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Bulgarian state-owned National Electricity Co. (NEK) launched a tender for the supply and replacement of two out of four turbines in pumped storage hydropower plant Chaira, the biggest one in Southeastern Europe. The facility has been out of order for more than two years.
Bulgaria is leaning strongly on energy storage in its decarbonization efforts. Such systems are essential for the integration of wind and solar power as they are intermittent – depending on weather. The country had a hard time navigating the recent energy crisis since major breakdowns took the Chaira pumped storage hydropower plant offline in 2022.
It is or, rather, was the biggest facility of the kind in Southeastern Europe, consisting of four units. The crash followed a failed rehabilitation project that lasted several years.
With the system in operation, National Electricity Co. (NEK) could have stored electricity when it was cheap – at times of low demand and surplus renewable energy. The nominal capacity of the Chaira pumped storage hydropower plant is 784 MW in pumping mode and 864 MW for generating electricity.
NEK acknowledged that reversible turbines 1 and 4 were beyond repair. It launched a tender for entirely new generators and other equipment, together with control systems. The contractor would also be tasked with project design, dismantling the two units and replacing them as well as training staff, testing and commissioning.
Public call for unit 4 repair brought no bids
The company, which operates within state-owned utility Bulgarian Energy Holding or BEH, has aborted the first tender. No company responded to the public call, which it issued earlier this year. It was only for repair and only for turbine 4. The indicative price was EUR 27 million.
NEK and the authorities now count on greater interest in the job. Estimated investment costs are EUR 112 million excluding value-added tax. The condition is that the equipment lasts at least 50 years.
Bids are received until November 15. The selected company or group would have three and a half years for the works.
Bulgaria currently has two operating pumped storage hydropower plants and projects for two more under development, while unit 2 in Chaira may get back online by the end of the year
The pumped storage plant is part of the Belmeken-Sestrimo-Chaira hydropower complex, Bulgaria’s largest. NEK marked the completion of the rehabilitation of the Belmeken pumped storage hydroelectric plant in February. It consists of five units with 373.5 MW in generation capacity. Two are reversible, enabling 104 MW in pumping mode.
Bulgaria’s third pumped storage hydroelectric system is called Orphey. Installed inside the Dospat dam in the country’s south, it comprises four turbines with just under 164.8 MW in total. One unit can work both ways, where the pumping mode capacity is 47.4 MW, NEK’s data shows.
Bulgaria is developing a plan for another two large facilities of the kind and conducting a competitive process for subsidies for standalone energy storage systems.
Toshiba to participate in replacement of turbines in Chaira pumped storage hydroelectric facility
In any case, Toshiba Energy Systems and Solutions Corp. must participate in the endeavor as the manufacturer of the original equipment. It also produced the documentation for the Chaira pumped storage system. Toshiba only built and commissioned units 1 and 2, in 1995, while the remaining ones came into operation in 1999 using the same technology.
In parallel, NEK is repairing reversible turbines 2 and 3. According to the Bulgarian media, unit 2 could become operational again by the end of the year.
The Belmeken lake, of 144 million cubic meters, is the upper reservoir. It is located 689 meters above the turbine hall, which is 350 meters underground. The dam of the lower reservoir, Chaira lake, can hold up to five million cubic meters of water.
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