Toshiba Signs MoU with Bulgaria’s NEK on the Restoration and Sustainable Operation of the Chaira Pumped Storage Power Plant
April 27, 2026
Kawasaki, Japan – Toshiba Corporation has announced that Toshiba International Europe Ltd., its UK-based subsidiary, has signed a memorandum of understanding (MoU) with National Electricity Company EAD (Natsionalna Elektricheska Kompania EAD; NEK EAD), Bulgaria’s state-owned electric utility. The agreement establishes a framework to explore collaboration on the restoration of the Chaira pumped-storage hydropower plant and its sustainable long-term operation.
Atsushi Mikuni, President of Toshiba International Europe Ltd. (seated on left), and Georgi Dobrev, CEO of NEK EAD (seated on right) signed the MoU. H.E. Chikahisa Sumi, Ambassador Extraordinary and Plenipotentiary of Japan to Bulgaria (standing, left), and Valentin Nikolov, CEO of the Bulgarian Energy Holding*1 (standing, right), attended the signing ceremony.
As Europe accelerates its energy transition, renewable energy is expected to account for 91%*2 of power generation by 2050. This shift is expected to significantly increase the need for flexible balancing capacity to ensure grid stability. Pumped-storage hydropower plays a critical role in this context, storing energy during periods of low demand and generating electricity during peak demand, thereby helping to manage fluctuations in renewable energy supply.
In line with these trends, Bulgaria is currently considering pumped storage hydropower projects with a total capacity of approximately 4.5 GW*3. The Chaira pumped-storage hydropower plant (PSHPP), the largest in the country, has an installed capacity of 864 MW across four units. However, due to aging infrastructure, some units are currently out of operation, underscoring the urgent need for comprehensive restoration and optimized plant-wide operation.
Under the MoU, Toshiba will provide technical support that aims to restore Chaira PSHPP and secure its sustainable operation. Toshiba has already been commissioned to carry out repair work on Unit 1 and will also conduct studies on and provide technical support for the plant as a whole, including operational and maintenance support for Units 2, 3 and 4, as well as recommendations to enhance the reliability and efficiency of key equipment such as pumped-storage turbines and generators.
Toshiba has a long-standing presence in Bulgaria’s power generation infrastructure, dating back to 1994, when it supplied pumped-storage turbine and generator for Unit 1 of the Chaira PSHPP. It subsequently expanded its deliveries to cover all four units, providing a total of four turbines (864 MW) and four generators (940 MVA). More recently, the company has also been involved in the rehabilitation project of the Maritsa East 2 Thermal Power Plant.
Toshiba Group offers a comprehensive portfolio of hydro turbines and generators to accommodate a wide range of flow conditions, hydraulic heads, and output requirements. Going forward, Toshiba remains committed to supporting the global transition to carbon neutrality by delivering high-quality products, maintenance services, and technical expertise that enable the sustainable and reliable operation of power infrastructure.
- Bulgarian Energy Holding EAD is the holder of the capital of NEK EAD.
- Source: Regional Energy Transition Outlook, page 16, Table S1, jointly published by IRENA (International Renewable Energy Agency) and the European Commission.
https://cisp.cachefly.net/assets/articles/attachments/95016_irena_out_reto_eu_2025.pdf (PDF) - Source: News release issued by NEK EAD on September 30, 2025.
https://nek.bg/index.php/en/news-en/2306-large-scale-energy-storage-the-missing-piece-in-the-energy-puzzle
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