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From biobased & geosourced materials to building hygrothermal transfers: A review of modeling, simulation and experiment
No full textInternational audienceThe review explores coupled heat and moisture transfers in bio-based and geosourced materials from experimental and numerical viewpoint. Itsummarizes the underlying physical phenomena, the models developed over several decades, and the resulting simulation tools up to the buildingscale. The article deals with an analysis of results, limitations, recent advances, and key points requiring clarification. This work emphasizes theimportance of simulation software in assessing energy efficiency, preventing moisture-related issues, and ensuring occupant comfort. Variousstrategies, including model simplifications, model order reduction, and the use of neural networks, are presented to mitigate computation time inaddressing hygrothermal issues. Additionally, standardized experimental methods for determining model input parameters are discussed,acknowledging the associated uncertainty. The establishment of a database on experimentally measured thermal performance of earth constructionis also attempted. The review highlights studies comparing experimental results and simulations at the wall scale, emphasizing influential factors inhygroscopic materials such as hysteresis. Classical models are deemed less than entirely satisfactory, especially concerning moisture profiles withinhygroscopic materials, but recent improvements show promise in addressing this issue. Finally, the main subjects at the building scale dealing withthe hygrothermal behavior, the indoor comfort and the building energy consumption are reviewed. It underscores the limited number of studiescomparing hygrothermal simulations to sensors outputs in occupied building
Lighting and Health IEA 4E SSLC Webinar Series: Webinar 2. Glare and Photobiological Safety
No full textÉcole thématiqueIn October 2024, the IEA 4E SSLC Platform published a report that represents a synthesis of health and lighting studies published over the last decade. The effects of lighting on health are technology agnostic, however advances in physiology and medicine have contributed to new awareness and understanding of the impacts of light on human health. This study examines some features of SSL products that may pose a risk and which could be improved or applied differently to achieve better outcomes in terms of health and well-being. The report covers both acute effects (effects that develop during or immediately following an exposure) of optical radiation on the eye and the skin, discomfort glare, circadian disruptions, neuro-behavioural effects, and temporal light modulation (TLM), as well as long-term effects (effects that build over months or years) including age-related macular degeneration, myopia and cancer risk. In order to communicate the broad set of findings from this report, the SSLC Platform convened a series of webinars. The findings were divided up into three one-hour webinars which were each presented twice, once for Australian/Asian time zones and once for American/European time zones
Photovoltaic failure diagnosis using imaging techniques and electrical characterization
No full textInternational audienceInspections of 48 photovoltaic (PV) modules within a 302.4 kWp solar array were undertaken to expose the presence of defects after 12 years of operation under the harsh environmental conditions of Djibouti. To this end, a multiple-technique testing protocol was conducted including visual inspection (VI), infrared thermography (IR), current-voltage curve characterization (I-V), ultraviolet fluorescence (UVFL) and electroluminescence imaging (EL). The main visible degradation features observed were discoloration, bubbling and snail trails with occurrences of 100%, 93.7% and 2.1% respectively. According to the IR imaging results, hotspots were observed on cells affected by snail trails. IR was combined with convolutional neural network (CNN) techniques to automatically detect the different classes of failures that PV modules may experience. EL imaging reveals that the cracks of the cells underlie the observed snail trails during visual inspection and UVFL imaging. In addition, a decrease in STC power was observed after 12 yr of operation with a median reaching 5.5% corresponding to an average degradation rate of 0.46%/years. Conclusively, fault diagnosis with combined approaches of imaging and electrical techniques is crucial to prevent defects and minimize the investment losses; this will ensure uninterrupted power generation, extended service life and high safety of photovoltaic modules
Opinion of the French Agency for Food, Environmental and Occupational Health and Safety: "consideration in the regulatory framework of the effects on children's health of LEDs contained in toys"
No full textThis Opinion details a series of errors in the methodology that was used to derive the emission limits that are supposed to protect children against the retinal phototoxicity (blue light hazard) and the intense glare with the visible light emitted by LEDs. These errors were discovered in a 2012 scientific journal paper which was transposed in the IEC EN 62115 safety standard in 2020. As a result of these errors, the conformity assessment procedure has been overly permissive, allowing the use of LEDs that can dangerously dazzle children and damage their retinas, with possible consequences on their visual health at short and long terms. Furthermore, this safety standard allows the toy manufacturers to perform the assessment of the LEDs by themselves, whereas laboratory measurements were needed before 2020 in the EU and in the UK. Measurements carried out by France's national metrology institute LNE demonstrated that a significant fraction of currently available