seminar report on renewable source of energy called pelamis wave energy converter,a technology that uses the motion of ocean surface waves to create electricity.bright scope in future and emerging very fastly.
SEMINAR REPORT ON PELAMIS WAVE ENERGY CONVERTER Submitted in partial fullfillment for the award of the degree of Bachelor Of Technology In Mechanical Engineering BySUBMITED BY:-SUBMITED TO:-SUKHRAJ SINGHER. NARENDER BANSAL1809549ER. RAHUL GARGMECHANICAL ENGG.MECHANICAL DEPTT. Department of Mechanical Engineering HARYANA ENGINEERING COLLEGE JAGADHRI – 135003 (HARYANA)
ABOUT PELAMISThe Pelamis Wave Energy Converter is a technology that usesthe motion of ocean surface waves to create electricity. Themachine is made up of connected sections which flex andbend as waves pass; it is this motion which is used togenerate electricity.Developed by the Scottish company Pelamis Wave Power(formerly Ocean Power Delivery), the Pelamis became theworld’s first offshore wave machine to generate electricityinto the grid, when it was first connected to the UK grid in2004. Pelamis Wave Power have since gone on to build andtest five additional Pelamis machines. Three, first generationP1 machines which were tested in a farm off the coast ofPortugal in 2009 and two of a second generation ofmachines, the Pelamis P2, which started tests off Orkney in2010.
OPERATIONThe Pelamis machine is an offshore wave energy converter,operating in water depths greater than 50m. The machineconsists of a series of semi-submerged cylindrical sectionslinked by hinged joints. As waves pass along the length of themachine, the sections move relative to one another. Thewave-induced motion of the sections is resisted by hydrauliccylinders which pump high pressure oil through hydraulicmotors via smoothing hydraulic accumulators. The hydraulicmotors drive electrical generators to produce electricity.Electricity from all the joints is fed down a single umbilicalcable to a junction on the sea bed. Several devices can beconnected and linked to shore through a single seabed cable.
PRINCIPLESThe Pelamis is an attenuating wave energy converterdesigned with survivability at the fore. The machines longthin shape and low drag profile minimises hydrodynamicforces, namely inertia, drag, and slamming, which in largewaves give rise to large loads. The machine responds to thecurvature of the waves rather than the wave height. Aswaves can only reach a certain curvature before naturallybreaking this limits the range of motion through which themachine must move but maintains large motion at the jointsin small waves.The Pelamis has a novel joint configuration used to induce atunable cross-coupled resonant response. Control of therestraint applied to the joints allows this resonant responseto be ‘turned-up’ in small seas where capture efficiencymust be maximised or ‘turned-down’ to limit loads andmotions in survival conditions
TECHNOLOGYThe device consists of a total of 4cylindrical steel sectionswhich are connected together by 3hydraulic powerconversion modules (PCM) Total length of the device is 120mand device diameter is 4.6m. Individual units are arranged inwave farms tomeet specific energydemands ina particularsite.The following sections provide a high level overview of thedifferent subsystems that are device specific. Subsystemscovered include the power conversionmodules (PCM), thestructural steel sectionsand the mooring system.
The summary table below shows the key specificationsof the Pelamis.
POWER CONVERSION MODULE (PCM)Power conversion modules (PCMs) connect the 4 individualsteel tubes forming a Pelamis device. Each PCM contains aheave and sway joint. The modular power-pack is housed in asecond fully sealed compartment behind the rain bay so thatin the event of seal failure only the hydraulic rams areimmersed. Access to all system components is via a hatch inthe top of the power conversion module. Maximumindividual component weight is less than 3 tons to allowreplacement using light lifting equipmentThe wave-induced motion of each joint is resisted by sets ofhydraulic rams configured as pumps. These pumpoil intosmoothing accumulators which then drain at a constant ratethrough a hydraulic motor coupled to an electrical generator.The accumulators are sized to allow continuous, smooth
output across wave groups. An oil—to—water heatexchanger is included to dump excess power in large seasand provide the necessary thermal load in the event of lossof the grid. Overall power conversion efficiency ranges fromaround 70% at low power levels to over 80% at full capacity.Each of the three generator sets are linked by a common690V. 3 phase bus running the length of the device. A singletransformer is used to step-up the voltage to an appropriatelevel for transmission to shore, High Voltage power is fed tothe sea bed by a single flexible umbilical cable, then toshore via a conventional sub-sea cable.
