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Flux density measurement applied to central receiver systems delivers the spatial distribution of the concentrated solar radiation on the receiver aperture, measures receiver input power, and monitors and might control heliostat aimpoints. Commercial solar tower plants have much larger aperture suifaces than the receiver prototypes tested in earlier research and development (R&D) projects. Existing methods to measure the solar flux density in the receiver aperture face new challenges regarding the receiver size. Also, the requirements regarding costs, accuracy, spatial resolution, and measuring speed are different. This paper summarizes existent concepts, presents recent research results for techniques that can be applied to large-scale receivers and assesses them against a catalog of requirements. Direct and indirect moving bar techniques offer high measurement accuracy, but also have the disadvantage of large moving parts on a solar tower. In the case of external receivers, measuring directly on receiver suifaces avoids moving parts and allows continuous measurement but may be not as precise. This promising technique requires proper scientific evaluation due to specific reflectance properties of current receiver materials. Measurement-supported simulation techniques can also he applied to cavity receivers without installing moving parts. They have reasonable uncertainties under ideal conditions and require comparatively low effort. [ABSTRACT FROM AUTHOR]

The design and manufacture of a two-axis sun tracking system (rotation-elevation), which controls a heliostat of a solar furnace for clay brick firing is presented. The system works with motors controlled through a personal computer. The algorithm for the sun tracking system was developed in a visual programming language, calculates the primary and secondary tracking angles of the heliostat and shows them in a screen. The microcontroller is programmed to control the step driver engines, which move the heliostat of the solar furnace. The primary and secondary tracking is the same for the equinoxes, whereas for the solstices are different because the solar altitude is greater in summer than in winter in the northern hemisphere. The sun tracking system permits a more efficient capture of the solar radiation since it continuously follows the apparent movement of the Sun. [ABSTRACT FROM AUTHOR]