A solar energy concentrator assembly comprises flexible polymeric sheet which carries an integral optical element in the form of a Fresnel lens for concentrating a substantial amount of incoming solar radiation on a desired location on the earth's surface. Lofting elements such as propeller driven wings is attached to the sheet for providing aerodynamic lift thereto to maintain the optical element a predetermined distance above the surface of the earth. The propulsion system is powered electrically with energy derived from sunlight.