Sizable Energy has secured $8 million in funding to speed the commercial rollout of its long-duration ocean energy storage technology. The investment round, led by Playground Global with participation from several climate-focused funds, follows successful testing at the Maritime Research Institute Netherlands (MARIN) and the launch of new sea trials off Reggio Calabria, Italy.
The California-based company is developing an offshore pumped hydro system that uses the weight of high-density brine and ocean depth to store energy. During charging, brine is pumped from the seabed into a floating reservoir; during discharge, gravity returns the fluid downward through hydroturbines to generate electricity. The company says the system can be deployed at depths of 500 metres or more using standard marine infrastructure.
“As we scale renewables, storage becomes the critical bottleneck,” said Manuele Aufiero, CEO and co-founder of Sizable Energy. “Our ocean-based solution offers gigawatt-scale storage at competitive cost, improving grid stability and resilience.”
Industry forecasts suggest up to 120 TWh of long-duration energy storage (LDES) will be needed by 2040 – a tenfold increase over today’s capacity. While pumped hydro currently accounts for most installed long-duration storage, new projects face geographic and permitting constraints. Sizable argues offshore deployment offers a modular and rapidly scalable alternative.
Sizable completed wave-basin trials at MARIN in September, demonstrating performance under harsh sea conditions. Its current Italian pilot is validating full-scale floating components and installation processes ahead of a planned megawatt-class demonstration plant in the Mediterranean.
Commercial project development is targeted for 2026 in collaboration with regional manufacturers, utilities, and government partners.
