55 MWh battery storage system goes live in Bulgaria

Billed as the largest operating battery energy storage system in Bulgaria to date, the 25 MW/55 MWh facility, developed by Austria’s Renalfa IPP, came online at the start of the month.
Renalfa BESS in Bulgaria
Renalfa IPP's 25 MW/55 MWh battery energy storage system in the city of Razlog, southwestern Bulgaria. | Image: Renalfa

Vienna-based developer Renalfa IPP has started commercial operation at its 25 MW/55 MWh battery energy storage system (BESS) located in the city of Razlog, southwestern Bulgaria.

The system, which is connected to the transmission network and located alongside a 33 MW solar plant, successfully went live at the start of the month. Renalfa IPP claims the facility is the largest operating BESS system in Bulgaria and one of the first of such scale in Eastern Europe. 

The facility is being managed and optimised by KER Toki Power, a fully digital Bulgarian electricity trader. The system participates in capacity and balancing markets via the trader’s platform, providing automatic Frequency Restoration Reserve (aFRR) and manual Frequency Restoration Reserve (mFFR) services to the grid.

The main goal is to fully mitigate the PV profile risk of the generators.
Nick Antonov
Spokesperson for Renalfa IPP

Nick Antonov, spokesperson for Renalfa IPP, said the project marks the start of the company’s hybridisation of over 1 GW of renewable assets either in operation or in construction. He added the company is about to introduce similar solutions to its other wind and solar assets in the region, including in Hungary and Romania. 

Renalfa IPP’s says its portfolio of solar, BESS and wind projects equates to around 2 GW across Bulgaria, Hungary, North Macedonia and Romania, of which more than 455 MW is already operational.

“The main goal is to fully mitigate the PV profile risk of the generators,” Antonov added. “In the wider context of the energy transition, this facility demonstrates how advancements in technology are making renewable generation far more useful, dispatchable and flexible to supply and demand”.

The Bulgarian Ministry of Energy launched two renewables-plus-storage tenders in March, aiming to facilitate 1,425 MW of renewable energy generation capacity coupled with 350 MW of energy storage, with funding support only available for the storage component.

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