Abstract
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 (ηre-opt,loss) and minimum value of the optical efficiency (ηopt) 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 ηopt 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 ηre-opt,loss is 0.116%, which means the proposed the FFFSC can achieve fixed-focus.
Highlights
Serious environmental problems which affect human health due to fossil fuel consumption have drawn worldwide awareness in recently years [1,2]
The fixed-focus Fresnel lens solar concentrator (FFFSC) has the advantages of lower manufacturing cost than that of azimuth-elevation tracking systems and lower energy consumption by concentrating sunlight to a fixed small heat-receiving area in tracking the sun compared with that of the solar receiver needed to rotate with the solar concentrator
As can be observed in the table, the relative optical efficiency loss between the experimental group and the reference is lower than 1.87%, which means the FFFSC can achieve a fixed-focus in the experiment
Summary
Serious environmental problems which affect human health due to fossil fuel consumption have drawn worldwide awareness in recently years [1,2]. In order to ensure that the point-focusing systems can receive maximum solar irradiation at all times, a two-axis sun-tracking system is always used in the solar system, especially azimuth-elevation tracking systems. Alexandru et al [19] designed a polar dual-axis system for improving the energetic efficiency of a photovoltaic panel, it can reduce the angular field of the daily motion and the number of actuating operations, without significantly affecting the incoming solar energy. The FFFSC has the advantages of lower manufacturing cost than that of azimuth-elevation tracking systems and lower energy consumption by concentrating sunlight to a fixed small heat-receiving area (fixed-focus) in tracking the sun compared with that of the solar receiver needed to rotate with the solar concentrator. The optical performance of the FFFSC is tested experimentally and simulated numerically, considering the effects of different solar times, tracking errors, and periodical adjustment errors
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