• Return extends Alfen partnership with third major battery energy storage system installation in four years.
• New Alfen 100MW/200MWh system will be one of the largest in the Netherlands connected to TenneT’s TSO grid.
• Alfen’s system will help Return simplify the integration of more renewable energy sources into the Dutch grid by providing essential reserve capacity.
• The battery system is expected to be operational by the end of 2026, contributing mostly to Alfen’s 2026 revenues.
• The battery will help ease grid congestion by balancing supply and demand to facilitate a more resilient electricity network.

Almere, the Netherlands 24 April 2025 – Alfen is proud to announce the launch of its largest battery energy storage system (BESS) project to date with Return (formerly: SemperPower), a leading player in the development of independent large-scale energy storage projects. ‘Project Antares’, located in Waddinxveen, in the western part of the Netherlands, will help to alleviate grid congestion and ensure a more predictable and reliable electricity supply for residents and businesses.

“Effective local energy buffering solutions are key to balancing supply and demand, improving predictability and addressing the growing issue of grid congestion in the Netherlands,” explained Yves Vercammen, Sales and Business Development Manager at Alfen. “Together with Return, we’re excited to launch this first-of-its-kind solution, which will play a key role in helping the Netherlands transition to more sustainable energy sources like solar and wind. By ensuring that there’s always spare network capacity when other energy sources are unavailable, battery energy storage systems such as Alfen’s TheBattery Elements can enable the integration of more renewable energy sources into the energy mix.”

Like previous BESS projects that Alfen and Return have completed together, Project Antares will provide the Dutch grid with the flexible capacity needed to manage peaks and troughs in demand. Featuring over 600 Alfen TheBattery Elements modules, Project Antares will provide a capacity of 200MWh and 100MW of power when it becomes operational (scheduled for the end of 2026). This means that it will be able to store enough energy to light around 50% of the main streets in the city of The Hague.

It will also be one the first BESS installations in the Netherlands to successfully connect to the high-voltage power network operated by TenneT. This means that grid operators will be able to respond more quickly to power shortages, helping to avoid blackouts. With the growing prevalence of renewable energy sources, whose availability often fluctuates, this reserve capacity is becoming increasingly important.

“As always, we’re delighted to be working with Alfen to strengthen the Dutch grid, said David Verweij, Energy Transition Specialist at Return. “Alfen’s best-in-class technical capabilities, exceptional expertise and truly collaborative mindset were essential reasons why we chose to work with Alfen. These attributes are essential to our project’s success. We’re proud to be working with them once again to pave the way for a more resilient and sustainable energy network across Europe.”

Flexible capacity on demand
The Waddinxveen installation will be shared by two electricity suppliers for 5 years under agreements that let them lease the battery to trade or store electricity. Alfen will oversee the entire engineering procurement and construction (EPC) process, coordinating civil works including the concrete foundations and fencing around the site. In addition, Alfen’s smart monitoring software will ensure that any maintenance needs are quickly addressed.

Project Antares is the latest installation in a long-standing relationship between Return and Alfen, dating back to 2020, and marks a major milestone in terms of both scale and functionality. “Linking the site directly to the national high-voltage network will necessitate an extensive interface alignment process involving many stakeholders to ensure a smooth project execution,” concluded Yves. “Our great working relationship with Return and our close collaboration will be instrumental in adapting our innovation pipeline so that our solutions are better tailored to the specific requirements of buffering applications.”

About Alfen
Alfen is at the forefront of Europe’s energy transition, providing integrated solutions that help customers address their electricity challenges and achieve climate neutrality. With a history of innovation dating back to 1937, Alfen’s energy storage systems, smart grid solutions, and EV charging stations are installed across more than 30 countries in Europe.

The company has been developing energy storage systems since 2011, with installations totalling over 1+ GWh of energy capacity across 11 European countries. For more about Alfen’s TheBattery solutions, visit TheBattery.

About Return
Return is the leading European independent energy storage provider, committed to revolutionizing the energy sector. Driven by an entrepreneurial team of experts, Return offers innovative, sustainable solutions to store and intelligently manage energy, ensuring power is used efficiently when and where it’s needed most. Headquartered in Amsterdam and with a growing presence across Europe, Return is at the forefront of the energy transition, integrating large-scale battery energy storage systems (BESS) to support grid stability, renewable energy integration, and Europe's net-zero goals. As gamechanger in flexible energy, Return provides reliable energy storage that powers the future of clean energy. For more information: www.return.energy.

Media contact:
Sharda van der Helm - s.vanderhelm@alfen.com