喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:414951605或者1304139763 ======================== 喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:414951605或者1304139763 ======================== Design, construction, and ocean testing of a taut-moored dual-bodywave energy converter with a linear generator power take-offDavid Elwooda,*, Solomon C. Yima, Joe Prudellb, Chad Stillingerb, Annette von Jouanneb,Ted Brekkenb, Adam Brownc, Robert PaaschcaSchool of Civil and Construction Engineering, Oregon State University, Corvallis, Oregon 97331, USAbSchool of Electrical Engineering and Computer Sciences, Oregon State University, Corvallis, Oregon 97331, USAcDepartment of Mechanical Engineering, Oregon State University, Corvallis, Oregon 97331, USAa r t i c l ei n f oArticle history:Received 27 December 2008Accepted 30 April 2009Available online 18 July 2009Keywords:WaveEnergyDirect-DrivePermanentMagnetLineara b s t r a c tThis paper presents an overview of the SeaBeavI project which began in the fall of 2006 and culminatedin the ocean testing of a 10 kW direct-drive wave energy conversion system in the fall of 2007. TheSeaBeavI project was an interdisciplinary effort bringing together researchers from electrical, mechan-ical, and ocean engineering. A systems design approach was used to develop the taut-moored dual-bodywave energy converter concept with the detailed design focused on production and ease of maintenance.? 2009 Published by Elsevier Ltd.1. IntroductionModernoceanwaveenergyresearchbeganduringtheoilcrisisofthe1970s.MuchoftheearlyworkwasconductedinEuropebySalter7 and Evans 2 in Great Britain and Falnes 3 in Norway, amongstothers. Several promising concepts were developed by 1980including point-absorber wave energy converters such as the infa-mous Salter duck 7 and oscillating water-column (OWC) devicesutilizingaWellsturbine1forpowertake-off.Withthedecreaseinoil prices in the early 1980s much of the funding for ocean waveenergy conversion was cut and no full scale demonstrations of thetechnology were constructed. Recently concerns about globalwarming and the increasing price of conventional energy has led toresurgence in research on ocean wave energy conversion.Currently several commercial developers are working to buildgrid-connected wave energy conversion systems. These include theoscillating water-column device, Limpet, installed on the Isle ofIslay off Scotland in 2000 8, and the Pelamis wave energyconversion system deployed off the coast of Portugal in the fall of2008 5. In the United States, Ocean Power Technologies (OPT) hasdeveloped a point-absorber wave energy conversion buoy for theUS Navy with a test buoy deployed off Oahu, Hawaii 4. OPT hasplans to deploy an array of these buoys off the coast of Reedsport,Oregonrepresentingthefirstgrid-connectedwaveenergyconversion plant in the United States.2. Concept designA systems design approach was used to develop the conceptualdesign of the SeaBeavI wave energy converter. The floating system,mooring, and power take-off concepts were optimized concur-rently in order to ensure that the combined system was as efficientas possible. Efficiency of the system was measured both in terms ofthe power capture efficiency and the overall cost of the system. TheSeaBeavI concept represents an original approach to the conversionof ocean wave energy into electricity.2.1. Floating systemThe floating systemconcept for the SeaBeavI consists of a centralcylindrical spar and an outer Taurus-shaped buoy. The spar ismoored to the bottomwith the buoy free to translate relative to thespar. Having two floating bodies allows for the central spar to berestrained laterally using a mooring system without limiting theheave of the buoy. This allows for a conventional mooring system tobe utilized without the need for subsurface floats to reduce the* Corresponding author. Tel.: 1 281 745 7343.E-mail address: (D. Elwood).Contents lists available at ScienceDirectRenewable Energyjournal homepage: see front matter ? 2009 Published by Elsevier Ltd.doi:10.1016/j.renene.2009.04.028Renewable Energy 35 (2010) 348354vertical forces on the system. Fig. 1 provides an illustration of thetwo-body floating system concept developed for the SeaBeavI.2.2. Mooring systemIn a two-body wave energy converter concept, the relativevelocity and force transferred between the spar and the buoy areused to extract energy from the ocean waves. To maximize thepower extracted by the system, the relative motion between thetwo bodies must be maximized while allowing for effective forcetransmission. The SeaBeavI concept uses a tensioned mooring torestrain the heave of the spar while still allowing the buoy totranslate. The tensioned mooring line allows for effective forcetransmission during both the upstroke and the down stroke of thebuoy. A tensioned mooring system also limits the watch circle ofthe system allowing for tighter spacing in arrays of devices.2.3. Power take-off systemConversion of the relative linearmotion betweenthe sparand