This paper deals with the experimental study of a parabolic concentrator prototype designed and tested in the UFHB solar energy laboratory. Its reflector is made of galvanized sheets. In order to take full advantage of the incident solar rays, a glass cubic box wraps the focus. In addition, as the diameter of the solar point in the home is small, it has been increased through the back axial distance from  the focal point. This back axial distance has been optimized by the Lagrange multiplier’s method. Thus, during the tests, the base of the pan remains at the back axial distance of the focal point. Experimental tests were carried out with and without the glass cubic box. Although the reflector is coated with galvanized sheets whose reflection coefficient is lower than that of the mirror, the experimental tests performed gave satisfactory results. Due to the cubic glass case  around the focus and the rear axial distance used, the energy losses were reduced as well as the cooking times.

parabolic solar cooker, glass cubic box, back axial distance of the focal point, Lagrange multiplier’s method, performance.