Photo: NEK
Bulgarian state-owned power utility NEK intends to add a 10 MWh battery energy storage system (BESS) by the end of the year to its recently reconstructed Vacha 1 hydropower plant. The company also launched a call to turn four other hydroelectric facilities into hybrid power plants. It estimated the expenses at EUR 63.2 million.
The National Electricity Co. (NEK) is about to upgrade its portfolio with batteries, Capital.bg reported. However, the state-owned hydropower plant operator, part of Bulgarian Energy Holding, is yet to fully cover financing. The pilot project for adding battery energy storage to the Vacha 1 hydropower plant, reconstructed in 2023, is planned for completion by the end of the year, the article reads.
The 14 MW facility was built in 1933. Vacha 1 is part of the Dospat-Vacha cascade in Bulgaria’s south. The battery segment would be 10 MWh. The company earmarked EUR 3.48 million from its own funds for the investment. The reconstruction has cost it EUR 4.91 million.
Bulgaria craves energy storage for flexibility, stability, but also to unleash business opportunities
BESS technology boosts the balancing capability of hydropower plants and even pumped storage hydroelectric systems. Namely, it normally takes them a few minutes to reach the desired capacity utilization, while batteries can kick in instantly and bridge the gap. Energy storage is essential for the integration of wind and solar power plants into the system, as their output depends on the weather and is unpredictable to a large extent.
In addition, infrastructure at existing hydropower plants lowers investment needs and requirements for batteries. BESS can store electricity from excess water in a reservoir so it isn’t wasted.
Batteries at hydropower and pumped storage hydropower plants bring multiple benefits
Overall, Bulgaria is potentially one of the most profitable markets for power arbitrage in the European Union. It is why the government leans heavily on energy storage investments for the country’s energy transition.
Last year Bulgaria was responsible for half of all disruptions in the European electricity grid, precisely because of the lack of sufficient balancing or maneuvering capacities, the news outlet pointed out.
NEK to install at least 279 MWh in battery storage at four other hydropower plants
Apart from the pilot project for its first battery, NEK is planning to add at least 279 MWh in total to four other hydropower plants. According to the current call for contractors, the endeavor is worth EUR 63.2 million.
The battery system for the Studen kladenets hydropower plant (81.3 MW) would have a minimum capacity of 101.5 MWh, the same as the one at the Aleko hydroelectric facility (71.4 MW). The projects are valued at EUR 22.8 million and EUR 22.7 million, respectively.
The contractors will be obligated to build BESS units capable to last two to three hours at maximum operating power
Devin (88 MW), which is upstream from Vacha 1, is getting a BESS of at least 56.4 MWh in capacity, for EUR 13.2 million. The remaining unit is a small hydropower plant called Topolnitsa, of 9.4 MW. The value of its battery system, of a minimum 20 MWh, is estimated at EUR 4.45 million.
All the sums exclude value-added tax. The batteries are required to have capability that enables them to last two to three hours at maximum operating power. For instance, it would be 33.8 MW to 50.8 MW for Studen kladenets and Aleko. The required service life is 6,000 cycles, calculated as fully charging and discharging them 365 times a year.
Troubles with EU funding
NEK also counts on funding from the RESTORE program under the National Recovery and Resilience Plan (NRRP). However, the European Union halted the payment of the second tranche from its Recovery and Resilience Facility (RRF). It is making the battery support scheme uncertain.
The company operates 31 hydropower plants, with a total capacity of 2.74 GW. However, only one of the four units in the Chaira pumped storage hydropower plant (864 MW) was repaired since it completely crashed in 2022.
The second-largest one in the fleet is Belmeken, at 375 MW in generation mode and a pumping system of 104 MW. Fourteen facilities are under 10 MW.
Projects underway for two pumped storage hydropower plants, two battery-backed floating solar parks
NEK is considering the possibility to install standalone battery storage units as well, on its land. Notably, it is also working on two pumped storage hydropower projects – Batak and Dospat, with EU’s help. They are valued at EUR 900 million apiece. The feasibility studies are due for completion by November.
A year ago, the company said it wants to build two floating solar power plants including 5 MW in energy storage operating power, at the Rozov kladenets and Ovcharitsa dams.
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