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Thanks to the efforts of the teams, in 2025, two hydro units will be repaired in parallel at the Chaira PSHPP site.

NEK signed a contract with Toshiba Corporation of Japan for the repair of Chaira hydro unit 1, which will ensure the safe operation of the facility in the medium term. The signing was attended by the Minister of Energy Vladimir Malinov and H.E. Hisashi Michigami, Ambassador of Japan to Bulgaria.  The agreement is the result of successful negotiations between the parties who demonstrated a high level of professionalism, commitment and expertise.

Toshiba Corporation is the designer and original equipment manufacturer of the plant and their high expertise will ensure the best technical solution for the facility. The hydro unit is in its original condition and no rehabilitation work has been carried out on it since its commissioning in 1995. It is expected that the contract works will commence as soon as possible and the unit will be back in operation in 2026.

NEK signed a contract with the Austrian consortium Voith-ABB for the repair and rehabilitation of hydro unit 3 of Chaira PSHPP. The signing was attended by the Minister of Energy Vladimir Malinov and Philipp Kupfer, Commercial Counsellor at the Austrian Embassy in Bulgaria. For the rehabilitation of the hydro unit, a special engineering solution will be developed and implemented, similar to the one implemented for the rehabilitation of hydro unit 2. Thanks to the successful implementation of a unique technological solution, hydro unit 2 was commissioned for 72-hour testing in late 2024, which were completed early this year. The preparatory works for the repair of hydro unit 3 are underway, and NEK has already completed the dismantling of the generator section of the hydro unit.

The signing of the two contracts represents an important milestone in the implementation of the strategy to fully restore the operation of the country's largest hydropower plant. The signed agreements underline the importance of long-term partnerships and innovative solutions in the energy sector, which play a key role in ensuring the security of the electricity system.

It should be recalled that in order to ensure sustainable long-term operation of Chaira PSHPP, NEK initiated a procedure for complete replacement of hydro units 1 and 4.

The implementation of the large-scale project for the restoration of the largest pumped-storage hydropower plant in the Balkans will contribute significantly to the successful integration of the growing renewable energy production in the whole region and to the achievement of the decarbonisation goals in national and European perspective. Bulgaria will also establish itself as a regional leader in green energy storage.

NEK has successfully completed the rehabilitation of Hydro Unit 2 of Chaira PSHPP and the plant can now participate in the country's electricity system. The synchronization of the plant to the grid was demonstrated during the visit of Prime Minister Dimitar Glavchev and Energy Minister Vladimir Malinov.

The achievement is the result of a unique technical solution developed and implemented for modification in the turbine of hydro unit 2. The implementation of this solution took 12 months of intensive activities on a three-shift basis by the teams of the contractor consortium and the NEK staff. Such modernization is a real achievement in the global hydropower industry.

"From the very beginning, the scale, complexity and lack of similar accidents in global practice exceeded the usual engineering challenges," said National Electricity Company CEO Martin Georgiev. "Innovative approaches and non-standard solutions were required. I am confident that this pioneering solution will leave a lasting mark on the history of engineering excellence. I would like to express my sincere gratitude to all the teams entrusted with the highly responsible task of restoring this key energy capacity for their unfailing professionalism, dedication, and commitment. Your work is not only greatly appreciated but a true inspiration to all engineers to think boldly and innovatively," he said.

Following the successful completion of the rehabilitation works on hydro unit 2, the same approach will be applied to hydro unit 3. The repair works are expected to continue until the end of 2025, as NEK has already completed the dismantling of the generator part of the hydro unit.

Intensive negotiations, which NEK is conducting with the original equipment manufacturer Toshiba, for a medium-term repair solution for hydro unit 1 are in the final phase. The hydro unit is in its original condition and no repairs have been carried out on it since it was commissioned in 1995.

It should be recalled that in order to ensure sustainable long-term operation of Chaira PSHPP, NEK initiated a procedure for complete replacement of hydro units 1 and 4.

The implementation of the large-scale project for the restoration of the largest pumped-storage hydropower plant in the Balkans will contribute significantly to the successful integration of the growing renewable energy production in the whole region and to the achievement of the decarbonisation goals in national and European perspective. Bulgaria will also establish itself as a regional leader in green energy storage.

Additional information

NEK is purposefully implementing a rehabilitation programme for modernization of its hydro engineering facilities. At the beginning of 2024, a large-scale rehabilitation of the largest hydropower cascade in Bulgaria, Belmeken-Sestrimo-Momina Klissura with a total installed capacity of 735 megawatts in generating mode and 104 megawatts in pumping mode was completed.

In addition to the modernization of existing hydropower facilities, NEK is also developing projects for new green capacities. Intensive work is underway for the construction of two new pumped-storage hydropower facilities on the Batak and Dospat dams. According to preliminary estimates, the expected effect of the construction of the two new capacities will guarantee an energy storage capacity of between 30 and 50 gigawatt hours, which is significant not only for Bulgaria but also for Europe.

In addition, the Company is implementing a strategy to develop energy storage systems. It is currently developing its pilot project of an electricity storage system on the territory of Vacha 1 HPP with a capacity of 10 MWh. Through this project, Vacha 1 HPP will become the first hybrid hydropower plant in Bulgaria where the two technologies - generation and storage - will complement each other, ensuring more efficient and reliable operation. Such hybrid systems are planned for 4 more plants.