Sizable Energy Secures $8M To Develop Offshore Energy Storage Solutions

The company is developing gigawatt-scale storage using an offshore pumped-hydro method. Founded by engineers with expertise in nuclear, mechanical, energy, and maritime fields, Sizable aims to provide reliable, cost-effective long-duration energy storage (LDES).

Its patented system adapts pumped-hydro principles to the ocean, storing energy by pumping saturated sea-salt brine from the seabed to a surface reservoir, using ocean depth to maximize efficiency.

With the International Energy Agency projecting a demand of up to 120 TWh of long-duration energy storage (LDES) by 2040—around ten times current capacity—Sizable Energy offers an offshore alternative to onshore pumped hydro, overcoming slow construction, geographic limits, and environmental challenges.

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The modular, cost-effective system is invisible from shore, scalable from single-digit to hundreds of GWh, and built using readily available materials that can be manufactured and installed at depths of 500+ meters leveraging existing maritime infrastructure, targeting a low levelized cost of storage.

Sizable Energy has successfully tested its core technology in wave-basin labs and open-ocean trials. Recent MARIN tests showed it can operate reliably in tough ocean conditions a key milestone before moving to a megawatt-scale pilot. An upcoming sea trial off Reggio Calabria, Italy, will validate the floating components, assembly, and deployment, setting the stage for a multi-MWh demonstration plant in the Mediterranean.

The new funding will speed up the development and deployment of Sizable Energy’s offshore pumped-hydro system, delivering cost-effective, reliable long-duration energy storage (LDES).

About Sizable Energy

Sizable Energy develops offshore long-duration energy storage using patented pumped-brine technology. Its modular, easily deployable system leverages the gravitational potential of dense sea-salt brine at hundreds of meters depth, extending pumped-hydro solutions offshore. The approach provides secure, cost-effective and sustainable energy storage for a more reliable and resilient grid.