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Optimisation of CaCl2 impregnated expanded graphite and alginate matrices – Targeted salt loading

Jack Reynolds, Bahaa Abbas, Geraint Sullivan, Jonathon Elvins, Eifion Jewell Orcid Logo, Justin Searle Orcid Logo, Lorena Skevi, Xinyuan Ke Orcid Logo

Energy Conversion and Management, Volume: 302, Start page: 118145

Swansea University Authors: Jack Reynolds, Bahaa Abbas, Geraint Sullivan, Jonathon Elvins, Eifion Jewell Orcid Logo, Justin Searle Orcid Logo

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Abstract

The incorporation of salt hydrates in thermochemical energy storage is often limited by poor kinetics and mechanical instability during charge and discharge cycles. This study explores the influence of salt loading on the energy storage capacity and charge/discharge performance of salt-impregnated e...

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Published in: Energy Conversion and Management
ISSN: 0196-8904
Published: Elsevier BV 2024
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa65721
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Abstract: The incorporation of salt hydrates in thermochemical energy storage is often limited by poor kinetics and mechanical instability during charge and discharge cycles. This study explores the influence of salt loading on the energy storage capacity and charge/discharge performance of salt-impregnated expanded graphite and alginate composites. By controlling the salt bath concentration during composite synthesis, the quantity of salt within the bead can be regulated. Four composites have been synthesised with salt wt% values ranging from 63.7 to 77.2 %, resulting in salt volumetric densities form 0.22–0.52 g/cm3 and energy densities between 1052 and 1281 kJ/kg. The study found that increasing salt bath concentration above 60 % significantly decreases the porosity within the composite. This reduces moisture transfer kinetics and also fails to accommodate for salt expansion and deliquescence. Consequently, composites at near-maximum salt capacity displayed diminished discharge performance and charge efficiency. Conversely, samples below the saturation threshold exhibited greater heat output and charge efficiency, contained overhydration, and maintained structural integrity. These findings highlight the importance of carefully balancing energy storage capacity with improved reaction kinetics and stability to achieve an optimal storage solution in solar thermal systems or waste heat recovery.
Keywords: Thermal energy storage; Expanded graphite; Calcium chloride; Alginate; Salt loading
College: Faculty of Science and Engineering
Funders: The authors would like to thank the Materials and Manufacturing Academy and COATED CDT (COATED M2A) in Swansea University, TATA Steel Colors, Engineering and Physical Sciences Research Council (EPSRC via UKRI) EP/S02252X/1, and the European Social Fund via the Welsh Government (WEFO) (c80816) for supporting the work described in this article.
Start Page: 118145