Pumped storage is a decades-old technology with a relatively simple concept: When electricity is cheap and plentiful, use it to pump water up into a reservoir above a turbine, and when electricity is scarce and expensive, send that pumped water down through a turbine to generate more power. Often, these pumped storage facilities are auxiliary to other electricity-generating systems, and they serve to smooth out fluctuations in the amount of power on the grid.
A German research institute has spent years trying to tailor pumped storage to ocean environments. Recently, the institute completed a successful four-week pilot test using a hollow concrete sphere that it placed on the bottom of Lake Constance, a body of water at the foot of the Alps. The sphere has a diameter of three meters and contains a pump and a turbine. Much like traditional pumped storage, when electricity is cheap, water can be pumped out of the sphere, and when it's scarce, water can be let into the sphere to move the turbine and generate electricity.
The Fraunhofer Institute for Wind Energy and Energy Systems Engineering envisions spheres with inner diameters of 30m, placed 700m (or about 2,300 ft) underwater. Assuming the spheres would be fitted with existing 5 MW turbines that could function at that depth, the researchers estimate that each sphere would offer 20 MWh of storage with four hours discharge time.
(Score: 2, Informative) by anotherblackhat on Wednesday March 08 2017, @03:58PM
A 30m sphere has about 14,000 m^3 of volume, and 2800 m^2 of surface area.
If that was water, it would weigh about 14,000 tonnes, so to a first order approximation it would have 14,000 tonnes of buoyancy.
14,000 tonnes of concrete means the walls are about 2 meters thick.
Given the scale of the project, 14,000 of concrete isn't a big deal.
Also, a sphere with 2 meter thick concrete walls is going to have an insane amount of structural integrity.