Design, construction and testing of an ocean renewable energy storage scaled prototype

Abstract

The concept for a new form of pumped storage hydro is being developed within the Precision Engineering Research Group at MIT: the Ocean Renewable Energy Storage (ORES) project. Large, hollow concrete spheres are created, fitted with a reversible pump-turbine and deployed to the sea floor. Water is then allowed to flow through the turbine, into the sphere, to produce power and power is stored back in the device by running the turbine backwards as a pump and evacuating the sphere. The first prototype of that concept is presented here. A land-based system was designed, built and tested to demonstrate its ability to store energy and test the viability of the manufacturing methods planned. The device was successfully built and cycled, storing 2Wh of energy. The round-trip efficiency of the device was severely affected by the low efficiency of the scaled down rotating equipment. It was also found that casting a monolithic sphere is preferable to assembling multiple pieces and that the interior of the sphere should be maintained at atmospheric pressure via a vent line.