Candelilla Wax-Fatty acids eutectics as thermal energy storage materials: A comprehensive study for solar collector applications

• This study develops novel bio-based eutectic PCMs by blending Candelilla wax with fatty acids, providing tunable melting temperatures, high latent heat, and strong thermal stability suitable for medium-temperature TES. • Thermal stability up to 170 °C, confirmed by TGA, ensures safe operation in solar collectors and reliable charging/discharging. • COMSOL simulations show effective temperature regulation and efficient charging of selected eutectics (CS37, CP37, CM55). • Future work will focus on enhancing thermal conductivity, assessing long-term durability, and validating outdoor performance. The present study develops and characterises novel bio-based eutectic phase change materials (PCMs) by blending Candelilla wax (CW) with fatty acids (stearic, palmitic, and myristic acids) for medium-temperature thermal energy storage (TES) in solar flat plate collectors. Differential scanning calorimetry (DSC) revealed tuneable melting temperatures ranging from 48.3 °C to 65.5 °C and latent heat values between 113 and 192 kJ.kg −1 , depending on composition. Thermogravimetric analysis (TGA) confirmed thermal stability up to 170 °C, while FTIR and SEM analyses verified physical compatibility and smooth surface morphology favourable for cycling stability. The eutectics CS37 (CW-SA), CP37 (CW-PA), and CM55 (CW-MA) exhibited optimal thermophysical performance with thermal conductivity values of 0.111 Wm −1 K −1 , 0.108 Wm −1 K −1 , and 0.095 Wm −1 K −1 , respectively. Incorporation of these PCMs into a solar flat plate collector considering the airflow simulated in COMSOL Multiphysics. The Result showed the reduction in the absorber plate’s temperature and air temperature from 18 to 25 °C, 14 to 16 °C, respectively. The energy in the PCM rose to about 680 kJ for CS37, 530 kJ for CS47, and 440 kJ for CM55 during charging. So, these eutectics are promising consolidates for solar thermal energy storage applications.