Experimental and Numerical Study of the Influence of String Mismatch on the Yield of PV Modules Augmented By Static Planar Reflectors

International audiencePhotovoltaic (PV) modules are generally installed by the application of empirical rules aimed at reducing shadows during the periods of high solar irradiation. A traditional installation on a horizontal surface results in largely spaced rows of modules with a relatively low tilt angle. The addition of inter-row reflectors results in more direct and diffuse flux transmitted to the cells. The " Aleph " (Amélioration de l'Efficacité Photovolta¨que) project aims to define clear rules for optimal settings of systems of PV module rows with fixed inter-row planar reflectors in a given location and under a given climate. Two PV technologies are tested for performance with this type of system: amorphous silicon (a-Si) and polycrystalline silicon (p-Si). This work combines experiments on panel behavior in an outdoor environment on the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique) meteorology platform and a multiphysics numerical model used to couple all the important physical phenomena and accurately describe the system behavior. The model includes a ray tracing radiation/optics module based on the Monte-Carlo method, as well as an electrical module simulated in SPICE. This work presents the influence of the string mismatch losses, present at periods of heterogeneous illumination, on the yield of PV modules augmented by static planar reflectors

Solar irradiances measured using SPN1 radiometers: uncertainties and clues for development

International audienceThe fast development of solar radiation and energy applications, such as photovoltaic and solar thermodynamic systems, has increased the need for solar radiation measure-ment and monitoring, for not only the global but also the diffuse and direct components. End users look for the best compromise between getting close to state-of-the-art mea-surements and keeping low capital, maintenance and operat-ing costs. Among the existing commercial options, SPN1 is a relatively low cost solar radiometer that estimates global and diffuse solar irradiances from seven thermopile sensors under a shading mask and without moving parts. This work presents a comprehensive study of SPN1 accu-racy and sources of uncertainty, drawing on laboratory ex-periments, numerical modelling and comparison studies be-tween measurements from this sensor and state-of-the art in-struments for six diverse sites. Several clues are provided for improving the SPN1 accuracy and agreement with state-of-the art measurements

Parallel illumination for depletion microscopy throughacousto-optic spatial light modulation

State-of-the-art super-resolution microscopy techniques, including Stimulated Emission Depletion (STED), Reversible Saturable Optical Fluorescence Transitions (RESOLFT), and Switching Laser Mode (SLAM) microscopies, implement Laguerre-Gaussian beams, also known as vortex or doughnut beams to capture fluorescence information within a sub-wavelength area of the observed sample, effectively surpassing the diffraction limit and significantly improving the quality of the image. However, these techniques typically operate at point by point basis, involving time-consuming scanning of the sample to construct a complete, meaningful image. Therefore, for real-time live cell imaging purposes, the parallelization of illumination is crucial. In this study, we demonstrate the parallel generation of arbitrary arrays of Gaussian and Laguerre-Gaussian laser foci suitable for super-resolution microscopy. We achieve rapid scanning through the sample using acousto-optic spatial light modulation, a technique we have previously pioneered across various fields. By employing parallelized illumination with both Gaussian and doughnut beams, we aim to capture super-resolution images

Wind power predictions from nowcasts to 4-hour forecasts: a learning approach with variable selection

We study the prediction of short term wind speed and wind power (every 10 minutes up to 4 hours ahead). Accurate forecasts for those quantities are crucial to mitigate the negative effects of wind farms' intermittent production on energy systems and markets. For those time scales, outputs of numerical weather prediction models are usually overlooked even though they should provide valuable information on higher scales dynamics. In this work, we combine those outputs with local observations using machine learning. So as to make the results usable for practitioners, we focus on simple and well known methods which can handle a high volume of data. We study first variable selection through two simple techniques, a linear one and a nonlinear one. Then we exploit those results to forecast wind speed and wind power still with an emphasis on linear models versus nonlinear ones. For the wind power prediction, we also compare the indirect approach (wind speed predictions passed through a power curve) and the indirect one (directly predict wind power)

[1,9-Bis(3,5-di­methyl­pyrazol-1-yl-κN2)-3,7-di­thia­nonane-κ2S,S']­palladium(II) bis­(tetra­fluoro­borate)

