Bulgarian state-owned power utility, the National Electricity Company (NEK), plans to install a 10 MWh battery energy storage system (BESS) at its recently reconstructed Vacha 1 hydropower plant by the end of this year. Additionally, NEK has launched a tender to convert four other hydropower plants into hybrid power plants, with estimated costs totaling EUR 63.2 million. The company, which is part of Bulgarian Energy Holding, is in the process of expanding its portfolio with battery storage, though it has not yet fully secured financing for the projects, according to Capital.bg.
The Vacha 1 hydropower plant, originally built in 1933 and part of the Dospat-Vacha cascade in southern Bulgaria, underwent reconstruction in 2023. The addition of a 10 MWh battery storage system is part of a pilot project that aims to enhance the plant’s capabilities. NEK has allocated EUR 3.48 million of its own funds for the battery installation, with the total reconstruction cost of Vacha 1 reaching EUR 4.91 million. Battery energy storage technology improves the balancing ability of hydropower plants and pumped storage systems, which typically take minutes to reach full capacity. Batteries, on the other hand, can quickly provide power and help bridge gaps in generation. This technology is also essential for integrating renewable energy sources like wind and solar, which are variable and weather-dependent.
BESS technology also reduces the need for significant new infrastructure, as existing hydropower plants can store excess energy, such as water stored in reservoirs, instead of wasting it. With energy storage systems in place, Bulgaria is seen as a potentially profitable market for power arbitrage within the European Union. The government is focusing on energy storage as a key component of the country’s energy transition.
In addition to the Vacha 1 pilot project, NEK is planning to add significant battery storage capacity at other hydropower plants. The Devin hydropower plant (88 MW), located upstream from Vacha 1, is set to receive a BESS with a minimum capacity of 56.4 MWh, at an investment of EUR 13.2 million. The Topolnitsa plant, a smaller facility with a 9.4 MW capacity, will receive a battery system with at least 20 MWh, estimated at EUR 4.45 million. These investments, like others, are exclusive of value-added tax.
The batteries for these projects are required to last between two to three hours at maximum power, with capacities ranging from 33.8 MW to 50.8 MW for plants like Studen Kladenets and Aleko. The expected service life of the batteries is 6,000 cycles, equivalent to fully charging and discharging the batteries 365 times a year.
Last year, Bulgaria was responsible for half of all disruptions in the European electricity grid due to insufficient balancing and maneuvering capacities, highlighting the need for enhanced storage and grid management solutions. Beyond the pilot project at Vacha 1, NEK aims to add a total of at least 279 MWh of energy storage across four other hydropower plants, with the full expansion valued at EUR 63.2 million. This includes the Studen Kladenets and Aleko plants, with projects worth EUR 22.8 million and EUR 22.7 million, respectively.
