1

Pyroelectric Energy Harvesting Devices

Student Design Team:

Trent Borman1, John Etherington2, Thomas Geske1, Joshua Grindeland2

Faculty Advisors & Clients:Scott Beckman1 and Sumit Chaudhary2

Donor:Pete Onstad (to foster EE/MSE senior design collaboration)

1 Department of Material Science and Engineering; Iowa State University; Ames, Iowa; USA2 Department of Electrical and Computer Engineering; Iowa State University; Ames, Iowa; USA

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Problem StatementConvert waste thermal energy to electricity.

Design a system to utilize the pyroelectric effect in materials with high entropy transitions.

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Market Survey• Waste heat is abundant• No clear industry leader in thermal energy to

electric energy conversion• Modern high entropy materials exceed bulk

ceramics in performance

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Background &Motivation

4

5

Coupling Thermal and Dielectric Properties

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A pyroelectric crystal spontaneously changes polarization when its temperature is changed

The electrocaloric effect is when a crystal spontaneously changes temperature when its polarization changes

The pyroelectric effect allows us to convert between thermal energy and electrical energy

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Basic Operation of Engines and Refrigerators

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Refrigerator

System

ThermalReservoir

(Cold)

ThermalReservoir

(Hot)

Environment

Work

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Basic Operation of Engines and Refrigerators

Engine

System

ThermalReservoir

(Cold)

ThermalReservoir

(Hot)

Environment

Work

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Engine & Refrigerator in Phase Space

Engine Refrigerator

Pres

sure

VolumePr

essu

reVolume

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Common Engineering Principles• A material is used to transfer heat between

thermal reservoirs• Complementary adiabatic processes facilitate the

thermodynamic cycle

Equilibrate with hot thermal reservoir

Equilibrate with cold thermal reservoir

Adiabatic Transformation

Adiabatic Transformation

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Example: Perovskite pyroelectric crystal: ABO3

Figure courtesy of Dr. Beckman

BaTiO3

-ΔT

-ΔT-ΔT

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Electric Field

Pola

rizati

on

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Electric work

Thigh

Tlow

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The ordering of atomic scale dipoles causes a change in the entropy

The change entropy requires a change in heat

In an adiabatic system, this causes a change in temperature

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Why does this work?

Field Direction-ΔT

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Pyroelectric vs. Thermoelectric• Oscillating thermal

cycle• Dipole orientation• Applied electric field• Exhibited by few

materials

• Static thermal gradient• Charge carrier motion• No applied field• Exhibited by all

materials

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What can we use to get a larger change in entropy?

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Liquid Crystals

Nanostructures

Polymers

Figure from Longyi Bao Nanotechnology (2013)

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Material Effect

Figure from Yyang340 - Wikipedia

Electric FieldP

olar

izat

ion

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Goals & Progress

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Functional Requirements• Demonstrate the pyroelectric effect in liquid

crystals and polymers• Convert waste heat to electrical work• Measure properties of specimens• Design a switching and harvesting circuit• Expose pyroelectric device to a thermal cycle• Withstand 400V across element

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Non-functional Requirements• Well documented for future work• Modular for varying pyroelectric materials• Scalable to significant current and power levels• Safety

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Deliverables• Pyroelectric specimens

• Liquid crystal cells• P(VDF-TrFE) films

• Characterization circuit• Electrical property measurements

• Harvesting circuit• Microcontroller code

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Risks• High risk project utilizing new, unproven materials

and techniques• Potentially transformative for thermal energy

harvesting industry

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Work breakdownTrent Borman

-Group leader

-Liquid crystal device fabrication

-P(VDF-TrFE) device fabrication

-Material electrical property curves

-Management of bill of materials

John Etherington

-Project timeline

-Communication (weekly report)

-Control systems and control code

-Circuitry design

Joshua Grindeland

-Web page design

-Circuitry design

-Pspice circuit design

-Electrical device research

Tommy Geske:

-Bibliography and Sourcing

-Liquid crystal device fabrication

-P(VDF-TrFE) device fabrication

-Thermodynamic curve generation

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System Block Diagram

Microcontroller

SwitchingControl

Produced EnergySource/Load Switching

Circuit

VHigh VLow

ΔQIndependent Frequency Adjustment

TempReading

Pyroelectric MaterialContact

Contact

Heat Transfer System(pyroelectric device housed

within)

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Design Stages1. Pyroelectric specimens2. Characterization circuit3. Harvesting circuit

1

2 3

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Polymer Specimens• P(VDF-TrFE)• Spin coating• 1.2 micron thickness• ITO substrate• Pinholing shorts ITO to top

electrode• Process being refined

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Polymer Specimen Troubleshooting• Solvents• Atmospheric conditions• Contacts• Thickness

