Drift is ubiquitous in heliostat fields, and may be caused by diverse geometrical inaccuracies during heliostat installation and operation. This phenomenon is studied for three important primary errors in the present paper: Angular offset in the drive mechanism, pedestal tilt, and canting error. Each error produces characteristic signatures, but there is a diversity of behavior depending on the error parameters and location of the heliostat. The variation of the extent of drift curves is studied as a function of distance, for fixed error parameters. It is found that, in general, this extent is not proportional to distance, except for far heliostats, and depends on a complicated manner on the different parameters involved. Moreover, even though the extent of drift curves becomes proportional to distance for far heliostats, the convergence is very slow, and very variable with the error parameters. V C 2014 AIP Publishing LLC. [http://dx.

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Heliostat image drift is defined as the wandering of the irradiance spot produced by a heliostat on a receiver or observation screen. Two factors producing heliostat image drift have been analyzed theoretically in the present paper: errors in reference position, and time delay. Some regular behavior is found in the drift curves. Maximum deviations from target tend to be linearly dependent with either angular error, or time delay. In particular, the curves produced by this later effect are circular or elliptical. Heliostats at different distances from a tower have been analyzed. For heliostats far from the tower the drift curves due to errors in reference position also have a more or less elliptical shape. Results are presented as dimensionless quantities. Some practical implications of these results are discussed.

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