Proposed experimental results from the solar tracker show the power usage of the tracking motors throughout the day and the tracking error. A pole and slider mechanism is used with an electronic sensor which allows the parabolic dish to follow the sun throughout a typical day. In this paper the method of tracking for the experimental setup is discussed.
Two-axis tracking is required to align the parabolic dish with the sun. For this study a 4.8 m diameter parabolic dish reflector with rim angle of 45° is required for an experimental setup to reflect sun rays onto a receiver which heats the working fluid. Solar thermal Brayton cycles utilise concentrated sun rays and can be used to power micro-turbine generators. Methods of improving the tracking accuracy are given in the paper. SolTrace results show that for the proposed dish and receiver, assuming a 10 mrad optical error, a tracking error of 1° is acceptable however, tests show that the proposed experimental setup has a tracking error of 2°. Experimental results show the tracking error of a proposed solar tracking sensor throughout a typical day. The effects of tracking errors and optical errors on the net heat transfer rate and heat flux of the proposed solar receiver in the experimental setup are investigated with SolTrace as ray-tracing tool. The collector of the experimental setup consists of an 18 m 2 parabolic dish on a two-axis solar tracking system with a rectangular open cavity tubular receiver.
An experimental setup of this cycle is currently underway at the University of Pretoria to study the benefits of using entropy generation minimisation as optimisation tool for the system components. The small-scale open solar thermal Brayton cycle can be applied to generate electricity in Southern Africa.
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