Ocean Grazer and the EIC Accelerator: A Battery Not Yet Built

Ocean Grazer, a spin-off from the University of Groningen, is developing a pumped hydro energy store that works without mountains: water is pumped between reservoirs to store renewable electricity and released through turbines to recover it. Originally conceived as an "Ocean Battery" on the seabed, it was selected in the EIC Accelerator's January 2023 cut-off and received an EU grant of €2.50 million for OCEANBATTERY, a €4.43 million project that ran from July 2023 to June 2025, according to CORDIS. The project's challenge, in the company's words, was "to demonstrate the technical and economic feasibility of underground PHS by demonstration in an sand excavation lake".

The project is closed, but CORDIS holds only its first periodic report, to June 2024. It says the design was reworked into "Ocean Battery 2.0", which can be installed inshore, near shore or offshore, growing the company's estimated European market from 15 GW to at least 200 GW, and that a digital twin and cost model were developed, according to the CORDIS reporting page. In March 2025 the company announced a site at Sellingerbeetse in Groningen for a 2.5 MWh pilot, part of RWE's OranjeWind project, and said it aimed "to start construction of the pilot in the second half of 2026", according to an archived copy of its website.

Where Ocean Grazer Stands Now

The company now markets its system as AquaVault. In September 2026 its homepage and project page returned a WordPress "critical error"; the last working copy in the Internet Archive dates from August 2026. No announcement that pilot construction has started has been found, and no final report has been published on CORDIS more than a year after the project ended.

The Technology: Pumped Hydro Without Mountains

Conventional pumped hydro stores energy by pumping water uphill and needs mountains. Ocean Grazer creates the height difference artificially with an underground reservoir, which it says gives pumped hydro's long life and near-unlimited cycles anywhere. The company says the system was successfully tested in Eemshaven and won a CES Best-of-Innovation award.

What the EIC Award Promised, and What the Record Shows

The project's own stated challenge was a demonstration in a sand-extraction lake. By its end in June 2025, the company had redesigned the system, modelled it and chosen a site, but had not built the demonstrator; construction was then scheduled for more than a year later. Only the first-year report is public, so what happened in the second year cannot be checked.

1. System redesignDeliveredOcean Battery 2.0.
2. Digital twin and cost modelDeliveredPer first report.
3. Lake demonstrationNot builtConstruction aimed for H2 2026.
4. Final reportingMissingOnly period 1 public.

The Money

The EU paid 56% of the project's cost. Ocean Grazer's investors, revenue and losses are not public in free sources, and it has not announced who will finance the pilot's construction.

What Cannot Be Checked

Why Europe Should Care

The company's report cites a need for 600 GW of energy storage in Europe by 2050, against deployment of about 1 GW a year. Long-duration storage that works anywhere would help. But the EIC funded a demonstration, and the demonstration has not yet happened.

The Verdict

Ocean Grazer and the EIC have not been asked for comment for this article. It is based entirely on public records and published statements, linked throughout.