Research on the compensation of the end loss effect for parabolic trough solar collectors

In this paper, an optical analysis on the end loss effect of parabolic trough solar collector (PTC) with horizontal north-south axis (PTC-HNSA) is performed, and a method to compensate its end loss effect is presented. The calculation formulae for the optical end loss ratio and the increased optical efficiency (the optical collection efficiency increment of PTC system after this compensation method is used) are derived; the daily optical end loss ratio, yearly optical end loss ratio, daily increased optical efficiency and yearly increased optical efficiency in different latitudes are calculated; the variation of optical end loss ratio and increased optical efficiency with trough's length and latitude angles are analyzed and discussed. It is indicated through the analyses that this compensation method is very applicable for regions with the latitude over 25° (especially over 30°) and short trough collectors. In order to verify the feasibility of the compensation method, a five-meter PTC-HNSA experimental system was built. The increased thermal efficiency of the experimental system is measured, and the result that the experimental value (increased thermal efficiency) substantially agreed with the theoretical value (increased optical efficiency) is gained. All these works can offer some valuable references to the further study on high-efficiency trough solar concentrating systems.