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

Paper Number: 156139

156139 - Development of L-Valve Particle Metering Correlation for Thermal Energy Storage 

Abstract: 

High temperature thermal energy storage (TES) systems can decouple energy use from supply for industrial process heat or electrical power generation through thermal power cycles.  A common method of TES is through sensible heating of solid materials. Particles are heated using excess grid energy or through concentrated solar power, and stored in large, insulated tanks. When energy is needed, particles are conveyed from storage and through a heat exchanger where heat is transferred from the particles into a working fluid to generate electricity from a thermal power cycle or provide direct heat. Particle mass flow must be accurately controlled to maximize energy extraction and minimize losses. Existing particle conveying mechanisms are often inadequate to handle the extreme temperatures or pressures of the TES system, and wear on moving parts from abrasive particles can drastically reduce the lifespan of these components.  This study tested a nonmechanical L-Valve as a candidate for particle metering, as it does not contain moving parts, is easily controlled through a single air flow meter, and requires minimal maintenance.  L-valves have long been used in gasification processes or in coal-fired power plants to effectively meter particles.  However, sizing correlations for L-Valves found in literature vary significantly.  The objective of this study was to determine correlations between air flow rate, aeration point, and particle size to the particle mass flow rate so it can be reliably used in TES systems. Silica sand particles with mean diameter of 1068 microns (Sand #1) and 775 microns (Sand #2) were used. Testing conditions include using aeration points of 0.0 D, 0.5 D, 1.0 D, 1.5 D above the centerline of a 4-inch diameter valve, and air supply ranging from 2.8 to 5 SCFM. It was found that for sand #1 the aeration point with the highest mass flow rate under a constant air flow rate was 1.0 D. The aeration point with the least variation in terms of flow rate between each experiment occurred using the 0.5 D aeration point. The air flow rate at which particles started flowing occurred at around 3 SCFM and 2.8 for sand #1 and #2, respectively. It was found that smaller particle type #2 obtained a higher overall mass flow rate under the same aeration conditions. The highest mass flow rate achieved within the tested range was 0.53 kg/s (sand #1) and 0.65 kg/s (sand #2) at 5 SCFM using aeration point 0.0 D and 1.0 D respectively. This test supports the use of an L-Valve as a viable option for particle flow for TES systems.

Presenting Author: Brecht Boonman-Morales National Renewable Energy Laboratory

Presenting Author Biography: Brecht Boonman graduated with a mechanical engineering degree from the New Jersey Institute of Technology in 2024. He then joined the Thermal Energy Systems Group as a Science Undergraduate Laboratory Intern at the National Renewable Energy Laboratory. His interests include fluid mechanics and thermal energy storage systems.