Hydraulic turbines are eroded by sediment-laden high-speed flow. Turbine erosion has negative effects on the cost of electricity production and on the energy efficiency. To mitigate these negative effects, the sediment load, turbine erosion and efficiency were monitored in a case study and a prediction model was calibrated.

The problem of turbine erosion is most severe in high-head hydropower plants (HPPs) operated on sediment-laden rivers (Fig. 1a). Such HPPs are equipped with Pelton turbines, in which the velocity of the water jets is for example 100 m/s. At such velocities, erosion cannot be fully prevented even if special hard-coatings are applied (Fig. 1b).
For the optimization of such HPPs, the knowledge on the relevant processes needs to be improved. Therefore, an interdisciplinary research project mainly based on a field study at the HPP Fieschertal in the Canton of Valais, Switzerland, has been initiated in 2012. The sediment concentration and particle size distribution have been measured continuously and in real-time. An innovative combination of measuring techniques has been used, including in-situ Laser Diffraction and Vibrating Tube Densimetry. The erosion on the Pelton runners and the changes in turbine efficiency have been quantified repeatedly. The relation between the sediment load and the erosion on coated Pelton runners is investigated and a prediction model was calibrated.
The findings of the study allow optimizing the operation of such HPPs, for example with turbine switch-offs in periods with high suspended sediment concentration. This contributes to the sustainable and energy efficient use of the hydropower potential.

Figure 1: a) River water containing suspended sediment particles, b) local erosion damages on a coated runner of a Pelton turbine (Pictures: VAW, ETH Zürich).

The ESC member involved in this project is Prof. Robert M. Boes, head of the Laboratory of Hydraulics, Hydrology and Glaciology (VAW). VAW performs research in the areas of hydraulic engineering, river engineering and glaciology. Further involved VAW collaborators are Dr. Ismail Albayrak and Dr. David Felix. The project is conducted in collaboration with Hochschule Luzern and industry partners.

Further Details

Further details can be found on the project website and in the related PhD thesis.