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CITRIS sponsored WAVE ENERGY CONVERTER 2013. UC Davis Mechanical Engineering. Alex Beckerman, Kevin Quach , Nick Raymond, Tom Rumble, Teresa Yeh. Contents. Introduction An overview of the CITRIS Renewable Energy Grant proposal, and project’s scope Preliminary Design and Research

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Citris sponsored wave energy converter 2013


UC Davis Mechanical Engineering

Alex Beckerman, Kevin Quach, Nick Raymond,

Tom Rumble, Teresa Yeh



  • Introduction

    • An overview of the CITRIS Renewable Energy Grant proposal, and project’s scope

      Preliminary Design and Research

  • Technical Review

    • Terminology and main features of our WEC design.

    • Subsystems

    • Buoy

    • Spar

    • PTO

      • Hydraulics

      • Electronics

    • Heave Plate

  • Construction

    • A comparison of the two hydraulic motors regarding power performance, efficiency, and cost.

  • Next Stage

    • Testing in Bodega Bay

    • Instruction Manual

Project introduction

Project Introduction




  • 2012 CITRIS Sustainability Competition Winners

  • $10,000 Renewable Energy Research Grant

  • (+ $5,400 funding for testing)

  • Complete project within one year from award




1. Design and fabricate a Wave Energy Converter (WEC)

2. Use standard parts and components to build the PTO

3. Create a set of instructions and share information over website

Preliminary designs and research

Preliminary Designs and Research

Preliminary design research

Preliminary design & Research

Potential Test Site: Bodega Bay, Ca

  • Exposed to Pacific ocean waves and wind swell

  • Local university facility to assist with deployment

  • Steep ocean floor topography (bathymerty)

  • Close proximity to UC Davis

  • Team has personal knowledge of area


Preliminary design research1

Preliminary design & Research

Bodega Bay Marine Lab


Preliminary design research2

Preliminary design & Research

Significant Wave Height 1981-2008

  • NOAA Buoy 46013

  • NOAA provides ocean data for last 28 years

  • Buoy anchored 14 miles off shore

  • Dominant wave period remains constant

  • Wave height expected to increase closer to shore

Dominant Wave Period 1981-2008


Preliminary design research3

Preliminary design & Research

Bond graph Modeling

  • Transfers system from mechanical translational domain to the electrical domain

  • Determines hydraulic damping coefficient for given electrical resistance

  • Damping coefficient used in state space dynamic modeling

Preliminary design research4

Preliminary design & Research

  • State Space Modeling

  • Model to represent the dynamics of our physical system in ocean

  • Linear wave model: approximation of ocean waves as sinusoids. [1]

  • Equations developed within state space using a free body diagram.

  • The system is modeled as a two body system with individual forces acting on each

  • body.

MatLab Simulation for Different Heave plate sizes used in Iteration Process

Free Body Diagram of Buoy- Heave Plate Dynamics

Preliminary design and research

Preliminary design and research

[ WEC_001]

[ WEC_002 ]

[ WEC_003 ]

Technical background

Technical Background

Technical background1

Technical background




47.3 ft

Have Plate

[ WEC_004 ]

Sub systems buoy


Citris sponsored wave energy converter 2013


Citris sponsored wave energy converter 2013


  • Preliminary testing of foam

  • Fabricated one cubic foot mold out of plywood and wood screws

  • Filled mold with two part expanding polyurethane foam

Results From Initial Foam Test

Citris sponsored wave energy converter 2013


Lining the mold with plastic to assist with releasing the foam from the mold

Positioning the PVC pipes

Citris sponsored wave energy converter 2013


  • Marine grade polyurethane foam

  • Mixture come in two parts, expands when mixed

  • Final volume is 15 times the original volume after 20 minutes of curing

Citris sponsored wave energy converter 2013


Releasing the foam from the mold

Citris sponsored wave energy converter 2013


The foam was cut with a chainsaw to form the 45°chamfer

Citris sponsored wave energy converter 2013


The buoy was then sanded down and coated with a pigmented epoxy resin

Citris sponsored wave energy converter 2013


Steel plates mounted on the upper and lower surfaces of the buoy

All thread compresses the plates and secures buoy to the spar

Sub systems spar


Citris sponsored wave energy converter 2013



Citris sponsored wave energy converter 2013


Citris sponsored wave energy converter 2013


The bolt holes were drilled on the mill to assist in accurate alignment.

Welded components into framework

Citris sponsored wave energy converter 2013


Housing for springs and hydraulic shaft

Wire rope alignment housing

Citris sponsored wave energy converter 2013


Addition of strut members

Citris sponsored wave energy converter 2013


Strut members welded to the spar

Secured to the buoy bottom plate

Spring alignment

Spring alignment

Alignment brackets

Alignment brackets

5 spring alignment brackets to keep the 6 springs inline

Alignment brackets1

Alignment brackets

Bushing doubles as spring alignment and linear guide for hydraulic rod extension

Alignment brackets2

Alignment brackets

Cylinder alignment bracket

Sub systems power take off system


Power take off system

Power take-off system

Power take off system1

Power take-off system

  • Hydraulic Subsystem elements:

  • Hydraulic Ram

  • Bladder Type Accumulator

  • Piston Type Motor

  • Standard hydraulic hoses and fittings

  • System Operation:

  • Direct drive

  • Reverses direction with each stroke

  • Accumulator displaces cylinder rod volume

Power take off system2

Power take-off system

  • Hydraulic Motor Drain Port By-pass:

