Five hundred meters below the Pacific, off the coast of Los Angeles, a hollow concrete sphere the size of a small house will soon sit anchored to the seabed. When the grid needs power, a valve opens, seawater rushes in, and a turbine spins. When surplus electricity needs somewhere to go, the water is pumped back out. No lithium. No rare earth metals. Just concrete, pressure, and physics. This is StEnSea (Stored Energy in the Sea), a project from Germany’s Fraunhofer Institute for Energy Economics and Energy System Technology, now heading for its first full-scale ocean test off Long Beach, California, by the end of 2026.
