Optical Efficiency Impact of OffAxis Aberration on 100 kW Beam Down Optical Experiment

  • Juliana Beltran Torres

Student thesis: Master's Thesis


Concentrated Solar Power (CSP) technology provides solar power with the capability of day-night energy storage. This technology has been under development for more than four decades and these developments have led, over the years, to changes that improve efficiency and simplicity of CSP plants as well as reduce operating and initial cost per unit annual yield. The Masdar Beam-Down Optical Experiment (MBDOE) is a 100-kWth CSP pilot project at the Masdar Institute Solar Platform. This project begins as a modification to a typical central receiver layout of heliostats and a central tower. In this case, there is a double reflection arrangement, in which solar beam radiation (DNI) is reflected first from the heliostat banks towards the central reflector mirrors at the top of the tower. The second reflection is from the central reflectors towards the inlet aperture of a thermal receiver, which is located close to the ground at about 25% of tower receiver height that would be required in this size plant. The purpose of this thesis is to investigate how the optical efficiency can be improved by changing the configuration of the heliostat banks and applying an off-axis correction. The MBDOE was designed with azimuth-elevation heliostats which are commonly used in the industry. In this thesis we will analyze the same plant but with spinningaxis heliostats, which have shown promise in conjunction with on central tower CSP systems. First of all, a previously created ray-tracing model was translated from Matlab into Python. The Python program is then coupled with TracePro software for raytracing simulation [1]. Simulations were carried out for various zenith and declination angles which cover the range of sun position throughout a full year. The optical efficiency of the heliostat-central reflector subsystem is calculated to show the improvement, relative to the existing altitude-azimuth heliostat, of using a spinningaxis heliostat configuration. Optical efficiency is calculated in parts to show the relative optical losses associated with shading, blocking, and spillage around the central reflector mirrors. A final modification was done to the model, in which an off-axis correction of heliostat facet canting is implemented. The reduction in spillage (intercept factor improvement) is reported as function of solar zenith angle and declination.
Date of AwardDec 2016
Original languageAmerican English
SupervisorPeter Armstrong (Supervisor)


  • Concentrated Solar Power
  • Solar Power Technology
  • Masdar Beam-Down Optical Experiment
  • Masdar Institute
  • Optical System.

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