• Energy Research

Parabolic reflectors, also known as parabolic troughs, are widely used in solar thermal power plants. This kind of power plants is usually located on desert climates, where the combined action of wind and dust can be of paramount importance. In some cases it becomes necessary to protect these devices from the joined wind and sand action, which is normally accomplished through solid windbreaks. In this paper the results of a wind tunnel test campaign, of a scale parabolic trough row having different windward windbreaks, are reported. The windbreaks herein considered consist of a solid wall with an upper porous fence. Different geometrical configurations, varying the solid wall height and the separation between the parabolic trough row and the windbreak have been considered. From the measured time series, both the mean and peak values of the aerodynamic loads were determined. As it would be expected, mean aerodynamic drag, as well as peak values, decrease as the distance between the windbreak and the parabolic increases, and after a threshold value, such drag loads increase with the distance.

Abstract The present study focuses on the wakes of two wind turbines that, depending on the wind direction, experienced different degrees of interactions, by processing field wake observations made from a 7-month ground based scanning LiDAR measurement campaign. This duration ensures an acceptable statistical convergence of the ensemble-averaged flow fields obtained after a classification according to the wind speed at hub height and the wind direction, and limited to neutral atmospheric stability. The mean flow fields showed a well-defined wake evolution for all configurations. As expected, the wake centerlines are aligned with the wind direction, however when wakes are in intermediate interaction, wakes centerlines are skewed. This has been imputed to the wake center determination method, which is not appropriate to dissociate multiple wakes. For the lower degree of interactions, the mean wakes are aligned. However the standard deviation of the instantaneous wake centerlines shows the mutual influence that one wake has on the other. Obtained results showed an increase in the turbulence intensity within the wake, but an asymmetric distribution was observed. Listing the possible reasons, no plausible explanation has been found. The wake meandering had been quantified by the standard deviation of the instantaneous wake centerlines, showing that this phenomenon is amplified by the level of interactions. The velocity deficit recovery showed a good agreement with proposed models, as soon as there is no neighboring wakes. If that is the case, the velocity deficit is increased in function of the position of the neighboring rotor.