TUBULAR STEEL SECTIONSThere are a total of 4 tubular steel sections which are themain structural elements of the device. Each steel section is25m long and weighs roughly 7Otons. The main tube sectionsare manufactured in segments using steel plates that arerolled into shape. Once formed individual sections arewelded together to form a segment. This manufacturingprocess is extensively used in the wind industry tomanufacture wind turbine towers. The process can beautomated and lends itself well to cost reduction.Cast end caps on the steel tubes incorporate hinges, whichthen interconnect to the Power Conversion Modules. Inorder to properly ballast the device, sand is added.Alternative construction materials were evaluated under acontract by the Department of Trade and Industry.Materialsanalyzed and compared to each other were steel.pretensioned concrete and GRP (filament wound composite).
MOORING SYSTEMThe mooring arrangement ofPelamis needs to be designedspecifically for the site conditions. Similar to a wind turbinefoundation, which needs to be type approved, the Pelamismooring system needs to be designed by OPD and adapted tospecific site conditions. Survival conditions, maximum currentvelocity, water depth, seafloor soil densities and otherfactors will need to be considered in a detailed design phase.For the purpose of this project, the reference mooringsystem used for Ocean Power Delivery prototype testing wasused to establish a costing base case as shown in Figure.The pelamis mooring system is catenary type mooring using acombination of steel wires,chain, dead weightsandembedment anchors.
ELECTRICAL INTERCONNECTIONEach Pelamis device houses a step-up transformer toincrease the voltage from generator voltage to a suitablewave farm interconnection voltage. The choice of the voltagelevel is driven by the grid interconnection requirements andthe wave farm electrical interconnectiondesign. A flexibleriser cable is connecting the Pelamis to a junction box, sittingon the ocean floor. If multiple devices are connectedtogether, they are daisy- chained by a jumper cable whichruns from one device to the next. Only at certain strong-points the electrical cable is then brought to the ocean floor.This approach reduces the number of riser cables requiredand makes the cabling more accessible for maintenance fromdie surface. Riser and jumper cables undergo a large numberof cyclic loadings and it is likely that they will need to bereplaced after 10 years of operation.SUBSEA CABLINGUmbilical cables to connect offshore wave farms (or windfarms) to shore are being used in the offshore oil & gasindustry and for the inter-connection of different locations orentire islands. In order to make their suitable for in—oceanuse, they are equipped with water—tight insulation andadditional armor which protects the cables from the harshocean environment and the high stress levels experiencedduring the cable laying operation. Submersible power cablesare vulnerable to damage and need to be buried into softsediments on the ocean floor. While traditionally sub-seacables have been oil-insulated recent offshore wind projectsin Europe showed that the environmental risks prohibit theuse of such cables in the sensitive coastal environment. XLPEinsulations have proven to be an excellent alternative havingno such potential hazards associated with its operation.
ONSHORE CABLING AND GRID CONNECTIONTraditional overland transmission is used to transmit powerfrom the shoreline to a suitable grid interconnection point.Grid interconnection requirements are driven by localutilityrequirements. At the very least, breaker circuits needto be installed to protect the grid infrastructure from systemfaults.
PROCUREMENT AND MANUFACTURINGFor the single-module Pelamis plant it was assumed that the3 Power Conversion Modules are procured from OceanPower Delivery (OPD) and is shipped from the UK toCalifornia and that the structural steel sections are builtlocallyan appropriate shipyard. Manufacturing facilities whichare capable of constructing tile larger steel sections do existin California. Figure shows the Pelamis prototype underconstructionin Scotland. The picture shows that hydraulicram being mounted in one of tile Power ConversionModules.Thepicture showstile largetubular steel sections ofthe Pelamis being completed.
INSTALLATION ACTIVITIESInstallation and operational offshore activities require specialequipment such as anchor handler vessels, barges and heavyuplift cranes. In order to understand the offshore installationand removal activities and their impacts on cost, detailedprocess outlines were created to be able to estimateassociated resource requirements. Results were verified withOcean Power Delivery who deployed a prototype device thisyear, local offshore operators in Oregon and Sea EngineeringHawaii who managed the installation of Ocean PowerTechnologies Power Buoy in Hawaii. The major installationactivities for both pilot demonstration plant and commercialwave farm are:1. Install cable landing and grid interconnection2. Installation of sub-sea cables3. Installation of Mooring System4. Comissioning and Deployment of PelamisOffshore handling requirements were established based ontechnical specifications supplied by Ocean Power Delivery.