The Montafon Rellswerk

Pumped storage power station in operation

Thomas Steinwender

The Montafon Rellswerk power station in Vorarlberg after completion of the construction work. (Image: Nägele Hoch- und Tiefbau)

The latest pumped storage power station in Vorarlberg has been in operation since the middle of 2017. The power station facilitates an increase in peak and balancing energy production and is an important part of the upper Ill-Lüner Lake group of power stations. A consortium with the PORR subsidiary Nägele Hoch- und Tiefbau GmbH was awarded to build the equalisation basin and the machinery building.

After extensive planning, the construction work on the Rellswerk conducted by Vorarlberger Illwerke AG began in 2014. The goal was to generate electricity exclusively from hydropower and other renewable energies. The slope of the upper Rellsbach can now be optimally utilised for the Lüner Lake power station.

The main function of the Rellswerk is to supply water from the inlets at the upper Rellsbach to the works water system of the Lüner Lake power station, thereby increasing its water resources. The water from the inlets is temporarily stored in an equalisation basin, then pumped via a pressure pipeline into the Lüner Lake-Latschau works water penstock, and finally pumped into the Lüner Lake. Around 17 million m³ flow into the lake each year.

Equalisation basin

A reservoir lake was built for the new Rellswerk. Construction work on this equalization basin was commissioned by the Rellswerk Vandans consortium, which included the PORR subsidiary Nägele Hoch- und Tiefbau GmbH. The equalization tank has a usage volume of 44,000m³, while the tank’s shape and the appearance of its shore areas were designed to blend in with nature and the landscape. The Rellsbach was diverted during the construction work and now runs along the base of the dam. The maximum static dam height is approximately 14m.

Machinery building

The construction of the machinery building, which was to be integrated in the upper section of the artificial dam, was even more complex than construction of the equalisation basin. Only the access portal remains visible from the outside after completion of the building. The operator had requested that the entire power station remain as inconspicuous as possible. The majority of the hydropower technology is located underground. The power station is not accessible in winter and therefore runs completely unattended.

Project data

Employer Vorarlberger Illwerke AG
Contractor Consortium Rellswerk Vandans with Nägele Hoch-und Tiefbau GmbH, Wilhelm+Mayer Bau GmbH, Gebr. Haider Bauunternehmung GmbH, Max Streicher Österreich GmbH
Project type Structural engineering . Special skills . Alpine construction . Power plant construction.
Project scope Construction of a equalisation basin and machinery building
Start of construction 2014
End of construction 2017
Country Austria
Construction works at equalisation basin. (Image: Nägele Hoch- und Tiefbau)

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