Return, Alfen and Vattenfall partner on HV transmission-connected 200MWh Dutch BESS

April 25, 2025
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Investor Return has started construction on a 100MW/200MWh BESS project in the Netherlands, with energy storage technology supplied by system integrator Alfen and power company Vattenfall enlisted as long-term offtaker.

The 2-hour battery energy storage system (BESS) in Waddinxveen will be the first to connect directly to the high-voltage network of transmission system operator (TSO) TenneT when it comes online in 2026, Return claimed.

Bank ING led €85 million (US$96.5 million) of project financing for the project, called Antares, with smaller participations by financing firms Meewind and Nationaal Groenfonds.

Netherlands-headquartered Alfen will provide the BESS technology for the project with 600 of its Alfen TheBattery Elements modules as well as overseeing the engineering, procurement and construction (EPC) process, coordinating civil works. Engineering firm SPIE Nederland has also been enlisted as project partner.

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Based on images provided for previous projects, Alfen primarily deploys projects using BESS units from China-based CATL, the world’s largest lithium-ion OEM. The firm recently relocated a BESS project from one site to another in the Netherlands, something relatively rare.

Meanwhile, Swedish state-owned utility, power generator and energy trader Vattenfall will be one of several offtakers for the Antares project, contracting for 50MW of its capacity over an eight-year period. Return said Vattenfall is one of multiple capacity offtakers, but didn’t name the others. Alfen meanwhile said the project will be shared by two electricity suppliers for five years under agreements where they lease the BESS.

Return starts deploying projects under its own name

Return has been active in the grid-scale BESS market in the Netherlands but only now is deploying projects under its own name.

Until now, it deployed projects through its SemperPower platform, which has deployed what are currently the two largest projects in the Netherlands (though larger ones are expected online this year) and is deploying a large-scale one in partnership with Corre Energy. In February, SemperPower was rebranded to the name of its parent company.

Return is also an investor in Lion Storage, a developer-turned-owner-operator which recently reached financial close on a 1.4GWh BESS project called Mufasa, in Vlissingen, which Tesla will deploy as EPC and BESS provider. Return said Antares is the second-largest BESS project in the Netherlands after Mufasa.


24 February 2026
InterContinental London - The O2, London, UK
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9 June 2026
Stuttgart, Germany
Held alongside The Battery Show Europe, ESS Germany — Stuttgart Edition provides a focused platform to understand the policies, revenue models and deployment conditions shaping Germany’s utility-scale storage boom. With contributions from TSOs, banks, developers and optimisers, the Summit explores regulation, merchant strategies, financing, grid tariffs and project delivery in a market forecast to integrate 24GW of storage by 2037.
1 December 2026
Italy
Battery Asset Management Summit Europe is the annual meeting for owners, operators, investors, and optimisation specialists working with operational BESS assets across the continent. The Summit focuses on how to maximise performance and revenue, manage degradation, integrate advanced optimisation software, navigate evolving market and regulatory frameworks, and plan for repowering or end-of-life strategies. With insights from Europe’s most active storage markets, it equips attendees with practical guidance to run resilient, profitable battery portfolios as the sector scales.

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