Ocean batteries – storage for offshore power

Pumped hydro-like storage systems are under development to store energy at sea from offshore wind turbines.

Apparently the most advanced concept is the Dutch start-up Ocean Grazer’s ‘Ocean battery’, with the first commercial demonstrators currently under development.

The technology is described as a “pumped hydro system in a box”. To store energy, e.g. when there is excess, the system pumps water from rigid reservoirs into flexible bladders on the seabed, which store the water under high pressure.

When there is demand for power, the water flows back from the bladders to the low pressure rigid reservoirs, driving multiple hydro turbines to generate electricity.

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Ocean Grazer, a spin-off from the University of Groningen where the concept was conceived, state their technology is based on proven technologies and is almost maintenance free.

Moreover, it is modular and scalable up to gigawatthour scale and has an ROI estimated from 8-10 years.

The Ocean Battery has received support from the European Union among other parties and also has attracted an unnamed angel investor to advance development.

The team is targeting a 10% market share in Europe by 2030 and in time 10-15% of the market.

The PowerBundle

Hot on the heels of Ocean Grazer is Luxemburg headquartered Subsea 7, an established player in offshore energy projects and services, with which technology partner FLASC is developing the ‘PowerBundle’ concept for energy storage.

The PowerBundle, one of the emerging storage technologies awarded funding from the Department for Business, Energy & Industrial Strategy’s (BEIS) Longer Duration Energy Storage Demonstration programme, is described as combining FLASC’s proprietary hydro-pneumatic energy storage technology and Subsea 7’s proven subsea pipeline bundle technology to result in a scalable and robust offshore energy storage solution.

Again of pumped hydro concept, FLASC’s technology is comprised of a storage vessel in which energy is stored under pressure using a hydro-pneumatic liquid piston driven by a reversible pump-turbine and is released when the water is released.

In phase one of the award, the technologies will be mobilised to be followed in the second phase with further funding to build and test a grid connected full-system demonstrator.

Netherlands based FLASC, a spin-off from the University of Malta, has prototyped its technology in Malta’s Grand Harbour with over more than 400 charge/discharge cycles claiming >98% average thermal efficiency and more than 98% system availability.

Another company awarded funding from the BEIS Longer Duration Energy Storage Demonstration programme is Los Angeles headquartered RCAM Technologies, which specialises in 3D concrete printing.

The company envisages its pumped hydro concept storage – named Marine Pumped HydroElectric Storage – in multiple large hollow concrete spheres on the seafloor.

With the funding for a feasibility study, RCAM Technologies’ proposal is the least advanced at this stage. But with the prospect of major growth in offshore wind all of the technologies have promise in contributing to a potential future market mirroring the onshore utility scale storage market.