toys with blue and white LEDs would have been excluded from the EU market if they had been tested using the previous conformity assessment procedure of 2005. The ANSES recommends vigilance regarding the use of LEDs incorporated in toys, pending the necessary revisions of the safety standard and the associated regulations worldwide.Cet avis détaille une série d’erreurs dans la méthodologie qui a été utilisée pour calculer les limites d'émission réglementaires qui doivent protéger les enfants contre la phototoxicité rétinienne et l'éblouissement intense produit par la lumière émise par les LED. Ces erreurs ont été découvertes dans une publication scientifique dont le contenu a été transposé en 2020 dans la norme de sécurité IEC EN 62115. En conséquence de ces erreurs, la procédure d'évaluation de la conformité est trop permissive, permettant l'utilisation de LED qui peuvent éblouir dangereusement les enfants et endommager leurs rétines, avec des conséquences possibles sur leur santé visuelle à court et à long terme. De plus, cette norme de sécurité permet actuellement aux industriels du jouets de réaliser eux-mêmes l'évaluation de la dangerosité des LED, contrairement aux pratiques antérieures à 2020 (des mesures en laboratoire étaient alors requises).Les mesures effectuées par le LNE ont montré qu'une fraction importante des jouets actuellement disponibles avec des LED bleues et blanches auraient été exclus du marché européen s'ils avaient été testés selon la précédente procédure d'évaluation de la conformité.L'ANSES recommande la vigilance quant à l'utilisation des LED incorporées dans les jouets, dans l'attente des révisions nécessaires de la norme de sécurité et des réglementations associées dans les pays concernés dont ceux de l’Union Européenne et le Royaume-Uni
Bringing the future back to the present: the role of prefiguration in European climate justice activism
No full textInternational audienceSocial movement scholarship has long attempted to apprehend the dynamic qualities of social movements. Considering the temporal embeddedness of social movement activities is essential because it leads to an understanding of continuity and change in the content and form of social movements in the long run. Because the past, the present, and the future are co-defined, more attention should be paid to the way different time frames shape one another. In this article, we focus our attention on the influence of visions of the future on present practices. Drawing on qualitative research mainly in Belgium, France, and Germany, we explore how projected climatejust futures influence the practices of grassroots climate justice organizations in the present. For this purpose, we center our analysis on a macro-level vision that depicts a climate-just world as a world where domination systems (aka. capitalism, colonialism, or patriarchy) have been replaced in order to let a more egalitarian society strive. We use the concept of prefiguration to illustrate how this vision transforms organizing and mobilizing activities. Such transformative effects are exemplified in attempts at developing an alternative organizational culture and building alliances with marginalized groups, with more or less success
Oscillatory burning regime in a gas-fueled compartment fire
No full textInternational audienceThe paper presents a series of 48 enclosure fire experiments carried out in a m cubic compartment with a door-like opening of m width and a variable height from 0.25 to m. The fire source was a propane-fueled square burner of m side length positioned in the center of the compartment and delivering a steady mass flux that has been varied in the tests from 0.5 to g/s. In addition to the well-known well-ventilated and under-ventilated regimes, an oscillatory combustion regime has been uncovered for an opening height of 0.25 or m. This regime is characterized by an alternation between the well-ventilated regime (combustion exclusively inside the compartment) and the under-ventilated regime (combustion inside and outside the enclosure). It is believed that the time for the onset of the oscillations is linked to the smoke filling time. Furthermore, depending on the specific conditions, the oscillations are either steady (until shut-off of the fuel supply) or transitory (leading to a sustained under-ventilated regime). The frequencies ranged from about 9 to mHz. The oscillatory regime has previously been mainly reported for liquid fuels and thus associated to radiative heat feedback effects. The new data for a gaseous fuel calls upon a better understanding and a further analysis of the underlying physics
Going beyond carbon: Influence of structural parameters on the environmental impacts of typical building structures
No full textInternational audienceThe construction sector has a large impact on the environment, be it climate change, biodiversity loss or resources depletion. Part of those impacts comes from construction materials, and more specifically, concrete and steel building structures. Early-stage design tools including environmental damage assessment are therefore required to achieve sustainable construction practices. This article presents a parametric approach aiming at studying the influence of early-stage structural parameters on the environmental impacts of a structure. The developed methodology combines parametric structural design with a multicriteria cradle-to-grave Life Cycle Assessment, applied to typical housing structures such as grid based beam column structures with a central core for lateral stability. Results show that span, number of levels and materials greatly influence the environmental impacts of considered structures. Climate change scores per floor area range from 80 kgCO2/m 2 for short span timber structure to 215 kgCO2/m 2 for long span steel buildings with few levels. Beams and slabs have the largest contribution in such impacts. Changing the production processes of materials is a way to reduce greenhouse gas emissions. However, decarbonizing steel production processes or reducing the cement content of concrete participate in burdenshifting with increased scores in several impact categories, such as carcinogenic toxicity or ozone depletion
