Between 2023 and 2025 we put mobile batteries on congested parts of the Dutch grid for Enexis and Alliander, at a substation in Den Bosch, at the Efteling and on grid hubs in Arnhem, Amsterdam and Zwolle. These were pilots, run to learn how flexibility at a congested point would work before anyone bought it at scale. For Enexis, what we learned became the basis of a national tender. The lessons that mattered most weren't about batteries.
1. Size from the grid's data, not from the catalogue. At Den Bosch the expected winter peaks were about 1 MW, over roughly two hours. That profile, not a supplier's standard container, set the answer: five units of 250 kW. A set-up sized for the worst imaginable day would have cost far more and done the same job.
2. The contract decides as much as the hardware. Within Alliander's Powered programme we ran two contracts on the same four batteries: a capacity limitation contract called day-ahead, and a redispatch contract called intraday. Together they let the grid operator both stop charging during congestion and ask for energy when it needed it. The same hardware under one contract would have been worth much less.
3. Several parties can share one asset, if the rules are clear. The Alliander pilot had a CSP, a BSP, two battery owners and a site owner. The technical control was the easy part. Agreeing who calls the battery when, and who is paid for what, was the real work.
4. Idle assets are the cheapest flexibility there is. Rental batteries sit idle between jobs. On grid hubs they earned money in that downtime; in 2024 Atlas Copco Rental reported about €2,600 per MW per week. Our own data showed the same batteries cycle very little on rental projects, so the extra wear was small.
5. Speed is the argument grid operators need. Reinforcement takes years; a pilot set-up took weeks. That gave grid operators something rare: real operating experience before they wrote a tender.
Those lessons are why Skoon now works as an independent advisor. The question is rarely "which battery". It is which combination of data, contract, parties and hardware gets a yes from everyone at the table.
