Parameter optimization of the parabolic solar trough mirror with a cavity receiver unit

Abstract

In this article, we discuss design approaches to a receiver enclosed in an opaque cavity and heated by a solar parabolic trough collector. Most cavity receivers are only capable of receiving radiation through an aperture, or “cavity window”, at a very limited angle. This paper discusses how to optimize a realistic interaction of a cavity receiver with the solar radiation from a collector mirror, which presents challenges not found in conventional receivers and is vital in order to benefit from the advantages of using a cavity sleeve. We needed our mirror to minimize the focal line to allow passage of the concentrated solar radiation through the aperture window and used COMSOL Multiphysics simulation software to obtain the heat map of radiation incident on the absorber pipe. We proposed three different focal plane positions relative to the receiver and found their efficiency regimes via our own simulations. We also determined the relative sizes of the receiver elements. A focal plane close to the surface of the absorber pipe was the most efficient in our temperature range, with maximum efficiency at 62%. We built an experimental cavity receiver and parabolic trough system guided by our generic simulations. We validated the simulation of our experimental setup against the measured data and found a maximum discrepancy of 8%. We also applied a novel method using the cooling behavior of the receiver to confirm our physical parameters via simulations. The results of this paper illustrate a novel, systematic method for integrating a parabolic collector mirror with a cavity-type receiver in a generic way.