Pollux
Operating, 30 MW · 68 MWh, in Vlissingen, owned by Return (formerly SemperPower). Every fact below is as a published source states it, with the address beside it; a field not shown is one no source gave, and nothing is guessed.
The battery
| Power | 30 MW |
| Capacity | 68 MWh |
| Duration | 2.3 hours |
| Status | Operating, as of 20 October 2026 |
| Stated date | 20 December 2023, energisation announced |
| Municipality | Vlissingen, Vlissingen-Oost, Zeeland |
| Placed on the map | at the site itself, as mapped on OpenStreetMap (Pollux) |
| How sure | A dated source confirms it |
Who is behind it
| Owner | Return (formerly SemperPower) |
| Traded by | Return |
| Built by | Alfen turnkey |
What the sources say
Conflict: RVO (April 2026) gives 60 MWh; ESN gives 68 MWh. The Alfen 30 MW / 68 MWh story (ESN 24 February 2023) is this project, not a separate one.; Owner figure used: Return 60 MW / 120 MWh combined with Castor, 30 / 60 each per RVO (April 2026). Energy-Storage.news and Alfen gave 68 MWh. Confirmed.
Evidence and sources
- source: energy-storage.news/largest-bess-in-the-netherlands-online
- source: return.energy/locations
- position: openstreetmap.org/way/1184809988
From the owners’, developers’ and builders’ own releases, grid operators’ and permit notices and the trade press, read by Vitreous. No Dutch body publishes a meter, an instruction or a payment for a named battery, so this page carries none. List id NL-B03.