Heat transformation performance of salt hydrate-based thermochemical energy storage sorbent during hydration

Abstract

Given that the outstanding benefits of high energy storage density (ESD) and long-term energy storage ability with ignorable heat losses, thermochemical energy storage (TCES) in salt hydrates is a promising way to bridge the gap between supply and demand sides for renewables in residential heating. In this article, the hydration process (for heat discharge) of the sorbent composed of binary lithium-based salt hydrate and expanded graphite (LiOC@EG) in an individual thermal energy storage (TES) module is numerically investigated. For the airflow of 0.2 m/s and 20℃ with 80% relative humidity (RH), the bed temperature and outlet temperature dramatically rise with 30 min, and the maximum values are around 46 ℃ and 52 ℃, respectively. With hydration reaction advancement, the water vapour concentration increases in the bed due to the slowdown of adsorption kinetics. The temperature gradient and hydration reaction difference alone radial direction in the TES unit is almost negligible, and the time required to basically complete the hydration process (α > 95%) is ∼6.5 h, indicating the thermochemical sorbent coupled with the TCES unit is appropriate for home heating supply. The results of this study may provide reference and prediction on heat and mass migration behaviours of TCES system.