The Lanai Pumped Storage Project is a 300 megawatts (400,000 hp) energy-storage project for Hawaii, under feasibility study by Gridflex Energy.
It would use the Pacific Ocean as the lower reservoir, saving a considerable amount of money during construction.
The proposed project would consist of the following: (1) An artificial, lined 57-acre reservoir created by the construction of embankments; (2) an approximately 11,650-foot-long conduit joined to the Pacific Ocean; (3) three reversible pump-turbines, totaling 300 megawatts (MW) of generating capacity, with up to 100 MW of additional pumping capacity; (4) an approximately 6-mile-long, single-circuit 230-kilovolt transmission line; and (5) appurtenant facilities. The estimated annual generation of the Lanai Pumped Storage project would be 919,800 megawatt-hours.
Wind energy, at a lower cost, would be used to pump the water to the upper reservoir, to be released during periods of high demand on the grid. The project was proposed to complement wind development on the island of Lana'i in the event that the proposed Inter-Island Cable project extends to that island.