Mechanics-driven evolution of effective thermal conductivity in salt-hydrate thermochemical energy storage materials

Inorganic salt hydrates are promising thermochemical energy storage (TCES) materials because of their low cost, high energy density, and moderate operating temperatures. However, hydration/dehydration cycling produces large volumetric changes that alter microstructure, generate internal stress, and drive progressive degradation, limiting long-term cyclic stability. Because heat-transfer performance depends on the evolving effective thermal conductivity, keff, predictive TCES models must account for how reaction-induceddeformation and damage modify conductive pathways during cycling.This work develops a representative volume element (RVE) based finite element framework to quantify the mechanics-driven evolution of keff in salt-hydrate TCES materials. The framework combines coupled thermo-chemo-mechanical simulations with a guarded-hot-plate-style numerical measurement of effective thermal conductivity. Void-based and particle-based RVEs are examined over a range of relative densities and boundary conditions to isolate the roles of porosity, pore morphology, inter-particle contact, and reaction-induced deformation. The results show that keff is not governed by relative density alone; microstructural topology and mechanical constraint play a central role in determining how conductive pathways evolve during reaction.To capture cyclic degradation, we further introduce a probabilistic chemo-mechanical damage framework that links reaction-induced cracking to pellet-level conductivity loss. Using experimentally informed cycle-dependent crack densities, the model predicts progressive reductions in keff over repeated hydration/dehydration cycles. Together, the RVE simulations and damage framework connect evolving microstructure, mechanical degradation, and heat-transfer performance in salt-hydrate TCES systems.