Currently in contact with a group which creates PVDF films at Nebraska

Purchasing commercial polymer films to test concepts

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Barium Titanate Multi-layer Capacitors• Backup if high risk organic materials do not work• Confirm functionality of harvesting circuit• Well documented in literature• Preliminary testing of BaTiO3 MLCs show high

breakdown resistance

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Liquid Crystal Specimens• Commercial cells• 5CB liquid crystal• Increasing polarization

with electric field• Frequency tuning

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Instec Inc. Type SA and SB Liquid Crystal Cell

Structure of 5CB Liquid Crystal

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Liquid Crystal Specimens

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Liquid Crystal Troubleshooting• Applying 210V results in breakdown preventing the

voltage from rising above 150V in the future• 400V breakdown observed by other groups

• Solutions investigated• New liquid crystals (hygroscopic)• Other liquid crystals (longer chain length)• External contacts (prevent conduction)• Increase temperature (phase change)

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Liquid Crystal Troubleshooting

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0.1µF

8MΩ

22kΩ VV

The values of the resistors and capacitor will be modified to match the various pyroelectric samples.

Characterization: Sawyer-Tower

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Harvester: Switch-level Model

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PyroelectricHarvesting

Load

PyroelectricBeyond

Curie Temp

Harvesting Load

PyroelectricHarvesting

Load

PyroelectricHarvesting

Load

1 2

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VLow

VLow VHigh

VHigh

Increase Applied Voltage

Heat Pyroelectric

Connect to Load

Cool & Connect to

Voltage

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Harvesting Circuit

vRL

100k

DeviceTemp

+-

USBPWR

RESET3.3v5vGNDGNDVIN

A0A1A2A3A4A5

AREFGND

1312

~11~10~9

8

7~6~5

4~3

2Tx> 1Rx< 0

POWER

ANALOG

DIG

ITAL

(PW

M~)

RESET

Arduino UNO

ICSP

TMP36

+-

47k

240

100µ 330k

1k

100

100

Vcontrol

10kOffsetNull

Vs

Vs

10k 5M 1µ

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Results

Voltage

Current

Device Characteristics

Future Work - Concept SketchThe device consists of three

subsystems:

Mechanical/Heat Transfer – Piston, stepper motor, silicone oil, heat sink, heating band.

Material – Pyroelectric material and contacts.

Electrical – Thermocouples, harvesting circuit, switching circuit, and motor controller.

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Conclusion• Electrical characterization has preliminary results,

but is an ongoing project• Preliminary circuits designed• Heat transfer system will be explored later

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Acknowledgements• We would like to thank Scott Beckman and Sumit

Chaudry for their role as our advisors

• We would like to thank our client Pete Onsted for his generous donation to foster collaboration between materials science and electrical engineering

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Additional Information

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Safety• High voltages

• Lockout tag out• Insulating gloves

• Temperatures• Heat resistant gloves• Oil resistant clothing• Safety goggles

• Chemicals• Chemical resistant gloves• Storage and disposal plan• Fume hood• Safety goggles

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Cost Analysis – Liquid Crystals

Supplier Name Unit Quantity Price Subtotal

Sigma Aldrich4’-Pentyl-4biphenylcarbonitrile Gram 1 $ 72.30 $ 72.30

Sigma Aldrich4’-Hexyl-4biphenylcarbonitrile Gram 1 $ 90.20 $ 90.20

Sigma Aldrich4’-Octyl-4biphenylcarbonitrile Gram 1 $ 84.80 $ 84.80

Instec Inc.Homeotropic alignment LC cells Holders 20 $ 14.00 $ 280.00

Total $ 527.30

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Cost Analysis – PolymerSupplier Name Unit Quantity Price Subtotal

Delta Technologies

ITO coated glass slides Piece 20 $ 8.00 $ 160.00

Piezotech PVDF-TrFE 70/30 Gram 2 $ 10.00 $ 20.00

Sigma AldrichN,N-Dimethylformamide Liter 1 $ 85.40 $ 85.40

Fisher Scientific

1oz/30mL Polypropylene Bottles 12ct Pack 2 $ 12.53 $ 25.06

Total $ 290.46

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Cost Analysis – Lab Supplies

