Estudio de la fotoluminiscencia en obleas y células solares de Silicio

El estudio de las imágenes de fotoluminiscencia (PL imaging) en células solares, es uno de los métodos de caracterización de células solares más destacado en la actualidad. Este proyecto pretende a través del PL imaging poder establecer una correlación entre el rendi- miento eléctrico de un grupo de muestras de células solares, y el nivel de fotoluminiscencia de estas muestras. Las distintas tecnologías existentes en las cámaras CCD (silicio, InGaAs, etc) ofrecen resultados muy dispares a la hora de la captar la luminiscencia. En este TFG se comparan los resultados obtenidos por una cámara CCD de InGaAs y una cámara CCD de silicio en ensayos de fotoluminiscencia sobre células solares de distintos rendimientos eléctricos y sobre obleas de silicio de diferentes resistividades. En el presente Trabajo Fin de Grado se expone con detalle tanto los equipos empleados en las medidas, así como la metodología de trabajo usada para la adquisición de imágenes y el proceso de análisis de los resultados obtenidos.Departamento de Física de la Materia Condensada, Cristalografía y MineralogíaGrado en Ingeniería Eléctric

Herramientas TIC en la formación profesional de la rama de electricidad y electrónica. Estado del arte y aplicación real de un caso práctico

El uso de herramientas de las tecnologías de la información y la comunicación (TIC) es una poderosa herramienta para facilitar el proceso de enseñanza-aprendizaje en todos los niveles educativos. Se ha llevado a cabo una revisión bibliográfica sobre el uso de las herramientas TIC en los ciclos formativos de FP, además, también se han realizado entrevistas a varios profesores de FP de la rama de electricidad y electrónica para concluir que el uso de metodologías didácticas que integren herramientas TIC en este tipo de formación está muy poco extendido. Se ha diseñado e impartido una secuencia de actividades con herramientas TIC en un CFGM de la rama de electricidad y electrónica, con el objetivo de facilitar el proceso de aprendizaje sobre la programación de autómatas. Además, se han desarrollado métodos de evaluación de estas actividades, analizando los resultados obtenidos y sacando las conclusiones pertinentes.Information and communication technologies (ICT) are a powerful tool to facilitate the teaching-learning process at all educational levels. A bibliographic review has been carried out about ICT tools in vocational training studies, in addition, several interviews have also been carried out with several vocational teachers, specialized in electricity and electronics curses to conclude that the use of didactic methodologies that integrating ICT in this type of training is not implementing. A sequence of ICT activities has been designed and taught in a vocational training curse of electricity and electronics speciality, with the aim of facilitating the learning process about programmable controllers. In addition, several evaluation methods for these activities have been developed, analysing the results obtained and drawing the pertinent conclusions.Departamento de Física de la Materia Condensada, Cristalografía y MineralogíaMáster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma

Technical Audit of an Electronic Polling Station: A Case Study

P. 16-30This paper shows the lack of standard procedures to audit e-voting systems and also describes a practical process of auditing an e-voting experience based on a Direct-recording Electronic system (D.R.E). This system has been tested in a real situation, in the city council of Coahuila, Mexico, in November 2008. During the auditing, several things were kept in mind, in particular those critical in complex contexts, as democratic election processes are. The auditing process is divided into three main complementary stages: analysis of voting protocol, analysis of polling station hardware elements, and analysis of the software involved. Each stage contains several items which have to be analyzed at low level with the aim to detect and resolve possible security problemsS

Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells

Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electrical activity of defects in mc-Si solar cells. In this work, upgraded metallurgical grade Si solar cells are studied using these two techniques.Ministerio de Economía, Industria y Competitividad (ENE2014-56069-C4-4-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. Project VA081U16

Improve Quality of Service for the Internet of Things using Blockchain & Machine Learning Algorithms.

[EN] The quality of service (QoS) parameters in IoT applications plays a prominent role in determining the performance of an application. Considering the significance and popularity of IoT systems, it can be predicted that the number of users and IoT devices are going to increase exponentially shortly. Therefore, it is extremely important to improve the QoS provided by IoT applications to increase their adaptability. Majority of the IoT systems are characterized by their heterogeneous and diverse nature. It is challenging for these systems to provide high-quality access to all the connecting devices with uninterrupted connectivity. Considering their heterogeneity, it is equally difficult to achieve better QoS parameters. Artificial intelligence-based machine learning (ML) tools are considered a potential tool for improving the QoS parameters in IoT applications. This research proposes a novel approach for enhancing QoS parameters in IoT using ML and Blockchain techniques. The IoT network with Blockchain technology is simulated using an NS2 simulator. Different QoS parameters such as delay, throughput, packet delivery ratio, and packet drop are analyzed. The obtained QoS values are classified using different ML models such as Naive Bayes (NB), Decision Tree (DT), and Ensemble, learning techniques. Results show that the Ensemble classifier achieves the highest classification accuracy of 83.74% compared to NB and DT classifiers.SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Defect characterization of UMG mc-Si solar cells using LBIC and luminescence imaging techniques

