The student pilot was practicing solo takeoff and landings in a tailwheel-equipped airplane on a dry, hard surfaced runway. At the beginning of the flight, the winds were light and variable, but during the last landing, the wind had shifted to a slight tailwind. During the landing, the pilot lost control of the airplane, and ground looped, sustaining substantial damage to the right wing. The pilot reported no preaccident mechanical anomalies with the airplane that would have precluded normal operation.