Abstract
A particle-based pumped thermal electricity storage system stores high-temperature heat (∼1000 °C) in low-cost silica sand and generate power through an efficient power cycle. Central to this system is a counterflow direct-contact gas/particle fluidized-bed heat exchanger, which can significantly improve the heat exchange process due to large heat transfer surface area of particles. To showcase a lab-scale 10–20 kWe heat exchange process with particles heating up to 300 °C, a comprehensive hydrodynamic analysis of the fluidization condition inside the heat exchanger was conducted. The heat exchanger was designed to target for heat exchange process of 10 20 kW and accommodating air mass flow rate of 0.3–0.7 kg·s−1. The fluidization condition was set to maintain stable bubbling fluidization, thereby maximizing the particle-to-air heat transfer. An air distributor was designed to equally distribute air over the bed that can avoid de-fluidized zones in the heat exchanger. Additionally, particle handling systems including L-valves, screw conveyors, and pneumatic conveyors were developed for the prototype heat exchanger, efficiently conveying high-temperature particles at 0.2–0.5 kg·s−1. This work lays the foundation for scaling up the system and integrating it into larger energy storage applications, demonstrating its potential for efficient, high-temperature thermal energy storage and power generation.
