Passengers in the 27,000 cars which daily cross the river Elbe at Hamburg will have noticed the recent addition of a wind turbine to the Georgswerder rubbish dump on the outskirts of the city. A Tacke TW 500 machine has joined the two existing AN Bonus turbines installed on the 40 metre high mound, a 50 kW turbine and a 150 kW unit. The Tacke machine is owned by the Hamburg utility HEW and a second TW 500 will be installed within a year, this time for the city of Hamburg, which also owns the smaller Bonus machines. The Tacke 500 kW is forecast to generate 670,000 kWh a year. Experience with siting of the Bonus turbines on the dump has revealed they are sinking six centimetres a year, says Helmut Häusser from consultants Ingenieur-Werkstatt Energietechnik of Hamburg. To counteract this problem, the Tacke turbine is installed on a foundation plate, 16 metres across, while the whole structure can be adjusted to vertical through the use of two wedge-shaped rings at the base of the tower, allowing for 3.3% movement.