Reduction of the subcooling of bischofite with the use of nucleatings agents

Abstract

The use of by-products or wastes as phase change materials (PCM) in thermal energy storage (TES) systems is a good option to decrease the cost of such systems. One of the main disadvantages of PCM if inorganic materials are used is subcooling, as was found with bischofite, a by-product from the Chilean non-metallic industry, which subcooling is about 36 °C. Subcooling can be reduced by the addition of nucleating agents, but the selection of the best nucleating agent should be done taking into consideration the physical and chemical parameters of the salt hydrate. In this paper the parameters considered were the solubility of the materials in water, the chemical structure and the crystalline structure (crystal system, lattice parameters, density, cell volume, Z, and space group). It could be concluded that solubility, chemical structure and the crystal system have no influence in the nucleation capacity of a salt hydrate. The parameter that needs to be considered when selecting a nucleating agent for a salt hydrate is the lattice parameters of the crystal structure (cell longitude or angle).

The work at the University of Antofagasta was supported by CONICYT/FONDAP No. 15110019, and the Education Ministry of Chile Grant PMI ANT 1201. Andrea Gutierrez would like to acknowledge to the CONICYT/PAI No 7813110010 and Education Ministry of Chile her postdoctorate scholarships ANT 1106. The work is partially funded by the Spanish Government (ENE2015-64117-C5-1-R and ENE2015-64117-C5-2-R). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123) and research group DIOPMA (2014 SGR 1543). This project has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under Grant agreement No. PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). Dr. Camila Barreneche would like to thank Ministerio de Economia y Competitividad de España for the grant Juan de la Cierva, FJCI-2014-22886.