train the backing dish 35 may be attached to the support column 36 by a suitable means such as a gimbal which provides freedom of movement in azimuth and elevation or a more restricted sliding tongue and groove arrangement the above is only an example of a tracking mechanism the exact means for accomplishing tracking movement of the reflector surface 15 and its supporting structure 13 and 35 are seen as being well within the purview of a person of ordinary skill in the art and will not be further discussed the polymeric film 15 that forms the reflecting surface of the concentrator of the present invention is preferably an aluminized polymeric plastic which has a high modulus of elasticity such as a surface cross linked polymer or a polymer metal composite this plastic film is mounted on a supporting hoop 13 which in turn is fastened to a backing dish 35 in a manner that forms a sealed interior 49 between the reflecting surface 15 and the backing dish 35 by drawing a vacuum on this formed interior 49 by means of a suitable vacuum pump 45 through umbilical cord 47 the highly elastic reflecting surface 15 is deflected in a convex manner as illustrated by dashed lines 46 thereby forming a three dimensional concentrating surface the reflecting surface 15 can be shaped into a surface curvature that can be either a catenary of revolution 53 a parabolic dish 57 or a hemi spherical dish 61 depending on the loading on the surface of the reflecting membrane 15 a catenary of revolution 53 is.