Solid-State Lighting: Health Effects and Knowledge Gaps
No full textInternational audienceThe health effects of LED lamps and luminaires used for general lighting were reviewed by an international team of researchers working under the 4E implementing agreement of the International Energy Agency (SSLC platform). Effects on the general population and subsets of sensitive groups were studied considering interactions with eye and skin, glare, circadian regulation, neuro-behavioral effects, effects of temporal light modulation, and long-term effects, such as age-related macular degeneration, myopia, and risks of cancer. This paper presents the conclusions and recommendations of the expert group. Knowledge gaps are detailed in each effect category
Caractérisation de la matière organique de résidus de la gestion décentralisée des eaux usées domestiques et des eaux pluviales
No full textInternational audienceLa gestion des eaux usées domestiques et des eaux pluviales peut être réalisée directement à l’échelle du bâtiment, de la parcelle ou du quartier, par des ouvrages de rétention, de filtration et/ou d’infiltration des eaux. Les objectifs sont, sur le plan hydraulique, de pallier l'absence de réseau ou de les désengorger, et sur le plan épuratoire, d'assurer la protection sanitaire et/ou de limiter les rejets de contaminants dans les milieux récepteurs. Néanmoins, ces modes de gestion génèrent des résidus solides mélangés : dépôts (sédiments et boues) de matières particulaires ou dissoutes (par transformation biologique) provenant des eaux ; et matériaux filtrants utilisés pour le traitement.L’accumulation de matières particulaires, le colmatage et l’éventuelle détérioration des massifs filtrants peuvent mettre en péril le bon fonctionnement hydraulique et épuratoire des ouvrages, rendant les sujets de l’extraction et du devenir de ces matériaux prégnants. Or, ces résidus ont en commun une fraction organique significative (environ 10 à 95 % en masse), résultat d’un équilibre entre l’apport par les eaux entrantes et son évolution au sein des ouvrages. Alors que les travaux existants ont mis en évidence l’importance de cette matière organique dans le comportement des matériaux avant et après extraction (colmatage, rétention de certains contaminants et réactivité biogéochimique), sa nature précise demeure complexe et méconnue.Dans ce contexte, cette étude caractérise quantitativement et qualitativement la fraction organique de résidus pour (i) comparer les matériaux à gérer entre eux (variété de contextes et vieillissement) et (ii) les rapprocher de matrices mieux connues. Les échantillons étudiés ont été prélevés dans divers contextes : sédiments de l’assainissement pluvial de bassins Lyonnais et Nantais, et résidus usagés (fragments de coco) utilisés dans la filtration des eaux usées domestiques. Une méthodologie de caractérisation basée sur des techniques rapides et complémentaires a été retenue (spectroscopie infrarouge à transformée de Fourier, thermogravimétrie et calorimétrie différentielle). Ces techniques se sont révélées pertinentes dans l’objectif de comparaison inter-matrices. Les premiers résultats indiquent que la matière organique des sédiments de l’assainissement pluvial présente une signature commune, y compris pour des contextes différents (nature de l’ouvrage, bassin versant, météorologie) et pour des durées d’accumulation variables. Cette signature géochimique est éloignée de celle des matériaux filtrants usagés, mais présente des similitudes (comportement thermique et signature spectrale) avec des sédiments marins ou continentaux contaminés. Cela ouvre la voie au développement de filières de gestion communes, pertinentes pour une meilleure valorisation de leur fraction organique
Experimental characterization of SVOC cotton/air partitioning in Micro-Chamber/Thermal Extractor
No full textInternational audienceIndoor exposure to semi-volatile organic compounds (SVOCs) is known to be influenced by their partition between air, particles, and surfaces. Due to their low volatility, phthalates, alternative plasticizers, and organophosphate ester flame retardants (OPEFRs) are found on objects, clothes, and occupants’ skin. Children are particularly susceptible to the effects of endocrine-disrupting SVOCs due to their behavior.Cotton textiles are used as curtains, bedding, and clothing. Therefore, cotton can be considered both an SVOC sink and a medium through which they can diffuse to the skin, increasing dermal exposure.This work aims to develop an experimental procedure to estimate the partition coefficients (Kcotton/air) of potentially harmful SVOCs between cotton and air in a Micro-Chamber/Thermal Extractor. A commercial PVC furniture covering containing TPP, EHDPP, and DINCH is placed on the walls of the cells (including the lid surface) as an SVOC source. A cotton curtain sample is placed in the cell until a stable concentration of SVOCs in the air is reached (yeq, sampled at the micro-chamber outlet by Tenax tubes). The surface concentration (qeq) is then obtained by Accelerated Solvent Extraction.The cotton/air equilibrium is described by a Langmuir isotherm: Kcotton/air=qeq/yeq. At 40°C, the results are 500 m, 800 m, and 1700 m for TPP, EHDPP, and DINCH, respectively, in accordance with previously published data for stainless steel.This method could be applicable to sink surface of any material. Further measurements are planned to confirm the suitability of dynamic conditions for determining a linear surface/air partition coefficient