A novel sorption reactor for sorption heat transformers: Thermal energy storage system

Abstract

This study addresses some of the critical limitations of current sorption heat transformer systems, particularly their cost, size and weight, which hinder their widespread adoption in various applications. A novel shell-and-tube sorption reactor design was proposed, featuring a lightweight shell instead of the conventional vacuum chambers typically used to encase the sorption reactor. In the proposed design, the sorbent material, synthesized in a disk-shaped form, was placed inside the tubes, while the heat transfer fluid flowed between the shell and the tubes. Comprehensive material characterization, including thermal diffusivity measurement, thermogravimetry, and porosimetry, was performed on the sorption materials. A proof-of-concept demonstration lab-scale prototype was designed, built, and tested. Using the disk-shaped composite, a significantly more active sorption composite per available volume was installed in the proposed sorption reactor which increased the energy storage density, while reducing the complexity and the cost of the system. Calorimetric large pressure jump tests on the proposed sorption reactor have shown a 0.74 MJ/kg energy storage density, a coefficient of performance for heating of 0.98 for 20-minute cycle time (1.4 for 90-minute cycle time), and specific power of 267 W/kg (20-min cycle time) for a 4.3 dm³ module under the nominal operating conditions of 90 °C, 30 °C, 30 °C, 15 °C, desorption, sorption, condenser, evaporator, respectively; where there is considerable room for performance improvement in the current sorption reactor. Considering that the energy density range for lithium-ion batteries is 0.46–0.72 MJ/kg, this demonstrates the competitiveness of thermal storage, particularly in comparison to the more expensive lithium-ion batteries.