Phase change characterization of eco-friendly isopropyl palmitate-based graphene nanoplatelet nanofluid for thermal energy applications

Abstract

• Design of stable isopropyl palmitate-based nanoenhanced phase change materials. • Analysis of solid–liquid transition and enthalpy-temperature curves. • Reductions in sub-cooling higher than 2 K, increases in the latent heat up to 5.9%. • The IPP polymorphism was not significantly altered due to the GnPs dispersions. • Reductions up to 12% in the isobaric heat capacities compared to the base material. Thermal energy storage (TES) facilitates the integration of renewable energy by decoupling production and consumption, mitigating intermittence issues. However, current TES systems use fossil fuel-based products as storage media, so the development of sustainable and efficient materials should be investigated. This work aims to the design and characterization of new eco-friendly nanoenhanced phase change materials (NePCMs) based on dispersions of graphene nanoplatelets of two different lateral sizes (7.2 and 40 μm) in isopropyl palmitate for cold storage applications. The stability of the NePCMs was analysed by dynamic light scattering, selecting Span® 80 as surfactant to improve the stabilization of both nanomaterials within the base material. The influence of the nanoadditive concentration on the temperature transitions and on the solid–liquid phase change were comprehensively studied by differential scanning calorimetry, finding out that the dispersed nanoadditives do not alter the polymorphism of the isopropyl palmitate. Additionally, reductions in the sub-cooling effect higher than 2 K for both nanoplatelets were found, with increases in the latent heat up to 5.9 and 3.9% for the shorter and the longer nanoplatelets, respectively. Isobaric heat capacities were also determined by temperature-modulated differential scanning calorimetry, reporting maximum reductions of 12% compared to the base material.