The thermal energy storage, harvesting, and delivery using the phase change capsules (PCCs)-embedded heat transfer fluids (HTFs) have been received comparable attention as one of the sustainable energy technologies because the PCC based thermal energy storage can meet overall and peak hour energy demand through temperature-triggered reversible latent heat storage and release. Robust and thermal conductive PCCs are critical for permanent and effective use as an HTFs to utilize the waste heat. Here, we introduce PCCs encapsulated with cross-linked poly(2-hydroxyethyl methacrylate) (<i>c</i>-pHEMA) shell that showing durability and low thermal hysteresis for effective heat uptake and release. The increase of thermal hysteresis before-and-after encapsulation of the PCCs with c-pHEMA was low compared to other reported PCCs due to the high thermal conductivity of c-pHEMA shell. The thermal energy storage/delivery performances and long-term stability of the capsules-dispersed HTFs under thermal-mechanical loads were evaluated using the circulation system. The heat circulation study using micro-PCCs has been rarely attempted compared to nano-PCCs because the reported micro-PCCs had a low durability that may break during the circulation. In our operating conditions, the enthalpy change of the water improved up to 41.1% due to the enhanced heat capacity of HTFs with increasing amount of PCCs. And high PCC recovery ratio of 92 wt% was achieved after 1,500 cycling that accompanies a phase transition owing to the flexibility of the hydrous <i>c</i>-pHEMA. Thus, it was clearly confirmed that more thermal energy can be stored and transferred using the phase change fluids in the form of latent heat by the PCCs and we believe that our micro-encapsulation strategies for the high thermal conductive and robust PCCs can accelerate an actual application of PCCs-embedded HTFs in industries.

Water-absorbable soft microcapsules-embedded heat transfer fluids for thermal energy storage and delivery

2019 Spring National Meeting

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