3D simulation of complex shading affecting PV systems taking benefit from the power of graphics cards developed for the video game industry

Shading reduces the power output of a photovoltaic (PV) system. The design engineering of PV systems requires modeling and evaluating shading losses. Some PV systems are affected by complex shading scenes whose resulting PV energy losses are very difficult to evaluate with current modeling tools. Several specialized PV design and simulation software include the possibility to evaluate shading losses. They generally possess a Graphical User Interface (GUI) through which the user can draw a 3D shading scene, and then evaluate its corresponding PV energy losses. The complexity of the objects that these tools can handle is relatively limited. We have created a software solution, 3DPV, which allows evaluating the energy losses induced by complex 3D scenes on PV generators. The 3D objects can be imported from specialized 3D modeling software or from a 3D object library. The shadows cast by this 3D scene on the PV generator are then directly evaluated from the Graphics Processing Unit (GPU). Thanks to the recent development of GPUs for the video game industry, the shadows can be evaluated with a very high spatial resolution that reaches well beyond the PV cell level, in very short calculation times. A PV simulation model then translates the geometrical shading into PV energy output losses. 3DPV has been implemented using WebGL, which allows it to run directly from a Web browser, without requiring any local installation from the user. This also allows taken full benefits from the information already available from Internet, such as the 3D object libraries. This contribution describes, step by step, the method that allows 3DPV to evaluate the PV energy losses caused by complex shading. We then illustrate the results of this methodology to several application cases that are encountered in the world of PV systems design.Comment: 5 page, 9 figures, conference proceedings, 29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam, 201

Synthesis and processing of MAX phases by Powder Injection Moulding and Additive Manufacturing

