Edinburgh Napier University

  Renewable energy sources must supply between 30 and 45 % of the global energy consumption to achieve "net zero" emissions. However, renewable sources, such as solar, are intermittent, so they must be combined with thermal energy storage (TES) to continue supplying energy. Organic phase change materials (PCMs) that include fatty acids, sugar alcohols, and polymers have recently been explored as materials for TES because they store significant amounts of latent heat, are thermo-chemically stable, and are non-toxic. In recent years, bio-organic PCMs such as stearic acid have attracted too much attention since they come from renewable sources and retain the same properties. However, organic PCMs have poor thermal conductivity, limiting heat transfer into the storage. One of the methods to enhance thermal conductivity is the incorporation of highly conductive nanoparticles such as metal, metal oxide, and carbon-based nanoparticles. Graphene is one of the carbon-based particles that is used because of its high thermal conductivity, relatively low densities, and large aspect ratio. The fundamental thermophysical properties to design a TES application are heat capacity, thermal conductivity, latent heat, viscosity, and density. These data significantly influence the simulation results and, as a consequence, the design and operation of the TES.2 In this context, we present experimental thermal conductivity, viscosity, and density data of stearic acid with 2 wt%, 4 wt%, and 6 wt% graphene nanoplate. This work provided new knowledge on the impact of graphene nanoplate on the thermal conductivity, density, and viscosity of the stearic acid matrix of PCMs. Molecular dynamics simulations carried out to compute the thermodynamics properties listed below. They were compared to experimental results providing a novel molecular behaviour about the interaction between graphene and stearic acids.