Standalone grid storage at national scale, under Next Generation EU

The background

RESTORE is Bulgaria’s national renewable-energy plan under the Next Generation EU framework. Spanning RESTORE 1 (9.7 GWh) and RESTORE 2 (4 GWh), it far exceeds the original 3 GW renewable target, with the ambition of building a European-scale energy-storage network. SAKETE was awarded a portfolio of standalone BESS projects totalling 1.1 GWh — roughly 11% of the whole programme.

The challenge

A storage network of this scale has to do more than hold energy — it has to stabilise a national grid absorbing fast-growing wind and solar, and be delivered to strict EU standards on a tight programme timeline.

• Provide grid stability and flexibility as renewable generation scales up across the country.
• Deliver six separate sites — from 20 MWh to 600 MWh — to one consistent engineering and safety standard.
• Meet EU safety, fire and grid-code requirements, with full traceability across manufacturing, shipping and commissioning.

The solution

A standalone, containerised BESS portfolio engineered for grid services and shipped factory-ready to cut on-site work and risk.

The award spans six standalone storage sites: Pleven (600 MWh and 200 MWh), Stara Zagora (200 MWh), Kameno (50 MWh), Silistra (40 MWh) and Balchik (20 MWh).

Each site uses liquid-cooled container battery systems with central PCS and integrated MV transformer — a turnkey block that arrives pre-tested rather than assembled on site. Liquid cooling holds the cell-to-cell temperature difference within 3 °C, protecting cycle life in the field.

Grid-forming PCS provide the stability and flexibility services the grid operator needs. Units were factory-acceptance-tested (FAT) before dispatch, shipped over 9,000 nautical miles, then cold- and hot-commissioned (SAT) on site to international standards.