Development af a Hybrid Absorption Thermal Energy Storage Technology for Higher Storage Density And Efficiency with Lower Charging Temperature

Project: Research

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The building sector accounts for a large proportion of the total energy consumption in different regions. Thermal energy storage (TES) technologies play a significant role in building energy efficiency by balancing the mismatched timing and intensity between renewable energy supply and building energy demand. Compared to other existing TES technologies, the absorption TES (ATES) stands out due to its high energy storage density (ESD), low charging temperature, relatively high coefficient of performance (COP), and fast charging/discharging. These merits can facilitate much better utilization of renewable and waste energy for buildings. In addition, the low-grade thermal energy stored by ATES systems can be discharged in the form of cooling, heating, or dehumidification, offering a wider flexibility than current TES systems. Although the ATES technology has been increasingly studied, it still suffers from two critical shortcomings: (1) the crystallization risk of the conventional working fluids limits the ESD and system reliability; and (2) the charging temperature of the conventional ATES cycle (minimum of 80 °C) cannot be further decreased while maintaining an efficiency at satisfactory level. These two key problems seriously limit the wider adoption of the ATES technology.To maximize ATES’s contribution to energy saving and emission mitigation, a hybrid compression-assisted ATES (CATES) system using ionic liquids (ILs) as novel working fluids is proposed in this project. This hybrid CATES can be charged at temperatures as low as 50-60 °C with high COPs and be charged to more concentrated solutions (free of crystallization) with high ESDs. In this study, property models of various novel IL-based mixtures and dynamic thermodynamic models of the hybrid CATES cycle will be established for characterizing various cycle performance indices and charging/discharging behaviors. An experimental prototype of the hybrid CATES will be developed for performance measurement and model validation. Various groups of ILbased working fluids will be screened to identify their best performance and applicable domain for the hybrid CATES system. The compression ratio of the hybrid CATES system will be optimized for more efficient control under various conditions. A transient building energy simulation platform will be established to investigate the annual performance of the hybrid CATES to facilitate the design and operation in different buildings and climates. This project will motivate further progress in academia and industry, providing a promising approach towards sustainable buildings and societies by making the best of the natural resources in Hong Kong and all over the world. 


Project number9048169
Grant typeECS
Effective start/end date1/08/19 → …