thebuoytoelectricityisachievedthroughtheuseofapermanentmagnetlinear generator. The generator consists of a stack of permanentmagnets housed in the buoy and an armature composed of copperwireandbackironinthespar.Asthemagnetstranslaterelativetothecopper wires, current is induced in the wire due to the changingmagneticfield.The generator topologyallows for theheavier magnetsectionto belocatedinthehigherbuoyancy buoy.Withthe armaturelocated in the spar, the power take-off cable is attached to a taut-moored floating body, limiting theforces onthe cable. Fig. 2 providesan illustration of the power take-off system concept.3. Detailed design3.1. Principal dimensionsDimensions of the buoy and spar were constrained by thelimitations of the long wave flume at the O.H. Hinsdale WaveResearch Laboratory. Prior to testing in the ocean, the system wasintended to be tested in the laboratory under controlled conditions.The maximumwater depth of the long wave flume is 10 feet, whichlimited the overall draft of the system. The diameter of the buoywas constrained by the width of the flume in addition to depth.Since the flume is 12 wide, the maximum diameter to ensurea blockage of less than 33% is 4.95 feet. The final configuration ofthe system had an overall draft of 8.17 feet with a buoy diameter of5.08 feet. A buoy diameter greater than the initial target wasrequired to provide adequate stability based on the as-built weightof the generator. Fig. 3 provides a rendering of the spar and buoyand their internal arrangements (Table 1).3.2. Buoy structureThe buoy structure was designed in a modular fashion to allowfor ease of construction and maintenance. The buoy was con-structed of glass reinforced plastic (fiberglass) with high densityfoam to provide extra buoyancy. Because the linear generatordepends on magnetics for the contactless force transmission andthe generation of electricity, the use of magnetic materials in thestructure of the buoy and spar is not desirable. In addition, fiber-glass does not corrode in salt water making it a preferred materialfor salt water applications.The magnet section of the linear generator was integrated intothe buoy structure so that it was modular and removable for latertesting of the generatoron a linear testbed. A keywayat the top andbottom of the magnet section transfers the lateral forces betweenthe magnet section and the hull of the buoy. Rubber o-rings wereused to seal the joint between the magnet section and the keyway.To hold the magnet section in place and provide compression forthe o-rings, a heavy fiberglass lid was attached to the buoy struc-ture with 12 half inch stainless steel bolts. A general arrangementofthe buoy structure is included in Appendix 1.Fig. 1. Dual-body wave energy conversion system concept.Fig. 2. Power take-off system concept.Fig. 3. Rendering of spar and buoy general arrangement.D. Elwood et al. / Renewable Energy 35 (2010) 3483543493.3. Spar structureThe spar structure was designed in three sections allowing thearmature to be removed for maintenance and testing. Like the buoy,the spar is made entirely of fiberglass with stainless steel fasteners.Havinganon-magneticsparisimportantsincethesparlieswithinthefield of the magnet section. The bottom section of the spar housesa ballast tank used in the tensioning of the mooring system. A halfsphericalbaseonthebottomoftheballasttankprovidesastrongpointfor attaching the mooring line. The power take-off cable attaches toa wet mateable waterproof connector at the base of the spar.The center section of the spar houses the armature of the lineargenerator along with the battery to power the ballast control anddata acquisition systems. Twelve sections of inch stainless steelthreaded rod join the center section to the top and bottomcompartments of the spar. Compression plates with two sets ofrubber o-rings ensure that the entire spar is sealed. A bilge pump inthe lower section of the spar provides both dynamic ballast controland protection against leaks in the operating condition.The top section of the spar houses the ballast control and dataacquisition systems. A linear position sensor utilizing a magneticpickup records the relative displacement between the buoyand thespar. Thermocouples mounted on the inside of the armature recordthe temperature of the coils during operation of the generator.Wireless communication is used to transmit the measured data toa nearby research vessel along with providing control signals forthe pumping system. A fiberglass lid attached with a 12 bolt patternand sealed with a rubber o-ring isolates the top section of the sparfrom the sea. A general arrangement of the spar structure isincluded in Appendix 1.3.4. Linear generatorThe generator consists of an 1196 mm long magnet sectionhoused in the buoyand a 286 mm long armature in the spar 6. Themagnet section is composed of over 900 individual high densityneodymium iron boron magnets held in place using aluminumretainers. The back iron on the magnet section is radially laminatedto reduce eddy current losses. A composite