Power lines con nect to the local e

lectric

al grid

Electrical Transform er

Graph

Wind blowing across the surface of the ocean transfers kinetic energy to the water and generates consistent smooth waves, or swell. Ocean swell travels vast distances in deep water and is capable of gaining energy as the wave height increases over prolonged exposure to the winds, [4]. The wave’s energy begins to dissipate once the swell reaches depths of 200-meter or less, and at 20-meter depths the energy is reduced by approximately 1/3 that of deep water [4]. It has been estimated that the total average wave energy

depths of 60-meters, is approximately 2,100 Terawatt-hours(TWh) or 18% of the United State’s yearly primary energy requirements, [1].

As interest in the research and development of alternative energy increases,

One approach to harnessing wave power is with the design of a Wave Energy

the motion of the swell to drive a linear generator. In this experiment, a pro-totype WEC using a linear generator is constructed and its electric output is analyzed when subjected to the periodic waves generated in a water tank.

source: http://www.weather.gov/

TheoryMagnetic Flux: the measurement of the strength and quality of the mag-

Electromagnetic Induction: is the generation of voltage across a

(EMF) generated can be calculated from Faraday’s Law, where N represents the

Magnetization: magnetization is the magnetic moment per unit volume of the material. The magnetic moment is directly related to magnetic spin and or-bital motion of the electrons within the material, and is a characteristic of the ma-terial.

Ferromagnetic Material: ferromagnetic materials act like a collection -

Lenz’s Law: the electromotive force induced in a closed circuit will travel in a

by the negative sign in Faraday’s law and will predict the direction of the induced current.

da B

ε = -N dΦdt

B

Introduction

Linear GeneratorAn induction generator creates electricity through the use of magnetic induc-

explores the principles behind a linear moving generator. The linear generator consists of two main features, a rotor and a stator, with the space between the rotor and the stator referred to as the air gap. See diagram 1.

The rotor is made from a stack of rare earth neodymium magnets sandwiched in-between ferromagnetic spacers called shoe-poles. These ferromagnetic shoe-

and into the stator. For this experiment the shoe-poles where made from low carbon steel washers found at the local hardware store.

The stator was made from three individual coils of copper wire connected in series. The coils used in this experiment were made from 32-gauge copper wire that had been baked in order to keep their rigid shape.

maximized as it travels though the shoe poles. By increasing the number of turns

the output of the generator. Previous research has shown that encasing the coils

this project.

emanating from the magnets is conducted through the shoe poles perpendicular

rotor

statorair gap

(diagram 1) (diagram 2)

Linear displacemnt of buoy moves the rotor housed

SetupThe power output of the WEC was tested in a laboratory by using a wave tank. The small wave tank was built from a glass aquarium (48”x20”x12”)

back and forth it was possible to generate rolling waves in the tank. Stag-gered PVC shafts were placed at the end of the tank to dissipate the

the production of standing waves that would interfere with the experi-ment. See diagram 3 of wave tank.

When the WEC was placed in the tank and subjected to the wave motion, it was possible to measure the current and voltage generated. Logger Pro 3.6 software was used to collect data and graphically show the phase of the individual coils.

Experiment setup of wave tank and WEC prototype. 3D modeling generated using Autodesk Inventor software

Design and Characterization of a Linear Generator as a Prototype Wave Energy Converter, (WEC). Nick Raymond Faculty Sponsor: Younes Ataiiyan Ph.D.

Engineering and Physics Department Santa Rosa Junior College

ResultsWith a wave height of four inches peak to peak, it was found that the linear generator produced AC current and that Coil#1 had a maximum output of 1.5 volts, while Coil#2 and Coil#3 had a maximum output of 0.8 volts. During the testing, this experiment was limited by the size of the wave tank and was not able to collect data from varying wave heights. Future experiments should be

production.

From the graph below it was observed that the outputs from the coils were in phase, however further research will be required to determine the maximum output of this particular WEC design.

This experiment was successful in illustrating the basic principles of a linear generator when applied as a Wave Energy Convertor. It has been shown that waves traveling through water are capable of providing the necessary energy to move a linear generator and produce electricity. This small scale experiment parallels larger projects that are being tested glob-ally to verify the economic feasibility of ocean power as a renewable energy source, [5].

A practical application of this technology would be on a much larger scale, and would require WECs in a concentrated area to form a “wave farm”, [4].

customized to support the local needs of coastal towns and cities. Power

from the wave farm to the power grid on shore.

The environmental impact of WECs is expected to be small, and in some

-sive studies and localized regulations to insure any impact to surrounding ecosystems are minimized.

At the moment, the initial investment in wave energy technology is expen-sive and few designs have been tested for prolonged exposure and use. In addition to the initial investment, there is the continual cost of mainte-nance to ensure that systems remian functioning. Even still, the ocean is a hostile environment and designing an anchoring system capable of with-standing the extreme forces of ocean storms limits the actual construction of many projects, and slows the growth of the industy. With emerging technology and future testing, the initial cost of production will become competitive as it meets the rising energy prices and gains support from a

Summary

the U.S. energy requirements could be supplied by ocean power.

Characterization of magnetic Main components of linear generator

Application

ReferencesFeasibility Demonstration Project. EPRI Global.

Danielsson, O. (2003). Design of a linear generator for wave energy plant. Engineering Physics Programme Uppsala Unviversity School of Engineering .

Making Waves in Power. (2006). Retrieved from Ocean Power Technologies: http://www.oceanpowertechnologies.com/

Minerals Management Services Renewable Energy and Alternative Use Program U.S. Department of Interior. (2006). Wave Energy Potential on the U.S. Outer

Univerza v Ljubljani. (2004). 2 Archimedes Wave Swing. Power Egnineering , 16-22.

Finite Element Method Magnetics Software, Designer David Meeker, Ph.D.http://www.femm.info/wiki/HomePage

Special thanks to:Professor Younes Ataiian for his support and mentorship throughout project

andDaniel Spangler and Ethan Katz for their machining skills and expertiese

andJetTronics of Santa Rosa, Ca for their generous contribution of specialty coils

1.

2.

3.

4.

5.

6.

Characterization of Coils in Linerar Generator

12” Tall

Cement Base

PVC ExteriorCasing

Rotor

Stator (coils)

Buoy

Power Cable