Wind Energy Storage Solution Employing Concrete Spheres

Offshore wind holds tremendous promise, however the intermittent and unpredictable presence of wind imposes limits on this technology. However a new approach from researchers at MIT may have solved this problem with an approach that stores energy to be used when there is no wind.

This concept employs huge concrete spheres which would anchor wind turbines to the sea floor.
When a wind turbine produces more energy than is needed, power would be diverted to drive a pump attached to the underwater structure, pumping seawater from a 30-meter-diameter hollow sphere. Then when there is no wind the water would flow back into the sphere through a turbine attached to a generator, producing energy.

A 25-meter sphere could store up to 6 megawatt-hours of power. One thousand spheres attached to wind turbines could produce as much coal or nuclear plant.

The system could also operate with shore based renewable sources of electricity like solar plants. Preliminary estimates indicate that one such sphere could be built and deployed at a cost of about $12 million but as the spheres are mass produced costs would come down. This could result in an estimated storage cost of about 6 cents per kilowatt-hour.

A 30-inch-diameter prototype was built in 2011 demonstrated the feasibility of the concept. MIT has filed for a patent on the system.

Due to its carbon emissions profile, one of the major problems associated with the concept is the amount of concrete that would be required. To address this problem the concrete spheres could be made, in part, using large quantities of waste fly ash from existing coal plants

The researchers at MIT estimate that these concrete sphere floating wind turbines could create enough capacity to supply one-third of U.S. electricity needs.

Click here to see a full report on the concept published in IEEE Transactions and co-authored by Alexander Slocum, the Pappalardo Professor of Mechanical Engineering at MIT; Brian Hodder, a researcher at the MIT Energy Initiative; and three MIT alumni and a former high school student who worked on the project.