Comparative study of various adsorbents for adsorption-based thermal energy storage

Abstract

Adsorption-based thermal energy storage (ATES) systems can potentially replace conventional heating technologies. This research explores the application of ATES systems for heating, focusing on the performance of various adsorbents using lumped parameter modeling. UiO-66, MOF-801, and their modified counterparts are evaluated alongside silica gel in terms of total and useful energy for end-users. Analysis of the ATES system encompasses Coefficient of Performance (COPh), Specific Heating Power (SHP), and Temperature Lift (ΔT) across different operating conditions. Isotherm characteristics reveal that (CH3)2-MOF-801 and NH-UiO-66 excel in water uptake at low relative pressures (Henry's region), resulting in high total and useful energy density. Notably, higher cooling water flow rates generally enhance Energy Storage Density (ESD) for materials like silica gel, UiO-66, and NH2-UiO-66, albeit at the cost of reduced SHP and COPh. Conversely, lower flow rates can lead to higher temperature lift (ΔT) for specific materials, although with a slight ESD decrease. Adjusting the chilled water inlet temperature typically favors ESD and COPh with higher temperatures while affecting SHP and ΔT differently. Heat source temperature impacts ESD and SHP variably due to isotherm characteristics and dynamic water uptake. The results highlight the superiority of (CH3)2-MOF-801 and N-UiO-66, achieving 91 % and 76 % of total energy density, with 94 kg of (CH3)2-MOF-801 covering 89 % of energy requirements for a single South Korean home annually.