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Bio-Inspired wind energy harvesterAdvisors: Dr. Manish Paliwal and Dr. Lisa Grega

Kevin HynesDavid Talarico

Energy Demand

At the current time, we have used somewhere around half of the earths natural supply of fossil fuelsHow will we continue to supply society with the energy it needs to function?Energy Demand1 in 4 people in the world live without electricityThis energy poverty is the biggest limitation to improving living conditionsNeed for a cheap open source design

Modern Wind PowerThe 3 rotor horizontal-axis wind turbine

Blades spin a central shaftShaft runs to a gearboxGearbox steps up shaft speed to 60Hz in generator

Problem StatementUse linear, oscillatory movement to improve wind energy capture technology in one or more of the following categories:Overall efficiencyEnergy produced per dollar inputEnergy produced per unit area of land usedDesign a system that exploits rather than mitigates vortex energyMake design as simple and modular as possible Lower shipping and maintenance costsOpening the door to open source useUse vibrational modeling to widen range of resonant behaviorVIVACEVortex Induced Vibrations for Aquatic Clean Energy

VIVACEVortex Induced Vibrations for Aquatic Clean Energy

Drucker E G , Lauder G V Integr. Comp. Biol. 2002;42:243-257Vortex Shedding Characteristics Forces exerted on cylinder only from vortex shedding

Forces exerted on airfoil to due pressure differential (lift) as well as vortex formation and sheddingSynchronization of a vibrational system occurs where driving frequency approaches natural frequencyMass ratio defined as m* = mass of system/mass of displaced fluidVortex Shedding Characteristics Plot of oscillatory frequency vs. This occurs over a large range of flow speeds if the mass ratio is very lowLow mass ratio allows the system to respond more quickly

Delayed StallProves concept that a leading edge vortex (LEV) provides an additional lift force during the time that it remains in contact with the wing

E. Swanton, B. Vanier, and K. Mohseni, Leading Edge Vortex Stability in a Flapping Model Hummingbird Wing, 38th Fluid Dynamics Conference and Exhibit, AIAA paper 2008-3718, Seattle, OR, June 23-26, 2008.Vortex Shedding Characteristics Proposed SystemPitching- rotational movement of wingPlunging- translational movement of wing

Coupling these two motions will allow the design of a system that can extract flow energy through lift and vortex formation

Kinsey and Dumas 2008Design ParametersPlunge Amplitude (Ho)Pitch Amplitude (o)Effective angle of attack ()Chord Length (c)Airfoil ThicknessPitching Center Frequency of OscillationFlow Speed (U)Motion characteristicsVibration constants

Design Concepts

Design ConceptsReduced frequency = f* = fc/UThickness has a negligible effect on efficiencyOur Design: More flexibility on selection of airfoil design

Design ConceptsOptimal pitching center location found to be 1/3Efficiency increases with Reynolds numberOur Design Re~30,000

Design Concepts

Sine curve is position vs. timeSlope is velocityResultant of lift and drag resolved into X and Y componentsPower vs. PropulsionEffective angle of attackY-component in phase with velocityQuasi-steady assumption

Design ConceptsPropulsion = High energy wakePower extraction = Low Energy wakeOur Design: Must keep Y-component of force in phase with velocity

Energy Harvesting through Flow-Induced Oscillations of a FoilDesign Concepts

A Leading Edge Vortex (LEV) is formed at the leading edge of an airfoil that is about to undergo flow separationLEV energy can be recovered at the trailing edge depends on LEV-foil interaction and timingThis occurs over a large range of flow speeds at a low mass ratioUnsteady phenomenon

Design ConceptsLeading Edge Vortex Synchronization (LEVS) dependent on maximum pitching amplitude and reduced frequencyOptimal pitching amplitude ~ 75Optimal reduced frequency ~ 0.15Our Design: Use as baseline

What is the most efficient form of movement?- Power extraction dominated by vertical force in phase with vertical velocity- Square wave ensures that the movement of the wing spends the most time in the power stroke, highlighted below, where the Y-component of force and velocity are both at their maximum- Power Strokes ended by rapid pitching of airfoil and change in vertical direction

Design Concepts

Sinusoidal vs. Non-Sinusoidal (Square Wave) OscillationDesign Concepts

Extracting Power from the Jet Stream: Pushing the Performance of Flapping Wing Technology Platzer et. al. SummaryMass ratio of wing must be very lowThickness has a negligible effect on efficiencyOptimal pitching center location found to be 1/3Efficiency increases with increasing Reynolds number Pitching amplitude and reduced frequency extremely important parametersStrive for 0 75 and f*=0.15 for highest efficiencyOptimal vertical motion of wing section is a square waveMethodologyExceptional complexity of the CFD modeling in this situationBeyond our scope of knowledgeUse studies presented to create an adjustable experimental apparatus

