Coconut shell–derived activated carbon–enhanced water phase change material for cold thermal energy storage

In building cooling, the demand for cooling surges during specific times, stressing air-conditioner operation, and additional cooling is often wasted during low-demand periods. Water-phase change material (W-PCM)–based thermal energy storage (TES) allows for load shifting and effective management of peak demand by storing cooling energy when the demand is low. This stored energy can be deployed during peak hours, decreasing energy usage and associated CO2 emissions. However, the use of W-PCMs was hindered by phase separation, slow energy transfer, and high supercooling degree (SCD). We synthesized coconut shell (CNS)–produced activated carbon (ACC) to use as a thermal enhancer in W-PCMs for the first time. First, ACC was synthesized from CNS via steam activation. Then, transmission electron microscopy was used to confirm the pore morphology of the CNS-ACC. The synthesis of the W-PCM with various weight percentages (0.1, 0.6, and 1.2) of CNS-ACC was accomplished in two steps. Zeta potential distribution analysis revealed that the W-PCM with CNS-ACC exhibited colloidal stability. Thermal conductivity (TC) and thermogram analyses revealed that a dose of 1.2 wt