Sizable Energy raises $8M to launch ocean-based energy storage

Italy-based Sizable Energy, a developer of long-duration ocean energy
storage, has raised $8 million in a round led by Playground Global, with
participation from Verve Ventures and Unruly Capital.

Sizable Energy is building gigawatt-scale storage using an offshore
pumped-hydro approach. Founded by engineers across nuclear, mechanical, energy,
and maritime disciplines, the company aims to deliver long-duration energy
storage (LDES) for a more reliable and cost-effective grid. Its patented system
applies proven pumped-hydro principles to a marine architecture designed for
modularity and scale, storing energy by pumping saturated sea-salt brine from
the seabed to a surface reservoir and leveraging ocean depth for efficiency.

With the International Energy Agency estimating a need for up to 120 TWh
of LDES by 2040, about ten times today’s capacity, Sizable targets and constraints are facing onshore pumped hydro (slow builds, geographic limits, environmental
concerns) with an offshore solution that is modular, cost-effective, and
designed for rapid deployment.

Invisible from shore, the system targets a low levelized cost of storage,
scales from single-digit to hundreds of GWh, and uses readily available
materials that can be manufactured and installed at depths of 500+ meters using
existing maritime infrastructure.

The company has validated its core technology in wave-basin laboratories
and open-ocean trials. Recent testing
at MARIN indicated reliable operation in harsh ocean conditions, a key
milestone ahead of a megawatt-scale pilot. A new sea trial off Reggio Calabria,
Italy, will validate major floating components and the full assembly and
deployment process, paving the way for a multi-MWh demonstration plant in the
Mediterranean.

The new funding will accelerate the development and
deployment of Sizable Energy’s offshore pumped-hydro system to deliver economical, reliable LDES.