Mención Internacional en el título de doctorMAX phases are a family of ternary materials with a fixed stoichiometry and a general formula of Mn+1AXn, where M is a transition metal, A is generally an element of groups IIIA and IVA of the periodic table, X is either carbon or nitrogen and n a value between 1 and 3. Their nano-laminated structure gives these materials an unusual combination of (1) metallic properties, such as, good electrical and thermal conductivity, machinability, high damage tolerance; and (2) ceramic properties such as high rigidity, resistance to corrosion and oxidation and good mechanical properties at high temperatures. This unique combination of properties makes these materials very promising candidates for industrial applications with demanding conditions, which has prompted the study, design and development of these family of materials. Some of the conventional consolidation routes for MAX phases are pressureless sintering, hot pressing or spark plasma sintering, however they have limitation in the production of parts with complex shapes. In this work, the design and optimisation of the synthesis route was performed for different MAX phases with the aim of obtaining high purity powders studying the reaction mechanism during the synthesis. Ti3SiC2 and Cr2AlC MAX phases were selected for this work. The synthesis of these MAX phases was successfully carried out from different elemental powders (Ti, SiC, C, Cr and Al). In addition, the scalability of the powder production was achieved maintaining high phase purity while controlling the particle size distribution of the powders. To assess the quality of the powders produced, various conventional powder metallurgy processing routes were studied, such as pressureless sintering and hot pressing. For these samples, porosity measurements, mechanical properties (cyclic compression test) and wear behaviour were analysed, studying the influence of the processing route on the behaviour of the materials. In this context, the main challenge of this PhD is to demonstrate the viability of nonconventional processing techniques such as Powder Injection Moulding (PIM) and Composite Extrusion Modelling (CEM) for the production of near-net-shape MAX phase samples. These two technologies start from pelletised feedstocks and allow the production of samples with a higher freedom of design, reducing post-processing steps. The objective was to produce complex-shaped parts as well as increasing the application range of MAX phases, their reproducibility and production volume. For the successful production of MAX phase samples by PIM and CEM the selection of the binder system as well as the optimisation of the solid loading of the feedstocks is necessary and, for this purpose, the rheological properties of the materials were characterised. Two multicomponent binders were selected for this study, firstly, an environmentally-friendly binder consisting of a combination of a sustainable polymer (polyethylene glycol, PEG) and a biopolymer (cellulose acetate butyrate, CAB), and secondly, a binder composed of the same sustainable polymer (PEG) and polypropylene (PP). Porous MAX phases with tailored porosity were obtained by PIM processing, avoiding the use of spacer holder. Additive manufactured parts by CEM were also successfully produced, using the same feedstocks. Debinding and sintering processes were optimized in both cases. In conclusion, it was possible to obtain good quality parts with custom geometries through PIM and CEM for both Ti3SiC2 and Cr2AlC MAX phases, suitable for industrial applications with special requirements, such as catalytic devices, filters or as high temperature heat exchangers.Las fases MAX son una familia de materiales ternarios con una estequiometría fija y una fórmula general Mn+1AXn, donde M es un metal de transición, A es generalmente un elemento de los grupos IIIA y IVA de la tabla periódica, X es carbono o nitrógeno y n un valor entre 1 y 3. La estructura nano laminada de estos materiales proporcionan una combinación inusual de propiedades metálicas, tales como, buena conductividad eléctrica y térmica, fácil mecanizado y alta tolerancia al daño, y de propiedades cerámicas como alta rigidez, resistencia a la corrosión y oxidación y buenas propiedades mecánicas a altas temperaturas. Esta exclusiva combinación de propiedades ha hecho que las fases MAX sean considerados para aplicaciones industriales en las que se requieren condiciones exigentes, lo cual ha impulsado el estudio, diseño y desarrollo de esta familia de materiales. Algunas de las rutas convencionales de consolidación para este tipo de materiales son compactación y sinterización, prensado en caliente o spark plasma sintering, pero tienen limitaciones en la producción de piezas con formas complejas. En este trabajo, el diseño y optimización de las rutas de síntesis para diferentes fases MAX han sido estudiadas con el objetivo de obtener polvo con una alta pureza analizando los mecanismos de reacción durante la síntesis. Las fases MAX seleccionadas han sido Ti3SiC2 y Cr2AlC. La síntesis de estas fases MAX se ha llevado a cabo con éxito a partir de distintos polvos elementales (Ti, SiC, C, Cr y Al). Además, el escalado de la producción del polvo se logró manteniendo la alta pureza de las fases MAX procesadas controlando la distribución de tamaño de partícula. Con el objetivo de evaluar los polvos producidos, diversos procesados convencionales de la pulvimetalurgia fueron estudiados como, por ejemplo, presión y sinterización y hot pressing. Para las muestras consolidadas se estudió la porosidad, las propiedades mecánicas (compresión cíclica) y el comportamiento a desgaste, analizando la influencia de las rutas de procesamiento en el comportamiento de los materiales. En este contexto, el principal reto de esta Tesis Doctoral es la de demostrar la viabilidad de procesar fases MAX a través de rutas “no convencionales” como son el moldeo por inyección de polvos (PIM) y el Composite Extrusión Modelling (CEM). Todo esto para la fabricación de piezas near-net-shape de fases MAX. Estos dos tipos de procesado parten de feedstocks en forma de pellets permitiendo la producción de piezas con una mayor libertad de diseño, reduciendo posteriores etapas de postprocesado. El objetivo principal es fabricar piezas complejas y de esta manera aumentar los posibles campos de aplicación para las fases MAX, así como aumentar la reproducibilidad y el volumen de producción para estos materiales. Para la producción de fases MAX a través de PIM y CEM es necesario la selección adecuada de los polímeros que van a conformar el binder y, además, una optimización de la cantidad de sólido que se va a utilizar para la producción de feedstocks. Es por ello por lo que las propiedades reológicas de estos materiales han sido estudiadas en profundidad. Dos sistemas ligantes multicomponentes han sido utilizados para la producción de feedstocks. Por un lado, un binder respetuoso con el medioambiente compuesto por polietilenglicol (PEG) y un biopolímero (acetato butirato de celulosa, CAB). Por otro lado, se desarrolló otro sistema ligante con el mismo polímero sostenible (PEG) y polipropileno (PP). A través del procesamiento por PIM, se obtuvieron piezas con una porosidad a medida, evitando el uso de sistemas espaciadores. Por otro lado, se fabricaron con éxito piezas por manufactura aditiva a través de la tecnología CEM. Además, se optimizaron los procesos de debinding y sinterización de las piezas. Como conclusión, cabe destacar que mediante PIM y CEM fue posible obtener piezas de buena calidad con geometrías a medida tanto para la fase MAX Ti3SiC2 como para la fase Cr2AlC, aptas para aplicaciones industriales con requerimientos especiales como, por ejemplo, dispositivos catalíticos, filtros o como intercambiadores de calor de alta temperatura.Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de MadridPresidente: José Manuel Torralba Castelló.- Secretario: Javier Hidalgo García.- Vocal: Konstantina Lambrino

Analysis and synthesis of the variability of irradiance and PV power time series with the wavelet transform

The irradiance fluctuations and the subsequent variability of the power output of a PV system are analysed with some mathematical tools based on the wavelet transform. It can be shown that the irradiance and power time series are nonstationary process whose behaviour resembles that of a long memory process. Besides, the long memory spectral exponent α is a useful indicator of the fluctuation level of a irradiance time series. On the other side, a time series of global irradiance on the horizontal plane can be simulated by means of the wavestrapping technique on the clearness index and the fluctuation behaviour of this simulated time series correctly resembles the original series. Moreover, a time series of global irradiance on the inclined plane can be simulated with the wavestrapping procedure applied over a signal previously detrended by a partial reconstruction with a wavelet multiresolution analysis, and, once again, the fluctuation behaviour of this simulated time series is correct. This procedure is a suitable tool for the simulation of irradiance incident over a group of distant PV plants. Finally, a wavelet variance analysis and the long memory spectral exponent show that a PV plant behaves as a low-pass filter

