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Published on November 30th, 2014 | by Tina Casey


US Navy Shells Out 3 Million Clams For Wave Energy

November 30th, 2014 by  

It’s been a while since we checked into the US Navy wave energy test site in Hawaii, but our friends over at Columbia Power Technologies steered us in that direction to check out their new StingRAY wave energy converter. The device, which is slated for utility-scale wave energy generation, will get its first full open-water demo at the facility. The US Navy has funded the project through its Naval Facilities and Engineering Command to the tune of $3 million.

Those of you familiar with wave energy (and its sister, tidal energy) know that this emerging alternative energy field is fraught with challenges, especially when you’re talking about utility-scale development. While the kinks are being worked out you’re going to see a lot of variation in design, so let’s take a look and see how Columbia Power’s StingRAY works that out.

wave power navy stingray 1

StingRAY wave energy converter (courtesy of Columbia Power).

Wave Energy From Columbia Power

Basically, wave energy converters rely on the natural movement of waves to drive a piston up and down, move a drive shaft, or stir up some other form of mechanical motion. The mechanical energy gets converted to electricity by a generator and there you have it.

That sounds simple enough, but aside from Scotland, which seems to have taken the ball and run with it, the global wave energy field hasn’t been keeping up with other forms of alternative energy, most notably wind and solar.

That could be about to change. The wave energy field seems to be taking some lessons learned from wind energy, as demonstrated by the StingRAY wave energy converter. The heart of the converter is a direct-drive system that eliminates excess moving parts, along with permanent magnet generators.


The StingRAY is built from corrosion-resistant composite materials, and it is designed with modularity in mind to reduce the cost of maintenance and repair. Also helping to build in efficiencies and lower costs is a single-point mooring system.

wave energy stingray navy 3

Courtesy of Columbia Power

The spars (the long poles in the schematic above) and the floats behave independently as each wave passes, enabling the floats to rotate freely. As they rotate, they move a drive shaft connected to a generator.

There are two generators, one for each float, located in the section marked “PTO Modules.” That section, as in the wind energy field, is called the nacelle.

The generators convert the energy to electricity, which is then stabilized for grid compatibility before being sent off the device via cable. Columbia Power envisions an offshore “substation” to assemble the electricity from multiple devices before sending it to the grid.

From Wind Farms To Wave Energy Farms

The StingRAY was designed with an eye toward avoiding some of the aesthetic concerns that can bedevil offshore wind farms, most notably in the case of the Cape Wind project off the coast of Massachusetts.

As you can see from the photo, and the “waterline” indication on the schematic, the StingRAY has a low above-water profile, which is practically nothing when compared to offshore wind turbines. The system was designed for deployment in depths of more than 60 meters, typically located at least a mile or more offshore.

Don’t hold your breath for the full scale demo project to hit the water — it’s slated for 2016 — but in the meantime you can check out more projects at the Navy’s Wave Energy Test Site (WETS — cute, right?).

More And Better Wave Power

We’ve also been following a company called Ocean Power Technologies, which is developing its PowerBuoy with the help of the Navy and Energy Department.

Last we heard, the PowerBuoy was getting a wave energy workout off the Oregon coast, and last month the company announced that it was launching a new test site off the New Jersey coast.

We wonder if Ocean Power knows what it’s getting into, give the state’s recent history of obstructing offshore wind development.

Who knows, maybe they’re figuring to sneak into the water while state energy regulators are distracted by the wind energy thing. The company already has its APB 350 PowerBuoy wave energy model operating 20 miles off the New Jersey coast in collaboration with NOAA. It was developed in partnership with the US Navy and was deployed by the US Coast Guard.

The company’s PB40 PowerBuoy was shipped out from its manufacturing facility in Spain some time around October 20 and it has probably made its way to port in Bayonne by now. We’re guessing its final destination is off the coast of Atlantic City, where a prototype of the PB40 PowerBuoy was tested from 2003 to 2008.

Just to spice things up a bit, let’s note that the PB40 test project was supported in part by New Jersey’s Board of Public Utilities. That would be the same outfit that just put the kibosh on a long-planned offshore wind farm at Atlantic City, so hold on to your hats.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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