Performance feedback & control of solar concentrators using wave front sensing techniques

The major requirement for using concentrating Solar Thermal devices is the proper placement of the focal spot on the absorber to provide heating of the working fluid to produce thrust or to generate electricity. Without proper placement of the focal spot, either in a spacecraft or ground unit, solar energy is not transferred to the propellant or working fluid or at best case, a significantly smaller proportion of the incident energy is transferred to the fluid.; A control system is needed for ground units to track the Sun across the sky or to track the Sun as the spacecraft maneuvers. The control system would use a fine focus controller after acquiring a general location for the Sun. Fine focus was discussed for a 0.1 degree Sun misalignment and 0.1 inch offset in focal spot location.; The research problem is to: (1) develop a sensor that provides information about the location of the focus beam from the concentrator that also can tolerate the extreme temperatures involved in providing solar heating, and (2) develop the mathematics of a control system that will focus the concentrator in an optimal fashion based on the sensor measurements. The sensor developed in this dissertation solves the temperature issues by using the absorber as a wave front Sensor and imaging that device with a Charge Coupled Device (CCD) to determine the location of the focal beam.; A hardware model of the absorber and concentrator was used to generate images for analysis. Images generated with the hardware models are analyzed by first searching the images for intensity areas on the sensor, and then profiles of the intensity areas are integrated to find centroids of the intensity areas. Once the centroid is found for the intensity areas, the controller can generate commands to move the focal beam to proper focus.; Results from this research indicate that the modified wave front Sensor method worked and provides control information to properly control the concentrators to provide optimal heat transfer to the heating fluid.