structure utilizingstainless steel rods, aluminum end pieces, and a fiberglass shell wasused to provide structural support for the magnets and back ironduring construction and installation. This structure also enabledthe generator to be tested without the support of the buoy struc-ture. A thin stainless steel tube adhered to the inner radius of themagnet section isolates the permanent magnets from the sea waterand provides a smooth surface for the linear bearing system.The armature also utilizes radially laminated back iron withslots filled with windings of 14 gauge copper wire. Each coil of thearmature consists of 77 turns of wire with 4 coils for each of the 3phases of the generator. The structural rigidity of the armature isprovided by two fiberglass compression rings tied together using inch stainless steel rods. Each phase of the generator wasterminated into a central junction box and the power was fed out ofthe spar through the power take-off cable. A rendering of themagnet section and armature is included as Fig. 4.3.5. Linear bearingsTo enable efficient conversion of the linear motion between thespar and the buoy into electricity, the gap between the magnetsection and the armature must be small (5 mm). This gap needsto be uniform around the entire circumference of the spar in orderto ensure that the magnetic normal forces between the magnetsection and the armature are balanced. If the alignment is notprecise, the normal force between the two sections becomesextremely large and increased friction will result.Thin strips of a laminated plastic material hold the gap betweenthe buoy and the spar and provide a smooth bearing surface to rideagainst the stainless steel tube adhered to the inside of the magnetsection. Twelve 1/2 inch wide strips are glued into grooves evenlyspaced around the circumference of the outer shell of the spar. Thematerial used to manufacture the bearing strips is designed to bewater lubricated making it ideally suited for marine applications.3.6. MooringThe tensioned mooring system consists of a single-anchor-legmooring with a mushroom anchor. The buoyancy of the spar isgreater than its weight, generating 650 pounds of pretension in themooring line. This pretension is sufficient to ensure that the linewill not go into compression during the down stroke of the buoy.Mooring pretension is achieved through the use of spar waterballast during installation. The spar ballast tank is filled with waterprior to installation and the mooring line is attached slack to thebase of the spar. Slack in the mooring system is removed usingTable 1Principal dimensions of the SeaBeavI wave energy converter.BuoyDiameter5.08feetDraft6.00feetDepth7.50feetFreeboard1.50feetDisplacement6473.90lbfSPARDiameter2.00feetDraft8.17feetDepth10.71feetFreeboard2.54feetDisplacement1616.42lbfFig. 4. Crosssection of the magnet section and armature.D. Elwood et al. / Renewable Energy 35 (2010) 348354350a tensioner system and the water is pumped out of the ballast tankto achieve the desired pretension.The mooring line is composed of steel bottom chain andsynthetic rope joined together using forged anchor shackles.A cluster of trawl floats is used as a mid-column float to remove theweight of the bottom chain from the spar. A pear link at the top ofthe mid-columnfloatallows forthe tensioner systemtobe attachedby divers during installation of the device. Two 3:1 polycarbonateblocks and 300 feet of synthetic line make up the block and tacklesystem used to tension the mooring. Once the tensioner has beenattached to the mid-column float by a dive team, the system can betensionedanddetensionedfromthesurface.Ageneralarrangementof the mooring system is included in the Appendix.4. ConstructionConstruction of the SeaBeavI wave energy conversion systemwas completed during the summer of 2007 with the subsystemshaving been built separately by their respective manufacturers. Thestructural components were built at Plasti-Fab Inc., a structuralfiberglass manufacturer in Tualitin, Oregon. While the fiberglasscomponents were being fabricated, the magnet section and arma-ture were being constructed by graduate research assistants atOregon State. Simultaneously, the mooring was being assembled bythe staff rigger at Englund Marine in Newport, Oregon.4.1. Structural componentsThe outer shell of the buoy was constructed using a filamentwinding process on a large diameter mandrel. Both the bottom ringframe and the inner shell of the buoy structure were molded usinga vacuum driven resin transfer process. To provide extra buoyancyand stability for the buoy, high density structural foam was addedto the exterior of the outer shell and sealed with a layer of fiberglassmat. The lid for the buoy was constructed of fiberglass with a foamcore. Keyways for the top and bottom of the magnet section werealso molded and grooves for the o-rings machined using a 3DOFcomputer controlled router. Pictures of the buoy structure can beseen in Fig. 5.The outer shell of the spar was constructed from two sections of24 inch