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by Nancy Steinberg
Marine renewable energy scientists Brendan Cahill, Bret Bosma, and Rob Cavagnaro are all heading overseas to work abroad for a time, but none of them will miss the misty coasts, green hills, turbulent seas, or friendly folks at home.
That’s because they are all trading one turbulent sea, misty coast, and set of friendly faces for another, in an exchange between NNMREC and the Hydraulics and Maritime Research Center (HMRC) of University College Cork in Ireland. Cahill, who just completed his doctorate at HMRC, is settling in in Corvallis, where he will spend the upcoming year at Oregon State University. Bosma, who earned his Ph.D at OSU in the spring, and Cavagnaro, who is in a doctoral program at University of Washington, will both head to Ireland in the coming months.
HMRC is a member of the Irish Maritime and Energy Resource Cluster (IMERC), an umbrella organization that also includes other research groups at University College Cork, the Cork Institute of Technology and, Irish Naval Service. These groups are moving into the state-of-the-art National Beaufort Centre and recently received a 25 million euro grant from Science Foundation Ireland (SFI) to advance marine renewable energy in Ireland. IMERC and NNMREC signed a memorandum of understanding in 2012 to collaborate in areas of mutual interest and exchange students, staff, and faculty between Ireland and the Pacific Northwest. “Brendan, Bret, and Rob are the start of a strong and enduring partnership between our institutions,” said Brian Polagye, NNMREC’s co-Director. “We look forward to exchanges like this moving marine renewable energy forward on both sides of the Atlantic.”
Brendan Cahill visiting Newport, OR
Cahill was the first of the three to cross the ocean, arriving in early September in Corvallis. Although he had been to the U.S. before, including for an entire summer spent in San Francisco, he had never been to Oregon; the state welcomed him with an impressive rainstorm, complete with thunder and lightning. He and his girlfriend are settling in, amazed by the beauty of the area and the friendliness of the people they’ve met.
Cahill’s doctoral research at HMRC focused on characterizing the wave energy resource off the Irish coast using measured and modeling data. He examined how much energy is contained in waves, specifically at the Atlantic Marine Energy Test Site (AMETS), a full-scale test site off the coast of the town of Belmullet, and a quarter-scale test site in Galway Bay. This information is critical to the industry’s continued development, as they need to know not only how much extractable energy is contained in waves, but also what type of conditions their equipment will need to endure in the ocean. “Until a couple of years ago there was not much wave data from the Irish coast,” he explained. “Very few instruments of decent quality were being deployed. Around the time I started my Ph.D there were more instruments being deployed so I was able to use that data to paint a broader picture of the characteristics of the resource.” His results revealed that past estimates may have relied on a range of incorrect assumptions, leading to an underestimation of the resource, in some cases by as much as 20%.
Another fascinating aspect of Cahill’s work is his examination of extreme wave conditions at AMETS. In reviewing data collected, he identified what he believes to be the largest wave ever recorded in Irish waters, a 24-m behemoth that coursed through AMETS in November of 2010. Apart from this monster, the site commonly sees waves of 12 m or more in the winter, prompting consideration of designating the site as a “survival test site.” “Any device that can spend a year out there in those wave conditions should be OK anywhere,” Cahill commented.
Cahill will be continuing this line of research while at OSU working with Belinda Batten and Bob Paasch, both of NNMREC. He would also like to collaborate with Tuba Ozkan-Haller in the College of Earth, Ocean & Atmospheric Sciences. Cahill will focus on the question of scalability – how measurements at a scaled test site, like the one in Galway, can be scaled up to provide relevant information about full-scale test sites. He’ll compare scalability in Irish systems to scalability here in Oregon, where devices are tested in the comparatively benign conditions of summer. He is intrigued by the similarities between the Irish and Oregonian coasts. While he believes the Irish ocean to be more energetic, the two systems are quite similar in other ways: both are on exposed western coasts, and share the same seasonality.
