The pilot of the glider reported that about 2 hours 30 minutes into the flight, he was unable to locate a thermal and began losing lift. He located a field that he felt was long and wide enough to land in; however, the field was surrounded by powerlines and trees. He elected to conduct his approach from the southwest over the tree line. During the landing flare, he landed further down the field than anticipated; the glider overran the runway, impacted a fence, crossed a road, and impacted another fence, causing substantial damage to the wings and fuselage. The pilot further reported that the flight log revealed a tailwind of approximately 13 knots on the final leg of the approach, and stated that there was no mechanical malfunction with the glider.