… to deploy and retrieve a mobile wave energy test platform
by Nancy Steinberg
It was a busy summer for the Northwest National Marine Renewable Energy Center’s Ocean Sentinel mobile wave energy test platform, tethered to the seafloor at the Pacific Marine Energy Center-North Energy Test Site (PMEC-NETS) off of Yaquina Head in Newport, OR. While it might have appeared to the untrained eye like the bright yellow, 20-foot-long boat-shaped platform was simply bobbing in the waves and soaking up the sun, a lot was going on below the surface. The subject of tests this summer was the Sentinel’s mooring and anchoring system. The resulting numerical and experimental mooring analysis will enable improved modeling and design of wave energy device mooring systems in addition to advancing the Ocean Sentinel’s own mooring system design, deployment, and recovery process.
The deployment, monitoring, and retrieval of the Ocean Sentinel this year was an unparalleled example of the value of using partnerships to conduct complex research and development. The summer’s testing was possible only through the cooperation of dozens of individuals from the local community as well as scores of agencies and entities, from Oregon State University’s Northwest National Marine Renewable Energy Center (NNMREC) to the U.S. Navy, from Ocean Observing Initiative (OOI) personnel to the Marine Mammal Institute’s ship’s crew, with essential funding coming from the U.S. Department of Energy and the State of Oregon.
All exercises using the Ocean Sentinel are coordinated by NNMREC, with leadership provided by Director Dr. Belinda Batten and Sean Moran, Ocean Test Facilities Manager. Use of the ocean test facility is driven by NNMREC’s mission: to facilitate the development of marine energy technology, inform regulatory and policy decisions, and to close key gaps in scientific understanding with a focus on student growth and development.
If an energy company has a device that they feel is ready for testing in the ocean, they go to NNMREC for guidance and support. “Sometimes devices are not quite ready to go into an ocean test site and we guide the companies towards testing in the O.H. Hinsdale Wave Research Lab first,” explained Sean Moran. If the device is ready for prime time, NNMREC helps the company get the device out and floating. NNMREC served as the coordinating entity for Ocean Sentinel deployment and research this summer, although there was no wave energy converter attached to it.
Another critical group at OSU is the faculty supporting the Wallace Energy Systems and Renewables Facility (WESRF) in the School of Electrical Engineering and Computer Science. This group provides research, testing and consulting services related to machines and drives, power electronics, hybrid electric vehicles, power systems and renewables. Dr. Annette von Jouanne at WESRF has been a national leader in advocating for wave energy development since the late 1990s, and pioneered and led the project to develop the Ocean Sentinel. Electrical test engineer Dr. Ean Amon has also been instrumental in developing and deploying the Sentinel.
Deployment planning and execution relied heavily on the expertise of the OOI staff in the College of Earth, Oceanographic, and Atmospheric Sciences at OSU. The OOI is a program of the National Science Foundation that is in the process of installing an array of buoys, cables, and other monitoring equipment off of the Oregon Coast to conduct long-term ocean observing. These people know their moorings, buoys, anchors, and ocean dynamics. Walt Waldorf from OOI led the operations design and execution for the summer’s deployment and subsequent retrieval of the Ocean Sentinel. Chris Holm and Ricki Verlini helped with equipment fabrication and logistics and provided both shore-based and marine support.
Getting the Ocean Sentinel and its associated equipment out to the test site and back again safely was accomplished aboard the R/V Pacific Storm, a retrofitted trawler now owned by OSU’s Marine Mammal Institute (MMI). Skipper Yogi Briggs and Ship’s Engineer Ken Serven helped to design and execute a safe deployment and retrieval, masterfully maneuvering the 84-foot vessel around the test site at sea.
Although the Pacific Storm is not operated by OSU’s Ship Operations, they supported the mission as well, helping with loading, staging, and storing equipment and allowing use of their shop and dock.
A hive of researchers buzzed around the data collected by the Sentinel and its accessory equipment. Sarah Henkel at the Hatfield Marine Science Center is examining the benthic community near the deployment. Joe Haxel of the MMI listened to the site to determine the acoustic environment there.
Josh Baker, a Naval officer and graduate student, used models and data collected from the site to examine the mooring system used this summer. He used “load cells,” instruments placed in line with the mooring lines, to determine the forces the mooring lines were subjected to; other instruments measured wind, wave, and current conditions at the site so that the measurements of load on the mooring lines can be correlated with environmental conditions.
