Abstract
Development of novel solar-based energy storage technologies are considered to be one of the primary solutions to fulfill the energy demand. Sugar alcohol based phase change materials are gaining more attention as a storage medium in thermal energy storage applications. The current study focuses on the synthesis of D-Mannitol (DM) based capsules using the sol-gel technique. The main objective is to control the seepage of DM during phase transition and to increase the thermophysical properties of DM. The synthesis is carried out with pH ranging from 2.0 to 7.0. SEM images showed a well-defined morphology with the uniform spherical shape at pH between 2.6 and 3.0. FTIR spectrum showed the characteristic peaks of silica and DM which suggested the successful encapsulation of DM with silica shell from TEOS source. The average particle size of the microencapsulated DM (MEDM) varied in the range of 45–60 µm. MEDM is subjected to thermal cycling to study the change in heat transfer properties upon cycling. The thermal conductivity of MEDM is found to be 1.77 W/m K, an increase from 1.32 W/m K of DM. From DSC thermograms, the encapsulation ratio and efficiency were observed to be 89.60% and 85.02% respectively. DM exhibited a subcooling temperature of 44.21 °C which was reduced to 11 °C for MEDM. DM is found to degrade initially at a temperature of 276 °C whereas MEDM is found to be 302 °C. The charging and discharging characteristics showed that the time taken to complete one cycle by MEDM lowered compared to DM. The characteristic study of MEDM reveals that it can be used as potential PCM in solar thermal energy storage system.
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