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

Thermal energy storage (TES) systems enable energy to be delivered when demand is higher than conventional generation technologies. A common method of TES is through heating solid materials to elevated temperatures. Particles are heated using excess grid energy, when available, and stored in large, insulated tanks. When energy is needed, heat is transferred from the particles into a working fluid to generate electricity via a thermal power cycle or provide direct heat. To achieve this, particle and air mass flow must be precisely controlled. This study tested an L-Valve as a candidate for the particle conveyance, as it does not contain moving parts, is easily controlled, and requires minimal maintenance. Silica sand particles belonging to Geldart group D were used: particles with a mean diameter of 1157 ..mu..m and 825 ..mu..m. 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 L-valve, and air supply ranging from 1 to 5 SCFM. It was found that L-valves can effectively move particles of this size and the particle flow rate did not strongly depend on aeration point. These results support the use of an L-Valve as a viable option for particle flow for particle-based TES systems.