Return and Vattenfall have signed a long-term agreement for the 200 MW/800 MWh Sirius battery energy storage system (BESS) project located in Winschoten, Groningen, Netherlands. The project is being delivered by Huawei, Hanab and Omexom, covering battery technology, construction and installation. Under the agreement, Vattenfall will secure access to the project’s charging, storage and power delivery capacity in exchange for a fixed fee. The project is expected to commence operations in the fourth quarter of 2027.
Furthermore, the project involved an investment of approximately €180 million. Project financing has been secured under Return’s wider BESS portfolio framework, which provides commitments of up to €400 million. Project financiers include ING, NatWest, Deutsche Bank, ABN AMRO and Rabobank, alongside Return’s existing investors. The project will connect to TenneT’s Meeden substation and operate under a time-dependent transmission rights agreement.
In July 2026, Return and ENGIE signed a 10-year long-term flexibility agreement for a BESS portfolio in Basque Country, Spain. The agreement covers three BESS projects with a combined capacity of 55 MW/220 MWh. Return will develop, own and operate the assets, while ENGIE will optimise the portfolio across Spain’s wholesale and ancillary services markets. Project construction is already underway, with commercial operations expected to commence by the end of 2027.