Planning is underway in Bulgaria to install two underground pumped storage hydropower facilities with a combined capacity of 1.6 GW. At the same time, Chaira, the largest system of the kind in Southeastern Europe, remains offline. It was heavily damaged in a series of breakdowns and failed repair attempts.

Prime Minister Nikolay Denkov and Minister of Energy Rumen Radev told the National Assembly of Bulgaria that the government would initiate studies to determine the potential for two pumped storage hydropower plants. Such systems are in effect batteries, essential for integrating the intermittent production of electricity from renewables into the grid.

Pumped storage hydroelectric facilities are still the only conventional energy storage technology. They use reversible turbines, which can work in both modes, or pumps.

Water is taken from a lower to an upper reservoir during times of low demand for electricity and when there is a surplus of wind and solar power. When the balance shifts, pumped storage generates electricity by releasing the water downward through turbines.

Government hopes to complete both projects in 2032

The two facilities, envisaged with 800 MW each, are planned to be installed underground and connected to the dams Dospat and Batak. They are run by the National Electricity Co. (NEK). The authorities estimated both systems could be completed in 2032.

The locations are in Bulgaria’s southwest, in the Rhodopes.

NEK already has an underground pumped storage hydropower plant, Chaira, in a nearby area. At a nominal 864 MW in capacity and 788 MW in pumping mode, it is the largest in Southeastern Europe. But Chaira, part of the troubled Belmeken-Sestrimo-Chaira cascade, has been offline for the past year and a half, after a series of outages and disastrous rehabilitation attempts.

Some of the four dysfunctional units could be repaired by the end of next year, officials estimated. As for long-term plans, the capacity should be increased in a project involving the construction of the Yadenitsa dam.

NEK is using the Kozloduy nuclear power plant decommissioning fund for the rehabilitation of the hydropower complex that includes Chaira and Belmeken

The Belmeken pumped hydropower facility, located upstream, has a maximum generating capacity of 373 MW. Out of five turbines, two are reversible and have a total pumping ability of 104 MW.

NEK has the Kozloduy International Decommissioning Support Fund (KIDSF) at its disposal for the rehabilitation of the complex. The facility was launched by the European Bank for Reconstruction.

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 165 MW in total, of which a 38 MW unit can work in both modes.

As for the rest of the region, North Macedonia has just chosen a strategic partner for one such facility. Albania and Turkey are also working on their first pumped storage endeavors. There is a dormant project in Kosovo*. Serbia, Greece, Romania and Slovenia already have some capacities. In recent years they all launched or revived plans for more investments in the segment.

Belene nuclear power project is officially scrapped but site could be used after 2035

Of note, the two units at the Kozloduy nuclear power plant are set to be shut down. But Denkov’s government wants to build two more at the same location and is also developing plans for small modular reactors.

Conversely, this week the Council of Ministers formally abolished the plans for nuclear plant Belene, which was supposed to be built in cooperation with Russia. However, Minister Rumen Radev said the site remains suitable for the purpose, indicating that new units could be built there after 2035.