At the Stegenwald hydropower plant in Austria, Global Hydro has implemented a new turbine concept: A revolutionary combination of a vertical Kaplan spiral turbine and a horizontally installed pit turbine. What makes this layout unique is its top-down water inflow, replacing the traditional front-facing design. This not only eliminates the need for an entire weir field - significantly reducing civil construction costs - but also enables floodwater discharge through the turbine inlets, enhancing safety and operational flexibility. Supported by extensive CFD simulations, the plant achieves an efficiency gain of up to 1.5 %, delivering a total output of 14.3 MW. A true milestone in hydropower engineering.
The technological centerpiece of Stegenwald is a turbine concept that was completely redeveloped specifically for this project. It combines the principles of a vertical Kaplan spiral turbine with those of a horizontal pit turbine in a compact layout tailored to the site conditions. Global Hydro has previous experience with pit turbines, and this knowledge was directly incorporated into the Stegenwald solution, reducing technical risk despite the novelty of the configuration.
Instead of admitting water directly from the front, the flow is guided from above through an inlet ramp and a specially shaped intake spiral. The generator and gearbox are positioned in front of the turbine rather than on top of it, which is the usual arrangement for similar plants. The design target was to find the best possible compromise between a vertical spiral turbine and a horizontal pit turbine in terms of efficiency, structural integration and cost. The result is a layout that delivers a higher efficiency by approximately 1 to 1.5 percentage points compared to conventional solutions, a significant gain over the lifetime of the plant.
Improving flood handling.
By combining the features of a vertical spiral turbine with those of a horizontal pit turbine, the design team was able to avoid the need for a third weir field at Stegenwald. The plant layout uses:
In flood events, not only the two weir fields but also the flap gates can be operated to discharge high flows. This means that the plant can pass more water during flood conditions than would have been possible with a conventional layout that relied on an additional weir field.
This concept makes the plant more flexible in operation, optimizes costs on the civil side and increases safety and robustness during extreme hydrological events.
Through development partnerships.
The turbine concept and its hydraulic geometry were developed in close cooperation with technical universities. The process included:
The turbine was designed to withstand temperature dependent and load dependent deformations. Special attention was given to the load paths and the axial bearing arrangement. The axial bearing, located in the gearbox, was moved to the front side and integrated into a conical housing so that forces are kept locally where they arise. This optimized load introduction concept reduces structural stresses and contributes to long term reliability.
Engineered for hydraulic resilience.
The Salzach carries significant bed load, which makes sediment management a key design factor. The turbines and the hydraulic design were therefore optimized with sediment passage in mind.
Key measures include:
These hydraulic and structural measures help maintain turbine performance over time, reduce abrasion related damage and support stable plant operation during varying sediment loads.
Stegenwald is a run-of-river hydropower plant on the Salzach River in Austria. It was designed to combine high efficiency, operational flexibility and a compact layout tailored to the specific site conditions.
From a project delivery perspective, this hydropower plant is equally remarkable. After a lengthy preparation and permitting phase of more than 10 years, the actual construction and implementation were completed in only about 2.5 years, from the start of civil works in early 2023 to commissioning in the second quarter of 2025.
Global Hydro delivered and implemented the entire electromechanical scope for Stegenwald, including turbines, generators, gearboxes, cooling units, lubrication and hydraulic units as well as all turbine related steel structures and auxiliary systems.
The project was divided into two main lots:
Global Hydro handled all relevant designs in an integrated way, covering mechanical, hydraulic and structural aspects on the machine side and in close coordination with the civil works. This holistic approach ensured that all system interfaces were controlled and that the technical solution was coherent from initial concept to final operation.
In Global Hydro’s Innovation and Manufacturing Hub in Austria, the components were manufactured and pre-assembled in functional groups. The process followed a clear strategy:
By transferring as much work as possible into the controlled factory environment, Global Hydro ensured high quality and minimized on-site risks and delays.
The transport of the main components to Stegenwald was a project in itself, with access only via narrow routes, a tight railway underpass and a temporary construction bridge limited to 85 tons. To stay within this limit, the individual delivery units, such as the wicket gate and the traction chain were designed so that their weight on the truck did not exceed 32 tons. All assemblies were predesigned, preassembled and then put into suitable transport units, ensuring that they remained roadworthy while still allowing efficient and technically robust reassembly on-site.
Before each special transport, route inspections and planning meetings were held. Mobile cranes were arranged in advance and positioned to allow direct lifting into the turbine shafts where possible, especially on the weir bridge. This minimized intermediate handling and further reduced time and risk during installation.
The project followed a just in time delivery philosophy. Colli were scheduled to arrive when needed to avoid congestion at the site, while civil works and mechanical installations progressed in parallel. Weekly coordination meetings involving all key stakeholders and Global Hydro’s project and site management teams ensured that short-term changes could be accommodated while keeping the overall schedule on track.
Precision, planning and experience were key to a smooth on-site assembly. Thanks to a high degree of factory pre-assembly and well-coordinated logistics, the installation of the turbine systems could be carried out in two clearly defined phases - efficiently, safely and on schedule.
A key milestone was reached in January 2025 when the first turbine shaft was flooded and the Salzach River was diverted through the new turbine. After the successful leak tests and checks, the second turbine followed in March 2025.
The commissioning sequence included:
1. Dry commissioning
2. Wet commissioning
3. Grid synchronization and performance tests
The plant entered trial operation in the second quarter of 2025 and was fully commissioned in line with the project schedule. Probationary operation for the second machine set was completed in mid-June, and for the first machine set by the end of July. Since then, both turbine units have been running in regular operation.
Feedback from the operator has been very positive. The turbines operate very smoothly and reliably, and the overall system’s performance exceeds expectations.
Stegenwald showcases a completely new turbine design that combines hydraulic, structural and operational advantages. The project has significantly expanded the know-how of everyone involved, particularly in the fields of combined spiral pit turbine design, complex logistics and high pre-assembly strategies. Stegenwald is a reference plant for both national and international customers who are looking for innovative hydropower solutions and state-of-the-art technology that can be implemented within tight schedules.
The project demonstrates how Global Hydro’s expertise in design, manufacturing, logistics and project execution can be combined to deliver complex projects safely, on time and with high performance. It shows that hydropower still offers substantial potential for innovation when site specific challenges are addressed with a holistic engineering approach.
Innovative hydropower projects often face tough conditions: ambitious goals, complex site constraints, tight schedules and pressure to reduce costs. These challenges came together in this project along with the customer’s vision for a completely new turbine design. By combining technical excellence with smart project strategies, we help our clients meet demanding requirements without compromising on performance or budget.
Global Hydro developed and implemented a completely new turbine solution - a world-first in hydropower engineering. By rethinking established principles, our team created a unique concept that combines proven technologies in a novel configuration, tailored precisely to the site’s challenges. The result: higher efficiency, simplified civil structures and greater operational flexibility.
With Stegenwald, we prove that technological innovation pays off: The new turbine concept delivers measurably higher efficiency and allows for significant cost reductions on the civil works side by simplifying the plant layout. For investors, plant owners and operators, this means: lower investment risk, reduced construction complexity and higher long-term returns.
When it comes to pioneering turbine concepts, Global Hydro leads the way. We turn complex site challenges into smart, cost-efficient solutions and support our clients every step of the way. From first idea to commissioning, we’re your strongest partner for innovation that delivers real value.
Thierry Burckhart
Director Revitalization
+1 (970) 710 1285
thierry.burckhart@global-hydro.eu Contact
