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Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Sajjad Bigham

Committee Member 1

Fernando Ponta

Committee Member 2

Chunpei Cai

Committee Member 3

Sunil Mehendale


Sorption Thermal Energy Storage (STES) systems are deemed superior to conventional sensible and phase-change Thermal Energy Storage (TES) options owing to their remarkably high volume/mass-based stored energy densities and long-term storage capabilities with negligible heat loss. The STES systems exchange energy through reversible chemical reactions between a sorbent (i.e., solid or liquid desiccant) and a sorbate (i.e., refrigerant). However, the adaptation and widespread acceptance of STES systems, particularly liquid-desiccant-based STES systems, have been plagued by several challenges including their low power densities at which the stored energy can be extracted.

In this thesis, a novel membrane-based thin-film liquid-to-liquid STES concept is introduced to both eliminate the melting issue and limited cyclic lifetime associated with the salt-in-matrix STES systems and humidity boundary layer formed in air-to-liquid STES systems. The new approach relies on a single-species liquid refrigerant (e.g., water) instead of a two-species refrigerant (e.g., air) in conventional air-to-liquid STES systems.

Extensive experiments were conducted to validate and evaluate the performance of the proposed membrane-based thin-film liquid-to-liquid STES systems in both open (i.e., atmospheric) and closed (i.e., sub-atmospheric) conditions. Experimental results show that the performance of the proposed system substantially outperforms the conventional STES systems (i.e., an absorption rate of ~0.1 versus 1 g/m2-s). It was also found that the absorption rate and mass-based power density of the closed thin-film liquid-to-liquid STES system are significantly higher than those of its open counterpart. For instance, when the water vapor pressure potential increases from 3.1 to 5.2 kPa, the mass-based power densities of the closed and open liquid-to-liquid STES systems improve from 1043.6 to 1405.6 W/kg and from 503.8 to 732.5 W/kg, respectively. In other words, the mass-based power density of the closed liquid-to-liquid STES system is 92% higher than that of the open STES system at a water vapor pressure potential of 5.2 kPa. This confirms the improvement of water vapor transport rate and thermodynamic state of the system. The insights from this work help to improve the cyclic longevity issue and low power densities of sorption thermal energy storage systems for heat/cold load shedding, shifting, and modulation in buildings and more.