Bulgaria has returned another generating unit at the Chaira pumped-storage hydropower plant to operation, strengthening one of the country’s most important assets for grid stability and system balancing.
During a visit to the facility, caretaker Energy Minister Traicho Traikov stated that two of the plant’s four units are now operational, emphasizing Chaira’s growing role in supporting the national electricity system. He highlighted that the plant is crucial for maintaining balance in the network and ensuring overall system security.
Hydro unit 3 has successfully completed repair works and passed its final start-up and pre-commissioning tests. The unit is currently operating in test mode and will continue under this regime until it receives Act 16, the official certificate required for full commercial operation. Testing began on 17 February with dry start-up procedures, aimed at verifying coordination across all major systems. According to Minister Traikov, the unit has already completed a successful 72-hour trial run.
At the same time, hydro unit 2 is already in operation and is expected to switch into pumping mode, taking advantage of periods with lower electricity prices. This flexibility is a key feature of pump-storage plants, allowing them to store energy when prices are low and release it back into the system during periods of higher demand.
Minister Traikov also underlined the plant’s strategic importance in emergency situations, noting that Chaira can provide internal electricity supply to the Kozloduy nuclear power plant in the event of a system-wide disruption. He described the facility as one of the most valuable stabilizing resources in Bulgaria’s energy sector.
Preparations are now underway for further rehabilitation, with documentation being finalized for the public procurement process related to hydro unit 1. The equipment supply has been separated from construction and installation works, a structure expected to attract strong market interest. This unit is currently planned to return to operation in 2028.
The Ministry is also exploring future pump-storage developments across the country. Analyses have already identified ten potential locations suitable for similar projects. Meanwhile, according to Krasimir Dimitrov, CTO of the state-owned National Electricity Company (NEK), all command and control systems on hydro unit 3 have been fully modernized. The unit is expected to receive its operating permit in May.
