.7 9.5 points; p < 0.019). The students with an itinerary on sports performance were the respondents with the highest anti-doping knowledge (67.2 10.2) points, followed by the students with an itinerary on health (66.7 9.5 points). The knowledge of basic anti-doping rules and doping prevention strategies of the bachelor students in sports sciences in Spain was suboptimal. Increasing doping prevention information in the syllabus of the bachelor’s degree in sports sciences is essential as these future professionals will directly work with populations at risk of doping.post-print1143 K

Disclosing the polysilicon deposition process

The chemical route for producing hyperpure silicon, referred to as polysilicon, is energy intensive. In this work two paths are analysed to reduce energy consumption during polysilicon deposition: reduce power loss and increase polysilicon productivity. The solutions proposed for reducing power loss are: enlarging the reactor capacities and increasing the wall reflectivity. The proposals for increasing the productivity are: working at the optimum deposition conditions, that maximises the polysilicon growth rate, and stopping the process at higher rod diameters. By doing so, the process uses the energy more efficiently

The Impact of Silicon Feedstock on the PV Module Cost

The impact of the use of new (solar grade) silicon feedstock materials on the manufacturing cost of wafer-based crystalline silicon photovoltaic modules is analyzed considering effects of material cost, efficiency of utilisation, and quality. Calculations based on data provided by European industry partners are presented for a baseline manufacturing technology and for four advanced wafer silicon technologies which may be ready for industrial implementation in the near future. Iso-cost curves show the technology parameter combinations that yield a constant total module cost for varying feedstock cost, silicon utilisation, and cell efficiency. A large variation of feedstock cost for different production processes, from near semiconductor grade Si (30 €/kg) to upgraded metallurgical grade Si (10 €/kg), changes the cost of crystalline silicon modules by 11% for present module technologies or by 7% for advanced technologies, if the cell efficiency can be maintained. However, this cost advantage is completely lost if cell efficiency is reduced, due to quality degradation, by an absolute 1.7% for present module technology or by an absolute 1.3% for advanced technologies