Thermally stabilized heliostat

Claim 1

In a heliostat for reflecting solar energy onto a collector including: a. a main support structure; b. means for pivoting and tilting said heliostat so as to keep said solar energy focused on said collector, and c. a plurality of mirror modules for reflecting said solar energy; the improvement comprising having each said mirror module thermally stabilized against curvature induced by temperature changes and comprising: d. internal support structure having sufficient rigidity to support said mirror cantilevered from said main support structure and to withstand predetermined loads; e. front and back sheets attached to said internal support structure; said front and back sheets having the same coefficient of thermal expansion such that no curvature is induced by temperature changes; said front and back sheets having adequate structural strength to stabilize said internal support structure; and f. a layer of adhesive grease adhering said mirror to said front sheet; said adhesive grease being water repellant and having adequate set strength to support said mirror and having sufficient shear tolerance to permit differential expansion of said mirror and said front sheet when the temperature changes without inducing stresses or curature effects; said adhesive grease being adapted to prevent fluttering of said mirror with respect to said front sheet and to protect the mirror backside against the adverse effects of weather.