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Tender description :
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Tenders are invited for: Grimsel 4 pumped storage power plant - main construction lot The Grimsel 4 pumped storage power plant utilizes the existing potential between the two existing reservoirs, Grimsel and Raterichsbodensee, with two machine groups without additional captured water. Due to the short distance between the two lakes and the already existing plant components, an economically attractive power plant can be realized with the Grimsel 4 pumped storage power plant.
In addition to the mentioned reservoirs, the project also utilizes other existing plant components, particularly the access and supply facilities of the existing power plants at Grimsel, as well as the intake structure of Grimselsee, which was already realized in connection with the replacement of the Spitallamm dam (pre-investment Grimsel 4). The new structures to be built generally include the continuation of the upper water side pressure water system from the throttle chamber with flat section and pressure shaft, the cavern central station, the lower water side pressure water system with underwater tunnel and outflow structure, as well as additional access tunnels.
The new power plant has a total output of 150 MW with a flow rate of 70 m3/s and closes the existing bottleneck in the hydraulic system between Grimsel and Raterichsbodensee. In addition, the power plant also serves lake and inflow management, which can prevent water losses during floods and make a significant contribution to flood protection.
Thanks to its flexible operation, the Grimsel 4 pumped storage power plant can respond to short-term grid fluctuations and cover peak loads in circulation operation. In times of overcapacity in the grid, excess energy can be absorbed and stored. In demand situations, the stored energy is available as peak power. This not only supports the smoothing of load profiles but also stabilizes voltage and frequency in the transmission grid.
The Grimsel 4 pumped storage power plant is also capable of being operated in a so-called hydraulic short circuit. In this case, part of the pumped water is immediately turbined again without completely passing through the storage circuit. This mode of operation allows for very quick responses to changing grid conditions without having to interrupt the pumping operation. This significantly increases the responsiveness of the power plant and makes it an extremely valuable tool in modern grid operation.
In addition to energy production, the Grimsel 4 pumped storage power plant also offers system services such as primary, secondary, and tertiary control. The high flexibility of the pumped storage power plant enables it to provide regulating energy in the shortest time, which represents a decisive advantage given the increasing volatility of electricity markets.
With these characteristics, the Grimsel 4 pumped storage power plant plays a central role in the energy transition and significantly contributes to supply security and the efficient use of hydropower resources.
Scope of work / main quantities
The following structures are to be newly constructed as part of the main construction lot for the Grimsel 4 pumped storage power plant:
- Pressure water system with
- Remaining excavation upper water pressure tunnel flat section I (odf i)
- Upper water pressure shaft (ods)
- Upper water pressure tunnel flat section II (odf ii)
- Distribution line upper water (vow)
- Distribution line lower water (vuw)
- Lower water pressure tunnel (uds)
- Intake and outflow structure in Raterichsbodensee (abr), excl. pre-cut (etr)
- Cavern central station (zgr4)
- Various access, supply, and construction logistics tunnels
The pressure water route between the two reservoirs, Grimsel and Raterichsbodensee, is stretched. The route has been optimized for minimal length of the pressure water route. The small horizontal total length of only about 1.2 km allows for both upper (ow) and lower water (uw) to do without a water lock without having to accept greater operational restrictions. Submission of tender: 09.10.2026, 16:00
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