A solar furnace consists of an evacuated chamber with transparent windows, through which concentrated solar radiation is passed. Concentration may be achieved by mounting the furnace at the focal point of a large curved reflector that tracks radiation incident directly from the sun. The furnace may be used to evaluate the behavior of materials at elevated temperatures, and we wish to design an experiment to assess the durability of a diffuse, spectrally selective coating for which ?? = 0.95 in the range ? 4.5?m. The coating is applied to a plate that is suspended in the furnace.

(a) If the experiment is to be operated at a steady-state plate temperature of T = 2000 K, how much solar irradiation GS must be provided? The irradiation may be assumed to be uniformly distributed over the plate surface, and other sources of incident radiation may be neglected.

(b) The solar irradiation may be tuned to allow operation over a range of plate temperatures. Compute and plot G s as a function of temperature for 500

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Direct solar radiation Transparent window Plate, T Gs Gs Vacuum Concentrating solar reflector