Ocean Power Enters Adolescence
A decade or more behind wind and solar energy, recent developments in ocean wave power technology may put it on the threshold of practical commercialization

by Lee H. Goldberg

The growing amounts of capital and technical expertise being applied to produce the first commercially-viable ocean power systems point to a day when our seashores may take their places along side the wind belts and sun belts as sources of abundant, sustainable electrical energy. Although several previous generations of technical entrepreneurs have attempted to build wave-powered electrical generators, all of them have failed when even their sturdiest creations could not stand up to the sea's fury. But, recently, a new set of players has stepped up to the challenge. If they are successful, ocean wave power systems could help plug a big hole in today's renewable energy gap. It could also mean big business opportunities for the power electronics industry.

There is no firm consensus about what exactly has caused the recent flurry of activity in ocean wave power technology. It may be that the change began a few years ago when the technology finally matured enough to be ready for commercialization or it may just be a result of the venture capital community's recent fascination with renewable energy. But whatever the cause, the recent jump in activity and investment may be indicators that it's on the threshold of a breakout to commercial feasibility similar to what occurred with wind and solar around the turn of this century.

The roots of today's wave energy boom can be traced back at least as far as 2003/2004, when Oregon State University began a project with the Electric Power Research institute (EPRI) and the Oregon Department of Energy to develop a wave energy test and demonstration facility. The university's Motor Systems Resource Facility now has several promising technologies in development, including a system based on a buoy anchored about one or two miles offshore in more than 100 feet of water that uses the up and down motions of large ocean swells to generate electricity by pushing large electrical coils through a magnetic field (see Fig. 1).

Further down the coast, California is aggressively pursuing wave power as part of its renewable energy program. According to a 2005 report prepared for the California Energy Commission entitled California Small Hydropower and Ocean Wave Energy Resources, the state's potential ocean wave energy represents 7460 MW worth of generating capacity, or more than three times the 1927 MW available from traditional hydropower sources.

One of the more intriguing projects being explored by California's initiative involves a pumped storage technology known as SEADOG. Developed by Minnesota-based Independent Natural Resources, Inc. (INRI), SEADOG uses a simple, rugged ocean-wave energy pump (see Fig. 2), to move large volumes of seawater to an elevated onshore reservoir where it is returned back to the ocean through a turbine that generates electricity. Alternatively, the SEADOG pump can be used to deliver high volumes of water at sufficient head pressure to supply water for shoreline desalination facilities. In either case, the nearly fail-proof SEADOG pump takes the beating while the more complex and sensitive equipment remains safely onshore.

A prototype SEADOG unit has been successfully tested in the Gulf of Mexico off the coast of Freeport, TX for the past year, where INRI says it exceeded expectations for performance and durability. INRI is currently constructing a scaled-up version which will be tested in the more challenging environment off the rugged coast of Northern California; in the Table Bluff area of Humboldt County. If the prototype SEADOG survives its one-year ordeal intact, plans call for a small-scale 16-pump pilot wave farm which will be used to fill a 50,000 gallon storage tank attached to a hydroelectric generator. If the $3 million phase-I trial is able to reliably deliver the 500+ kW (enough to light around 600 homes) INRI hopes to expand the project to a 200-pump 6.7 MW system that would produce power at a cost of around 3.5 cents/kW-hr, a price that approaches typical wholesale rates for fossil-generated power.

Meanwhile, back on the East Coast, we're seeing lots activity as collaborations such as that between the Maine Technology Institute and Ocean Renewable Power to develop an engineering prototype of its ocean current turbine generator and test it off the Maine coast in the Western Passage and Cobscook Bay. While Ocean Renewable's technology is not strictly a wave power system, each of the submerged turbines (see Fig. 3) will pull 100 - 500 kW of power from the relatively gentle and regular tidal and marine flows without having to endure the pounding that their wave-borne brethren must operate in.

There's also lots of wave power activity in Europe, including the Wave Hub, a $26 million demonstrator project off the coast of Cornwall which provides the infrastructure for testing multiple wave generation technologies. The project, scheduled for completion in 2007, will serve as a test bed for generating devices from Ocean Prospect Ltd, Ocean Power Technologies, and Fred Olsen Ltd, while pumping 10 - 30 MW into Cornwall's regional power grid.

While many technical hurdles remain to actually producing generators that can reliably withstand the ocean's fury long enough to pay for themselves, the future looks bright for wave power technologies. This also represents a tremendous opportunity for the power electronics sector which will be tasked to develop the control, regulation and conversion systems that transform the raw wave-generated electricity into grid-ready energy. Some of this will evolve from existing products used in today's wind and hydroelectric systems but it's likely that the unique characteristics of the wave generators and the power they produce will demand equally unique technologies to manage them.

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