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Thermal performance analysis of a solar energy storage unit encapsulated with HITEC salt/copper foam/nanoparticles composite

Xiao, Xin; Jia, Hongwei; Wen, Dongsheng; Zhao, Xudong

Authors

Xin Xiao

Hongwei Jia

Dongsheng Wen



Abstract

HITEC salt (40 wt. % NaNO2, 7 wt. % NaNO3, 53 wt. % KNO3) with a melting temperature of about 142 °C is a typical phase change material (PCM) for solar energy storage. Both aluminum oxide (Al2O3) nanopowder and metal foam were used to enhance pure HITEC salt, so as to retrieve the limitation of composite PCMs with single enhancement. The morphologies and thermo-physical properties of the composites were firstly characterized with Scanning Electron Microscope, Fourier-transform Infrared spectroscopy and Differential Scanning Calorimeter, respectively. A pilot test rig with a heater of 380 W located in the inner pipe was built, which was encapsulated with HITEC salt, nano-salt (HITEC salt seeded with 2 wt. % Al2O3 nanopowder) and salt/copper foam composite seeded with 2 wt. % Al2O3 nanopowder as storage media. Then heat storage and retrieval tests of the energy storage system were conducted both for pure HITEC salt and composite PCMs at various heating temperatures. The temperature evolutions and distributions of the PCMs at different locations were measured, including radial, angular, and axial locations, and the energy and volumetric mean powers during heat storage/retrieval processes were calculated subsequently. The results show that metal foam is generally compatible with the nano-salt. The maximum deviation of the melting/freezing phase change temperatures of the nano-salt/copper foam composite is 3.54 °C, whereas that of the nano-salt/nickel foam composite is 3.80 °C. The specific heats of the nano-salt are apparently enhanced with the addition of Al2O3 nanopowder both in solid and liquid states. The system encapsulated with the nano-salt/copper foam composite can be considerably enhanced, e.g. the time-duration of heat storage process at the heating temperature of 160 °C can be reduced by about 58.5%, compared to that of pure salt. The volumetric mean power of heat storage for the nano-salt/copper foam composite at the heating temperature of 180 °C increases to 109.32 kW/m3, compared with 53.01 kW/m3 of pure HITEC salt. The information will be helpful for solar system design, construction and application using molten salt for solar energy storage.

Citation

Xiao, X., Jia, H., Wen, D., & Zhao, X. (2020). Thermal performance analysis of a solar energy storage unit encapsulated with HITEC salt/copper foam/nanoparticles composite. Energy, 192, 116593. https://doi.org/10.1016/j.energy.2019.116593

Journal Article Type Article
Acceptance Date Nov 21, 2019
Online Publication Date Nov 22, 2019
Publication Date Feb 1, 2020
Deposit Date Jan 22, 2020
Publicly Available Date Mar 29, 2024
Journal Energy
Print ISSN 0360-5442
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 192
Pages 116593
DOI https://doi.org/10.1016/j.energy.2019.116593
Keywords General Energy; Pollution; HITEC salt; Aluminum oxide nanopowder; Metal foam; Thermal characterization; Heat storage/retrieval
Public URL https://hull-repository.worktribe.com/output/3219389
Publisher URL https://www.sciencedirect.com/science/article/abs/pii/S0360544219322881?via%3Dihub

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