Experimental and numerical evaluation of drift errors in a solar tower facility with tilt-roll tracking-based heliostats.

In this work, we experimentally and numerically evaluate the drift errors in a solar tower facility with tilt-roll tracking-based heliostats. For this investigation, the solar tower facility located at IMDEA Energy in Móstoles (Spain) is used as a test case. By acquiring flux maps at different times of the day and representing their maximum irradiance point as a function of the time, the drift is evaluated experimentally. We observed that the experimental drift can be divided in two components, vertical and horizontal, with a constant velocity of the maximum irradiance point of -7.4 cm/h and 2.2 cm/h, respectively. In order to investigate the source of the drift observed in the experiment, detailed Monte Carlo ray-tracing simulations including possible misalignments in the heliostat tracking system were performed. We found out that by considering rotations of the heliostats pedestal, the experimental drift is very well reproduced by the simulations. In particular, for a rotation of the pedestal of 17 mrad towards the east, the velocities of the maximum irradiance point in the simulations are -7.6 cm/h and 1.1 cm/h for the vertical and horizontal drift components, respectively. [ABSTRACT FROM AUTHOR]

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