NOVELTY - The element has a reflective sheet (1) e.g. glass sheet, provided with a reflective coating for reflecting solar radiation, a corrugated metal reinforcement sheet (2) and a foam layer (3) arranged between the reflective sheet and the reinforcement sheet. Thicknesses of the glass sheet, the reinforcement sheet and the foam layer are 0.8-4 mm, 0.5-1.5 mm and 20-200 mm, respectively. Density of foam e.g. rigid polyurethane foam, is 30-80 kg per cubic m. A surface of the reflective sheet and/or the reinforcement sheet in contact with the foam layer includes a coating to increase adherence.    USE - Sandwich-type composite reflective element for anchoring to a bearing structure of a heliostat (claimed) for producing electric power from a solar radiation.    ADVANTAGE - The element is formed in a single manufacturing step by eliminating mirror-under frame duality, thus providing a self-supporting composite reflective element for being anchored directly to a bearing structure of a heliostat without the need for intermediate support elements. The element is light-weight and economical to manufacture. The reflective sheet can be made of plastic, metal or glass sheet so as to assure the required reflection properties. The reinforcement sheet presents a corrugated profile to increase the flexural rigidity of the composite reflective element, thus minimizing the tensile stresses on the reflective glass sheet. The element utilizes a metal grid structure as reinforcement so as to increase the mechanical strength of the assembly and minimize the tensile stresses on the reflective glass sheet. The glass sheet is not exposed, so that the risks of breaking during the solar field maintenance operations can be minimized, thus preventing the element from accidentally breaking during mounting operations. The sheet of mirror remains in contact with the adhesive even if the element is broken, thus enabling the element to carry out the function of reflecting radiation continuously.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for manufacturing a reflective element.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a planar composite reflective element.    Reflective sheet (1)    Corrugated metal reinforcement sheet (2)    Foam layer (3)