Energie Electrique du Simplon (EES) has invested over 20 million Swiss francs in the complete refurbishment of the Tannuwald hydropower complexes in the Zwischbergental Valley in the Swiss canton of Valais. The project is also being funded by the Swiss government as part of its Energy Strategy 2050. Work was completed in July 2020. when the power plant was able to resume its reliable production of power from renewable energy. The official opening had been delayed until now due to the coronavirus pandemic. Father Frank Sommerhoff performed the official ceremony with speeches given by Daniel Squaratti, the leader of the Gondo-Zwischbergen local council, MPs Beat Rieder (VS) and Martin Schmid (GR) as well as the Chairman of the EES Board of Directors, Amédée Murisier. An open day gave local residents the opportunity to take a look behind the scenes and see how power is produced.
Within less than one year, EES replaced the seven reversible pumps commissioned in 1981 with two more powerful groups. One group comprises a ball valve, a five-nozzle Pelton turbine and a generator. The control unit, transformers and power lines are also new, as is the entire 2.8-kilometre-long penstock, which connects the Fah compensation basin with the power plant. Although the shell of the power plant building remained in place, the height was raised to house the new vertically-oriented machine groups.
This total refurbishment has boosted EES's average annual production at its Tannuwald power plant from 17 to around 22 million kilowatt hours (kWh). The additional production of 5 million kWh is the equivalent of the average power demand of around 1250 households.
The entire Zwischbergental Valley is on Switzerland's list of landscapes and natural monuments of national significance, making it one of Switzerland's landscapes deemed worthy of special protection. Back in 2016, EES was one of the first production companies in Valais to implement wastewater treatment.
The modernisation of the Tannuwald power plant also saw very close cooperation with the authorities and environmental organisations right from the very beginning of the undertaking, thus helping to implement the project with due consideration for environmental and landscape protection and meet requirements in terms of refurbishment aimed at water conservation. In terms of rehabilitation measures, EES has already upgraded the headwaters near the Tannuwald power plant by creating various ground depressions where water can gather. There are also plans for enhanced landscape integration of the existing location for deposits of natural sediments (above the Tannuwald power plant) and to upgrade them to create a habitat for asp vipers.
The Tannuwald power plant is part of the EES hydropower complex. It is located in the Zwischbergental Valley and uses water from the Fah reservoir, situated at an altitude 1759 meters. The Gondo and Gabi power plants as well as the Eggen and Sera compensation basins also belong to EES. Now that Tannuwald is back in service, EES has a total of 80 MW at its disposal, producing an average of 250 million kWh of power a year, which is the equivalent of the electricity consumption of approximately 60,000 households.
The EES shareholders – Alpiq (82%), EnAlpin (10.8%), EWBN (3%), FMV (2.7%) plus private shareholders (1.5%) – are continuously investing in the various plants in order to ensure efficient and productive operations over the long term. Back in 2017, Energie Electrique du Simplon refurbished Machine Group 3 at the Gondo hydropower plant. The company is currently planning to modernise its Gabi power plant, with implementation scheduled for 2022/23. The modernisation of the EES power plants is geared towards optimising utilisation of the potential of hydropower potential and is thus in line with the Swiss federal Energy Strategy 2050.