In the crystal structure of the title compound, [Pd(C17H28N4S2)](BF4)2, the PdII atom is coordinated by one N atom from each of the pyrazolyl groups and the two thio¬ether S atoms in a slightly distorted square-planar geometry

Anàlisi de molècules molt eficients per millorar la síntesis orgànica

Mitjançant tècniques experimentals i informàtiques, els autors d'aquest treball van analitzar l'eficiència d'alguns grups de molècules, derivades de compostos de pirazol, usades com a precatalitzadors en els processos de síntesis orgàniques realitzats amb la reacció de Heck.A través de técnicas experimentales e informáticas, los autores de este trabajo analizaron la efectividad de algunos grupos de moléculas, derivados de compuestos de pirazol, usadas como precatalizadores en los procesos de síntesis orgánica realizados mediante la Reacción de Heck.Based on a combined experimental and computacional study, authors of this work analized the effectiveness of some groups of molecules derivated from pirazol, used as precatalists in organic synthesis developed by Heck reactions

Community structure in mediterranean shallow lentic ecosystems : size-based vs. taxon-based approaches

The main environmental variables determining the community structure and the functioning of Mediterranean shallow lentic ecosystems are described. These ecosystems are characterized by the unpredictability of their water inputs and the high variability in their water level and physical and chemical composition. Variations in flooding, salinity, and water turnover are determinant in species composition and nutrient dynamics. Taxon-based and size-based approaches to the study of the community structure of aquatic organisms that colonise these ecosystems are also compared. The conventional taxonomic approach, based on the determination of species composition, has been used for the identification of patterns in species richness, distribution and temporal dynamics, and for ecological requirements of species and their potential use as ecological indicators. This taxonbased approach has been compared with a size-based approach, where individuals are classified by their size. Size-based approach gives complementary information about community structure and dynamics, especially when communities are dominated by a single species. The use of size diversity combined with species diversity is suggested for a more complete understanding of community structuring in this type of ecosystem. Detailed examples of two Mediterranean shallow lentic ecosystems, the salt marshes of the Empordà wetlands and the Espolla temporary karstic pond, which differ in hydrology and water origin, are used to discuss the suitability of these different approaches.Los ecosistemas leníticos someros mediterráneos se caracterizan por la impredictibilidad en las entradas de agua y por la elevada variabilidad en el nivel del agua y su composición física y química. Se describen aquí las principales variables ambientales que determinan la estructura de la comunidad y el funcionamiento de estos ecosistemas. Variaciones en la inundación, la salinidad y la tasa de renovación del agua son determinantes en la composición de especies y en la dinámica de nutrientes. Se comparan también aproximaciones al estudio de la comunidad basadas en la composición taxonómica con las basadas en la distribución de tamaños. La aproximación taxonómica convencional, basada en la determinación de la composición de especies, es adecuada para la identificación de patrones en la distribución y en la dinámica temporal de la especies, así como para el análisis de los requerimientos ambientales de las diferentes especies y su uso potencial como indicadores ecológicos. Esta aproximación taxonómica se ha comparado con otra aproximación basada en el tamaño corporal, donde los individuos se clasifican por su tamaño. La aproximación basada en el tamaño proporciona información complementaria de la estructura y dinámica de las comunidades, especialmente cuando en estas comunidades hay una especie dominante. Se sugiere el uso combinado de una diversidad de tamaños y una diversidad de especies para una comprensión más completa de la estructuración de las comunidades en este tipo de ecosistemas. Para discutir si estas diferentes aproximaciones son o no adecuadas, se presentan datos de dos ecosistemas mediterráneos leníticos y someros: las marismas de Aiguamolls de l'Empordà y la laguna de Espolla, una surgencia cárstica de inundación temporal

Fonament de l'arc de Sant Martí

Aquest fenomen té lloc per la reflexió i la refracció de la llum del Sol a traves de les gotes d'aigua que es troben en suspensió en l'aire. L'arc de Sant Martí tant sols es pot veure en una determinada direcció. Això es pot explicar físicament pel fet que el joc de reflexions i refraccions de la llum natural té una direcció privilegiada que és la mateixa per a tots els feixos de llum incident