IN Brief:
- The Iron Gates II battery will provide 64MW of power and 434.76MWh of energy storage.
- Synergy Construct has secured the RON296.8m contract, with RON43.4m also provided through Romania's Modernisation Fund.
- At rated output, the battery's energy capacity equates to approximately 6.8 hours of discharge.
Hidroelectrica has awarded a RON296.8 million contract for a 64MW/434.76MWh battery energy storage system at its Iron Gates II hydropower complex in Romania. Synergy Construct has secured the work following a public procurement process, giving Hidroelectrica its largest battery project to date.
The system combines 64MW of power with 434.76MWh of stored energy, equivalent to approximately 6.8 hours of continuous discharge at rated output. That duration gives the project considerably more energy-shifting capability than batteries configured mainly around short frequency-response services.
Synergy Construct will deliver the project with subcontractors and third parties including Kseo Enerji, Professional Land Survey, Zoork, Tripol Sistem Construct, Inemko, and Rogotehnic. Hidroelectrica has also secured RON43.4 million through Romania’s Modernisation Fund programme for electricity storage investment.
The battery is intended to optimise Hidroelectrica’s production across the daily operating cycle, retaining electricity when immediate system or market value is lower and releasing it later when demand or prices increase. Adding electrochemical storage to a hydro-dominated generating portfolio introduces another controllable energy reserve without requiring an immediate change in water releases.
Hydropower and batteries offer different forms of flexibility. Reservoir conditions, water availability, environmental restrictions, and plant configuration govern the response available from a hydroelectric station, while a battery can react rapidly within its power, energy, and state-of-charge limits. Coordinating the two technologies can therefore broaden the operating choices available to a utility across balancing, energy shifting, and portfolio optimisation.
The Iron Gates II award joins a rapidly growing Romanian storage pipeline. Other Romanian battery developments have also moved into large-scale delivery, with storage increasingly being combined with renewable generation and reinforced grid connections rather than developed solely around narrow ancillary-service markets.
At Iron Gates II, integration with an established generation site provides both opportunities and engineering constraints. Existing high-voltage infrastructure offers a stronger starting point than many greenfield battery developments, but the BESS must still be incorporated into the site’s protection, metering, supervisory control, communications, auxiliary supplies, and operating procedures.
The power conversion system will control the flow of energy between the battery and the AC network, while transformers, switchgear, protection relays, and control equipment will have to accommodate repeated transitions between charging and discharging. Fire detection, thermal management, isolation procedures, and emergency response will form another substantial part of the installation around the battery cells themselves.
The project’s 434.76MWh energy capacity is particularly significant because it allows operation across several hours rather than minutes. A long discharge duration broadens the potential use of the asset into intraday energy shifting and renewable balancing, although profitability will depend on wholesale spreads, ancillary-service revenues, efficiency losses, battery degradation, and the capacity reserved for different services.
Romania is expanding renewable generation while adding more storage to its electricity system. As variable output rises, assets capable of absorbing generation during periods of surplus and returning it during later demand periods can reduce curtailment pressure and give system operators greater flexibility. Storage cannot remove structural transmission constraints, but it can alter when power must move through them.
The Modernisation Fund contribution also reflects the capital intensity of utility-scale storage beyond the battery modules. Civil works, inverters, transformers, cabling, switchgear, control systems, cooling, protection, testing, grid-code compliance, and commissioning all contribute to the final cost of a plant of this size.
Long-duration daily cycling will place particular emphasis on efficiency and thermal control. More stored energy passing through the power electronics during each full cycle increases the cumulative effect of losses, while cell temperature and state of charge must remain within operating limits that preserve performance and usable life.
Hidroelectrica has not announced a commissioning date in the project information available for the award. The next evidence of progress will therefore come through detailed design, equipment procurement, construction, electrical installation, and energisation. Once operational, the 434.76MWh system will provide a substantial new flexibility asset alongside one of Romania’s major hydroelectric sites, adding flexible capacity at scale.
