The Spanish company is commissioning CATL battery cabinets for the energy storage systems at the Mercadal and San Antonio substations.
Alicante, September 2026. Red Eléctrica is progressing with one of the most significant energy storage projects ever developed in Spain: the installation of battery energy storage systems fully integrated into the electricity transmission network at the Mercadal substation in Menorca and the San Antonio substation in Ibiza. Together, the two facilities will provide 140 MW of power and 105 MWh of storage capacity, making them the largest Storage as Transmission Asset (SATA) system in southern Europe and the first of its kind in Spain, according to Red Eléctrica.
The project forms part of Red Eléctrica’s strategy to strengthen the security and quality of electricity supply in the Balearic Islands while maximising the capacity of the interconnections linking the islands to Mallorca. The initial phase included the planning and permitting of the new infrastructure, as well as the expansion of the Mercadal and Dragonera substations to facilitate the connection of new renewable energy projects.
Construction of the Mercadal battery energy storage system began in February 2025, with an anticipated investment of €50 million. The facility consists of two 25 MW systems, providing a combined storage capacity of 37.5 MWh, and is designed as a fully integrated component of the transmission network.
The San Antonio project in Ibiza further expands the scale of the development, delivering 90 MW of power and 67.5 MWh of storage capacity. Its integration will significantly strengthen the electrical interconnection between Mallorca and Ibiza, increasing transfer capacity and providing greater operational flexibility for the power system.
At this stage of execution, the involvement of TERA Batteries is particularly significant, as the company is responsible for commissioning the CATL battery cabinets that form part of the storage infrastructure. This work includes the energisation, testing and verification of the equipment, ensuring that all system components operate in accordance with technical specifications and are fully prepared for integration into grid operations.
One of the distinctive features of the project is its modular architecture, as opposed to solutions based on large containerised systems. The use of independent modules simplifies on-site deployment, enables configurations to be adapted to the specific characteristics of each location, and makes maintenance, replacement and future expansion more straightforward. In addition, the system benefits from extended operational life and enhanced performance through independent liquid-cooling systems integrated into each cabinet.
At Mercadal, the facility comprises 176 modules, delivering the system’s 50 MW of power and 37.5 MWh of storage capacity. In San Antonio, a larger-scale configuration has been deployed to achieve 90 MW and 67.5 MWh of storage capacity.
Both facilities operate as part of a coordinated system rather than as standalone projects. They are interconnected through a wide-area control system that enables their operation to be synchronised, effectively allowing them to function as a single energy storage resource serving the needs of the Balearic electricity system.
For TERA Batteries, participation in this project represents another important step in consolidating its role within the energy storage sector, particularly in highly demanding projects linked to critical electrical infrastructure. The company brings extensive expertise in battery energy storage systems and commissioning activities, contributing to a landmark project that sets a new benchmark for the integration of energy storage as a key element of the electricity transmission network.
