(511h) Correction of the DRIFT in Solar Tracking Systems through Closed LOOP Control

Two-axis solar tracking systems in solar concentration applications require greater precision in the automatic tracking of the apparent position of the Sun, this in order to keep the focal area in a fixed position with respect to the focal axis of the concentrator system, since that a slight variation translates into a deviation of the concentrated sun image from the area of interest. This work focuses on the discussion of the methods implemented to solve the problems of drift and correction of elevation angles and azimuths in solar tracking systems.

The proposed method is based on an open loop control system in which the angles of the solar vector (azimuth and elevation) are calculated using a solar position algorithm. For the closed-loop control system, two types of feedback were implemented, the first refers to an algorithm for image processing obtained by a digital camera that directly observes the sun, thus allowing a position correction to be obtained in both axes of the monitoring system.

The second feedback sensor is based on an adjustable peephole which consists of a cylindrical body with four cylindrical tunnels longitudinally angled and distributed orthogonal to each other at the same radial distance, which house an LDR photoresistor that provides a voltage. proportional to the sunlight incident on them. This voltage is translated into a position correction angle on the two tracking axes.

To carry out the evaluation of the drift correction, three two-axis solar tracking systems were used. A 36 m2 Heliostat (E3) and a parabolic mirror solar tracker (2M) located in the Hermosillo Solar Platform, Sonora, Mexico. The third monitoring system used is a Fresnel-type solar concentrator for the characterization of photovoltaic cells (FRESNEL) located at the IER-UNAM in Temixco, Morelos, Mexico. The results obtained from the comparison of the open-loop and closed-loop control by analyzing the drift of the concentration spot of the three monitoring systems are discussed.

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