Engineering Phase Transformations in Metal Hydrides for High-Temperature Energy Storage

Tae Wook Heo | 21-FS-005

Project Overview

Phase transformations are widely leveraged to improve mechanical or functional behavior of materials ranging from metallic alloys to ceramics. One particularly promising application lies in the use of phase transformations at high temperatures to store and utilize thermal energy. A thermal energy storage medium should rapidly store/release a large amount of latent heat during its phase transformation process. However, controlling thermodynamic and kinetic behavior of phase transformations is extremely challenging at elevated temperatures due to co-evolving phase microstructure and associated thermal/chemical instabilities. To this end, development of reliable modeling capabilities for understanding, predicting, and controlling high-temperature phase transformations is critical for rationally designing thermal energy storage tailored to application needs. This LDRD Feasibility Study (FS) project established the integrated mesoscale computational and theoretical models for systematically investigating thermodynamic and kinetic mechanisms of phase transformations and associated complex microstructural effects in materials for high-temperature energy storage applications. Focusing on metal hydrides for thermal energy storage that rely critically on elevated-temperature phase transformations, this project successfully demonstrated two objectives. First, we developed mesoscopic models that can be used for 1) computing microstructure-aware thermal conductivity; 2) analyzing the effects of mechanics and grain size on mass transport; and 3) simulating heat generation during hydride formation. Second, we applied the mesoscale models to quantifying key microstructural effects, which can be utilized for optimizing kinetic thermal storage mechanisms.

Mission Impact

This project helped to support Lawrence Livermore National Laboratory's (LLNL's) missions of Energy Security/Advanced Materials and Manufacturing by contributing to mesoscale science for realistic materials for energy applications. By demonstrating the feasibility of establishing key mesoscopic models and theoretical approaches for analyzing microstructural impacts on thermal transport, mass transport, and latent heat generation, the project strengthens LLNL's integrated mesoscale modeling approach, filling the current gap in capabilities for high-temperature applications. Further, this has the potential to place LLNL in a leadership position for mesoscale microstructure science and high-temperature energy storage, which can be directly applied to a variety of industrially relevant materials systems. In particular, the demonstrated modeling and theoretical framework form one of key foundations for a new joint theory-experiment LDRD Exploratory Research (ER) project focusing on hydrogen-material interactions for high-temperature applications.