A solar concentrator may have a horizontal circular track on the ground, a tower centered on a vertical axis of the track, and a rotatable structure around the track having an upper, concave mounting surface approximating the shape of part of a sphere centered on the top of the tower. Articulated concave mirrors are attached to the rotatable structure, and the mirrors have a focal length approximately equal to the radius of a sphere portion formed by the concave mounting surface. Sunlight is focused at a receiver mounted atop the tower, and the receiver may convert sunlight into thermal or electrical energy. As the position of the Sun changes, sunlight is maintained on the receiver by turning the rotatable structure toward the Sun, turning the receiver about said vertical axis to face the mirrors, and articulating the mirrors toward the receiver in response to the changing elevation of the Sun.