INTRODUCTION

This functionality if FluxTracer is used for calculating the flux distribution on surfaces, i.e. Figure 1. Currently, the functionality supports calculation of the flux on cylindrical receivers and flat surfaces. As for most of FluxTracer's functionalities, in the ray-tracing simulations the user should not include any receiver at the focal point of the concentrating system, but instead, a virtual surface (plane) should be present above the focal point. Within Tonatiuh, the different segments that define a ray can be identified based on their interceptions with the surfaces of the solar concentrating system. For this case, the ray segments that are saved for post-processing are those that are reflected by the heliostat field and reach a "virtual" plane that is placed at an appropriate distance over the focal point. Virtual here means that the plane's optical properties are treated so as to allow the rays to pass freely from the light source surface (i.e. the sun) to the heliostat field without changing any of their characteristics, but the reflected rays form the heliostat to the virtual plane are stopped on the latter. The absence of a receiver in the ray-tracing simulations and the addition of the virtual plane, allows obtaining rays from Tonatiuh which are independent of the receiver size and dimensions and spatial position.

FLUX ON FLAT SURFACE

For generating the flux on a flat surface, the user needs to specify the following parameters as shown in Figure 2:

• Xmin and Xmax, Ymin and Ymax, designating the dimensions of the plane
• Xdivs and Ydivs, designating the number of bins to divide the plane in order to calculate the flux
• Z coordinate designating the vertical position of the plane

Of course, the user may ask FluxTracer to evaluate the flux on a number of surfaces simultaneously (i.e. of different Z positions) just by running FluxTracer once. The output of the functionality is a .vtk file.

FLUX ON FLAT CYLINDRICAL SURFACE

For generating the flux on a cylindrical receiver surfaces, the user needs to specify the following parameters as shown in Figure 3:

• rho, designating the radius of the receiver to evaluate the flux
• phiDivs, designating the number of divisions to divide on the circumferential direction
• Zmin and Zmax coordinates designating the height of the cylindrical surface
• Zdivs, designating the number of division on the vertical direction

Of course, the user may ask FluxTracer to evaluate the flux on a number of cylindrical surfaces simultaneously (i.e. of different radii) just by running FluxTracer once. The output of the functionality is a .vtk file.