The Kühtai 2 project is a 260MW pumped-storage hydroelectric power project (HPP) being developed in the Tyrol province of Austria.
Austrian utility company Tiroler Wasserkraft (Tiwag) is developing the facility with an estimated investment of approximately £869m (€1bn).
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While the preparatory works for the project were started in 2018, the main civil construction works were started in April 2021.
The Kühtai 2 pumped-storage hydro project was authorised by the environmental impact assessment (EIA) agency of Austria’s Tyrol provincial government in June 2016.
It is being developed as an expansion to the existing 781MW Sellrain-Silz series of power plants comprising the Silz and the Kühtai pumped-storage power stations that were commissioned in 1977 and 1981 respectively.
Scheduled to commence commercial operations by the end of 2026, the Kühtai 2 pumped-storage facility is estimated to generate up to 260-gigawatt hours (GWh) of electricity a year.
Location and site details
The Kühtai 2 pumped-storage hydroelectric power project is located in the Kühtai valley, in the municipality of Silz, Tyrol, Austria.
The project site lies at an elevation of 2000m above sea level, at the back of the Längental valley of the Tyrolean Stubai Alps, approximately 30km west of Innsbruck.
Kühtai 2 pumped storage facility make-up
The Kühtai 2 pumped-storage power project will involve the construction of an underground power plant, a new Kühtai reservoir, and a water diversion gallery with six water intakes.
The underground power plant will be equipped with two reversible spiral Francis pump-turbine units of 130MW of power generation capacity each. Each turbine will be designed to consume 140MW of electricity while operating in pumping mode.
The powerhouse will be connected to the new Kühtai reservoir and the existing Finstertal reservoir through a headrace channel.
Dam and reservoir details
The new Kühtai reservoir will have a storage volume of 31 million cubic metres (mcm), approximately half the size of the existing reservoir Finstertal. It will be created with the construction of a 113m-high and 510m-long earth core rockfill dam.
A 25.5km-long and 4.2m-diameter trans mountain water diversion tunnel will be constructed to deliver water into the new Kühtai reservoir from six water intakes, via the central and eastern Ötztal valley and the rear section of the Stubaital valley.
Power evacuation
The electricity produced by the Kühtai 2 pumped-storage facility will be evacuated through an underground 220kV power transmission line connecting the existing Kühtai power plant for onward transmission to the grid.
Construction equipment
The project will involve the construction of a concrete mixing plant, the installation of a bulk material processing plant, as well as the deployment of a tunnel boring machine (TBM) for tunneling works.
Contractors involved
A consortium of Swietelsky, Jäger, and Bodner was awarded a contract worth approximately £384.71m (€425m) for the main construction works of the project in October 2020.
Voith Hydro was contracted for the supply of pump turbines along with the associated subsystems in February 2021.
Andritz was placed an order for the supply of two 95MVA motor generators along with the auxiliary equipment for the project in the same month.
AFRY was awarded the engineering, design, and advisory services contract for the project in April 2021. The scope of the contract includes main cavern design and structural calculations, coordination with electro-mechanical parts, the preparation of formwork and reinforcement drawings along with a 3-D coordination model of the main structures.
iC Group was engaged for services related to vibration measurements study and prognoses as part of environmental impact assessment.
Geodata was engaged for the geotechnical survey for the construction of tunnels, caverns, and the embankment structure in March 2021.
