Case Study: Testing Wave Energy Converters Offshore

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1 Case Study: Testing Wave Energy Converters Offshore

2 Case Study: Testing Wave Energy Converters Offshore Northwest National Marine Renewable Energy Center Oregon State University Company Profile The Northwest National Marine Renewable Energy Center (NNMREC) is one of three U.S. Department of Energy-funded centers charged with facilitating the development of marine renewable energy technology via research, education, and outreach. Established in 2008, NNMREC is a partnership between Oregon State University (OSU) and the University of Washington (UW). While OSU focuses on wave energy and offshore wind energy, UW s emphasis is tidal energy. NNMREC was developed to facilitate wave and offshore wind energy development by bringing science to bear on the technical, environmental, and social dimensions of these ocean energy technologies. Business Situation Can wave energy meet our needs? Are wave energy conversion devices capable of generating sufficient energy to be connected to the grid? How can they be tested in the real world so we can quickly understand their performance and make improvements? Ocean wave energy is an area of increased interest, with over 100 conceptual wave energy converter (WEC) designs developed worldwide. Of these only a few have been built as full-scale prototypes and tested in open ocean. In order to help Oregon state reach its renewable energy power goals, NNMREC was tasked with developing a method to test WEC devices to determine their power output, their survivability in harsh marine conditions, and what type of wave situation would be ideal for the type of wave energy technology used. Ocean testing facilities are essential to enable wave energy developers to demonstrate performance and survivability, and to optimize devices. Currently, the U.S. marine energy industry is challenged by the lack of proper and standardized infrastructure to deploy and test devices in the marine environment. In addition, many WEC technologies are ready for field trials, but are not sufficiently mature to be connected to the electrical grid for commercial power production. A mobile wave energy test facility could be used by many companies and academic researchers in the quest to develop wave energy technology, measure and understand the wave resource, and study the energy output. Requirements for the primary functions of a mobile wave energy test facility are as follows: 1. Provide stand-alone electrical loading and power conversion for the WEC under test. 2. Measure and record WEC power output. 3. Configurable for different types of WECs. 4. Collect and store data transmitted from a wave measuring buoy moored nearby. 5. Transmit collected data to a shore station via a wireless telemetry system. 6. Conduct environmental monitoring. AXYS TECHNOLOGIES INC PAGE 2

3 Technical Situation OSU s current ocean testing facilities include the Wallace Energy Systems & Renewables Facility (WESRF) and the O.H. Hinsdale Wave Research Laboratory. The WESRF is home to the Linear Test Bed an instrument that creates the relative motion between a spar and heaving buoy to simulate wave action. Eleven wave energy device prototypes have been tested on the Linear Test Bed. The Hinsdale Wave Research Laboratory is a leading center for research and education in coastal engineering and nearshore science with facilities that include a Large Wave Flume (104m long), Tsunami Wave Basin with multi-directional wavemaker, and control room for on-site researchers. The Large Wave Flume is the largest of its kind in North America. While these facilities provide state-of-the-art simulations, NNMREC required a way for new technologies to be tested in a real environment offshore in the ocean. Solution To help NNMREC reach their goal of an offshore mobile wave energy testing facility, AXYS partnered with them to design a new buoy the Ocean Sentinel Instrumentation buoy. AXYS engineers worked with NNMREC staff to develop this custom buoy system that interfaces with numerous custom control and monitoring devices, as well as basic meteorological and oceanographic parameters. The system also provides real time communications that monitor all aspects of the system performance. The Ocean Sentinel platform is based on a proven NOMAD (Navy Oceanographic Meteorological Automatic Device) 6m hull design with 4 large watertight compartments able to withstand the most severe oceanic weather. The base design allows for a high degree of flexibility and expansion capacity in system architecture and to allow incorporation of a variety of hybrid power solutions. Data from the buoys are collected by AXYS' proprietary onboard WatchMan500 data acquisition system and transmitted to a shore station by satellite and cell phone telemetry. In addition, this buoy also has an Automatic Information System (AIS) transmitter which transmits buoy position and environmental data to passing ships. Authorized users can access buoy status and environmental data from their remotely located base station. The AXYS' Data Management System (DMS) permits remote control and configuration for the entire buoy network, down to the individual sensor. A TRIAXYS directional wave buoy will be deployed separately from the Ocean Sentinel and will provide precision wave measurements to quantify the wave resources in the test facility local. These wave measurements are also transmitted to the Ocean Sentinel. AXYS also designed and provided a custom 3 point mooring and deployment procedures for the Ocean Sentinel. WECs under test are moored approximately 125 meters from the instrumentation buoy and connected by an umbilical cable. Power generated by the WEC is controlled by switchgear and power conversion equipment located on-board the instrumentation buoy and dissipated in an on-board load bank. The Ocean Sentinel power conversion and load bank system provides a stand-alone load for the WEC under test. This system provides generator control for WECs in early stages of development that do not include onboard generator power conversion. A switchgear enclosure that includes the contactors along AXYS TECHNOLOGIES INC PAGE 3

