Temperature responsive optical switch

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a thermally responsive optical switch for controllably reflecting incident light.
A thermally initiated phase change of an optically transparent fluid medium precipitates a light scattering layer resulting in substantial reflection of incident light.
The optical device is capable of automatically controlling the maximum temperature of a solar thermal energy conversion device by reflecting incident light energy whenever the device temperature exceeds a predetermined limit.
As illustrative thereof, in FIG.
1 there is shown the optical switching device of the present invention embodied in a solar energy converter.
The solar energy converter, hereinafter referred to as a solar panel, is a conventionally arranged solar collection device having a thermally insulated base and sidewalls 10 and 11, respectively, and a generally upwardly facing transparent window 12 comprising a major area surface of said panel.
A solar absorbing layer 14 may comprise any of a number of radiation absorbing materials such as black paint, black plastic and electroplated black chrome, known in the art to efficiently absorb solar radiation and generally described as having a surface region characterized as displaying an absorption coefficient in excess of 0.
90 throughout solar radiation wavelengths.
Absorber layer 14, here shown as vertically supported by sidewalls 11, defines a thermal exchange plenum 16 between said layer 14, base 10 and sidewalls 11.
In the operation of the solar panel, a thermal exchange media (not shown) such as air or water fills plenum 16.
Inlet and outlet conduits 18 and 20, respectively, provide means for filling and extracting the thermal exchange media from said plenum.
A second plenum 22 is defined by the upward facing surface of said absorber layer 14, the sidewalls 11 and the transparent window 12.
Plenum 22 is filled with an optically transparent solution (shown in FIG.
2 as 32) comprising a metal sulfate salt dissolved in a liquid solvent