Project parameters
Major greenfield project
Deep in the south of Slovenia, near the Croatian border in the town of Brežice, stands a monumental achievement in modern hydropower: the Hydroelectric Power Plant (HPP) Brežice. For this major greenfield project, Litostroj Power stepped up as the Consortium Leader alongside KONČAR – KET to deliver a comprehensive solution for the plant's owner, HIDROELEKTRARNE NA SPODNJI SAVI, d.o.o. (HESS).
With a total contractual value of €36,508,000, the project showcased true engineering prowess—and eventually encountered a highly unusual challenge.
A complete keyturn scope
In alignment with robust capabilities for complete "Water-to-Wire" new installations, the delivery covered the full lifecycle of the mechanical setup. Because this was a greenfield project, Litostroj supplied entirely new equipment from the ground up to maximize the site's hydro-potential. The consortium was responsible for the initial design and physical model testing, followed by manufacturing, supply, site erection, erection supervision, and final commissioning.
The extensive mechanical and auxiliary scope of supply included:
- The whole distributor, large complex weldments, all embedded parts, two guide bearings, and one thrust bearing per unit, with the turbine shaft attached directly to the generator rotor.
- Critical auxiliary systems specifically designed to ensure safe and continuous operation.
- These systems included the Hydraulic Power Units (HPU), compressed air systems, complete machine hall and aggregate drainage, cooling water systems (CWS), digital turbine governors, and water level measurement systems.
- Heavy plant machinery was also provided, specifically a massive 130/16-ton bridge crane and a smaller 5-ton crane with their respective runways.
The challenge: a race against time and physics
The execution of HPP Brežice was not without its hurdles. The engineering teams faced a demanding set of constraints:
- Litostroj faced a very short delivery timeline combined with strict demands for high hydraulic efficiency and rigorous cavitation limits.
- Because the client had high expectations for reliable and safe operation, Litostroj's engineering teams had to implement numerous special design solutions specifically tailored to the plant's unique operational profile.
Despite the tight schedule, the consortium successfully delivered all services and equipment in accordance with professional standards and contractual requirements. The three turbine units officially entered commercial operation sequentially during the spring and summer of 2017:
- Unit 1 on March 22
- Unit 2 on May 21
- Unit 3 on July 27.
The unforeseen threat: manganese-eating bacteria
Following commissioning, the turbines demonstrated highly reliable and safe operation without any major mechanical problems. However, after a few years of continuous operation, maintenance teams discovered strange, unexpected damage on the Kaplan runner blades.
Litostroj's subsequent investigation revealed a highly unusual and fascinating root cause: the damage was biological, not mechanical.
- A specific strain of bacteria present in the river water was actively "eating" the manganese out of the turbine's steel alloy.
- Further tracing discovered that these bacteria originated from a pharmaceutical plant located upstream in the town of Krško.
- Because the contamination entered the river at that specific point, other hydropower plants located further upstream were not exposed to this unique manganese-eating bacteria.
Conclusion
Ultimately, the Brežice project stands as a testament to Litostroj's ability to swiftly execute complex, large-scale greenfield projects while adapting to and diagnosing the highly unpredictable environmental challenges that come with harnessing the power of natural river ecosystems.
