or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution This article has This been published in MARINE RENEWABLE EnERGY | TECHNOLOGY DEVELOPMEnt And DEPLOYMEnt BY ROGER BEDARD, PAUL T. JACOBSON, MIRKO PREVISIC, WALTER MUSIAL, And ROBERT VARLEY Oceanography , Volume 23, Number 2, a quarterly journal of The 23, Number 2, a quarterly , Volume An Overview of Ocean Renewable O Energy Technologies ceanography S ociety. ociety. © 2010 by The 2010 by ABSTRACT. Ocean energy is a term used to describe renewable energy derived from and tidal/open-ocean current energy the sea, including ocean wave energy, tidal and open-ocean current energy (sometimes resources. A small number of large O called marine hydrokinetic energy), tidal barrages, offshore wind energy, and ocean companies are leading the commercial- ceanography thermal and salinity gradient energy. Shallow water offshore wind is a commercial ization of offshore wind energy, ocean O ceanography ceanography technology (over 1,500 MW capacity installed in Europe). The technologies to convert thermal gradient, and salinity gradient S ociety. ociety. the other ocean energy resources to electricity, including deepwater offshore wind energy technologies. A technology, albeit in their infancies, exist. These technologies are ready for full- ll rights reserved. S ociety. ociety. scale prototype and early commercialization testing at sea. This paper highlights the OCEAN WAVE EnERGY S technology development status of various energy conversion technologies. COnvERSION TECHNOLOGIES or Th e [email protected] to: correspondence all end P Ocean waves are generated by the influ- article for use research. and this copy in teaching to granted is ermission IntRODUCTION tidal barrage plants: a 240 MW plant ence of the wind on the ocean surface, In the 1970s, the United Kingdom at LaRance, France; a 20 MW plant at which first causes ripples. As the wind had the most aggressive wave energy Annapolis, Nova Scotia, Canada; and continues to blow, the ripples become program in the world. Although the smaller plants in China and Russia. Tidal chop, then fully developed seas, and program contributed to important in-stream technology development has finally swells. In deep water, the energy research such as optimal control and been funded in Europe since the 1990s, in waves can travel for thousands of O tuning of wave power conversion and DOE started its wave, tidal, and miles before it is finally dissipated ceanography devices, it ultimately stalled as oil prices open-ocean current program in 2008. on distant shores. dropped and government funding Salinity gradient technology has received Many devices have been proposed to S ociety, ociety, stopped. The US Department of Energy attention in Europe, particularly in achieve the conversion of wave energy PO (DOE) funded an open-ocean current Norway and the Netherlands. into electricity. Various hydraulic or B ox 1931, ox R program in the 1970s, an ocean thermal Today, a large number of small pneumatic power conversion systems are reproduction, systemmatic epublication, R energy conversion (OTEC) program companies backed by government used, and in some cases, the mechanical ockville, MD 20849-1931, in the 1980s, and a wind program organizations, private industry, utili- motion induced by the wave energy is extending from the late 1970s to the ties, and venture capital are leading the converted directly to electrical power present, which includes a small offshore commercialization of technologies to (direct-drive). These devices can be wind component. There are a few generate electricity from ocean wave bottom-mounted or floating and vary USA . 22 Oceanography Vol.23, No.2 a b c d Figure 1. (a) PowerBuoy (courtesy of Ocean Power Technologies), (b) WaveDragon (courtesy of WaveDragon), (c) Pelamis (courtesy of Pelamis Wave Power), and (d) oscillating water column terminator (courtesy of OceanLinx). in size, orientation, and distance from Overtopping Terminator sea surface then turns conventional low- shore. Four of the best-known offshore A terminator reflects or absorbs all of head hydro turbines that are coupled to technology concepts are introduced the wave energy—hence it “terminates” generators to produce electricity. below and depicted in Figure 1. the waves. One type of terminator is an overtopping device that uses a Linear Absorber or Attenuator Point Absorber floating reservoir structure, typically A linear absorber, sometimes called Devices that are small compared to a with reflecting arms to focus the wave an attenuator, is a device that is large typical wavelength (waves of interest energy (Figure 1b). As waves arrive, they compared to a typical wave’s length. The for energy production vary from 40 overtop the ramp and are restrained in linear absorber structure is oriented to over 300 m in length) are termed the reservoir. The potential energy due roughly