Energiedienst Holding AG
Power Plants / Director of Hydraulic Engineering
We can see a major advantage of the hydropower screw in the overall project planning concept. After about 2 years of operation we can confirm that the system can manage without a grate cleaning machine and that the coarse grate with a distance between the bars of 150 mm is sufficiently cleaned by means of a back flushing cycle. We can certainly do without a grate cleaning machine in future.
For ecological reasons, the hydropower screw helps downriver fish migration. Smaller debris such as leaves and branches are also left in the water and do not require expensive disposal. In the floods that occurred in June 2011 after the system was commissioned, it was never throttled back and could be operated continuously at the maximum power available.
During the conceptual design process, it was necessary to choose between a Kaplan bulb turbine and a hydropower screw. In spite of the lower overall efficiency in the full load range, the ecological benefits of the hydropower screw and its recognised function as a downriver fish migration system made up for this disadvantage at this site because there would not be any additional water loss caused by a fish pass. It was possible to fully achieve the forecast of 1.9 million kWh in the first full operational year of 2012. In the first 5 months of 2013, it has already been possible to achieve 58% of the expected output.