Boosting stability of K₂CO₃ granules for thermochemical heat storage applications through innovative membrane encapsulation

Potassium carbonate sesquihydrate shows potential for low-temperature thermochemical heat storage applications. However, in contexts such as thermochemical heat batteries, salt hydrate particles are vulnerable to dissolution, caking, and disintegration due to intermittent exposure to water vapor during cyclic operations, posing significant challenges. In response, this study proposes an innovative encapsulation methodology that uses membrane technology to produce macrocapsules of potassium carbonate as a remedial strategy. The study includes a comprehensive experimental investigation that employs polyethersulfone (PES) porous membrane film as a water vapor-permeable layer for potassium carbonate granules. This investigation analyzes water permeability, pore structure, morphological transformations, cyclability, and outer shell flexibility. The aim is to facilitate water vapor diffusion, accommodate cyclic volume fluctuations, and prevent caking. By encapsulating potassium carbonate granules with a porous protective layer, the preservation of structural integrity over hydration-dehydration cycles is demonstrated, ensuring sustained energy density and kinetic stability. Specifically, the encapsulated granules achieved a volumetric energy density (VED) of approximately 0.6 GJ⋅m⁻³, and a power output at 90% conversion stabilized around 200 kW⋅m⁻³. These results indicate that the encapsulation approach significantly enhances the robustness and efficacy of potassium carbonate granules in thermochemical energy storage systems.