Thermal energy storage of molten salt –based nanofluid containing nano-encapsulated metal alloy phase change materials

Abstract

The availability of Thermal Energy Storage systems in Concentrated Solar Power plants makes them suitable to handle the gap between energy supply and power demand. Increasing the total thermal energy storage capacity of the Thermal Energy Storage materials used is of interest to improve their efficiency. In this work the thermal energy storage of the so called solar salt (60% NaNO3-40% KNO3) was improved by adding a phase change material composed of Al-Cu alloy nanoencapsulated with an aluminium oxide layer naturally formed when exposed to oxygen. The resistance of the oxide shell to thermal cycling up to 570ºC and its compatibility with the molten salt were proved. The specific heat and the total thermal energy storage were evaluated at different solid mass loads. Although the specific heat and thus the sensible heat storage decreases with solid content, the contribution of the phase change enthalpy and the latent heat storage can increase the total thermal energy storage up to a 17.8% at constant volume basis comparison. Besides, the thermal conductivity of the nanofluid was increased when adding the nanoparticles improving its heat transfer performance under some particular conditions.

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

“…Nanoparticle has a high particle surface energy due to its large specific surface area, and it can make slight improvement in thermal conductivity and lead to keep and increase the specific heat of pure PCM [17][18][19][20][21][22][23][24][25]. The nanocomposites synthesized with PCMs and nanoparticles have been studied extensively, both for thermo-physical properties and system performances.…”

“…The nanocomposites synthesized with PCMs and nanoparticles have been studied extensively, both for thermo-physical properties and system performances. Navarrete et al [18] characterized solar salt nano-encapsulated with Al-Cu alloy layer and pointed out that the total energy stored of the system can be increased owing to contribution of the latent heat storage of the nano-encapsulated PCM, e.g., the thermal storage capacity can be increased by 17.8% when the PCM was nanoencapsulated with an aluminium oxide layer. Mayilvelnathan and Arasu [19] prepared and studied the erythritol/graphene composite PCM.…”

Effect of Nanoparticle Concentration on the Specific Heat Capacity and Thermal Stability of Graphite Nanoparticle-based Molten Salt

“…Researchers all over the world are actively working towards the efficient harnessing of widely abundant solar energy due to its obvious importance in achieving clean and sustainable energy in the future [1]. But due to the intermittent nature of this form of renewable energy, storage media like storage batteries and TES systems in concentrated solar power (CSP) plants are necessary for the uninterrupted use of solar energy [2]. For achieving high thermodynamic efficiency in CSP plants, molten salt eutectics are employed as phase change materials (PCMs) for TES as they possess high thermal conductivity and high density [3].…”

Experimental Study of Thermo-Physical Characteristics of Molten Nitrate Salts Based Nanof luids for Thermal Energy Storage

“…The advantages include enhanced heat transfer, desired melting point, higher energy storage density, etc. A number of methods have been proposed to manufacture various composite nitrate salts to improve their different 6,7 properties, including form-stable nitrate salts for enhancing heat 8,9 transfer, microencapsulation to improve thermal stability and avoid [10][11][12][13][14] corrosivity, multi component nitrate salts for lowering melting points, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] molten salt based nanofluids to improve energy storage density, etc. Molten salt based nanofluid was prepared by adding a small amount of nanoparticles with one dimension smaller than 100 nm into 15 base salts.…”