Upgraded metallurgical-grade silicon (UMG Si) solar cells with different ranges of efficiencies were characterized through electroluminescence imaging (ELi) and light-beam induced current (LBIC) measurements. The results showed a good correlation between the EL intensity and the efficiency of the solar cells. ELi images gave a bright contrast at the defects, grain boundaries and intragrain defects, and dark contrast inside the grain bodies. Metallic impurities are much more present in some cells due to the directional solidification of the Si ingot. Local short-circuit current mapping with LBIC measurements revealed a bright zone in the neighborhoods of the defects due to the depletion of impurities. Internal quantum efficiencies (IQE) and effective diffusion lengths (Leff) were calculated using different excitation wavelengths. High resolution LBIC measurements revealed micrometric clusters of impurities around intragrain defectsSpanish MINECO project, ref. ENE2014-56069-C4-4-R and “Junta de Castilla y León (Spain)” project number VA081U1

Electroluminescence Imaging and Light-Beam Induced Current as characterization techniques of Multi-Crystalline Si Solar Cells

There is an increasing demand for characterizing multicrystalline solar cells at different stages of its service life. Luminescence techniques, e.g. electroluminescence (EL) and photoluminescence (PL), have acquired a paramount interest in the last years. These techniques are used in imaging mode, allowing to take a luminescence picture at a full wafer/cell scale. This imaging approach is fast and sensitive, but has a low spatial resolution, which avoids a detailed analysis of the defect distribution, which can led to misinterpretations about critical parameters as the minority carrier diffusion length, or the internal and external quantum efficiencies. If one complements these techniques with high spatial resolution techniques, such as light beam induced current (LBIC), one can study the electrical activity of the defects at a micrometric scale, providing additional understanding about the role played by the defects in full wafer/cell luminescence images. The combination of the macroscopic and microscopic resolution scales is necessary for the analysis of the full luminescence images in mc-Si solar cells.Proyecto de Investigación ENE2014-56069-C4- 4-R (MCIN)Proyecto de Investigación ENE2017-89561-C4-3-R (MCIN)Proyecto de Investigación VA081U16 (Junta de Castilla y León

Influence of Large Periods of DC Current Injection in c-Si Photovoltaic Panels

Nowadays, electroluminescence imaging (Eli) appears as an emerging technique in the maintenance of photovoltaic (PV) plants. There is a concern about how the current injection needed in ELi measurements can affect the PV modules service life, and how these periodical inspections can affect the long term life of the modules. In order to give a practical answer to this problem, a series of tests consisting of long periods of current injection on several monocrystalline silicon modules has been carried out. The modules tested had already fulfilled their useful life and present multiple defects. In order to analyze how the current injection affects the state of the module, images of infrared thermography (IRT) and ELi were acquired during the current injection period. The subsequent analysis of these images shows only a small effect during the heating period in the EL intensity results at the beginning of each test, not affecting the module performance.Proyecto de Investigación ENE2017-89561-C4-3-R (MCIN)Proyecto de Investigación RTC-2017-6712-3 (MCIN)Proyecto de Investigación VA283P18 (Junta de Castilla y León

Novel utility-scale photovoltaic plant electroluminescence maintenance technique by means of bidirectional power inverter controller

Producción CientíficaNowadays, photovoltaic (PV) silicon plants dominate the growth in renewable energies generation. Utility-scale photovoltaic plants (USPVPs) have increased exponentially in size and power in the last decade and, therefore, it is crucial to develop optimum maintenance techniques. One of the most promising maintenance techniques is the study of electroluminescence (EL) images as a complement of infrared thermography (IRT) analysis. However, its high cost has prevented its use regularly up to date. This paper proposes a maintenance methodology to perform on-site EL inspections as efficiently as possible. First, current USPVP characteristics and the requirements to apply EL on them are studied. Next, an increase over the automation level by means of adding automatic elements in the current PV plant design is studied. The new elements and their configuration are explained, and a control strategy for applying this technique on large photovoltaic plants is developed. With the aim of getting on-site EL images on a real plant, a PV inverter has been developed to validate the proposed methodology on a small-scale solar plant. Both the electrical parameters measured during the tests and the images taken have been analysed. Finally, the implementation cost of the solution has been calculated and optimised. The results conclude the technical viability to perform on-site EL inspections on PV plants without the need to measure and analyse the panel defects out of the PV installation.Ministerio de Industria, Economía y Competitividad (grant number RTC-2017-6712-3)Junta de Castilla y León (grant VA283P18

Nondestructive characterization of solar PV cells defects by means of electroluminescence, infrared thermography, I–V curves and visual tests: Experimental study and comparison

Photovoltaic (PV) modules are the core of every PV system, representing the power generation and their operation will affect the overall plant performance. It is one of the elements within a PV site with the higher failure appearance, being essential their proper operation to produce reliable, efficient and safety energy. Quantitative analysis and characterization of manufacturing, soldering and breaking PV defects is performed by a combination of electroluminescence (EL), infrared thermography (IRT), electrical current voltage (I-V) curves and visual inspection. Equivalent-circuit model characterization and microscope inspection are also performed as additional techniques when they contribute to the defects characterization. A 60-cells polycrystalline module has been ad hoc manufactured for this research, with different defective and non-defective cells. All cells are accessible from the backside of the module and the module includes similar kinds of defects in the same bypass string. This paper characterizes different defects of PV modules to control, mitigate or eliminate their influence and being able to do a quality assessment of a whole PV module, relating the individual cells performance with the combination of defective and non-defective cells within the module strings, with the objective of determining their interaction and mismatch effects, apart from their discrete performance.Ministerio de Ciencia e Innovación (Proyecto de Investigación ENE2017-89561-C4-3-R)Ministerio de Ciencia e Innovación (Proyecto de Investigación RTC-2017-6712-3