Buoy System Harnesses Wave Energy

ByJohn Yang

June 29, 2001 -- One future solution to the global energy crunch could be as old as the oceans.

Later this summer, a New Jersey company will launch a series of buoys in the Pacific Ocean more than a mile off the coast of Melbourne, Australia, to harness the power of the ocean's relentless waves.

The system is expected to generate up to 10 megawatts of electricity — enough to power about 10,000 homes — for the Melbourne-Sydney power grid. And the buoy system should generate the power far more cleanly than conventional plants that burn coal or gas.

"The ocean is a very forceful environment," says George W. Taylor, president of Ocean Power Technologies. "The energy is very concentrated."

Strung by Buoys, Run by Chips

The buoys are submerged more than a meter below the water's surface. Inside, a cylinder that moves around a piston-like structure as the buoy bobs with the rise and fall of the waves. That movement drives a generator on the ocean floor, producing electricity, which is sent to the shore along an underwater cable.

Computer chips constantly monitor the system's performance, disconnecting the system when unusually large waves threaten to disrupt it and reconnecting it when the waves return to normal.

The Australia project could have up to 20 buoys, each about 4.5 meters (or nearly 15 feet) in diameter and capable of generating 50 kilowatts of electricity. Ocean Power Technologies also has a contract with the U.S. Navy to install a 1-megawatt system for a base in Hawaii.

The company developed the technology with a grant from the Navy, first testing it for 11 months in an offshore station that recharged two-man research mini-subs in the ocean off Atlantic City, N.J. That system survived several major storms — even Hurricane Bonnie, which had waves as high as 30 feet.

Taylor envisions systems as big as 100 kilowatts powering small coastline communities or offshore oil rigs. Eventually, larger plants could plug into regional power grids, he says.

A Free Fuel

Taylor acknowledges that his system involves a larger initial investment than conventional technology. Small installations are projected to cost $5 million per megawatt; systems that would generate 100 megawatts would cost about $2.3 million per megawatt. That compares with about $1.5 million per megawatt for coal- or gas-fired generators.

But the fact that the "fuel" for wave power is absolutely free reduces the operating cost to the point where it is competitive with coal- or gas-fired generators — and much cheaper than wind- or solar-powered generators, according to company projections. In addition, the ocean's power is far more concentrated and predictable than wind or sunlight.

The idea of harnessing the tremendous power of the ocean's waves is not new. Water wheels turned by ocean waves dotted the coast of England at the time of the Crusades. Modern attempts to tap the ocean's power have involved turbines, complex mechanisms that tend to corrode over time.

Buoys, on the other hand, have long been reliable presences in the ocean as navigation aids, with life spans lasting as long as 40 years, Taylor says.

Taylor, an electrical engineer, says the roots of this technology likely go back to his youth in Australia. "You get the feeling of the force of the waves when you're out there surfing," he says. "That was probably buried deep inside of me."