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. Ocean Grazer B.V. was declared bankrupt by the court on 1 July 2025, the day after the project ended, and the bankruptcy was ended for lack of assets on 3 November 2026, according to the insolvency register record.

Where Ocean Grazer Stands Now

Before the bankruptcy, the company had renamed its system AquaVault. The court declared Ocean Grazer B.V. bankrupt on 1 July 2025 and appointed a curator; the register shows the bankruptcy was ended on 3 November 2026 because of a lack of assets, according to the insolvency register record. NOS reported in August 2025 that the curator estimated debts at €3 million to €4 million, and that the director of the University of Groningen's holding company said parties had pledged €13 million for an €18 million pilot but the remaining €5 million could not be raised. In September 2026 the company's homepage and project page returned a WordPress "critical error", and the homepage returned a server error on 7 November 2026. Sources reviewed on 7 November 2026 do not show that pilot construction started, and CORDIS lists no final report.

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 no demonstrator had been reported built; construction was then scheduled for more than a year later, and the company was declared bankrupt the next day. 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 builtNone reported before bankruptcy.
4. Final reportingNot publicOnly period 1 public.

The Money

The EU contribution was 56% of the project's total cost on CORDIS; how much of the grant was paid out is not public. Ocean Grazer's revenue and losses were not found in free sources, and the pilot financing described to NOS was not completed before the bankruptcy.

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 sources reviewed show none before the company's bankruptcy.

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.