A solar stove using a giant Fresnel lens has been developed in the Energy and Fuel Cell Laboratory at the University of Arizona. Solar tracking is required to control the Fresnel lens to maintain a stationary focal point on the heat transfer surface of the solar stove. A two-axis passive control system for solar tracking is adopted. Characteristics of the optical system are analyzed in order to find a reasonable tracking and adjustment frequency and overall system control accuracy. Defocus of the lens due to the angular offset (related to tracking resolution) of the lens’ axis versus the sunray and the change of the shape of the focal point on a static plate is calculated. The results of the analysis are used in the design of the control algorithm which has been implemented in the control system of the prototype solar stove. The proposed tracking scheme is expected to improve heat collection, thermal protection and thereby reduction of heat loss in the solar stove.

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