Screening of novel water/ionic liquid working fluids for absorption thermal energy storage in cooling systems

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Number of pages15
Journal / PublicationInternational Journal of Energy Research
Online published29 Oct 2019
Publication statusOnline published - 29 Oct 2019

Abstract

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 H2O/ILs are compared with H2O/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 Tg, [DMIM][DMP] yields higher COPs with Tg above 100°C and [EMIM][Ac] yields comparable ESDs (67.7 vs 67.1 kWh/m3) with Tg around 120°C, as compared with LiBr. The maximum COP is 0.745 for [DMIM][DMP]. With varying Tc, [DMIM][DMP] yields higher COPs with Tc below 38°C and [EMIM][Ac] yields higher ESDs with Tc below 33°C, as compared with LiBr. The maximum ESD is 87.5 kWh/m3 for [EMIM][Ac]. With varying Te, [DMIM][DMP] yields higher COPs with Te above 8°C, as compared with LiBr. The maximum ESD of ILs is 104.0 kWh/m3 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.

Research Area(s)

  • absorption thermal energy storage, cold storage, crystallization, ionic liquid, water, energy storage density, VAPOR-PRESSURE MEASUREMENT, SOLAR HEAT-STORAGE, IONIC LIQUIDS, 1-ETHYL-3-METHYLIMIDAZOLIUM ACETATE, THERMODYNAMIC PROPERTIES, REFRIGERATION SYSTEM, TERNARY-SYSTEMS, BINARY-MIXTURES, WATER-METHANOL, PLUS WATER