Thermochemical storage of middle temperature wasted heat by functionalized C/Mg(OH)2 hybrid materials

Abstract

For the thermochemical performance implementation of Mg(OH)2 as a heat storage medium, several hybrid materials have been investigated. For this study, high-performance hybrid materials have been developed by exploiting the authors' previous findings. Expanded graphite (EG)/carbon nanotubes (CNTs)-Mg(OH)2 hybrid materials have been prepared through Mg(OH)2 deposition-precipitation over functionalized, i.e., oxidized, or un-functionalized EG or CNTs. The heat storage performances of the carbon-based hybrid materials have been investigated through a laboratory-scale experimental simulation of the heat storage/release cycles, carried out by a thermogravimetric apparatus. This study offers a critical evaluation of the thermochemical performances of developed materials through their comparison in terms of heat storage and output capacities per mass and volume unit. It was demonstrated that both EG and CNTs improves the thermochemical performances of the storage medium in terms of reaction rate and conversion with respect to pure Mg(OH)2. With functionalized EG/CNTs-Mg(OH)2, (i) the potential heat storage and output capacities per mass unit of Mg(OH)2 have been completely exploited; and (ii) higher heat storage and output capacities per volume unit were obtained. That means, for technological applications, as smaller volume at equal stored/released heat.