Talum 3, Slovenia - 70 MW / 140 MWh

Talum 3 is NGEN's third battery in the Talum business zone in Kidričevo and its most ambitious project in Slovenia to date. Its 36 Tesla Megapack units give it 70 MW of power and 140 MWh of storage capacity. With Talum 1 (15 MW / 30 MWh) and Talum 2 (20 MW / 40 MWh) already in operation, NGEN's storage at the site will reach 105 MW and 210 MWh, making Kidričevo one of the main battery storage hubs in the country.

For decades Talum was the largest single electricity consumer in Slovenia, taking roughly a tenth of national demand. At full production the electrolysis plant drew around 130 MW, more than a terawatt-hour a year. Rising power prices made primary aluminium uncompetitive. The cells were wound down from 2018 and primary production ended in March 2023, leaving a 203 MW grid connection with very little load behind it.

Talum 1 and Talum 2 sit inside Talum's closed distribution system at medium voltage. Talum 3 connects one voltage level higher, directly to the 110 kV transmission network operated by ELES. It is a standalone battery, independent of any generating unit or industrial load.

Few substations hold enough spare capacity to connect a system of this size, and the reinforcement needed to create it is a heavy cost for a network operator to carry alone. Talum's own energy officer puts the connection point ahead of everything else as the hardest part of siting large storage.

Kidričevo is an exception. Talum holds a 203 MW connection built for electrolysis. Since electrolysis stopped, Talum's own demand has been between 4 and 8 MW, falling below 1 MW during the summer shutdown, and annual consumption has dropped from 1,200 GWh to under 50 GWh. Most of the connection capacity now sits unused.

What the system needs from that capacity has changed too. Solar and wind output rarely matches consumption hour by hour, so the constraint moves from how much electricity can be produced to how quickly supply and demand can be brought back into balance. Few assets on the system respond at the speed this now requires.

At 70 MW and 140 MWh, Talum 3 is a two-hour system. Talum has permanently assigned 70 MW of its connection capacity to the project and leased the land to NGEN for 20 years. The site was designed with expansion in mind, and the system can be enlarged to roughly twice its current capacity without major changes to the core infrastructure.

Construction moved into its main phase at the start of 2026. All 36 units were delivered to site while the transformers were being installed, and electromechanical integration followed over the next few months. Final tests of the complete battery system were completed in May 2026. On 13 August 2026 the first four transformers were energised, giving the site its first live connection to the grid. Commissioning is planned for October 2026, and the official opening will follow in November 2026.

Once in operation, Talum 3 will run on NGEN's own energy platform, which combines battery management, electricity trading and ancillary services. The platform monitors the battery, market conditions and system needs in real time and sets charging, discharging and the capacity offered to each market accordingly. All three Talum phases will be dispatched as one portfolio. Capacity will move between ancillary services and short-term trading as prices and system conditions change, and no megawatt will be offered to two products in the same period.

With 70 MW available, Talum 3 will respond to changes on the grid almost instantly. It will provide ancillary services to ELES, including frequency control, and will significantly expand the automatic frequency control NGEN already supplies to the transmission system operator. It will also shift energy from hours of surplus to hours of high demand, helping the system absorb more renewable generation.

Slovenia's largest battery

At 70 MW and 140 MWh, Talum 3 will be the largest battery storage system in Slovenia.

Stranded connection capacity put back to work

A 203 MW connection built for aluminium electrolysis is being reused for storage, with 70 MW assigned permanently to Talum 3.

Direct transmission connection

Talum 3 connects at 110 kV to the ELES transmission network, one voltage level above the first two phases.

Built to grow

The system can be roughly doubled in size without major changes to the core infrastructure.