ENERGY HARVESTING FROM VIBRATIONS AIR FLOWVIBRATIONS, AIR FLOW,   

& TEMPERATURE CHANGE

d ll l h dLindsay Miller, Alic Chen, Deepa MadanLee Weinstein, Peter So, Thomas Devloo,  

D Eli b th R ill D Yi i ZhDr. Elizabeth Reilly, Dr. Yiping Zhu, Prof. Paul Wright, Prof. Jim Evans

System on a Chip

Wireless Sensor Energy Storage MEMS Sensor

Sensor

Micro‐device

Energy storage

Cable

Piezoelectric MEMS Cantilever

Microscale Magnet

Output Voltage

Magnetic Field

Cable

Piezoelectric MEMS Cantilever

Microscale Magnet

Output Voltage

Magnetic Field

Energy h ti

Radio

Energy Harvesting Radio

harvesting

Radio

Multi‐source energy harvesting

PIEZOELECTRIC THERMOELECTRICVIBRATIONS

TEMPERATURE DIFFERENCE

AIR FLOWAIR FLOW

Progress made in past 6 months:PIEZOELECTRIC THERMOELECTRIC

VIBRATIONS

TEMPERATURE DIFFERENCE

• Composite materials improved

D l d l bl f b i ti

• Prms = 1.1 nW/beam,              micro device on ambient source

D l d t dif

TEMPERATURE DIFFERENCE

• Developed scalable fabrication process for meso‐scale devices

• P = 0.58 μW

• Developed process to modify frequency with printed mass

AIR FLOW

P   0.58 μW                             (ΔT = 10 K, 10‐couple device)

• Meso‐scale prototype developedMeso scale prototype developed

• Prms = 1.1 mW,  optimal conditions

Multi‐source energy harvestingPIEZOELECTRIC

VIBRATIONS

AIR FLOWAIR FLOW

Piezoelectric operating principle DEFORMATION 

(mechanical energy)VOLTAGE 

(electrical energy)

3PIEZOELECTRIC MATERIAL CANTILEVER BEAM

12

3

+

V+

-

S. Roundy, PhD Thesis UC Berkeley 2003 Figure: Wikipedia, 2010

Where we left you 6 months ago:PIEZOELECTRIC Beam voltage output vs Frequency

VIBRATIONS

• MEMS harvester fabricated 

put, mV

• Low resonance frequency achieved• Prms = 1 nW on shaker table• 1 beam tested on 1 ambient source ol

tage outp

• 1 beam tested on 1 ambient source• Printed capacitor on harvester die

Vo

Frequency, HzAIR FLOW

• Project was just starting

eque cy,

Progress: ambient vibration harvesting 2 /Hz

)

Ambient vibration source: compressor

2 /Hz

 or A

2

ACCELERATION (MEASURED)

Density

 (V2

Spectral D

BEAM OUTPUT (MEASURED)

TRANSFER FUNCTION (CALCULATED)

Power S

BEAM OUTPUT (CALCULATED)

BEAM OUTPUT (MEASURED)

T t d 9 b 7 bi t li bl d l

Frequency (Hz)

• Tested 9 beams on 7 ambient sources – reliably produce low power• Almost finished with model – measured accel. input  predicted beam output 

Progress: print mass modify frequency

Successfully printed on 6 released beams with no “casualties”

ω2 = k/mω  k/m

2.5 mm 1.5 mm

1.5 mm 1.5 mm

Progress: print mass modify frequency

Beam power output vs frequency

Shift in frequency with addition of printed mass

177.9 Hz BEFOREBeam power output vs frequency

Beam signals add in series!

