Tera Batteries completes construction of southern Europe’s largest grid-scale energy storage system

Tera Batteries is commissioning CATL battery containers in Spain as part of a 140 MW / 105 MWh energy storage system described as the largest facility of its kind in southern Europe.

Two locations, one system

Tera Batteries is commissioning and validating equipment at two substations in the Balearic Islands as the project enters its final phase. The project was developed by Spanish transmission system operator Red Eléctrica, which integrated the battery systems into the transmission grid at substations in Mercadal (Menorca) and San Antonio (Ibiza).

According to Red Eléctrica, the two sites together form the largest Storage as Transmission Asset system in southern Europe and the first of its kind in Spain.

Tera Batteries is currently commissioning and validating the equipment to ensure that the system meets technical specifications before full integration into the grid.

According to the company, the project is now in the final phase of implementation, installation and commissioning, with completion scheduled for early 2027.

Part of a strategy to strengthen the Balearic Islands grid

The project supports Red Eléctrica’s strategy to strengthen security of electricity supply in the Balearic Islands and increase the capacity of interconnections with Mallorca.

Earlier works included upgrades to the Mercadal and Dragonera substations to accommodate new renewable energy sources. Red Eléctrica awarded the battery supply contract to NHOA Energy in November 2024 following a tender worth €99.87 million.

Construction in Mercadal began in February 2025, with an investment of €50 million. The installation comprises two 25 MW units with a combined capacity of 37.5 MWh, fully integrated into the transmission grid.

Larger scale

The San Antonio substation adds another 90 MW / 67.5 MWh, strengthening the Mallorca–Ibiza interconnection and increasing the operational flexibility of the entire system.

The project uses modular battery containers instead of large, single-container units. This solution simplifies installation, allows the configuration to be adapted to each specific site and facilitates maintenance.

Independent liquid cooling for each module improves system performance and extends its service life. The Mercadal installation uses 176 modules for its 50 MW / 37.5 MWh system, while the larger San Antonio installation reaches 90 MW / 67.5 MWh.

The two sites are connected by a common control system, allowing them to operate as a single, integrated energy storage asset for the Balearic Islands power grid.