Mechanical Engineering ETDs

Publication Date

Winter 12-7-2020

Abstract

Falling particle receiver (FPR) systems are a rapidly developing technology for concentrating solar power applications. Solid particles are used as both the heat transfer fluid and thermal energy storage media. Through the direct solar irradiation of the solid particles, flux and temperature limitations of tube-bundle receives can be overcome leading to higher operating temperatures and energy conversion efficiencies. Particle residence time, curtain opacity, and curtain stability affect the performance of FPR designs. As the particles fall through the receiver the curtain accelerates, increasing its transmissivity thus decreasing the amount of energy absorbed. Multistage release trough structures catch and release the particles to decrease their downward velocity and regroup the freefalling curtain thus increasing curtain opacity and particle residence time while also improving curtain stability. A novel Staggered Angle Iron Receiver (StAIR) multistage release concept was tested at a small scale before being implemented in a 1 MWth receiver. The sloped angle iron troughs feature a front lip that accumulates the falling particles allowing subsequent particles to spill over thus passively decelerating the particles and ensuring a more stable curtain behavior. The effect the staggered angle iron geometry, vertical position, horizontal position, and orientation have on curtain transmissivity were studied at linear mass flow rates between 3.9 and 11.8 kg/s per meter of curtain width. Curtain transmissivity was measured 12” below a trough and compared to the freefalling curtain of the same mass flow rate. Trough vertical position and geometry had a larger effect on curtain transmissivity than trough orientation and horizontal position. A hybrid trough geometry located 36” from the curtain origin at a mass flow rate of 4.1 kg/m/s resulted in the largest gain in curtain opacity when compared to a freefalling curtain with an opacity of 60% for the freefalling curtain and 86% for the curtain following the trough. Two and three troughs were then tested in series to determine their effect on particle bounce and transmissivity. An optimal trough position and geometry was selected to be tested in an on-sun 1 MWth receiver test campaign. Cold flow tests inside the receiver were conducted to ensure particle attrition through the receiver aperture was not significantly higher than that of a freefalling curtain. On-sun testing was conducted with one and two trough configurations. Receiver efficiency and back wall temperatures were measured to determine the StAIRs performance.

Keywords

Falling Particle Receiver, Multistage Release, G3P3, StAIR

Degree Name

Mechanical Engineering

Level of Degree

Masters

Department Name

Mechanical Engineering

First Committee Member (Chair)

Gowtham Mohan

Second Committee Member

Peter Vorobieff

Third Committee Member

Clifford K. Ho

Document Type

Thesis

Language

English

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