Germany and us prepare for revolutionary ocean energy storage trials
A pioneering ocean energy storage project, dubbed StEnSea, promises to revolutionize the way we supply clean, renewable energy in the future. At first glance, the massive concrete spheres being deployed at the bottom of the sea appear to be little more than giant concrete balls abandoned in the ocean floor. But after a successful trial with a 9-meter diameter sphere in Lake Constanza, Germany and the US Department of Energy are now gearing up for a second test off the coast of California.
How it works
The system is surprisingly simple in concept. Placed on the seafloor at depths of a few hundred meters in areas with gentle slopes, the hollow concrete spheres feature two key components: a feeding system and a valve with a turbine pump. That's all these giant balls need to become fantastic energy storage devices.
By connecting them to the grid via an underwater cable, renewable energy sources can extract the water from inside the sphere, leaving it empty against the natural pressure of the surrounding water. It then sits idle, waiting to be called upon when extra energy is needed.
When power demand surges, for example at night when solar isn't sufficient or during periods of low wind for wind power, the underwater battery springs into action. Opening the valve allows the natural pressure at such great depths to force water into the sphere, causing the turbine to spin and generate electricity.
With an estimated efficiency of 75-80%, the cost of storage is a mere 0.046 euros per kWh. The spheres are expected to last around 50-60 years, with only the mechanical components of the valve and generator needing to be swapped every 20 years to ensure optimal performance.
As plans move forward to deploy 30-meter diameter spheres, that's equivalent to a 27-fold increase in capacity, opening the door to massive underwater energy parks that could help facilitate the widespread adoption of renewables and provide a key solution for meeting peak demand in real-time.