Sizable Energy raises $8 million for offshore hydro storage

Italian startup Sizable Energy has raised $8 million to accelerate the commercialization of its offshore pumped hydro energy storage technology. The funding round was led by Playground Global, with participation from Exa Ventures, Verve Ventures, Satgana, EDEN/IAG, and Unruly Capital.

The technology offers a sustainable alternative to lithium-based batteries by utilizing the density difference between seawater and brine. In a closed-loop system, brine is pumped from a seabed reservoir to a floating surface reservoir. To release energy, the brine flows back down through reversible turbines, generating electricity via gravity.

Designed to be modular and scalable, the system can provide capacities ranging from one to hundreds of gigawatt-hours. The infrastructure is intended for installation at depths of 500 meters or more, utilizing existing maritime shipbuilding and infrastructure. Following successful tests at the Maritime Research Institute Netherlands, new sea trials are being conducted in Reggio Calabria, Italy.