Other entities involved in the summer deployment include OSU’s dive operations, risk management, and contracting and procurement offices. Plenty of entities outside of OSU helped as well, including partners at the Oregon Wave Energy Trust, the permitting personnel at agencies from the Oregon Department of Fish and Wildlife to the U.S. Army Corps of Engineers, and the staff at the Port of Toledo, where the Ocean Sentinel will be in dry dock for the winter. Oregon Sea Grant, via personnel at the Lincoln County Extension Office, interfaced with the local community to keep them informed about progress and solicit their input. They serve as a point of contact for various ocean users with respect to equipment deployed in the coastal ocean. The fishing community is particularly interested in what the Ocean Sentinel is up to; they engage through a committee called Fishermen Involved in Natural Energy (FINE). All for one little test platform.
Ocean Sentinel Retrieval: An Example of the Strength of Partnerships
A perfect example of the collaborative nature of this summer’s deployment was provided by what would seem like the simplest task of all: taking the Ocean Sentinel out of the water for the summer. Wrapping things up for the winter is not as simple as it sounds. The retrieval mission was conducted over two days in early October, just as the skies returned to blue and the seas diminished after a late September surprise typhoon.
Dozens of scientists, engineers, divers, and other personnel from many of the entities already mentioned came together to take the Ocean Sentinel and two wave and current monitoring devices out of the water. On day one, they retrieved the four buoys marking the corners of the test site, along with a seafloor-mounted acoustic wave and current (AWAC) profiler.
Day two was dedicated to taking in a TRIAXYS wave and currents monitoring buoy and towing the Ocean Sentinel itself back to shore. The retrieval was carried out using the Pacific Storm and a small rigid-hulled inflatable boat (RHIB) also belonging to the MMI.
The operation began on day two with two divers suiting up to enter the cold Pacific waters and getting aboard the RHIB to get closer to the buoys. The divers, Walt Waldorf from OOI and Kevin Buch, OSU’s Dive Safety Officer, were accompanied by Ken Serven, Sean Moran, and Tully Rohrer, a mooring specialist from the Partnership for the Interdisciplinary Study of Coastal Oceans. The divers’ first task was to sever the TRIAXYS buoy’s mooring so the mooring line and heavy anchor could be heaved up onto the Pacific Storm separately from the small buoy itself. They floated the mooring line with bright yellow floats, which were snagged by some of those aboard the Pacific Storm. The Storm’s powerful crane system was then used to hoist the heavy anchor aboard, and a different crane system was used to pick up the TRIAXYS itself.
Then it was the Ocean Sentinel’s turn. A detailed consultation among all of the players took place first, so that everyone would be clear on the order of operations, the options in case “Plan A” didn’t work, and the roles each would play. The flat-calm day had turned slightly choppy by this time, so the operation became a little more complicated.
The Ocean Sentinel is held in place at the test site by three mooring lines, held to the seabed with three 8,500-lb deadweight anchors. These needed to be severed from the platform and the mooring lines brought aboard its hull. The “bow” mooring line is attached to a one ton bridle and chain; the chain would need to be pulled aboard the Sentinel as well but it was much too heavy to be done by hand.
Three retrieval personnel were deposited on the deck of the Ocean Sentinel. Divers severed the first of the three mooring lines, and the three “deckhands” pulled it, hand over hand, aboard the Sentinel. The second mooring line was able to be removed without the use of divers by personnel aboard the RHIB. The divers tried to work on the third mooring line, but the current had become too swift for them to operate safely, so they came out of the water. After a bit of a struggle, the third line was severed from the deck of the RHIB. The three anchors and their marker buoys will remain at the site all winter, providing additional opportunities for research, but the Ocean Sentinel itself was ready to be hitched to the Pacific Storm.
First, though, that enormous chain had to be brought onto the Sentinel’s deck. The test platform was maneuvered alongside the Pacific Storm, and the chain was brought up, one length at a time, by the Storm’s crane. Finally, the Ocean Sentinel was tethered behind the Pacific Storm to be towed to port. It will likely spend the winter in the Toledo Boatyard upriver from Newport.
This entire operation would have been impossible without the web of partnerships NNMREC and its many partners have built. This story illustrates the physical operations required for recovery of the ocean testing platform, but only provides a glimpse of the unprecedented collaborative teamwork and leadership required for planning, commissioning, deployment, and operations of the overall NNMREC mission. Students, scientists, and engineers will pour over the data the Ocean Sentinel collected this summer in order to develop improvements in deployment procedures and moorings for next season. While the test platform itself takes a vacation this winter, scientists, engineers, and students will be busy planning its next adventure.
Select photos by Pat Kight (Oregon Sea Grant) and Dan Hellin (NNMREC).