Session: 04-02: Particles and Materials for Energy Storage

Paper Number: 169839

169839 - Characterization of High-Temperature Flow Properties of Solid Particles for Electrical Thermal Energy Storage 

Abstract: 

Current and emerging storage technologies span thermal, mechanical, chemical, and electrochemical approaches, each addressing specific operational and scalability needs. Long-duration energy storage (LDES) may enhance grid resilience. However, LDES solutions must address the challenge of balancing the cost of large-capacity storage with the limited economic returns from infrequent charge-discharge cycles.

Molten nitrate salt-based thermal energy storage (TES) has been commercially deployed in concentrating solar power (CSP) systems, serving as a key enabler for their viability. However, its application is constrained by the relatively low operating temperature range, thermal stability issue at high-temperatures, and corrosivity. In contrast, TES using inert, thermally stable, and low-cost particles significantly broadens the operating temperature range and potential applications. Traditional TES in CSP systems harnesses solar radiation for charging and later converts stored thermal energy into electricity. In comparison, a thermal battery—an electrically charged TES (ETES) system—can integrate with various renewable sources. A particle-based ETES system captures surplus electricity as thermal energy and later releases it when demand is high.

An electric charging particle heater is a key component in ETES system to efficiently convert off-peak electricity to thermal energy stored in solid particles. The particle heater consists of an array of diamond-shaped ceramic heating element rods, stacked horizontally in a staggered configuration with small gaps between them. The heating elements produce heat through resistive heating when an electric current flows through them. The ceramic-based SiC heating elements can operate at very high temperatures up to 1600 °C. Cold particles travel downward by gravity through a narrow, serpentine-shaped pathway formed by the arrangement of heating elements. Heat from the high-temperature surface of the heating elements can efficiently transfer to the flowing particles through direct contact, heating them up to 1200 °C.

However, particle flow and associated heat transfer mechanisms are less understood compared to Newtonian fluids, and the temperature-dependent flowability of particles can significantly influence the performance of particle heaters. If the particle-wall friction is too high, it can lead to particle clogging/stagnation within the flow channel, resulting in critical system failure due to overheating. Conversely, if friction is too low, particle residence time may be greatly reduced, leading to inefficient heat transfer. To address these challenges, we have developed a characterization technique to measure particle flow properties (effective angle of friction and kinematic angle of friction) for particle-particle and particle-wall at elevated temperature up to 1000 °C. Measurements were conducted on silica particles with diameter of 625, 800, and 1200 µm, revealing that particle friction increases with decreasing particle size and rising temperature. These measured properties will be incorporated into the design of particle heaters, optimizing factors such as heating element shape, flow channel width, and heating element arrangement. Discrete element method (DEM) simulations will be used to maximize heat transfer performance based on these findings.

Presenting Author: Shin Young Jeong National Renewable Energy Laboratory

Presenting Author Biography: Shin Young Jeong is a postdoctoral researcher in the Thermal Energy Systems group at the National Renewable Energy Laboratory in Golden, Colorado.  He received his PhD in mechanical engineering from the Georgia Institute of Technology in 2023 on characterization of thermophysical properties and flow behaviors of bauxite particles in high-temperature for concentrated solar-thermal power application.  His current research focuses on development of particle-based concentrated solar-thermal power and high temperature thermal energy storage for power generation and industrial heats.