4 with an electrical disconnect, current and voltage sensors, and fuses is installed below deck in the forward compartment of the Ocean Sentinel, together with the power converter. Two 50 kw, air-cooled load banks are installed above deck. This system is controlled by a National Instruments CompactRIO based data acquisition system developed by NNMREC, which is also used to record WEC power and measured wave data. Because NNMREC anticipates testing WECs with different power outputs and generator configurations, the Ocean Sentinel loading system has been designed for a high degree of flexibility and is reconfigurable via terminations in the switchgear enclosure. The air cooled load bank can be reconnected for different voltage and power levels, and can be controlled by either contactor switching, converter control, or a combination of the two. WECs with output current to 125 A continuous can be accommodated, for a power capability of 100 kw at 460 V or 50 kw at 230 V. The on-board power system developed by AXYS can supply up to 400W of 24 Vdc and 120 Vac power to the instrumentation and power conversion equipment installed on the Ocean Sentinel, and to the WEC via the umbilical. Primary power is provided by 40x sealed lead acid batteries (2000 Amp-hours at 24V), which are maintained through the use of a 1 kw wind generator, 2x 210 W solar panels and a 3.2 kw standby diesel generator. The system can provide 400 W throughout a 3 month deployment period without refueling. This power system is controlled and monitored by the WatchMan500 data acquisition and control system. Two independent cellular telemetry systems are used between the Ocean Sentinel and shore, one for the WatchMan500 that controls and monitors the power system, and the other for the CompactRIO system that provides control and data acquisition for WEC testing. The Ocean Sentinel provides a standardized, accurate system to compare various wave energy technologies. The Ocean Sentinel instrumentation buoy facilitates open-ocean, stand-alone testing of WECs with average power outputs of up to 100 kw. Deployment is at a NNMREC test site that is approximately 2.5 nautical miles offshore from Yaquina Head, north of Newport, Oregon. NNMREC will operate the facility which is a one-square-mile site located about two miles northwest of Yaquina Head Oregon in open Pacific Northwest Waters carefully studied, both for its physical and biological characteristics. Deployment In late July 2012, AXYS technicians and engineers provided NNMREC personnel with the initial dockside system commissioning and training. The Ocean Sentinel was deployed in August 2012 for the first testing of a WEC. The Ocean Sentinel and WEC were moored at NNMREC s open-ocean test site north of Newport, Oregon for a six week period while the testing was performed. The Ocean Sentinel power converter was used to control the electrical generator on board the WEC device via the umbilical cable throughout these tests. This allowed WEC performance to be characterized while operating in several different control regimes and under a variety of sea conditions. A final paper will detail the deployment, testing and data analysis process. Benefits 1. Validate the performance of WEC devices in a real-world testing environment. AXYS TECHNOLOGIES INC PAGE 4

5 2. Understand how each WEC device performs in varying types of wave environments. Some WEC devices will operate better in low wave settings while others will have better performance with a more powerful wave resource. The Ocean Sentinel measures wave amplitude, device energy output, ocean currents, wind speeds, extremes of wave height and other data. 3. Gain a better understanding of the surrounding environment. 4. The creation of the Pacific Marine Energy Center (PMEC) as an expansion and continuation of the work started with the Ocean Sentinel. PMEC will be the first utility-scale, grid-connected wave energy test site in the United States. Subsea cables will transmit energy from the wave energy devices to the local power grid, and data to scientists and engineers at on-shore facilities. PMEC will have four test berths, open spaces of water dedicated to testing individual devices or small arrays of devices, each of which will be connected to the community s electrical grid. It will also collect data associated with environmental and human dimension impacts. The development and operation of this facility will provide jobs and other economic development as it attracts researchers and device developers to the Oregon coast from around the world.. References von Jouanne, A., Brekken, T., Lettenmaier, T., Amon, E., and Phillips, R. A Novel Ocean Sentinel Instrumentation Buoy for Wave Energy Testing. In Power and Energy Society (PES) Conference, Amon, E., Brekken, T.K.A., and von Jouanne, A A power analysis and data acquisition system for ocean wave energy device testing. Renewable Energy: An International Journal, vol. 36, pp Leijon, M., Waters, R., Rahm, M., Svennson, O., Bostrom, C., Stromstedt, E., Engstrom, J., Tyrberg, S., Savin, A., Gravrakmo, H., Bernhoff, H., Sundberg, J., Isberg, J., Agren, O., Danielsson, O., Eriksson, M., Lejerskog, E., Bolund, B., Gustafsson, S., and Thorburn, K Catch the wave to electricity. IEEE Power and Energy Magazine, January/February Le-Ngoc, L., Gardiner, A.I., Stuart, R.J., Caughley, A.J., Huckerby, J.A Progress in the development of a multi-mode self-reacting wave energy converter. In: OCEANS 2010 IEEE Sydney. pp Institute of Electrical and Electronic Engineers. Pitt, Edward. Assessment of performance of wave energy conversion systems: marine renewable energy guides. [London]; Orkney: Dept. of Energy and Climate Change; European Marine Energy Centre, Stauth, David. Public wave energy test facility begins operation in Oregon. Oregon State University News & Research Communications, Web. 8 July Testing Facilities and Facilities Partners. Oregon State University Northwest National Marine Renewable Energy Center, Web. 8 July Batten, Belinda. Newport selected as home of Pacific Marine Energy Center. Oregon State University News & Research Communications, July AXYS TECHNOLOGIES INC PAGE 5