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

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

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

Adductor squeeze test and groin injuries in elite football players: A prospective study

during the competitive season of professional football teams. Design: Prospective Cohort study. Setting: Controlled laboratory environment. Participants: Seventy-one players volunteered to participate. Main outcome measures: In the pre-season, maximal hip adductor strength was measured by means of the isometric adductor squeeze test. Hip adductor strength, normalized by body mass, was compared between players who suffered a groin injury (n ¼ 18) vs uninjured players (n ¼ 53). Risk ratios (RR) were used to evaluate the likelihood of players to suffer this type of injury. Results: Most of the reported groin injuries occurred during competitive matches (5.5 per 1000 match hours). Maximal isometric hip adductor strength was lower in the groin-injured group compared with their uninjured counterparts (429.8 ± 100 vs 564 ± 58.7 N, d¼ 1.58 and 5.40 ± 1.27 vs 7.71 ± 0.89 N/kg, d¼ 1.88, respectively). Results revealed that values of maximal isometric adductor strength lower than 465.33 N increased the probability to suffer a groin injury by 72%. Furthermore, values of force relative to body mass lower than 6.971 N/kg increased the probability to suffer a groin injury by 83%. Conclusion: The assessment of Hip adductor strength, in addition to other measurements, might help practitioners to determine the probability of suffering an overuse groin injuries in elite football players.info:eu-repo/semantics/publishedVersio

CENTESIL: An independent Research Centre on Polysilicon

The tremendous expansion of the photovoltaic technology and its relative avidity for silicon is producing a dramatic change in the polysilicon industry structure, increasing the efforts to produce a low cost, high quality Solar Silicon. In this context, the Centro de Tecnología del Silicio Solar (CENTESIL) was founded in 2006 as a private-public partnership venture, and is currently building a 50 t/a pilot plant for silicon purification following the chlorosilane route. Although an advanced state of the art technology has been selected as first choice, the purpose is to be able to undertake developments in any topic that has the potential to reduce the cost effectively. Additionally, the project includes facilities for monocrystalline growth and wafering, and also the solar cell processing line of the Instituto de Energía Solar, so that it will cover the whole value chain from feedstock to solar cell

Genetic profile in genes associated with muscle injuries and injury etiology in professional soccer players.

post-print1255 K

Chemical decomposition of silanes for the production of solar grade silicon

Esta Tesis Doctoral se centra en la reducción del coste y del consumo de energía durante el proceso de producción de silicio ultrapuro, el también llamado polisilicio. Estas reducciones ayudan a la tecnología fotovoltaica basada en silicio a alcanzar dos de sus principales objetivos para establecerse como una tecnología viable: bajos costes de producción y bajos tiempos de recuperación de la energía. Se ha definido una tecnología fotovoltaica, basada en silicio cristalino, y se han presentado sus costes de producción. Este análisis permite estimar el impacto de la reducción de costes de la materia prima, el polisilicio, en el producto final, el modulo fotovoltaico. También, mediante dicho análisis se ha podido estudiar el impacto sobre el coste del módulo de las dos principales vías para producir polisilicio: la vía química, con altos costes y altas calidades, y la vía metalúrgica, con menores costes y menores calidades. Este ejercicio de análisis muestra que la calidad de la materia prima (evaluada como la eficiencia de célula) es un inductor de coste muy importante. Como consequencia, esta Tesis Doctoral se centra en la vía química, capaz de producir polisilicio de mayor calidad, proponiendo alternativas y mejoras en el proceso para disminuir los costes de producción y el consumo energético. El análisis teórico del depósito de polisilicio en un reactor de depósito químico en fase vapor (CVD), presentado en esta memoria, comprende: (a) el estudio de las condiciones óptimas de depósito mediante la teoría fluido-mecánica; (b) el estudio de la radiación térmica de las varillas calientes de silicio por medio de la teoría de transferencia de calor por radiación; y (c) el estudio del calentamiento eléctrico de las varillas de silicio mediante la teoría electromagnética. Se ha presentado un modelo fluido-mecánico novedoso que propone expresiones analíti¬cas para la tasa de crecimento de polisilicio sobre las varillas de silicio y para las pérdidas energéticas por convección. La condiciones óptimas de depósito, basadas en el criterio de minimización del consumo energético, se han obtenido del modelo. La transferencia de calor por radiación dentro del reactor CVD se ha analizado en detalle para tres configuraciones que son estado del arte: 36 varillas organizadas en 3 anillos, 48 varillas organizadas en 4 anillos y 60 varillas organizadas en 4 anillos. Se han propuesto alternativas para disminuir las pérdidas energéticas por radiación: aumentar la capacidad de los reactores, mejorar la reflectividad de la pared del reactor e introducir escudos térmicos dentro del reactor. Un inductor importante para la reducción del consumo energético es el diámetro máximo de la varilla cuando se para el proceso. La principal limitación para aumentar dicho diámetro máximo es el riesgo de que se funda el centro de la varilla. El modelo para el calentamiento eléctrico de las varillas, presentado en esta memoria, permite conocer el perfil de temperatura dentro de la varilla de silicio, deduciendo el diámetro de varilla límite, en el cual el centro de la varilla se funde. Se han propuesto en esta Tesis Doctoral dos alternativas para incrementar el diámetro máximo mediante la homogenización del perfil de temperaturas: incrementar la reflectividad de la pared, introducir escudos térmicos y utilizar fuentes de corriente de alta frecuencia para calentar las varillas de silicio. Se ha propuesto un proceso de depóstico completo, basado en las aproximaciones teóricas presentadas en esta Tesis y caracterizado por el bajo consumo energético. Se han detallado las condiciones de depósito y las condiciones eléctricas, tensión y corriente, para calentar las varillas en un reactor CVD de 36 varillas. El análisis teórico se ha equilibrado con trabajo experimental, usando tanto triclorosilano como silano como gases precursores. El trabajo experimental ha mostrado las di¬ficultades para trabajar en la condiciones óptimas de trabajo, ya que pueden originarse dendritas. También el carácter corrosivo del triclorosilano se ha puesto de manifiesto du¬rante la operación de reactor de depósito a escala de laboratorio, diseñado, desarrollado y construido en el Instituto de Energía Solar. ABSTRACT This Doctoral Thesis comprises research on the reduction of cost and energy consumption of the production of ultrapurified silicon, so-called polysilicon. These respective reductions are essential to achieving two wider objectives for silicon based photovoltaic technology: low production cost and low energy payback time. A crystalline silicon photovoltaic module technology is defined and its production costs are presented. This allows cost and energy reduction measures to be compared and valued with regard to their impact on the final product. It further permits a cost-per-kilowatt comparison of the two main polysilicon production routes: the chemical route, with high quality and high cost; and the metallurgical route, with lower quality and lower cost. This costing exercise shows the quality of polysilicon (evaluated as the cell efficiency) to be an important driver for module cost-per-kilowatt reduction. Consequently, the presented research focuses on the high-quality chemical route. The presented theoretical analysis of polysilicon deposition in a CVD reactor consists in: (a) the study of the optimum deposition conditions by means of fluid mechanical theory; (b) the study of the thermal radiation of the hot silicon rods by means of thermal radiation heat transfer theory; and (c) the study of the electric heating of the silicon rod by means of electromagnetic theory. A novel fluid mechanical model is presented that proposes analytical expressions for the growth rate of polysilicon onto the silicon rods and for the energy loss by convection. The optimum deposition conditions, which reduce energy consumption, are derived from the model. The thermal radiation heat transfer within the CVD reactor is studied in detail for three state-of-the-art configurations: 36 rods arranged in 3 rings, 48 rods arranged in 3 rings and 60 rods arranged in 4 rings. Alternatives are presented regarding the reduction of the radiant energy loss during the polysilicon deposition: enlarge the reactor capacities, enhance the wall reflectivity and introduce thermal shields within the reactor vessel. An important factor affecting overall energy consumption is the maximum rod diam¬eter reached at the end of the process. The main limitation for increasing this maximum diameter is the risk of melting the rod core. The temperature profile within the silicon rod resulting from electrical heating is modelled, and the limiting diameter at which the core begins to melt is calculated. Two alternatives are proposed for increasing the maximum diameter by reducing the non-homogeneous temperature profile: increasing the wall re-flectivity/introducing thermal shields, and use of a high-frequency current source to heat the rods. Based on the presented theoretical study, a complete deposition process is proposed that is characterised by low energy consumption. The deposition conditions and the electrical conditions (current and voltage) for heating rods in a 36 rods CVD reactor are detailed. Finally, polysilicon deposition has been studied experimentally, and the practicability of the calculated optimum conditions has been tested. Silicon rods have been grown in the laboratory scale deposition reactor, designed, developed and constructed, in part by the author, at the Instituto de Energ´ıa Solar, using trichlorosilane and silane as prescursor gases. The experiments show the difficulty in working under the optimum conditions: undesirable dendritic growth was observed, and the trichlorosilane was seen to corrode the reactor. Further experimental study is required in the future to fully understand the polysilicon deposition process in a CVD reactor

