The Evaluation of Peak Shaving by a Thermal Storage System Using Phase-Change Materials in Air Distribution Systems

An air distribution system equipped with a storage device using phase-change materials (PCMs) was proposed for peak shaving. Mixtures of paraffin waxes were chosen as the PCMs, and experiments were conducted to identify thermal characteristics, such as melting temperature and latent heat. Although the mixtures had less heat storage capacity than the pure wax, the heat of fusion was around 90 kJ/kg (40 Btu/lb), which could be competitive with sensible storage materials. A simulation using the enthalpy method was conducted to evaluate system performance. The PCM was cooled during nighttime, and the stored heat was discharged from 13:00 to 16:00, while the heat source was stopped. The simulation program evaluated temperature fluctuation during the discharge period for each mixture and quantity of PCM. Installing 5 kg/m2 (1 lb/ft2) of PCM, the temperature during the discharge period could be maintained within an acceptable condition. It is concluded that this system could contribute to peak shaving for buildings.