Analysis of glint and glare produced by the receiver of small heliostat fields integrated in building façades. Methodology applicable to conventional central receiver systems

Abstract

The “Vertical Heliostat Field” (VHF) concept proposes a solution to integrate solar heliostat fields into urban communities with acceptable optical efficiencies for Concentrating Solar Power systems. It is based on a heliostat field arranged on a vertical surface, conceived to be integrated in a building façade. The glare phenomenon has been identified as a critical aspect for a VHF facility integrated in an urban environment and a potential source of hazard to nearby drivers, pedestrians or neighbors. The main goal of this work is the analysis of potential ocular hazards produced by the VHF. On the bases of the previous formulation, there has been developed a mathematical methodology that has led us to propose a series of general equations and graphs to characterize glare phenomenon produced by the receiver of a VHF, which are also applicable to conventional CSP central receiver facilities. The analysis focuses on temporary and also permanent eye damage hazards. In case of the receiver, the surface delimiting the border for permanent risk and temporary blinding is defined by the distance and the direction (angle) where the observer is placed, relative to the receiver. Thus, this border results in a revolution surface, whose largest section is obtained on the plane perpendicular to the plane of the receiver aperture. General graphs are presented, corresponding to those sections, depending on DNI and optical efficiency of the field and normalized by an areas factor. Integration of a VHF in a urban environment will always imply the establishment of an exclusion zone for vehicles and pedestrians.