Abstract
Shaped-glass evacuated solar collectors have the lower portion of the tubular glass vacuum envelope shaped and inside surface mirrored to concentrate sunlight onto an absorber tube in the vacuum. Upon evacuation, stresses are set up in the glass. The maximum surface tensile stress possible in glass, while keeping the probability of fracture small, is of the order of 7 MPa. This low maximum tensile stress places severe limitations on the amount the lower portion of the cross section of a cylindrical glass evacuated solar collector can deviate from circular to provide the concentration. Equations are developed for determining stress in the glass. Results of stress calculations leading to parameters for collector design are presented.
Published Version
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