Hydrated Salt/Graphite/Polyelectrolyte Organic-Inorganic Hybrids for Efficient Thermochemical Storage

Abstract

Hydrated salt thermochemical energy storage (TES) is a promising technology for high density energy storage, in principle opening the way for applications in seasonal storage. However, severe limitations are affecting large scale applications, related to their poor thermal and mechanical stability on hydration/dehydration cycling. In this paper, we report the preparation and characterization of composite materials manufactured with a wet impregnation method using strontium bromide hexahydrate (SBH) as a thermochemical storage material, combined with expanded natural graphite (G). In addition to these fully inorganic formulations, an organic polyelectrolyte (PDAC, polydiallyldimethylammonium chloride) was exploited in the structure, with the aim to stabilize the salt, while contributing to the sorption/desorption process. Different formulations were prepared with varying PDAC concentration to study its contribution to material morphology, by electron microscopy and X-ray diffraction, as well as water sorption/desorption properties, by thermogravimetry and differential calorimetry. Furthermore, the SBH/G/PDAC powder mixture was pressed to form tabs that were analyzed in a climatic chamber, which is evidence for an active role of PDAC in the improvement of water sorption, coupled with a significant enhancement of mechanical resistance upon hydration/dehydration cycling. Therefore, the addition of the polyelectrolyte is proposed as an innovative approach in the fabrication of efficient and durable TES devices.

Recent Status and Prospects on Thermochemical Heat Storage Processes and Applications

“…It is generally classified as a sorption process or a chemical reaction that does not involve sorption. However, compared to liquid absorption and solid adsorption, chemical reactions are mono-variant and lead to transformation about the volume of the solid [129][130][131][132][133]. The main chemical reaction storage materials developed and studied can be grouped into carbonate decomposition material, redox material, inorganic hydroxide material, ammonia decomposition material, metal hydride material, and methane reforming material.…”

Innovative composite sorbent for thermal energy storage based on a SrBr2·6H2O filled silicone composite foam

“…Such a behaviour is ascribed to the limitations in mass transfer since composites with higher content of salt results in more compact and dense blocks, that represent increased obstacles to mass and heat transfer. In the work reported by Salviati et al [23], the composites made with the salt hydrate, expanded natural graphite and polydiallyldimethylammonium chloride show good heat and mass transfer properties, but the mechanical resistance of the material proved to be a critical issue: severe damage in the form of cracks to the composite tabs occurred already after the first hydration/dehydration cycle. In another study by D'Ans et al [39], a strong humidity dependence of thermal and mass transport properties of composites based on CaCl2 encapsulated in microporous silica gel was evidenced: considering the small dimensions of the pores of the matrix, for high humidity values (i.e.…”

“…The results showed that the natural graphite could improve the hydration-dehydration kinetics by reducing hysteresis and increase the thermal conductivity of the material. More recently, Salviati et al [23] proposed the addition of an organic compound, PDAC, polydiallyldimethylammonium chloride, to the strontium bromide/graphite composites. Experimental outcomes of the investigation show that PDAC has a beneficial effect on water sorption and mechanical resistance upon hydration/dehydration cycling.…”

A Scaling Rule for Power Output of Salt Hydrate Tablets for Thermochemical Energy Storage

“…Mm-size particles are typically obtained by various methods from μmsize powders [10,[13][14][15][16][17]. There have been multiple attempts to make mm-size composite particles, with the aim to conjugate a newly achieved mechanical stability with additional functionalities in support of mass and heat transfer.…”