Session: 07-01: Technoeconomic Analysis of CSP Receivers and Particle Storage Technologies

Paper Number: 131538

131538 - Novel Particle Flow Control Using a Scoop Mechanism for Concentrating Solar Applications 

Abstract: 

Robust solid oxide particles have been identified as promising alternatives to molten nitrate salts (solar salts) currently used as heat transfer media (HTM) concentrating solar power (CSP) plants due to the ability of particles to operate at temperatures >750°C [1]. Despite the high energy density and ease of transport of solar salts, their operating temperatures between 290°C and 565°C, make them unviable as the HTM required for high-temperature CSP with thermal energy storage (TES) [2]. Pairing CSP-TES systems with next-generation highly recuperated Brayton power cycles that use supercritical carbon dioxide (sCO2) as the working fluid promises higher efficiencies and affordable, dispatchable electricity than conventional Rankine power cycles. These systems require heat to be delivered to sCO2 at temperatures, >700°C which can be delivered by oxide particles.

Most particle CSP-TES systems under development and on test sites implement a sliding-gate mechanism at the inlet and outlet hoppers of heat exchangers, receivers, and particle storage tanks for particle flow control [3]. With a sliding gate mechanism, there is always the tendency for particles to get stuck between the moving parts of the gate causing particle attrition and/or component wear. The friction associated with this development leads to frictional build-up that increases the resistance to the opening and closing of gates during testing and operations over time. Implementing sliding gate designs in falling curtain particle receivers and multi-channel heat exchangers also presents the challenge of the uniform flow of particles desired in these operations. Designing robust particle flow control systems that are easy to regulate, uniformly distribute particles, and do not grind against particles to not cause any wear on these particles or the gate components has been a challenge until now.

The design of a 40-kW_th multiple narrow channels fluidized bed heat exchanger led to the design of a novel particle flow control system that operates with a scoop mechanism. The scoop mechanism employed here relies on the angle of repose of particles to control flow with particles grinding against themselves or the gate.  This design presented here encourages the uniform flow of particles under the influence of gravity devoid of funnel flow. The operating mechanism involves a shaft controlled by a fan-cooled servomotor connected to an angled scoop that sits right at the bottom of the hopper. This rotary particle control scoop is displaced through an angle to allow the flow of particles over the edge along a line as a falling curtain that spans across the edge of the scoop uniformly. At the maximum opening angle of the particle scoop, CARBOBEAD HSP 40/70 particles flow from the scoop at particle flow rates  0.5 kg s^-1 supporting particles from a hopper that stores up to 35 kg of particles at room temperature and pressure. The servomotors also allow the scoop to learn angular positions as a function of motor position in CNTS that reproduce consistent flow rates over time and cycles. The scalability of this scoop mechanism provides a roadmap to full-scale CSP-TES systems that have reliable, robust particle flow controls.

[1]  N. Siegel, M. Gross, C. Ho, T. Phan, and J. Yuan, “Physical properties of solid particle thermal energy storage media for concentrating solar power applications,” in Energy Procedia, vol. 49, R. Pitchumani, Ed., 2014, pp. 1015–1023. doi: 10.1016/j.egypro.2014.03.109.

[2]  C. K. Ho, “Advances in central receivers for concentrating solar applications,” Sol. Energy, vol. 152, pp. 38–56, Aug. 2017, doi: 10.1016/J.SOLENER.2017.03.048.

[3]  K. J. Albrecht, H. F. Laubscher, C. P. Bowen, and C. K. Ho, “Performance Evaluation of a Prototype Moving Packed-Bed Particle / sCO 2 Heat Exchanger,” no. September, 2022.

Presenting Author: Gregory S. Jackson Colorado School of Mines

Presenting Author Biography: Prof. Greg Jackson has served in academia for 25 years including as Dept. Head of Mechanical Engineering at Mines from 2013-2017. Before joining Mines in early 2013, Jackson was a faculty member for over 15 years at the University of Maryland in the Dept. of Mechanical Engineering and in their campus-wide Energy Research Center, for which he served as Associate Director for several years.

At Mines, Dr. Jackson’s research group focuses on concentrated solar energy, high-temperature energy storage, and solid-oxide electrochemical systems. Dr. Jackson has led several research efforts on both reactive and inert oxide particles for high-temperature energy storage for concentrating solar power applications. He has published broadly on materials and processes for high-temperature catalysis and electrochemistry for a range of energy conversion applications. His group looks at a wide scale of phenomena from fundamental material characterization and modeling to full-scale system design and optimization.

Authors:

Winfred Arthur-Arhin Colorado School of Mines
Jesse R. Fosheim Brayton Energy/ Colorado School of Mines
Azariah Thompson Colorado School of Mines
Keaton J. Brewster Colorado School of Mines
Gregory S. Jackson Colorado School of Mines