Enhancement of the nonlinear optical response of Cu:Al2O3 nanocomposite films by multiple particle interaction effects

CLEO/EUROPE ; EQEC European Quantum Electronics Conference, Munich ICM, Germany, 22-27 June, 2003N

1 € per watt-peak advanced crystalline silicon modules: the crystalclear integrated project

CrystalClear is an Integrated Project carried out in the 6 th Framework Program of the European Union. The main project aim is to reduce the direct manufacturing costs of crystalline silicon PV modules to 1 €/Wp, when produced in next-generation plants. CrystalClear deals with the entire crystalline silicon value chain from silicon feedstock up to module manufacturing. In the course of the project, which started in 2004, several ‘overall’ technologies have been defined and developed. These technologies represent different combinations of wafer options, cell and module designs as well as processing approaches. They have been analysed in terms of their manufacturing costs, assuming large-scale production. It is found that crystalline silicon PV technology has the potential to reach direct module manufacturing costs of around 1 €/Wp on a relatively short term (i.e. within ≈5 years). This implies that wafer-based crystalline silicon photovoltaics is compatible with the requirements to achieve grid parity, see the Strategic Research Agenda of the PV Technology Platform, www.eupvplatform.org. Critical conditions to reach this cost level are: efficient silicon utilization (g/Wp module power), high total area module efficiency and high-throughput, high-yield productio

Role of surface-to-volume ratio of metal nanoparticles in optical properties of Cu:Al₂O₃ nanocomposite films

3 pags. ; 2 figs. ; 1 tab.We report on the role of the surface-to-volume ratio of Cu nanoparticles (NPs) both in the linear and nonlinear optical properties of Cu:Al₂O₃ nanocomposite films. The results show that when the shape of the NPs deviates sufficiently from that of a sphere, the increase of the fraction of metal atoms present at the surface (Ns) with respect to the total amount of atoms (Nt) in the NP leads to a substantial reduction of the enhancement of the local field. As a consequence, for Ns/Nt values above a certain threshold ( ≈ 0.4–0.5), the surface–plasma resonance is smeared out and the nonlinear optical response of the nanocomposite film becomes very weak and independent of the dimensions of the NPs or their volume fraction in the matrix.This work has been partially supported by the EU under the BRPR-CT98-0616 project and by MCyTsTIC2002-03235d.Peer reviewe