Mechanical Engineering
Ph.D Dissertation Defense

"TOWARDS A CARBON-FREE FUTURE FOR SOLAR THERMAL WITH NONIMAGING CONCENTRATORS"

 Yogesh Bhusal

Mechanical Engineering

University of California, Merced

Abstract:

Due to the pi-effect in tubular absorbers, the current commercial single-stage concentrating parabolic trough collectors are limited to the working temperature of 400°C with thermal oils and 550°C with molten salts. This work presents the design and development of a two-stage concentrating parabolic trough collector to surpass the working temperature of existing commercial systems and yield better conversion efficiency. The novel receiver developed in this work includes a nonimaging secondary concentrator designed to accept and further concentrate the wide-angle edge rays from the high rim-angle parabolic primary to the reduced size absorber. The receivers are designed and developed in commercially manufactured size and can replace the current commercial receivers but keep the same primary mirrors. The receivers with secondary concentrator would boost the concentration ratio of existing systems from 28X to 53X, surpass the working temperatures from ~500°C to ~650°C and beyond, and thus improve the solar-to-thermal-electric conversion efficiency  due to the reduced size absorbers.  In addition, the employment of the proposed secondary optics would homogenize the solar radiation flux on the absorber and prevent the uneven expansion related bending of the absorber tubes.

Biography:

Yogesh Bhusal is a Ph.D. candidate in the Department of Mechanical Engineering. He joined Prof. Winston’s lab (UC Solar) in the Spring of 2017 and has been working under his supervision to develop novel solar thermal collectors with nonimaging design for higher collection temperature and improved efficiency. Prior to joining UC Merced, he received a Bachelor’s  degree in Mechanical  Engineering  from Tribhuvan University in Nepal and worked as a hydromechanical design engineer for  3 years.