Supplier Name Unit Quantity Price SubtotalFisher Scientific

Acetone (Certified ACS) 4L Bottle 1 $ 22.06 $ 22.06

Fisher Scientific

Methanol (Certified ACS) 4L Bottle 1 $ 16.12 $ 16.12

Fisher Scientific Best Butyl II Gloves Pair 1 $ 50.47 $ 50.47 Fisher Scientific

4.4 x 8.4 Lint Free Wipers 280ct Box 2 $ 3.82 $ 7.64

Fisher Scientific

Cotton-Tipped Wooden Applicators 1000ct Pack 1 $ 7.71 $ 7.71

Fisher Scientific

Graduated Disposable Pipettes 500ct Box 1 $ 14.29 $ 14.29

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Cost Analysis – Lab Supplies

Supplier Name Unit Quantity Price SubtotalChem Stores

Disposable Nitrile Gloves 50pr/box Box 2 $ 6.04 $ 12.08

Ted Pella Inc.

Carbon Conductive Sheet Pack/10 1 $ 39.75 $ 39.75

Ted Pella Inc.

Copper Conductive Tape Roll 1 $ 41.25 $ 41.25

Ted Pella Inc.

Double Sided Kapton Tape Roll 1 $ 52.10 $ 52.10

Ted Pella Inc.

PELCO Water Based Carbon Paint 50g Bottle 1 $ 9.95 $ 9.95

Ted Pella Inc.

PELCO Colloidal Silver Paste 25g Bottle 1 $ 59.50 $ 59.50

TOTAL $ 332.92

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Cost Analysis - ElectricalSupplier Name Unit Quantity Price Total

Sparkfun Arduino Uno Board 1 $ 29.95 $ 29.95

Digkey 35V - 1uF - MLC - X7R Capacitor 5 $ 0.23 $ 1.13

Digikey DC/DC 1kV converter Unit 1 $ 189.02 $ 189.02

Digikey Transistor Optocoupler 6-DIP 10 $ 0.94 $ 9.40

Digikey 3 Row solderless BB Board 1 $ 122.04 $ 122.04

Digikey Temperature Sensor Unit 3 $ 1.42 $ 4.26

DigikeyK-type Temperature Probe Unit 3 $ 14.95 $ 44.85

DigikeyK-type Thermocouple female sockets Unit 3 $ 7.10 $ 21.30

Digikey AC/DC wall pack Unit 1 $ 4.68 $ 4.68

TOTAL $ 426.63

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Adiabatic Electrocaloric Effect

Pyroelectric Coefficient

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Manual Heat Transfer System• Manual rotation between cold and hot plates.

Figure from Olsen Journal of Energy (1982)

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Regenerative Heat Transfer System

Figure from Olsen Journal of Energy (1982)

Utilize a series of materials with a gradient of transition temperatures to maximize efficiency

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Automated Heat Transfer System

Figure from Olsen, Bruno, Briscoe, Dullea Ferroelectrics (1984)

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Polymer Spin Coating

• 3-4 drops of solution.• 5 wt% at 750-1250 rpm for

30-45s.• 10 wt% at 2000-3000 rpm for

30s, and 750 rpm for 60s.• 10 wt% at 3000 rpm for 30s

has uniform 1.2 micron thickness.

• Annealed for 30m at 80°C

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Preliminary Polymer Characterization

0 100 200 300 400 500 6000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

P(VDF-TrFE) Polarization - Electric Field

250 kV/cm 150 kV/cm

Electric Field (kV/cm)

Pola

rizati

on (μ

C/cm

2)

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Polymer Micrographs• Presence of pinholes and photoresist.

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Liquid Crystal Material• Nematic liquid crystals were chosen due to their

significant entropy change.• 4'-Pentyl-4-biphenylcarbonitrile (5CB) was chosen

due to literature on electrocaloric effect.• 4’-Hexyl-4biphenylcarbonitrile, and

4’-Octyl-4biphenylcarbonitrile were also purchased for their higher transition temperature.

Structure of 5CB Liquid Crystal

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Preliminary Liquid Crystal Characterization

• Shows increasing polarization with increasing field as expected.

• Max polarization should occur at max field.

-600 -400 -200 0 200 400 600 800-2.5

0

2.5

5

7.5

10

12.5

15

17.5

20

22.55CB Polarization vs Electric Field

200 kV/cm 300 kV/cm 400 kV/cm 500 kV/cm600 kV/cm

Electric Field (kV/cm)

Pola

rizati

on (μ

C/cm

2)

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Ceramic Nanosheets• Liquid crystal holders• Preliminary characterization in

progress

Nakato et al.Journal of Physical Chemistry C (2011)

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• Arduino Uno• Meets our specification• Low cost• Large user community,

base code• Compatible with our

stepper motor and driver

Isolator Trigger & Stepper Control

Thermocouples

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Microcontroller

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Thermocouple Testing