Evaluation of Performance Factors for a Multistage Falling Particle Receiver

An important factor identified for the efficiency of falling particle concentrating solar applications is the falling particle curtain opacity. Low curtain opacity results in increased radiative losses. Candidate multi-stage configurations that can increase particle-curtain opacity were simulated for the existing 1 MWth falling particle on-sun receiver at Sandia’s NSTTF. In the candidate configurations, falling particles were collected periodically in sloped troughs spanning the width of the receiver. A small lip at the front of each trough causes particles to accumulate, allowing subsequent particles to spill over. Particle surface boundary conditions were represented with an empirically based model created to approximate particle behavior observed in testing. Curtain opacity increased using a multi-stage approach and decreases in radiative losses were outweighed by decreases in advective losses which were the dominant loss mechanism. The ability to alter the flow of air within the receiver using multi-stage release resulted in the greatest efficiency gains by reducing advective losses. Additionally, multi-stage release substantially decreased back wall temperatures within receiver.