Abstract: The solar energy collector concentrates the sun's rays on a liquid medium that is used to power a mechanical energy device such as a positive displacement steam engine. A reflective surface of the solar energy collector is made from an arcuate portion of a circle having a trough-like surface to reflect and concentrate the sun's rays in a plane. A collector having a liquid medium flowing therethrough is located in the plane. The collector is constructed to extend across the entire plane for complete absorption by the liquid medium of the sun's rays reflected from the reflective surface. The collector and reflective surface are connected together for pivotal movement by an appropriate tracking apparatus so that the sun's rays are continually reflected during normal daylight hours through the plane in which the collector is located.