It’s only a proposal. But it’s an idea that could make offshore wind a lot more dependable and cost-effective, says the Massachusetts Institute of Technology (MIT): storing surplus energy from wind turbines in a concrete sphere under water. The principle is straightforward.
During periods when there is more wind energy than immediate demand, the additional power would be used to pump seawater out of a hollow, submarine sphere. Later, when power is needed, water would be allowed to flow back into the sphere through a turbine attached to a generator and the resulting electricity sent back to shore. MIT has calculated that a 25m sphere in 400m-deep water could store up to 6MWh of power.
Multiply that figure up and 1,000 turbines with this form of pumped hydro energy storage could rival a nuclear power station, for a matter of hours at least. The big drawback is a minimum 200m depth of water required to make the scheme feasible, especially as off-shore wind, which currently only enjoys popularity in Europe, is currently sited in waters shallower than 30m.
But the ability to provide despatchable energy without the need for large-scale batteries on or offshore is clearly a huge plus for the idea.