Abstract: A solar tracking mechanism utilizes a semicircle collector trough body having an inner concave surface having a focal point at the center of the circle defined by the uppermost flat surface of the trough body, the upper flat portion of the trough body normally being generally horizontally disposed. A plurality of solar collection modules mounted in a matrix about said concave surface, each of the modules comprising a radial passageway formed in the concave surface along a line intersecting the focal point. A strip of thermally expandable material mounted in the passageway with normally open switch means positioned adjacent said thermally expandable strip for switching an electrical circuit between on/off positions respectively responsive to expansion/contraction of said strip.