Increasing the charge/discharge rate for phase-change materials by forming hybrid composite paraffin/ash for an effective thermal energy storage system

Abstract

Low-temperature latent heat storage (LHS) systems are suitable for incorporating paraffin as the storage material. However, they face difficulty in actual implementation due to low thermal conductivity (TC). The present study used volcanic ash as an environmentally friendly and cost-effective material to increase the TC of paraffin. Three composites of paraffin/ash were prepared with ash proportions of 10 wt%, 30 wt% and 50 wt%. Characterizations were done to evaluate the average TC and properties. Thermal performance evaluation was conducted by analyzing the static charge/discharge cycle. The average TC for paraffin was 0.214 W/m·K. Adding volcanic ash improved the TC to 19.598 W/m·K. It made the charge/discharge performance of the composite better than that of pure paraffin. The charge rate for the composite ranged from 3.83 ℃/min to 5.12 ℃/min. The highest discharge rate was obtained at 4.21 ℃/min for the composite paraffin50/ash50. The freezing temperature for the composite is influenced by the ash proportion, which can be taken as a suitable approach to adjust the freezing point of paraffin-based thermal energy storage (TES). The detailed results for the characterization and thermal performance evaluation are described thoroughly within the article. The overall result indicates that volcanic ash is applicable for improving the TC and charge/discharge rate of paraffin-based TES.

Keywords

• ash
• paraffin
• phase change materials
• thermal conductivity
• thermal energy storage