Drinking water and energy

In the idyllic Mettental-Sachseln in the Swiss mountains of the Obwalden Canton, a classic example of environmentally friendly and efficient energy generation has been constructed. Most of the fresh water used by Sachseln comes from the Metten valley. Last year, the Sachseln water supply company constructed a new fresh water power station. The special feature of this project is that the water is used twice – as fresh water, an essential staple of life, and for the generation of renewable energy.
 
The main part of the overall system was the replacement of a 65-year old, 3 km long, damaged Eternit pipe from the springs in the Metten valley to the Obflue Reservoir by a pressurised pipe of ductile cast iron from Buderus. The pipes used were fresh water pipes of the nominal width 200 with longitudinal positive-locking BLS^® socket connections. A large-diameter pipe was chosen in order to improve energy generation, and to reduce pressure drops and pressure surges at full load operation. The water, which is under very high pressure, generates over one million kilowatt hours of electricity per year via a technically highly developed Pelton turbine, which is fed into the EW Obwalden network, and supplies up to 250 households. After passing through the turbine, the spring water goes into an existing reservoir, where it is brought up to drinking water quality by a UV system.

Despite the inaccessible terrain and the varying sub-surface conditions, work was quickly started. The use of a special walking excavator and around 500 helicopter flights were necessary in order to be able to lay the pipe in an appropriately short time.

As the client emphasised, the laying work went so quickly, despite the topographical difficulties, because the pipes with the reliable BLS^® connection are so robust enabling a rapid construction process, thanks to their easy handling. The Swiss Department of Energy has classified this unique fresh water power station, with the largest fall height in Switzerland, as a demonstration and pilot project, and also provided financial support.