Thermochemical Energy Storage in Low Flow Liquid Desiccant Regenerator

Abstract

Concentrated liquid desiccant (LD) presents an alternative means for energy storage for peak load shifting when appropriate supply for regeneration exists. The volumetric energy storage capacity is characterized by the stored energy per volume of the stored liquid desiccant. High flow liquid desiccant results in lower concentration spread of the solution and thus in lower storage capacity. In this paper, a liquid desiccant heat and mass exchangers was designed, built, and experimentally evaluated as a regenerator. The regenerator represents a low flow internally heated tube bundle. The main design-focus of the presented regenerator was to achieve improved heat and mass transfer coefficients, as well as higher chemical and thermal stability of the construction. The presented regenerator proved high thermal stability by high water temperatures up to about 90°C. A parametric analysis was performed to study the effect of varying desiccant flow rate, inlet air temperature, inlet desiccant temperature, and inlet heating water temperature on the water vapour desorption rate and the energy density. The experimental results showed a mass fraction spread in the range of 0.8 % to 5.7 % in the desiccant and a volumetric energy storage capacity of 17 to 117 kWh/m³