Characterization and real-time testing of phase-change materials for solar thermal energy storage

A study of real-time performance of phase-change material (PCM) for solar thermal energy storage was conducted using a commercially available 2.78m(2) (aperture) flat-plate solar thermal collector and a custom 60 L latent heat storage tank filled with dodecanoic acid as the PCM. A water-glycol heat transfer solution was circulated, and the charging performance of the system was observed in relation to incoming solar radiation. Municipal water was run in the cold loop of the heat exchanger to simulate domestic water use and to discharge the system. Temperature distribution within the PCM material was recorded using an array of thermocouples deployed throughout the storage tank. Characterization of two storage systems using identical mass of PCM and water indicated that the latent heat energy storage system (LHESS) would benefit from an improved heat exchanger design. Water-based storage had higher charging and discharging rates but a lower overall storage capacity. The dodecanoic acid LHESS was capable of outperforming an equivalent water storage system by absorbing 20% more thermal energy. A 14-hour solar charge in July 2014 melted the vast majority of PCM, raised storage temperatures to over 70 degrees C, and transferred 12 MJ of energy, with a peak power rate of 0.55 kW. The results suggest that LHESS can offer potentially important reduction in thermal storage volumes. Copyright (c) 2015 John Wiley & Sons, Ltd.