Energy Harvesters Utilizing Galfenol TechnologyEric SummersETREMA Products, Inc.

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Energy Harvesting and Storage USA

 2011

Electricity

Energy harvester

VibrationMotion

Goal: Generate Power from Ambient Vibrations

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‐ Utilizing the magnetostrictive material Galfenol

Energy Harvesting and Storage USA

 2011

What is Galfenol?

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‐ A Ductile, Formable, Machinable, and Weldable Smart Material

Energy Harvesting and Storage USA

 2011

Inverse Magnetostrictive (“Villari”) Effect

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Applied stress or force Flux density variationyield

Energy Harvesting and Storage USA

 2011

Villari Effect for Galfenol

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Compressive stress vs. flux density

~1 T  

~70 MPa  

Energy Harvesting and Storage USA

 2011

Energy Harvester Circuit Model

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+Voc–

Magnet (M)

flux return material (FRM) Coil

Magnetostrictivematerial (MM)

φ

Fixed end

F=F0 sinωt x

⎟⎠⎞

⎜⎝⎛=dt

dBNAV MM

OC

dtdFNd

tB

NAdtdB

NAV MMMMOC

*33=

∂∂

∂∂

==σ

σ

COIL

OCMAXOUT R

VP

4

2

≈

Energy Harvesting and Storage USA

 2011

Innovative Galfenol Energy HarvesterConvert small bending force to large axial-force in beamParallel beam structure

for bias

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Bank of 50 LED’s

Configuration

Principle

Power ∝ Volume & Force

Energy Harvesting and Storage USA

 2011

Parallel Beam Structure

Uniform

Stress distribution in axial direction

20MPa

20MPa

20 N

1 N- 20MPa

20MPa

Area 0.5 ×1 mm2

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Large axial force F(a)

Small bending forceF(b) < 1/20 F(a)

Energy Harvesting and Storage USA

 2011

Advantages

Equivalent circuit

Magnetostrictive curve under different temperatures

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Energy Harvesting and Storage USA

 2011

• Simple and robust consisting of rigid structure, no wearing of parts• High power density – 20 mW/cm3

• Efficiency > 15% measured at resonance• Low output impedance with good matching with anticipated loads• Heat resistive up to 150°C• Testing frequency bandwidth for power generation

DemonstrationsHarvester can generate electrical power for 50 LEDs by vibration of

electric toothbrush (Avg 5 mW, Max 25 mW)

10Harvester can generate electrical power for 400 LEDs by hitting (Avg

100 mW, Max 1 W)

Energy Harvesting and Storage USA

 2011

Energy Harvester• Concept was a structural member that operates in compression or tension along the axis of a Galfenol rod

• Vol. < 2 in3• Harvest energy generated by displacements (vibrations) from machinery

• Mechanical coupling to vibrating source is key

• Power conditioning electronics  also developed and tested• Voltage quadrupler• Voltage doubler

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Energy Harvesting and Storage USA

 2011

Test Setup

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Energy Harvesting and Storage USA

 2011

Galfenol EH w/Circuitry

• Power and voltage measured vs. resistance• Same frequencies and dynamic forces• Addition of voltage quadrupler (60 Hz) and doubler (200 Hz) power conditioning circuitry

• Max power:  2.2 – 4.7 kΩ• w/o circuitry device impedance ~ 100 Ω

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Doubler ‐ 200 Hz, 8 ksi preload, 7 lbsrmsdynamic force

Quadrupler ‐ 60 Hz, 8 ksi preload, 7 lbsrmsdynamic force

Energy Harvesting and Storage USA

 2011

Galfenol EH OutputFrequency

(Hz)

DynamicForce(lbsrms)

Power Generated,no circuitry

(mW)

Power Generated,circuitry(mW)

Voltage at Max Power,

no circuitry(Vrms)

Voltage at Max Power, doubler(VDC)

Voltage at Max Power, quad(VDC)

60 7 1.1 0.26 0.33 ‐ 1.1

60 21 4.6 2.1 0.69 ‐ 3.1

60 35 13.5 6.9 1.2 ‐ 5.7

200 7 8.6 6.8 1.1 5.6 ‐

200 21 35 31.5 2.4 12.2 ‐

200 35 95 82 4.0 19.6 ‐

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Energy Harvesting and Storage USA

 2011

• Table data collected at 8 ksi preload and optimal load resistances• Dynamic stress range:  0.5 – 3 ksi• Power scaling with increasing frequency (ω) and force (F)

• 2.5 mW/cm3 max measured power density• Test conditions did not result in a plateau 

Galfenol EH Power Spectra

15Voltage doubler circuitry – 180 Hz bandwidthVoltage quadrupler circuitry – 90 Hz bandwidth

Energy Harvesting and Storage USA

 2011

• Half‐power bandwidth of device quantified:  90 Hz & 180 Hz• No changes to Galfenol (energy harvester) hardware• Large bandwidth a combination of circuitry and displacement (force) nature of energy harvester

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Wireless Base Station

Energy Harvester

Ambient Vibrations

Power Management and Energy Storage

Microcontroller, DSP,and Data Storage

Sensor(s)and ADC

WirelessRadio

Mon

itored Event

or Con

ditio

nFuture Galfenol EH Development

Energy Harvesting and Storage USA

 2011

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Wireless Base Station

Ambient Vibrations

Power Management and Energy Storage

Microcontroller, DSP,and Data Storage

Sensor(s)and ADC

WirelessRadio

Mon

itored Event

or Con

ditio

n

Energy Harvester Voltage output is direct from EH –unrectified AC

• Current focus has been on energy harvester hardware development

Energy Harvesting and Storage USA

 2011

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Wireless Base Station

Ambient Vibrations

Microcontroller, DSP,and Data Storage

Sensor(s)and ADC

WirelessRadio

Mon

itored Event

or Con

ditio

n

Power Management and Energy Storage

Energy HarvesterVoltage output is boosted and conditioned –rectified DC

• Near‐term focus will be on designing and integrating power management and energy storage electronics

Energy Harvesting and Storage USA

 2011