For fully flow driven motion, three models were considered based off of relevant studiesSystem whose pitching movement was allowed through a rotational springSystem whose pitching movement was allowed to achieve a max value during power stroke and used a mechanical lever arm to change angles of attack, and thus, directionSystem which utilized a mechanically prescribed motionMethodologyWhile all three models have been confirmed to operate effectively with numerical simulations, the use of a mechanical lever arm was chosen on the basis of simplicity of design and higher efficiencyMethodologyLinear bearings needed to reduce friction and mechanical inefficiencyTwo wings attached to same track To apply as much force to the generator as possible, new systems wing sections will stand vertically weight will not counteract liftPrototype

Use of one track cuts costsUse of two wing sections increases power, eliminates unwanted momentsLever arm responsible for pitch angle reversal by coming into contact with a stopperMechanism by which ideal pitch reversal time will be approximatedNew Design

27Our PlanKinsey and Dumas 200873, f*0.15, H/c1Platzer et al. 2010Lever Arm TR = 0.3Design, Build, Test Small Scale Model

28That brings us to our plan, which is to design and build a small scale model for testing in the wind tunnel. The design parameters we will be working off of are those from two different numerical studies. The first was conducted by Kinsey and Dumas who solved for an optimal range of pitching amplitudes with respect to reduced frequency. We will be using the values that correspond to the highest efficiency case as a bench mark. The next was done by Platzer and others who improved efficiency by reducing the stroke reversal time to 0.3. In addition this group also built a physical model which implemented a simple lever arm to change directions.

28DesignDesignAdjustabilityPower TransmissionWing DesignTestingPIVVelocity Profile

29This is the basic design we came up with to prove this systems feasibility. Used this as a point of departure to design subsystems such as adjustability, power transmission, and wing design. 29AdjustabilityThe pitching amplitude will adjust by a series of holes on the bearing blockEach pair of holes will allow for a different maximum pitchBearing BlockHolesPegsAirfoil/ Lever ArmPivot3030AdjustabilityHeaving amplitude - Adjusted by moving a pair of locking collars on trackBearing BlockTrackLocking CollarLocking CollarAirfoil/ Lever ArmPivotFixed SupportsMechanical Stops3131Power TransmissionObjective: Linear Movement Electrical Energy Power TransmissionLinear GeneratorDIY/PatentsPneumaticExtremely InefficientPiezoelectricNeed Small DisplacementMechanical(Gear/Pulley)Many Options/High Efficiency3232MethodPower TransmissionLinear MovementOne-Way RotationRotary Generator

Flywheel Energy Storage33So the way went about this was by transferring the linear movement to intermittent one way rotation, storing the energy from that rotation in a flywheel which would then power the generator.The means by which this one way rotation was accomplished was through this selective locking mechanism mounted here. There will be two passes of cable going through the device, which will house two separate locking mechanisms one for each pass of cable. 33Power TransmissionFound that magnetic flux is directly related to rotor speed and efficiencyMost PM Generators designed for use at a given rotor speedUse of a flywheel for constant speed

Dynamic modeling of transverse flux permanent magnet generator for wind turbines -Maurcio B. C. SallesI; Jos R. CardosoI; Kay HameyerII3434Power TransmissionT0

0.5*H3535Wing DesignVery low massStrong enough to withstand forces of lift and momentum changeDurability must withstand outdoor weather conditionsEase of manufacturing and assemblyWing DesignInflatable Wing

Composite Wing

SailsStyrofoam

Wing DesignInflatable wing very light and cheap, but leaking may pose problemsComposite wing is very strong and lightweight, but it is difficult to manufacture and repairWing Design

ANSYS calculation for Styrofoam wingStress levels too high at peak power output levelsStyrofoam ruled outWing DesignSail is an attractive choiceCheapest optionMost DurableEase of manufacture, assembly and maintenanceReversible camberLose some efficiency lower CLPartially rigid wingsail best option

Movement will be translated to generator by timing pulley-belt systemFirst order vibration analysis of the system reveals its equation of motion, natural frequency and damping ratio

Vibration AnalysisVibration AnalysisPIV testing to be conducted on completed prototypeIntegration of the velocity fields around the airfoil can supply the vibrational models forcing functionAlgorithm inputs forcing function is used to optimize system

Kutta-Joukowski theorem( = free stream density, V = free stream velocity, and = circulation)Definition of Cirulation(C is the curve enclosing the airfoil and Vcos is the velocity tangent to the curve)Vibration AnalysisOptimize parameters in nonlinear systemNeed for algorithm that can input complex forcing functionFirst order approximationSimple sinusoidal forcing functionAmplitude determined from thin airfoil theory calculationsMATLAB - Runge Kutta Approximation for vibrational analysisUsed vibration hand calculations to supply governing equation

Cost Analysis

GanttChartQuestions?