High temperature shape – Stabilized phase change materials obtained using mesoporous silica and NaCl – NaBr – Na2MoO4 salt eutectic

• Published in: Solar energy materials and solar cells 2020-12, Vol.218, p.110760, Article 110760
• Main Authors: Mitran, Raul - Augustin, Lincu, Daniel, Ioniţǎ, Simona, Deaconu, Mihaela, Jerca, Victor Valentin, Mocioiu, Oana Cǎtǎlina, Berger, Daniela, Matei, Cristian
• Format: Article
• Language: English
• Subjects: Composite materials; Electron microscopy; Energy storage; Enthalpy; Eutectic; Eutectic temperature; Heat; Heat of fusion; Heat storage; High temperature; Latent heat; Light microscopy; Melting; Melting point; Melting points; Mesoporous silica; Microscopy; Molar volume; Molten salt; Molten salts; Optical microscopy; Phase change materials; Salts; Shape-stabilized; Silica; Silicon dioxide; Sodium bromides; Sodium chloride; Sodium molybdate; Solar heating; Solar power; Thermal energy; Thermal energy storage; Thermal power; Thermal stability
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110760

Thermal energy storage at temperatures above 400 °C is critical for efficient industrial processes and continuous solar thermal power generation. Phase change materials (PCMs) can be used for both latent heat storage and improved conversion efficiencies, but their use has been prevented by the large, 5–25 % change in molar volume. Herein, shape-stabilized PCMs are prepared using 20% wt. mesoporous silica matrices and NaCl–NaBr–Na2MoO4 salt eutectic. The pristine salt mixture has a total enthalpy of 216 Jg-1 divided into a solid-solid transition at 455 °C and solid – liquid transition at 522 °C. Six mesoporous silica materials of the MCM-41 (Mobil Composition of Matter No. 41), SBA-15 (Santa Barbara Amorphous) and mesocellular foam types were investigated as potential matrices for high temperature, shape-stabilized PCMs. All resulting composites have good thermal stability up to 650 °C. High – temperature optical microscopy shows that all samples retain their macroscopic solid shape above the salt melting point. Electron microscopy revealed a good dispersion of the silica matrix inside the molten salt phases. Both MCM-41 and SBA-15-type matrices yield PCMs with high total heat of fusion values between 169 – 178 Jg-1, in accordance to the 80% wt. salt fraction. The melting point is decreased with 5–10 °C for all composite materials, indicating nanoconfinement effects of the interparticle salt phase. This work therefore provides a new strategy for obtaining shape-stabilized materials useful for high – temperature heat storage. [Display omitted] •Shape-stabilized phase change materials obtained using mesoporous silica matrices.•5%NaCl–40%NaBr–55%Na2MoO4 (mol) eutectic as the high-temperature active phase.•All composites have high thermal stability (650 °C) at 80% wt. salt.•MCM-41 and SBA-15 best matrices for high heat storage (169–178 J/g).•With Declaration of interests.