Thermal energy storage enhancement of a binary molten salt via in-situ produced nanoparticles

Abstract

Thermal energy storage (TES) system is an essential component of any concentrating solar thermal power (CSP) plant to ensure a reliable plant operation even at night or cloudy weather. To enhance the TES capacity, a one-step method was proposed to synthesize nano-salts by in-situ production of CuO nanoparticles, via a high temperature decomposition of copper oxalate, in a binary salt used as a phase change material (PCM). The specific heat of the nano-salt both for solid and liquid phases were measured by differential scanning calorimetry (DSC) with the weight fraction of CuO nanoparticles varied from 0.1 to 3.0 wt %. The maximum specific heat increment of 7.96% in solid phase and 11.48% in liquid phase, were achieved at a CuO nanoparticle concentration of 0.5 wt %. A forming of intermediate layers composing of needle-like structures between nanoparticles and the salt was observed. The mixing model considering such an intermediate layer can be used to explain the observed specific heat enhancement at low particle † Corresponding author. Email address: duxz@ncepu.edu.cn (X. Du); D. Wen@leeds.ac.uk (D. Wen) concentrations. Both latent heat and onset temperature were decreased with increasing concentrations of CuO nanoparticles, while the melting temperature range was increased. When considering both latent heat and sensible heat contributions, the maximum increment of TES was achieved as 4.71% at 0.5 wt % CuO concentration in the temperature range from 160 ºC to 300 ºC.

Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage

“…Qiao et al reported numerical and experimental results for enhancing the specific heat of a binary nitrate salt mixture [34]. In 2017, Luo et al reported that the mixture of sodium nitrate and potassium nitrate was enhanced by CuO nanoparticles that are produced in situ via the high-temperature decomposition of copper oxalate with the nitrate salt mixture [35]. Most recently, in situ synthesized MgO nanoparticles enhanced the specific heat of a nitrate salt by up to 118% in the solid phase and 168% in the liquid phase [36].…”

Characterization of molten salt doped with different size nanoparticles of Al 2 O 3

“…For other samples with nanoparticles, the values of heat fusion are even lower than that of the base salt. The negative influence on fusion heat was also observed in the studies by Luo et al and Gimenez‐Gavarrell et al The variation of fusion heat is related to the formation of nanostructure around the particles. The nanostructure and its number are different for different size nanoparticles at the same mass concentration because of its different distribution characteristics in the base salt.…”

Regulation of natural convection heat transfer for SiO2–solar salt nanofluids by optimizing rectangular vessels design

“…However, some undesirable properties set a limitation on further applications of molten salts. Researchers have attempted to improve thermal performance by adding nanoparticles into molten salts, in order to formulate new nanofluids as working media, and excellent thermal storage characteristics have been obtained . Shin and Banerjee doped SiO 2 nanoparticles into carbonate salt and obtained enhancement of 5–15% and 25–28% for specific heat and thermal diffusivity, respectively.…”

“…Researchers have attempted to improve thermal performance by adding nanoparticles into molten salts, in order to formulate new nanofluids as working media, and excellent thermal storage characteristics have been obtained. [15][16][17][18] Shin and Banerjee 19 doped SiO 2 nanoparticles into carbonate salt and obtained enhancement of 5-15% and 25-28% for specific heat and thermal diffusivity, respectively. Awad et al 20 investigated the thermophysical properties of nitrate salt with various nanoparticles.…”