EVALITA Evaluation of NLP and Speech Tools for Italian - December 17th, 2020

Welcome to EVALITA 2020! EVALITA is the evaluation campaign of Natural Language Processing and Speech Tools for Italian. EVALITA is an initiative of the Italian Association for Computational Linguistics (AILC, http://www.ai-lc.it) and it is endorsed by the Italian Association for Artificial Intelligence (AIxIA, http://www.aixia.it) and the Italian Association for Speech Sciences (AISV, http://www.aisv.it)

Thermochemical heat storage: issues, solutions and applications

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Stockage thermochimique de la chaleur

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Récupération de la chaleur fatale

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CaCl2/bentonite composite: water sorption capacity and kinetics for heat storage applications

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Survey Summary on Salts Hydrates and Composites Used in Thermochemical Sorption Heat Storage: A Review

International audienceTo improve the proficiency of energy systems in addition to increasing the usage of renewable energies, thermal energy storage (TES) is a strategic path. The present literature review reports an overview of the recent advancements in the utilization of salt hydrates (single or binary mixtures) and composites as sorbents for sorption heat storage. Starting by introducing various heat storage systems, the operating concept of the adsorption TES was clarified and contrasted to other technologies. Consequently, a deep examination and crucial problems related to the different types of salt hydrates and adsorbents were performed. Recent advances in the composite materials used in sorption heat storage were also reviewed and compared. A deep discussion related to safety, price, availability, and hydrothermal stability issues is reported. Salt hydrates display high theoretical energy densities, which are promising materials in TES. However, they show a number of drawbacks for use in the basic state including low temperature overhydration and deliquescence (e.g., MgCl2), high temperature degradation, sluggish kinetics leading to a low temperature rise (e.g., MgSO4), corrosiveness and toxicity (e.g., Na2S), and low mass transport due to the material macrostructure. The biggest advantage of adsorption materials is that they are more hydrothermally stable. However, since adsorption is the most common sorption phenomenon, such materials have a lower energy content. Furthermore, when compared to salt hydrates, they have higher prices per mass, which reduces their appeal even further when combined with lower energy densities. Economies of scale and the optimization of manufacturing processes may help cut costs. Among the zeolites, Zeolite 13X is among the most promising. Temperature lifts of 35–45 °C were reached in lab-scale reactors and micro-scale experiments under the device operating settings. Although the key disadvantage is an excessively high desorption temperature, which is problematic to attain using heat sources, for instance, solar thermal collectors. To increase the energy densities and enhance the stability of adsorbents, composite materials have been examined to ameliorate the stability and to achieve suitable energy densities. Based on the reviewed materials, MgSO4 has been identified as the most promising salt; it presents a higher energy density compared to other salts and can be impregnated in a porous matrix to prepare composites in order to overcome the drawbacks connected to its use as pure salt. However, due to pore volume reduction, potential deliquescence and salt leakage from the composite as well as degradation, issues with heat and mass transport can still exist. In addition, to increase the kinetics, stability, and energy density, the use of binary salt deposited in a porous matrix is suitable. Nevertheless, this solution should take into account the deliquescence, safety, and cost of the selected salts. Therefore, binary systems can be the solution to design innovative materials with predetermined sorption properties adapted to particular sorption heat storage cycles. Finally, working condition, desorption temperature, material costs, lifetime, and reparation, among others, are the essential point for commercial competitiveness. High material costs and desorption temperatures, combined with lower energy densities under normal device operating conditions, decrease their market attractiveness. As a result, the introduction of performance metrics within the scientific community and the use of economic features on a material scale are suggested

Recent progresses in Thermochemical Heat Storage: materials and applications

International audienceThermochemical heat storage is among the most promising options to increase the use of renewable energy by bypassing the issue of the intermittence of related sources. In this review, articles based on hydroxide-based systems (working at high temperature, up to 500°C) are considered. Then, sorption systems, in particular systems constituted of salt hydrate-containing composites, are reviewed. These systems can be regenerated (charged) at temperatures around 150°C and they are then adapted for building applications. Issues on technical solutions as well as on storage material choice are still present and need to be solved before reaching a higher technology readiness level. The aim of this review is to provide a general view of the recent progress of materials for thermochemical heat storage systems

Layered double hydroxides and LDH-derived materials in chosen environmental applications: a review

International audienceWith increasing global warming awareness, layered double hydroxides (LDHs), hydrotalcites, and their related materials are key components to reduce the environmental impact of human activities. Such materials can be synthesized quickly with high efficiency by using different synthesis processes. Moreover, their properties’ tunability is appreciated in various industrial processes. Regarding physical and structural properties, such materials can be applied in environmental applications such as the adsorption of atmospheric and aqueous pollutants, hydrogen production, or the formation of 5-hydroxymethylfurfural (5-HMF). After the first part that was dedicated to the synthesis processes of hydrotalcites, the present review reports on specific environmental applications chosen as examples in various fields (green chemistry and depollution) that have gained increasing interest in the last decades, enlightening the links between structural properties, synthesis route, and application using lamellar materials

Insights on the influence of the precursors on the sol–gel synthesis of hybrid organic–inorganic saponite-like materials

International audienceLamellar organic–inorganic hybrid materials, especially talc- and saponite-like structures, have been broadly investigated over the past decades because of the combination of the thermal and mechanical properties of the inorganic part with the possibility to finely tune hydrophilic–hydrophobic balance, ion exchange capacity, and properties through the choice of the silicon source. These compounds are generally produced by coprecipitation or hydrothermal synthesis methods, allowing the formation of well-crystallized particles but it is time and energy consuming. Recently, hybrid organic–inorganic lamellar materials have been synthesized using sol–gel method, which is attractive as it is a one-step method performed under mild conditions, with low energy consumption and short formation times. The originality of this research stands in the study of the influence of the reactants on the formation of saponite-like hybrids and especially on the role of the aluminum source in the sol–gel synthesis of hybrid organic–inorganic lamellar materials. The obtained materials have been characterized by X-ray diffraction, Fourier transform infrared, and solid-state nuclear magnetic resonance spectroscopies and thermogravimetric analysis, and it was shown that hydrotalcite-like compounds can be obtained beside saponite-like compounds depending on the aluminum source.De nombreuses études ont été menées récemment sur les matériaux hybrides organiques–inorganiques de structure lamellaire, de types talc et saponite, notamment, dans le contexte de la combinaison des propriétés thermiques et mécaniques de la fraction inorganique, d'une part, avec la possibilité d'adapter la balance hydrophile/hydrophobe, la capacité d’échange cationique ainsi que les propriétés associées au choix de la source de silicium, d'autre part. Ces composés sont généralement synthétisés par co-précipitation ou par synthèse hydrothermale, ce qui permet la formation de particules bien cristallisées, mais demande beaucoup de temps et d’énergie. Plus récemment, ces matériaux ont été synthétisés par la méthode sol–gel, qui permet d'obtenir des matériaux de grande pureté en des temps très courts avec une faible nécessité énergétique. L'originalité de ce travail repose sur l’étude de l'influence des réactifs sur la formation de matériaux hybrides organiques–inorganique de structure de type saponite, notamment le rôle de la source d'aluminium dans la synthèse par voie sol–gel de matériaux hybrides organiques–inorganiques de structure lamellaire. Les matériaux synthétisés ont été analysés par DRX, IR-TF, RMN du solide et ATG, ce qui a permis de découvrir que des composés similaires à des hydrotalcites peuvent être obtenus selon la source d'aluminium employée