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  1. Project
28 July 2015

Obervermuntwerk II Pumped Storage Power Plant, Vorarlberg

Vorarlberger Illwerke, Austria’s state-owned energy supplier, is developing the 360MW Obervermuntwerk II pumped storage power plant in Vorarlberg, Austria.
The 360MW Obervermuntwerk II pumped storage power plant is being constructed in Austria’s Vorarlberg region. Credit: Asurnipal.
Construction of the new pumped storage power plant, parallel to the existing Obervermuntwerk plant, began in May 2014 and is expected to start operations in 2018. Credit: Public Domain.
Alstom is the supplier of two 180MW generators for the pumped-storage power station. Credit: Alstom.

Vorarlberger Illwerke, Austria’s state-owned energy supplier, is developing the 360MW Obervermuntwerk II pumped storage power plant in Vorarlberg, Austria. Illwerke has formed a partnership with EnBW to develop the project, which will be its second biggest pumped storage power station upon completion.

Construction of the €500m (approximately $553m) pumped storage power station began in May 2014, and it is expected to start operations in 2018.

Pumped storage power plant make-up



The 430MW hydroelectric power project is under construction in the Mühldorfer Graben region of Carinthia, Austria.


The new pumped storage power plant will be located parallel to the existing Obervermuntwerk plant, which has been operating since 1943. It is being constructed at an altitude of 1,700m above sea level and will feature an underground cavern powerhouse.

Obervermuntwerk II will utilise the existing water capacities of the Silvretta and the Vermunt (located 300m below Silvretta) reservoirs for generating energy. The project harnesses the natural power of water and utilises the difference in elevation between the upper (Silvretta) and lower (Vermunt) water reservoirs to generate electricity.

Water from the Silvretta reservoir will be fed to the underground powerhouse at Vermunt through a 170m-long inlet tunnel, with a diameter of 6.8m, as well as a 2,800m-long pressure tunnel. The Vermunt reservoir will act as a storage channel and will be connected to the cavern by a 380m-long underwater tunnel.

The underground powerhouse will be approximately 125m-long and accessed through an approximately 810m-long access tunnel. The powerhouse will consist of two ternary machine units with a capacity of 180MW each and two pumps of 180MW each. The turbines are expected to have a head between 240m and 310m and will operate at a speed of 428.6rpm.

Obervermuntwerk II power plant construction

The major works at Obervermuntwerk II will include the construction of infrastructure facilities including the site roads and access routes, ground and concrete work for the onsite buildings, as well as the concrete mixing facility and gravel preparation. The works also include the construction of a pre-cut for the tunnel portal, encircling embankment for outlet construction, concrete work for Obervermunt service chamber, outlet construction, portal construction and protection shaft and circulation tunnel for Silvretta.

A new headrace duct will be built for the existing Obervermuntwerk power plant, while the existing surface penstock will be removed.

Financing for the pumped storage power plant

“The project harnesses the natural power of water and utilises the difference in elevation between the upper (Silvretta) and lower (Vermunt) water reservoirs to generate electricity.”

The European Investment Bank (EIB) provided a €280m loan facility for the development of the Obervermuntwerk II pumped storage power plant.

Contractors involved in Obervermuntwerk II

The consortium of Jagerbau, PORR, Hinteregger and ÖSTU was awarded a €120m contract for the construction of the Obervermunt II power plant. Alstom is the supplier of two generators with an output of 180MW each, as well as exciters.

In January 2014, Andritz Hydro was contracted by Vorarlberger Illwerke for the supply of two Francis turbines. Under the contract, Andritz is responsible for the supply of a fully homologous model test, design, manufacturing, transport, installation and commissioning of two horizontal generating units including Francis turbines, and related equipments.

Voith Hydro was awarded the contract for the supply, assembly and commissioning of two 170MW storage pumps along with a hydraulic torque converter. The contract for the construction of the power transmission line for plant was awarded to Hunter.

Kuenz is the supplier of hydro-mechanical equipment, which include four intake gates for the Silvretta shaft, four draft tube gates for the powerhouse cavern, and a gate and screens for the Vermunt outlet structure.

Bilfinger VAM Anlagentechnik was contracted for the supply and installation of pressure piping systems and pressure-shaft plating for the Obervermuntwerk II power plant. Vorarlberg Illwerke engaged LCS Cable Cranes for the construction of a cable crane.

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