fiberglass water pipe with a 1/2 inch wall thickness. Theouter diameter of the pipe was machined and slots for the bearingstrips were cut using a CNC lathe. A molded half spherical fiberglassbottom plate was fixed to the bottom of the spar to provide anattachment point for the mooring line. One inch thick fiberglassring frames were molded for the top of the lower spar section, andthe top and bottom of the upper section. O-ring grooves were cutin the ring frames using the computer controlled router. Pictures ofthe spar structure during construction can be seen in Fig. 6.4.2. Linear generatorThe linear generator components were assembled by hand bygraduate research assistants (9). Each of the laminations for thearmature and magnet section was hand shimmed using hightemperature shim tape. The armature laminations were stackedusing the fiberglass compression plates to hold the laminations inplace during construction. The magnet section was constructed inquarter round sections that were assembled in a specially made jig.After the laminations were assembled, the quarter rounds andFig. 5. a) Buoy lid b) Buoy inner shell and ring frame c) Buoy outer shell with addedfoam.Fig. 6. a) Spar structure showing the ballast tank, armature, and electronics compartment b) Bottom plate with wet mateable connector and strong point c) Interior structureshowing fiberglass ring frame at the top of the armature.D. Elwood et al. / Renewable Energy 35 (2010) 348354351armature were dipped in high temperature epoxy resin to protectthe iron from corrosion and provide insulation between the lami-nations. The permanent magnets were fixed to the quarter roundsindividually and then the sections were assembled to form thecompleted magnet section. The copper was wound onto thearmature using a specially built winder with fiberglass insulationbetween layers of windings to prevent internal shorts betweenwires. Pictures of the armature and magnet section build can beseen in Fig. 7 a and c. The completed generator components can beseen in Fig. 7 b and d.4.3. Mooring systemEyelets were spliced into the ends of the spectra rope in order toprevent abrasion between the rope and the connecting shackles.A marker float for the mooring was built using a surplus 1 m steelfloat fitted with a mast and a 2 nautical mile solar powered lightprogrammed to flash 15 times per minute. The anchor for thesystem was an 8200 pound steel mushroom anchor purchased assurplus from a scrap yard in Seattle, WA. The tensioner systemconsisted of two Harken 75 mm Carbo triple blocks run with 300feet of Sampson Dura-Plex line. The tensioner was attached toa titanium eye nut anchored to the base plate of the spar. A ropeclutch was used to enable the tension of the system to be adjustedduring operation. Fig. 8 provides photographs of the as-builtmooring system.5. Installation and ocean testingThe installation and testing of the SeaBeavI wave energyconverter was completed between August and October of 2007. Thesystemwas installed in two phases, with the mooring system beinginstalled in mid-August and the floating system in early October.The SeaBeavI was tested on the pier at the Hatfield Marine ScienceCenter and in Yaquina Bay followed by testing in the open ocean.5.1. Installation vesselThe Research Vessel Pacific Storm was used for both themooring installation and the ocean testing of the wave energyconversion system. The Pacific Storm is a converted fishing trawlerowned by the Oregon State Marine Mammal Institute. The 80 footvessel is outfitted with a 10,000 pound crane used to launch thetwo rigid inflatable boats used for tracking and tagging whales.With the net reel and stern ramp removed, the working deck of thevessel is quite large, making it well suited for deploying oceano-graphic equipment.5.2. Mooring installationThe mooring system for the SeaBeavI was designed to beinstalled prior to the installation of the floating system. After theanchor, mooring line, and mid-column float were installed, SCUBAdivers would be used to attach the tensioner system to the mid-column float during installation of the floating system. A steelA-frame, shown in Fig. 9, was designed as a launching platform forthe mushroom anchor to facilitate the deployment of the mooringfrom the Pacific Storm. A pelican hook attached the shank of theanchor to the forward end of the A-frame, providing a quick release.Before the mooring system was installed, the components werestaged on the starboard rail of the aft deck of the Pacific Storm.The chain and spectra rope were coiled into barrels to ensure thatthe line fed freely as the system was deployed. Installation of themooring began by deploying the marker float using the boatscrane. The rest of the mooring system was then strung out behindthe vessel, as seen in Fig. 8b, and towed to the test site location.Once on station, the pelican hook was tripped and the weight of thehead of the mushroom anchor caused the anchor to pivot off theA-frame and into the water, pulling the mooring line down tothe bottom.5.3.