Bosma and Cavagnaro both head to the Emerald Isle late this year. Bosma has a few tasks to complete before he goes, chiefly his wedding in early December; his bride will accompany him abroad. His doctoral work focused on building and testing a quarter-scale prototype of a heaving point absorber wave energy converter, similar to the Ocean Power Technologies (OPT) device that was tested in Hawaii and Scotland. The device consists of a central vertical spar that stays relatively stationary, while a donut-shaped float rides the waves at the surface, sliding up and down on the central spar. Energy is extracted from the relative motion of these two components.
Bret Bosma and Annette von Jouanne inspect the prototype Autonomous Wave Energy Converter (AWEC) on the linear test bed in the Wallace Energy Systems and Renewables Facility (WESRF).
The device was tested successfully in OSU’s O. H. Hinsdale Wave Research Lab. “It all went really smoothly,” Bosma said. “We got a lot of great data and were able to test some advanced control schemes, which was one of the missions of the work.” At full scale, the device is targeted to produce 200 watts of power, enough electricity to provide juice for sensor packages, remote vehicle chargers, or oceanographic instruments.
While in Ireland, Bosma has proposed building another scale prototype device to be tested in their wave tank, with a focus on developing more sophisticated control devices. It will employ direct-drive rotary technology, in which the moving parts of the wave energy converter is coupled directly to the moving parts of an electrical generator, eliminating the need for intermediate mechanical devices such as turbines. He is looking forward to exploring all of the resources HMRC has to offer, although he will arrive prior to completion of the large new lab building being constructed for a reorganized maritime and sustainable energy program being developed at UCC.
Rob Cavagnaro is also heading to UCC/HMRC in December, and like Bosma and Cahill, will be abroad for a year. His work there will continue his Ph.D. research initiated at the University of Washington’s Department of Mechanical Engineering with Dr. Brian Polagye developing a small-scale tidal turbine system. When he started working on the project, four helical blades had already been constructed for the turbine, and he took on the tasks of designing a testing plan for the device as well as designing and constructing some other components – a support structure, a gearbox, and a monitoring system, for example. His device falls in the category of “micropower systems,” meaning it could be used to harness the tidal energy at a marine site to power devices like hydrophones and current profilers, providing 50 watts of continuous power for up to a year at a time. “Our goal is to be able to use the power that’s there [in ocean or tidal currents] to power instruments without needing to run a cable to the site or undertaking costly missions to go out and replace batteries every few months,” he explained.
Rob Cavagnaro preparing to tow test prototype device.
The prototype device was tow-tested successfully this past summer from a skiff in Lake Washington. The research team fully characterized the operation of the device under different “load” scenarios, producing a power curve for the device, and determined how it would operate under different conditions in the water. Results are promising, and the team is excited to refine its design and eventually develop a buffering system that will help collect and distribute electricity in a constant current. While there he will work on a control strategy for the turbine. “We want to find a control strategy that allows the turbine to operate efficiently all the time,” he said. His idea is to try a feed-forward control strategy, in which information about external conditions – flow, in this case – is measured and adjusted for before it affects the system. (An example of such a system would be a home heating system that has a sensor which can detect if a door to the house has been left open so that the heating system could kick on before the temperature drops. A feedback system would be one in which the heater would kick on in response to a drop in temperature, like a thermostat.) “This type of control strategy would have the advantage of potentially letting you run the device at an optimal rate for longer, but it also means that if you see something ahead that’s potentially dangerous for your device, like turbulence that could damage the turbine, you can program the device to take evasive action like dropping its load and letting it run freely.”
All three researchers participating in the NNMREC/UCC exchange acknowledge that all work and no play would be a waste of a great opportunity. Cahill plans to travel in the region and country as much as he can while he’s here. Bosma would also like to travel, by bicycle as much as possible. Cavagnaro is a climber and he can’t wait to scale some Irish peaks.
All three are sure they’ll return home with much to show for their time abroad, including new scientific insights and new friends. Stay tuned to learn more about what all three of them learned on their exchange, and to see whether each prefers Rogue Ales or Guinness once they’ve returned home!