Given the right sea conditions, a demonstration model of a wave-energy modular electricity-generating system could be installed off Hawaii this month or next.

WAVE RIDER Piston action generates 20 kw of electricity. (Image Source: Ocean Power Technologies Inc.)

The Navy has received an Army Corps of Engineers water permit to deploy a PowerBuoy wave-energy converter and support equipment offshore at Marine Corps Base Hawaii and is waiting for relatively calm water to begin work. The unit will be anchored in 100 ft of water about 3,900 ft offshore.

The PowerBuoy was developed by Ocean Power Technologies, Pennington, N.J., with a grant from the Navy, says Don Rochon, Navy public affairs officer. It has been tested offshore New Jersey in recent years. The steel buoy measures 15 ft dia by 45 ft long. Riding up and down beneath the surface, it pumps hydraulic fluid to a motor driving a 20-kw generator. The electricity will be fed via a 4.1-kv subsea cable into the Marine Corps base electrical grid. Company officials say the modules can be deployed in fields that could yield up to 100 Mw of power.

When meteorologists forecast two to three days of 4-ft waves, Sea Engineering, Honolulu, will drop and anchor a cable that will enable deployment of the PowerBuoy. Submerged equipment will be secured to the seafloor with rock bolts and protective split pipe sufficient for maintaining system integrity in case of a 500-year storm event, says Rochon. The generating unit and four pods to convert alternating current to direct current for transmission will be installed a month later.

The PowerBuoy locks down in large waves for self-protection. Data from sensors are sent to control systems housed in the canister, which determine when to lock and unlock the buoy.

Plans call for a second buoy to be installed later to generate up to 100 kw of electricity for the base. The Office of Naval Research is sponsoring the $9.5-million project, as well as providing program management. The Naval Facilities Engineering Service Center at Port Hueneme, Calif., will manage the project and provide technical oversight. The Pacific Division, Naval Facilities Engineering Command at Pearl Harbor, will manage onsite and environmental requirements for the project.

The objective of the program is to develop and validate the technology, to design and reliably operate an ocean-wave PowerBuoy, demonstrate the technical and economic feasibility of using ocean-wave power to reduce the total cost of facility ownership and reduce the Navy’s dependence on foreign oil.