parallel to the direction of wave “point absorbers.” Point absorbers are to the height of collected water above the propagation and is composed of multiple bottom-mounted or floating structures that absorb energy from all directions. Roger Bedard ([email protected]) is Private Consultant, Palo Alto, CA, USA. The power conversion system may take Paul T. Jacobson is Senior Program Manager, Marine and Hydrokinetic Energy Research, a number of forms depending on the Electric Power Research Institute, Palo Alto, CA, USA. Mirko Previsic is President, Re Vision selected configuration. Figure 1a shows a Consulting LLC, Sacramento, CA, USA. Walter Musial is Principal Engineer, National Wind floating buoy; however, a point absorber Technology Center, National Renewable Energy Laboratory, US Department of Energy, could as well be a bottom-standing Boulder, CO, USA. Robert Varley is Program Manager, Lockheed Martin Company, device with an upper floater element. Manassas, VA, USA. Oceanography June 2010 23 sections that rotate in pitch and yaw rela- system built into the coastline of the pressure water to an onshore turbine that tive to each other. That motion is used Island of Islay in Scotland in 2000 by generates electricity. to pressurize a hydraulic fluid, which WaveGen (now part of Voith Hydro); In the area of testing and test facili- then turns a turbine that is coupled the second unit is located on Pico Island, ties, the US marine energy industry is to a generator to produce electricity. Azores, Portugal. In 2003, WaveDragon currently challenged by the lack of Figure 1c depicts a slackly moored, was the first offshore, grid-connected proper and standardized infrastruc- floating, hinged-contour linear absorber. wave power unit and was deployed in ture to deploy and test wave energy The four sections move relative to each a protected bay in Denmark due to its conversion devices in the open ocean. other, and this motion is converted subscale nature. However, progress is being made toward into electricity at each hinge point by a In 2004, Pelamis, the first full- the development of such facilities. The hydraulic power converter system. scale, grid-connected wave power Northwest National Marine Renewable unit deployed at sea, was installed at Energy Center (NNMREC), led by OSU, Oscillating Water Column the European Marine Energy Center will provide wave energy developers Terminator (EMEC), a wave test facility, in the UK. with test berths to perform field tests and An oscillating water column (OWC) Based on the successful EMEC testing, demonstrations of subscale and full-scale terminator is a conversion device that the first commercial sale of an offshore devices. Pacific Gas and Electric (PG&E) harnesses the motion of the ocean wave power plant was announced in will provide an undersea electrical waves as they push an air pocket up or May 2005 and the first 2.25-MW stage of grid connection called “WaveConnect” pull it down. This device is a partially that plant was deployed off the coast of several miles offshore of California and submerged chamber with air trapped Portugal in 2008.1 will connect wave energy converters above a column of water (Figure 1d). As In the United States, Ocean Power from multiple vendors to the PG&E waves enter and exit the chamber, the Technologies (OPT) was the first to electrical grid (similar to the UK Wave water column moves up and down and deploy kilowatt-scale wave energy Hub funded by the UK government) and acts like a piston on the air, compressing converters off the coasts of Hawai’i and provide for testing and evaluation of the and decompressing it to generate a New Jersey in 2005. Columbia Power devices for commercial deployment. reversing stream of high-velocity air in Technologies (CPT) and Oregon State Additional demonstration projects are an exit blow hole. This air is channeled University (OSU) were the first to deploy ongoing and planned in the UK, Ireland, through a turbine/generator to produce kilowatt-scale wave energy converters Spain, Portugal, China, Japan, Australia, electricity. An OWC is also a type of off the west coast of the United States Canada, and the United States. If these wave terminator. in 2007 and 2008. OPT plans to deploy early demonstration schemes prove a 150-kW point absorber off the coast successful, medium-size wave farms with StATUS OF OCEAN WAVE of Reedsport, Oregon, with construc- capacities up to 50–100 MW could be EnERGY COnvERSION tion starting in 2010. CPT’s next ocean deployed within the next five to ten years. TECHNOLOGIES deployment is planned for late 2010. Today’s wave energy conversion tech- The first nearshore surge-type wave TIDAL And OPEN-OCEAN nologies are the result of many years energy converter to deliver electricity CURREnt EnERGY COnvERSION of testing, modeling, and development to the grid was the Aquamarine Power TECHNOLOGIES by many organizations.