Dome Window and Mount Design for a 5 MWth Solar Receiver

Abstract

Large windows are being evaluated for use in high temperature concentrated solar receivers to reduce radiative and convective losses, maintain a differential pressure, and separate reactants from ambient air in receivers for chemical processing. The design of a 1.7 meter diameter fused silica dome window is evaluated for its ability to maintain acceptable stresses when exposed to pressure differentials and large heat loads from solar irradiation and re-radiation from inside the receiver. The dome must be ableto withstand the operational pressure differential of 0.5MPa where the efficiency of the solar receiver combined with a recuperated gas turbine is maximized, and glass temperatures upwards to 800°C may be observed. Brittle materials like glass need the tensile stresses to be reduced to maximize the reliability of the dome window. However, glass does not possess a characteristic strength and it is dependent on the flaw size. Careful attention to the dome mount must be taken to minimize tensile bending stresses that can cause a catastrophic or rapid failure while maintaining an environmental seal.The Weibull failure probability method is used to arrive at a projected lifetime of the window under a constant state of stress. This stress is used to determine the maximum design stresses allowed during operation of the solar receiver. Window heat fluxes from a Monte Carlo Ray Trace of the heliostat field and receiver re-radiation is utilized to couple the thermal mechanical effects of the window and its mount. A finite element analysis (FEA) is presented evaluating the stresses when considering the heat absorption in the window from transmitted light and re-radiation from within the solar receiver, combined with the applied pressure differential between the solar receiver and atmospheric conditions. The preliminary design of the window shape, thickness, and mounting strategy is presented.