The present invention relates to an improved solar energy concentrating system and to a preferred way of moving the receiver, along a curvilinear path above the mirror surface to the optimal location where the instantaneous concentration of reflected rays is the largest. The system comprises a fixed, trough concentrating collector formed with a concave curvature, shaped as a section of an spiral, oriented along the East-West axis, with a movable receiver, inclined facing South and capable of adjusting the angle of inclination periodically, preferably twice a year. The invention overcomes some of the limitations and is capable of capturing more solar energy, on a more constant basis throughout the year and at a lower cost than the preferred, state-of-the-art, trough parabolic concentrating collectors oriented along the North South axis.