That’s enough power for ten homes. Much larger tests are planned. The kites use the much faster moving wind higher up, and thus are more efficient. Plus they fall slowly if the wind stops.
The always amazing Treehugger has more. Check Laddermill, the website of inventor Wubbo Ockels for lots of technical explanations, demo software, images, and more.
From the Laddermill Introduction Page
The Laddermill consists of a series of wings or kites all connected to a cable that forms a huge loop. Like the wings of an aeroplane will the wind cause an upward lift force to the wings. By changing the attitude of the wing (angle of attack with respect to the wind) can the lift force be made larger or smaller.
The wings on one side of the cable loop are all placed such that they produce the maximum lift force, while the wings on the other side of the loop will give a much smaller lift that in fact is just sufficient to support their own weight and the weight of the cable.
The result is a large difference in force between the two ends at the ground. When the cable loop is guided around a wheel on the ground the force difference will drive the wheel. By connecting the wheel to a generator electricity will be produced.
The wind energy aloft has thus been transferred to electricity on the ground.