Developing Thermal Energy Storage using PCM/ water Emulsion: Media Preparation and Optimized Design

Abstract

Maintaining thermal comfort and generating hot water in buildings consumes over 30% of global energy supplies. One of the key technologies that may help drastically reduce these consumption is thermal energy or cooling storage (TES). This project aims to develop phase-change-materials (PCM) based active TES technologies that can maximize the use of natural heating and cooling sources via solar thermal collectors and evaporative coolers, and raise the energy efficiency of the chillers operating at off-peak period. Utilizing the latent heat of melting/solidification processes, a PCM based TES system has two perceived advantages: it can store heat at a small temperature difference between the charging source and discharging user, and can potentially complete the charging in a short period. The former is critical in spaceconstrained urban applications, and the latter is critical in utilizing natural sources. Different PCM forms, namely bulk PCM, PCM/water emulsion and PCM microcapsule/ water slurry, will be experimentally investigated, and the storage unit involving heat-exchanger and fluid flow will be designed based upon optimization principles. This will be achieved through multi-disciplinary research collaboration, involving chemical engineering research and heat transfer investigation and optimization design. In the PCM preparation, nano-additives will be used to reduce the supercooling degree, which is related to the thermodynamic metastable phenomenon; and the optimization will be enhanced based on the constructal theory. In the optimization analysis, the material and preparation/processing costs of PCM media will be taken into account. It is expected that the new PCM and TES design to be developed will offer good life-cycle carbon reduction performances in building heating and cooling and hot water production.