Limberg I: modernizing the alpine legend at PSHPP

Limberg I is an iconic piece of alpine infrastructure

Located above the well-known tourist and skiing destination of Kaprun in the Austrian federal province of Salzburg, the pumped-storage hydropower plant (PSHPP) Limberg I is an iconic piece of alpine infrastructure. It connects the famous high-altitude alpine dams Mooserboden and Wasserfallboden, drawing water that originates mostly from the Pasterze glacier of Großglockner—Austria's highest peak.
To meet modern energy demands, Litostroj Power partnered with the Austrian energy utility Verbund to comprehensively modernize the plant.

The challenge: a demand for flexibility

The original units, dating back to 1956, featured a horizontal arrangement consisting of a synchronous generator, a traditional Francis turbine, and a double-intake two-stage storage pump. However, the energy landscape has changed significantly since then.

• The client required more flexibility and a higher operational range, particularly during pump operation.
• To achieve this, the original machinery had to be replaced with a cutting-edge, single-stage reversible turbine capable of operating at variable speeds instead of fixed speeds.

Engineering the solution

As a key contractor for this major refurbishment, Litostroj Power was tasked with supplying the new turbine mechanical parts. The engineering teams applied a creative approach to integrate modern technology into the historic power plant.

• Litostroj developed a completely new hydraulic profile, ensuring the new design respected and utilized the original plant structures as much as possible.
• The engineering phase included rigorous physical model testing to validate the compliance and efficiency of the new design.
• Following successful testing, Litostroj delivered all main turbine components, including the new Francis reversible runner, a new stay vane ring for the spiral case, a new draft tube, the regulation mechanism, and the bearings.

Results: increased power and variable speed

The upgrade from fixed to variable speed operation completely transformed the plant's operational capabilities. Not only did the new frequency converter and motor-generator setup provide the required operational flexibility, but it also achieved a significant boost in power capacity.

The modernization successfully increased the output of the units from the original 56/65 MW to an impressive 80 MW per unit. By pushing the boundaries of refurbishment, Litostroj ensured that PSHPP Limberg I will continue to serve as a highly efficient and crucial asset in Austria's renewable energy network.