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Nouveaux matériaux graphite/sel pour le stockage d'énergie à haute température. Étude des propriétés de changement de phase.

Abstract : This work is a contribution to the study of new graphite/salt composites dedicated to high temperature energy storage (>200°C). The aim is to analyse and to understand the influence of both graphite and composite microstructure on the phase change properties of salts. This PHD is carried out within the framework of two projects: DISTOR (European) and HTPSTOCK (French). The major contributions of this work are threefold:
1) An important database (solid-liquid phase change properties) is provided from the DSC analysis of six salts and the corresponding composites.
2) Rigorous modelings of salts melting in confined media in several geometries are proposed to understand why, during the first melting of the compression elaborated composites, problems of salt leakage are observed. These models show that the materials morphology is responsible for these phenomena: the graphite matrix restrains the volume expansion due to salt melting: salt melts under pressure, which leads to a melting on a large temperature range and to a loss of energy density. Sensitivity analysis of parameters (geometric and physic) shows that matrix rigidity modulus is the parameter on which it is necessary to act during the composites elaboration to blur this phenomenon.
3) Finally, this work proposes a thermodynamic formulation of both surface/interface phenomena and the presence of dissolved impurities being able to explain a melting point lowering. It seems that the melting point lowering observed (~5°C) are mainly due to the presence of dissolved impurities (brought by graphite) in the liquid, along with an additional Gibbs-Thomson effect (~1°C, related to the size of the clusters crystals).
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https://tel.archives-ouvertes.fr/tel-00276277
Contributor : Jérôme Lopez <>
Submitted on : Wednesday, April 30, 2008 - 3:40:47 PM
Last modification on : Friday, January 15, 2021 - 9:24:29 AM
Long-term archiving on: : Monday, October 22, 2012 - 12:15:16 PM

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  • HAL Id : tel-00276277, version 2

Citation

Jérôme Lopez. Nouveaux matériaux graphite/sel pour le stockage d'énergie à haute température. Étude des propriétés de changement de phase.. Energie électrique. Université Sciences et Technologies - Bordeaux I, 2007. Français. ⟨tel-00276277v2⟩

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