Screening of novel water/ionic liquid working fluids for absorption thermal energy storage in cooling systems. (29th October 2019)

• Record Type: Journal Article
• Authors: Wu, Wei; You, Tian; Leung, Michael
• Other Names: Chen Wei‐Hsin guestEditor.; Chong Wen Tong guestEditor.
• Is Part Of: International journal of energy research. Volume 44:Number 12(2020)
• Page Start: 9367
• Page End: 9381
• Publication Date: 2019-10-29
• Subjects: absorption thermal energy storage -- cold storage -- crystallization -- ionic liquid -- water/ionic liquid -- energy storage density; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.4939
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: Absorption thermal energy storage (ATES) is significant for renewable/waste energy utilization in buildings. The ATES systems using ionic liquids (ILs) are explored to avoid crystallization and enhance the performance. Property model and cycle model have been established with verified accuracies. Based on the preliminary screening, seven ILs are found feasible to be ATES working fluids, while four ILs ([DMIM][DMP], [EMIM][Ac], [EMIM][DEP], and [EMIM][EtSO4 ]) have been selected for detailed comparisons. The coefficient of performance (COP) and energy storage density (ESD) of the ATES using different H2 O/ILs are compared with H2 O/LiBr. Results show that the operating temperatures of LiBr are constrained by crystallization, limiting the COPs and ESDs under higher generation temperatures and lower condensation temperatures. With varying T g, [DMIM][DMP] yields higher COPs with T g above 100°C and [EMIM][Ac] yields comparable ESDs (67.7 vs 67.1 kWh/m 3 ) with T g around 120°C, as compared with LiBr. The maximum COP is 0.745 for [DMIM][DMP]. With varying T c, [DMIM][DMP] yields higher COPs with T c below 38°C and [EMIM][Ac] yields higher ESDs with T c below 33°C, as compared with LiBr. The maximum ESD is 87.5 kWh/m 3 for [EMIM][Ac]. With varying T e, [DMIM][DMP] yields higher COPs with T e above 8°C, as compared with LiBr. The maximum ESD of ILs is 104.0 kWh/m 3 for [EMIM][EtSO4 ]. Comparing with the volume‐based ESDs, the differences between ILs and LiBr are smaller for the mass‐based ESDs. This work can provide suggestions for the selection of novel working fluids for ATES for performance and reliability enhancement. Abstract : All the existing H2 O/IL working fluids are studied for absorption cooling cycles; this study aims to screen the suitable H2 O/IL working fluids for ATES. The major merit of using H2 O/ILs as novel ATES working fluids is that the solutions can be charged to be more concentrated while staying away from crystallization risk. In this manner, the ATES has higher reliability without crystallization and higher ESDs with enlarged concentration differences.