Multiwalled CNT and graphene nanoplatelets based nano-enhanced PCMs: Evaluation for the thermal performance and its implications on the performance of hybrid PV/thermal systems

The low heat conductivity of paraffin-based phase change materials (PCMs) makes them unsuitable for several practical uses. Carbon-based nanomaterials with high thermal conductivity have demonstrated promising results in improving the thermal characteristics of various fluids and PCMs. Among the different carbon-based nanomaterials, Multi-Walled Carbon Nanotubes (MWCNT) and Graphene Nanoplatelets (GNP) are chosen for this study to enhance the thermal performance of paraffin wax (PW) n a comparative study. Different wt% of nanomaterials were mixed with PW to prepare two distinct sets of nano-enhanced phase change materials (nanoPCMs). The prepared samples were characterized and their thermal properties were measured. A numerical model was developed using the experimentally measured properties to evaluate the impact of the nanoPCMs on the performance of a hybrid PV/Thermal system. The majority of the PW/MWCNT samples improved their thermal conductivity more than the PW/GNP samples, whereas the PW/GNP samples attained higher specific heat values. During melting and at 5% wt, the PW/MWCNT demonstrated a thermal conductivity enhancement of 13.9%, compared to 3.8% for the PW/GNP, both at 25 °C. At the same concentration, the specific heat of PW/GNP was higher than that of PW/MWCNT by 6.7%. On the other hand, when repeatedly cycled, the nanoPCMs samples displayed good thermal stability. Numerical analysis of the performance of a hybrid PV/Thermal system with the PW/GNP layer on the back showed superior cooling for the PV panel with an improved electrical and thermal efficiency. [Display omitted] •Experimental measurements of the thermal properties of PW-based nanoPCMs.•Characterization using FESEM to evaluate the distribution of nanoparticles.•Covers the effect of phase change direction and cycling on the measurements.•MWCNT is better for thermal conductivity and GNP is better for specific heat.•For PV/T, using GNP is better in general and MWCNT only at high concentrations.