Design and construction of the 4kW groundstation for the laddermill

This paper presents the design of a 4 kW Laddermill groundstation. The Laddermill is a novel concept to harvest electricity from high altitude winds. The concept’s operating principle is to drive a generator with kites. Several kites are high in the air at an altitude of more than 1 km. All kites are connected to a single cable that connects to a drum in the groundstation. The lower part of the cable is connected to the kites and is wound around a drum. The kites pull the rope from the drum, which in turn drives a generator. When all of the cable is pulled off the drum, the kites fly down in a configuration that generates significantly less lift than during the ascent. This way the lower part of the tether is retrieved onto the drum and the process is repeated. The concept allows very large single unit power. At Delft University of Technology, a 2 kW test model of the Laddermill was constructed and tested successfully. From this 2 kW Laddermill several valuable lessons were learned. Taking the lessons learnt into account, a 4 kW groundstation was designed.