Study on Diffusion Mechanism of CaO/Ca(OH)2 Molecules During Thermochemical Energy Storage Process Based on Molecular Dynamics
In CaO/Ca(OH)2 energy storage process,the energy storage and mechanical performance are related to the structure of CaO grains.This work investigated the lattice structure and molecular motion of CaO/Ca(OH)2 grains during CaO/Ca(OH)2 energy storage process using molecular dynamics simulations.The result indicates that during the dehydration stage,the movement of Ca(OH)2 molecules is consistent with the bulk diffusion mechanism.The diffusion pre-exponential factor for O/H atoms is 7.9×10‒8 m2/s,while that for Ca atom is only 4.7×10‒8 m2/s.The rapid diffusion of O/H destroys the original lattice structure,leading to a reduction in the crystallinity of CaO after dehydration.In the hydration stage,the diffusion pre-factor for outer molecules of CaO grains is 3.2×10‒8 m2/s,which is 2.5 times higher than that of inner molecules.Consequently,the molecular motion of CaO molecule is consistent with the surface diffusion mechanism.The diffusion strength of CaO molecule is weak during the hydration stage,resulting in minimal impact on the CaO lattice structure.The simulation determines the diffusion mechanisms of CaO/Ca(OH)2 molecules in the thermochemical energy storage process.This is crucial to understand the crystal structure evolution of CaO-based materials in CaO/Ca(OH)2 energy storage process.
CaO/Ca(OH)2 thermochemical energy storageCaO grainsMechanical performanceMolecular diffusionMolecular dynamics simulation
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