Simulation and experimental study on the optical performance of a fixed-focus Fresnel lens solar concentrator using polar-axis tracking

Most sun-tracking systems of solar concentrators are expensive, sensitive to operational costs, and complicated in optical design in which the receiver must be free to rotate about the axis. To overcome the aforementioned problems, this study presents a fixed-focus Fresnel lens solar concentrator (FFFSC) using polar-axis tracking which allows the Fresnel lens to concentrate sunlight to a fixed small heat-receiving area and the receiver remained fixed in location and rotation. Experimental research has been conducted to obtain the optical characteristics of the FFFSC for different solar times, tracking errors, and periodical adjustment errors. It has been found that maximum values of the relative optical efficiency loss (η_re-opt,loss) and minimum value of the optical efficiency (η_opt) of the FFFSC for different solar times are 1.87% and 71.61%, respectively. The mean value and maximum value of the local concentration ratio of the solar flux on the receiver are more than 86.64 and 1319.43, respectively. When the tracking error and periodical adjustment error are within 1°, the η_opt of the FFFSC can reach 70.38% and 68.94%, respectively. The optical characteristics of FFFSC is also verified numerically. Especially, according to the total year simulation of the FFFSC's optical characteristics, maximum value of η_re-opt,loss is 0.116%, which means the proposed the FFFSC can achieve fixed-focus.