  • Check valves

  • Swagelok fittings

  • Hydraulic subsystem waterproof housing

Power take off system3

Power take-off system

Power take-off systems conveniently contained within water proof boxes

Power take off system4

Power take-off system

  • Boxes mount to frame

  • Frame mounts to top of buoy

  • Easy to access and maintain

Power take off system5

Power take-off system

  • Permanent Magnet DC Motor:

  • Operated mechanically to function as a generator

  • Microcontroller:

  • Logs system data from voltage and current sensors in 16 MB SD card

Power take off system6

Power take-off system

Waterproof microcontroller housing

Power dissipates in 1500 Watt

1 ohm resistor

Power take off system7

Power take-off system

Sub systems heave plate


Heave plate

Heave plate

Heave plate1

Heave plate

Steel square tubing arranged into framework .

Test fitting before final welding of sheet steel

Supported from spar by connections of steel cables

Heave plate2

Heave plate

  • Sheet steel limits water flowing around steel frame

  • Hydrodynamic damping

  • “Added mass” effect

Sheet steel welded to frame using plug and bead welds

Heave plate3

Heave plate

Use of four individual modules advantageous for transportation and storage

Plug welds

Bead welds

Heave plate4

Heave plate

Steel cable, clips, and thimbles

Steel cable threads through eyelets welded on steel frame

Heave plate5

Heave Plate

Next stage testing


Ocean testing

Ocean testing

Mooring site at depth of 100 feet

Ocean testing1

Ocean testing

Lifting with crane

  • Ring hoists mounted to bottom of buoy, and section of steel frame

  • Allows for lifting and transportation

Ocean testing2

Ocean testing

Ring Hoists

Ring hoist selected due to ability to lift angled loads

Capacity of 5,000 lbs each

Ocean testing3

Ocean testing

  • Transporting WEC

  • List with 1 Ton crane in EFL

  • Placed onto trailer provided by EFL

  • Tow trailer and WEC with a FORD F-550

Ocean testing4

Ocean testing

UC Davis Bodega Bay Marine Laboratory

Ocean testing5

Ocean testing

  • BML Crane

  • 3 Ton lifting capacity

  • 15 foot boom span

  • Drive trailer directly onto dock

  • BML Boat

  • Mussel Point Research Vessel

  • Boat: 42 foot long, with winch system

  • Specifically designed operate in demanding waters nearshore and offshore

Ocean testing6

Ocean testing

2,000 lbs Anchor

Plan A: train axel

(vendor not responding)

Plan B: purchase scrap steel

$0.15/lbs and cut and weld

Plan C: purchase scrap steel

$0.40/lbs and vendor will weld

  • Float Bag

  • Plastic bag filled with air

  • Provided by BML

  • Can float 3,000 lbs

  • Will float anchor behind boat

Image provided by BML:

Example of a Float Bag and 2,000 lbs Anchor

Data and results

Data and results

  • Collect data and analyze power output

  • Compile results

  • Create a manuscript and instruction manual

  • Upload the instruction manual onto team website

  • Upload informational videos to website (x5)

  • Submit final report to CITRIS

Team website

Project Wiki



  • A Review of Wave Energy Converter Technology. Drew, B, Plummer, AR and Sahinaya, MN. s.l.: Department of Mechanical Engineering, University of Bath, Bath, UK.

  • Frequently Asked Questions. US Energy Information Administration. [Online] US Department of Energy, July 9, 2012. [Cited: November 20,

  • Department, Minerals Management. Technology White Paper on Wave Energy Potential on the U.S.Outer Continental Shelf. s.l. : U.S. Department of the Interior, 2006.

  • Hydraulics: 2X72X1.25 DA HYD CYL Item# 9-7707-72 . Surplus Center. [Online] 2010. [Cited: 02 18, 2013.] 72&catname=hydraulic.

  • McMaster- Carr Supply Company. Plastic Material Properties: More About Plastics. McMaster-Carr. [Online] 2012.

  • McMaster-Carr Supply Company. More About Steel Alloys. McMaster-Carr. [Online] 2010.

  • More About Aluminum and Aluminum Alloys. [Online] 2010. [Cited: 04 22, 2013.]

  • NOAA. NOAA Marine Environmental Buoy Database. National Oceanic and Atmospheric Administration. [Online]

  • NOAA Ocean Facts. National Oceanic and Atmospheric Administration. [Online] 2011 йил17- November. [Cited: 2012 йил 10-November.]

  • Surplus Center. Hydraulics: 4X96X2.25 DA HYD CYL HEAVY DUTY CROSSTUBE. Surplus Center. [Online] 2012. [Cited: 02 12, 2013.]

  • Urethane Technologies Inc. Floating Devices Catalog. Denham Springs, Louisiana, USA : s.n.

  • US Energy Information Administration. Annual Energy Outlook 2012- Renewable Energy Generating Capacity and Generation. Washington DC : US Department of Energy, 2012.

  • US Energy Information Administration. The Electric Power Monthly with Data for August 2012. Washington DC : US Department of Energy, 2012.

  • Willis, H. L., Welch, G. V., and Schrieber, R. R. Aging Power Delivery Infrastructures. New York : Marcel Dekker, Inc, 2001.

Citris sponsored wave energy converter 2013

Thank you for the opportunity to present our project.We hope you found this information useful. If you have any questions or comments, please feel free to ask.

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