April 2016 saw the successful commissioning of the new Vanazit hydroelectric power station in the northern Turkish province of Giresun. The plant operated by ‘Proen Energy and Trade Inc.’ (Proen Enerji ve Ticaret A.Ş.) is located in the Kesap district, close to the Black Sea and exploits the potential energy of the Büyük water mass to generate electricity. OSSBERGER GmbH + Co. KG is based in southern Germany and was awarded the contracts for the provision of all the necessary electromechanical infrastructure for the new water diversion power station. The successful project bid means this internationally experienced company has been charged with the production of their most powerful cross-flow turbine at that date – with a maximum power output of 3.46 MW.

Ossberger GmbH + Co. KG is based in the Middle-Franconian town of Weißenburg and has already enjoyed recent commercial success in the Black Sea region. For example, the company provided the turbine infrastructure required by several thermic power stations on the Black Sea coast for energy recovery from the cooling water systems. Having been awarded the contract for the Vanazit power plant by the operating company, Proen Energy and Trade Inc., Ossberger is now responsible for the implementation of another purely hydroelectric project in this part of the world. Holger Franke is Ossberger’s sales and distribution specialist for the Turkish market and responsible for project implementation.

PLANT TO BE COMPLETELY REBUILT
In order to construct the new water diversion plant, every single part of the power station needed to be completely rebuilt – from the powerhouse and weir system to the penstock. According to the specifications provided by the operating company, implementation would demand 18,000 m³ of concrete, 900 tonnes of reinforcing steel and 25,000 m² of casing material. The weir and powerhouse are both solid concrete structures.
Many aspects of the planning and implementation of the project were carried out by the operating company, Proen Energy and Trade Inc., a member of the PROKON EKON Group, a corporation working mainly in the building, industrial and energy production sectors. Ossberger deployed its own team of specialists to guarantee correct installation of the turbine, electrical and electronic infrastructure.

CROSS-FLOW TURBINE REPLACES TWO FRANCIS TURBINES
The original call for bids in 2012 envisaged twin Francis turbines for the generation of electricity at the plant. However, due to the (in some cases) extreme fluctuation in the amount of water available at the plant site at different times of the year, a single Ossberger turbine was considered to be the more effective technical solution. Holger Franke explains: “The cross-flow turbine is very efficient the whole year round and can deliver at least as much power spread across the year. This is in contrast to the originally planned Francis turbines, whose strengths become evident working at full capacity. Furthermore, compared with the costs of purchasing two Francis turbines and the expenditure required for the associated technical infrastructure, the acquisition of an Ossberger turbine is significantly more affordable.”

XXL CROSS-FLOW TURBINE
Diversion of the Büyük at the Vanazit plant is achieved with an available gross head of 113 m and a maximum flow volume of 3.5 m³/s. The system can generate a bottleneck output of 3.46 MW when flow supply conditions are at their best. “At the time of delivery this was the most powerful cross-flow turbine we had ever produced”, remarked Mr. Franke, who continued by explaining: “Despite the turbine’s power, its dimensions are relatively small, particularly in terms of its width. Due to the design of the machine, the steep drop made it necessary to realise a large rotor diameter of 1.25 m, while limiting the length of the rotor to less than 50 cm, which required the machine to be relatively narrow overall. The cross-flow turbine has a relatively low specific rotation rate. The optimum turbine rate for the Vanazit plant would be around 340 rpm. Hence, the decision to produce and install a power transmission gear system between the turbine and the generator, since a slow-rotation generator would be very expensive without being particularly efficient.”

COMPLETE OSSBERGER PACKAGE
For the new power station, the scope of delivery encompassed the turbine, generator, gear system, an extremely heavy maintenance butterfly valve, and all the electrical and control-related hardware. The electro-technical infrastructure had to be adapted to suit the norms and safety directives in force in Turkey. The generator manufacturer had to adapt the short circuit ratio to comply with Turkish guidelines. The plant is run using the tried and trusted Ossberger SCADA online control system. Online remote access to control processes facilitates fully automatic and highly effective electricity production. The overall package was rounded off with a medium voltage generator switching system and a transformer. The new Vanazit hydro-electric plant finally went online in April 2016. The plant has been producing an ecologically sustainable power supply for the public mains grid since the trial period was completed successfully. The operators estimate the average annual power output to be around 10 GWh.