Hydropower: Limberg III: Construction is underway

It is currently one of the single largest renewable energy expansion projects in Austria: Electricity company Verbund is investing around €480 million in the Limberg III pumped storage power plant. Construction began last fall near the town of Kaprun in the Hohe Tauern mountain region.

Austria’s objective is to meet one hundred percent of its energy needs from renewable sources as early as 2030. The Limberg III pumped storage power plant will make an important contribution in this respect: It expands the capacity of the existing Kaprun power plant group and will produce up to an additional 480 megawatts of climate-neutral electricity from 2025. At the same time, the new pumped storage power plant ensures the efficient intermediate storage of energy in times of surplus while allowing it to be quickly fed into the Austrian and Central European grids when needed. 

Limberg III is, in a sense, a twin of the Limberg II power plant which was built between 2007 and 2011. Like its namesake, Limberg III is being built between the high mountain reservoirs of Mooserboden (2,036 m) and Wasserfallboden (1,680 m). “The underground installation of the penstocks is particularly challenging from a technical point of view”, says Stephan Ebner, Head of the Hydropower Business Unit at Bilfinger Industrial Services Austria. “These pipes not only have to cover a height difference of more than 350 meters, they also have to be extremely pressure-stable once the system is in operation.” The reason for these special requirements relates to the way the pumped storage power plant works: Water is pumped through the penstocks into the upper reservoir. From there, it is released into the lower reservoir when needed, thereby powering the turbines to generate electricity. “Limberg III can only function when these pipelines fully perform their task”, says Ebner.

Time-Saving assembly technology Bilfinger is responsible for the engineering, manufacture, delivery, assembly and commissioning of the penstocks for the construction of Limberg III. Due to intense scheduling pressure, it is not possible to take to more traditional approach of first transporting the individual pipe sections up the mountain, where they are then roped down into the penstock shaft and welded together. Instead, to save time, the 35 pipes, each weighing 45 tons, are to be lifted from the valley floor into the 585-meter-long and 42-degree-inclined pressure shaft, placed upstream and welded directly in parallel with the other work in 48-hour shifts – the first time this has been done in assembly technology.

In addition to the penstocks, Bilfinger is also designing, manufacturing and installing the intake manifold dampers for the new hydropower plant, each of which is five meters wide and more than one-and-a-half meters high. These devices regulate the flow in the water distribution system through controlled opening and closing.

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