Temperature responsive optical switch

Claim 1

Means for providing automatic over-temperature protection for solar thermal energy conversion devices by controllably reflecting incident light energy whenever said device exceeds a predetermined temperature limit, said means comprising: solar radiation absorbing means for converting light energy into heat energy; a layer of optically transparent fluid, contiguous to said solar radiation absorber and interposed between said absorber and a source of said light energy; a predetermined amount of a solute comprising a metal sulfate salt in solution with said fluid, said solute being characterized as having decreasing solubility with increasing solution temperature, and said amount of solute being predetermined as the amount necessary to saturate said solution at said predetermined temperature limit; container means having at least one optically transparent window, said container means retaining said fluid contiguous to said absorber and maintaining an interpositioning of said fluid between the radiation absorber and said transparent window whereupon said absorber attaining a predetermined temperature, said sulfate salt precipitates from said solution to form a light scattering layer between said absorber and said source of light energy, reflecting said light and reducing the temperature of the solar absorber.