Tidal Energy in Maine


Ocean Renewable Power Company (ORPC) is Maine company that develops ocean and river power systems.

According to this NRDC blog post, ORPC’s Cobscook Bay tidal energy project in the Bay of Fundy in Maine is the first in the U.S. to receive a FERC license, include a power purchase agreement, and install and operate a power-producing tidal generator.

ORPC’s tidal generators are modular turbine-generator units that can be stacked in various configurations for bodies of water of different depths. The company has a RivGen model for small river sites, Ocgen for depths of more than 80 feet, and the TidGen for depths of 50-100 feet.

According to Cleantech PatentEdge™, ORPC owns at least seven U.S. and international patents and pending applications covering its tidal generator technology.

U.S. Patent No. 7,902,687 is entitled “Submersible turbine-generator unit for ocean and tidal currents” and directed to ORPC’s modular unit (’687 Patent). The turbine-generator unit (400) includes a support structure (410) mounting a pair of turbines (420) coupled by a rotatable shaft (430) to a generator (600).

Each turbine (420) has airfoil-shaped blades (500) mounted transversely to the direction of fluid flow for rotation in a plane parallel to the fluid flow. According to the ’687 Patent, the turbines are capable of rotation under reverse fluid flow and rotate in the same direction regardless of fluid flow direction.

U.S. Patent Application Publication No. 2009/0129928 (’928 Application) covers ORPC’s turbine structure. Entitled “High efficiency turbine and method of generating power,” the ’928 Application is directed to a turbine (100) having a plurality of blades (105) tracing a spiral wound path about a central shaft (110).

The blades (105) are connected to the central shaft (110) by a plurality of radial spokes (115), which are substantially perpendicular to the central shaft (110). The blades (105) have an airfoil, or hydrofoil, shaped cross-section (200) with a leading edge (210), a trailing edge (220) and a centerline chord (230).

According to the ’928 Application, the hydrofoil shaped cross section (200) preferably is asymmetrical, which helps generate maximum torque and thereby boosts efficiency. In addition, the hydrofoil cross section (200) presents a non-zero angle of attack for generating lift and maximizing generated torque.

The latest ORPC project update here said the company’s TidGen turbine generator is nearly complete and being prepared for deployment.

Eric Lane is a patent attorney at McKenna Long & Aldridge LLP in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@mckennalong.com

About Author

Walter’s contributions to CleanTechies over the past 4 years have been instrumental in growing the publications social media channels via his ongoing editorial and data driven strategies. He is the founder and managing director of Sunflower Tax, a renewable energy tax and finance consultancy based in San Diego, California. Active in the San Diego clean technology community, participating in events sponsored by CleanTech San Diego, EcoTopics, and Cleantech Open San Diego, Walter has also been a presenter at numerous California Center for Sustainability (CCSE) programs. He currently serves as an adjunct professor at the University of San Diego School of Law where he teaches a course on energy taxation and policy.

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