On the specification and testing of inverters for stand-alone PV systems

Inverter features are reviewed from a PV systems perspective, with a view to contributing to possible codes, procurement specifications and testing procedures, in order to assure the technical quality of these systems. A laboratory testing campaign has been carried out on a representative set of sixteen currently available inverters and a set of the most common AC appliances. The results of the tests are discussed with the aim of divulging the particular features of operating AC appliances in PV systems and the provisions to be taken into account in PV system design. The development of testing procedures has followed the motto ?keep it as simple as possible?, in order to make their application easier in conventional laboratories in developing countries

Music-based interventions in palliative cancer care: a review of quantitative studies and neurobiological literature

PURPOSE: This study aimed to review quantitative literature pertaining to studies of music-based interventions in palliative cancer care and to review the neurobiological literature that may bare relevance to the findings from these studies. METHODS: A narrative review was performed, with particular emphasis on RCTs, meta-analyses, and systematic reviews. The Cochrane Library, Ovid, PubMed, CINAHL Plus, PsycINFO, and ProQuest were searched for the subject headings music, music therapy, cancer, oncology, palliative care, pain, anxiety, depression, mood, quality of life, prevalence, neuroscience, functional imaging, endogenous opioids, GABA, 5HT, dopamine, and permutations of these same search terms. Data for the review were comprised of articles published between 1970 and 2012. References of all the cited articles were also reviewed. RESULTS: Available evidence suggests that music-based interventions may have a positive impact on pain, anxiety, mood disturbance, and quality of life in cancer patients. Advances in neurobiology may provide insight into the potential mechanisms by which music impacts these outcomes. CONCLUSIONS: More research is needed to determine what subpopulation of cancer patients is most likely to respond to music-based interventions, what interventions are most effective for individual outcomes, and what measurement parameters best gauge their effectiveness

Grupo de Innovación Educativa nos Estudos Ingleses e Irlandeses

[Resumo] Tanto a área das Humanidades como especificamente os Estudos Ingleses atópanse nun importante momento de transición durante o primeiro cuarto do século XXI. A situación xeopolítica actual, dominada polas tensións entre a globalización e as sensibilidades locais, invita a repensar as relacións dos individuos e das comunidades coa cultura e coas letras e, por este motivo, é importante xerar coñecemento que se adecúe ás necesidades do alumnado que estará exposto a este panorama social. Neste sentido, dende os Estudos Ingleses da Facultade de Filoloxía e os Estudos Irlandeses do Instituto Universitario de Estudos Irlandeses, estanse a facer esforzos por achegar ao noso alumando e á comunidade local e global o coñecemento cultural e académico que manexamos nas nosas actividades universitarias, e estanse a desenvolver iniciativas para dinamizar estes clusters informativos. Unha destas propostas educativas consiste no desenvolvemento dunha rede informativa sobre os recursos de investigación no ámbito dos Estudos Irlandeses. O grupo de investigación de Estudos Irlandeses está a crear unha páxina de contidos web que pretende ser pioneira no ámbito estatal, e que recollerá ferramentas de investigación relacionadas coa lingua, a literatura, a cultura, o cine e as artes do ámbito irlandés. O póster que se propón para as III Xornadas de Innovación Docente na UDC recolle os obxectivos, a metodoloxía, os potenciais resultados e as conclusións das diferentes ramas de noso grupo de innovación docent

An approach to build in situ models for the prediction of the decrease of academic engagement indicators in Massive Open Online Courses

Producción CientíficaThe early detection of learners who are expected to disengage with typical MOOC tasks such as watching lecture videos or submitting assignments is necessary to enable timely interventions aimed at preventing it. This can be done by predicting the decrease of academic engagement indicators that can be derived for di_erent MOOC tasks and computed for each learner. A posteriori prediction models can yield a good performance but cannot be built using the information that is available in an ongoing course at the moment the predictions are required. This paper proposes an approach to build in situ prediction models using such information. Models were derived following both approaches and employed to predict the decrease of three indicators that quantify the engagement of learners with the main tasks typically proposed in a MOOC: watching lectures, solving _nger exercises, and submitting assignments. The results show that in situ models yielded a good performance for the prediction of all engagement indicators, thus showing the feasibility of the proposed approach. This performance was very similar to that of a posteriori models, which have the clear disadvantage that they cannot be used to make predictions in an ongoing course based on its data.Ministerio de Economía, Industria y Competitividad (Projects TIN2014-53199-C3-2-R (AEI, FEDER), TIN2017-85179-C3-2-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA277U14)European Commission (Proyect 588438-EPP-1-2017-1-EL-EPPKA2-KA

Extreme overirradiance events in Sao Paulo, Brazil

Phenomena of overirradiance have been pointed all over the World. This note presents the most extreme enhancement event reported in Brazil, which contains an irradiance reading of 1590 W/m2 measured in São Paulo (latitude 23°32′S) at relatively low altitude (760 m a.s.l.)