192.8 Hz

(nW

rms)

172.9 Hz

Beam signals add in series!AFTER

r outpu

t (

Frequency (Hz)0.1 Hz resolution> 20 Hz shift

MS Po

we

Series, theoretical

Series, measured

R

Right, measured

Left, measured

Frequency (Hz)

Progress: air flow harvester designTop View

Back View

Cylindrical Obstacle

Fin

Stand

Progress: air flow harvester performance

Power output > 1 mWi l di iat optimal conditions 

For results shown:Fin: 7.5 cm wide x 7 cm longgFin material: balsa woodCylinder Diameter: 2.5 cmOptimum Load R: 194 kOhm

Multi‐source energy harvestingPIEZOELECTRIC THERMOELECTRIC

VIBRATIONS

AIR FLOWAIR FLOW

Multi‐source energy harvestingTHERMOELECTRIC

Thermoelectric (TE) Operating PrinciplesThermoelectric (TE) Energy Harvesting

Cold SideSubstrateHeat Sink

MetalInterconnects

N Type

N P

–– ++ΔT

Hot SideN‐Type

SemiconductorP‐TypeSemiconductor

Resistive LoadCurrent + –

Heat Source

Resistive Load

Sources of Waste Heat

Location  Source  Temp. Gradient 

Residential Boilers, Dryers, Freezers, Oven 10‐30K  Aluminum Smelter Boiler

Factories  Exhaust pipes, Boilers, Condensers  10‐80K 

Vehicles Engine, Exhaust pipes  60K 100Kg , p p >100K 

Airplanes  Cabin to External  10‐50K  Dryer

Thermoelectric DesignTE Power Output Optimization

Optimal Range 

Bulk elementsThin film elements

d l ff b •Diced elements from ingots•1mm height min.

• Labor intensiveM l i k & l

•Microfabrication processes•60μm max. height

•Materials intensiveMi l I

Dispenser Printing•Optimal Feature Sizes (100‐500μm) •Manual pick & placeMicropelt, Inc

Ferrotec, Inc.

( μ )•High throughput manufacturing

Where we left you 6 months ago:

THERMOELECTRICepoxyk THERMOELECTRIC

• Meso‐scale prototype 

p yresin mix ink

fabricated using dispenser printing techniqueadd active

particles• Printable 

semiconductor/epoxy thermoelectric materials 

p

synthesized25 mm

1mm D, 1.5mm H

25 mm

Progress: innovative design of TE harvesterSubstrate

A t ti f 1 5 t 2

Metal

• Aspect ratios from 1.5 to 2• Commercially available• Labor intensive assembly

N‐TypeSemiconductorP‐Type

MetalInterconnects

P TypeSemiconductor

Metal Interconnects

N‐type Semiconductor

• High aspect ratio pillarsInterconnects

P type

• High density arrays• 900+ couples for D = 1cm

• Takes advantage of printing 

18

P‐type SemiconductorFlexible

Substrateprocess

Progress: new design is easily scalableg g y1. Print Electrodes

2. Print N‐type Semiconductor

3. Print P‐type Semiconductor3. Print P type Semiconductor

4. Heat/Cure

• 3‐layer printing process l l h ll bl• Element lengths are controllable

• Printing process is scalable to larger prod ction processes (i e screenproduction processes (i.e. screen printing, flexography) 19

Progress: performance of TE prototypeThermoelectric Materials Flexible TE Devices

2.2 μW0.58 μW

•10 Couple Device•ΔT = 10 Kelvin• Losses from

Bi2Te3 Composites

Losses from contact resistance

2 3 p

Flexible Polyimide Substrate

Sb2Te3 Composites

Snyder et al (2008)

Printed TEMaterialsLeg Dim.: 5 mm Length, 500 µm width, 200 µm thick

Progress summaryPIEZOELECTRIC THERMOELECTRIC

VIBRATIONS

• Prms = 1.1 nW/beam, TEMPERATURE DIFFERENCE

• Synthesized efficient, printable composite TE materials (ZT ~ 0.4 )

Prms  1.1 nW/beam,              micro device on ambient source

• Modified frequency by 20 Hz with 

TEMPERATURE DIFFERENCE

• Developed scalable fabrication process for meso‐scale devices

• P 0 58 μW

printed mass • Beam signals add when in series

AIR FLOW• P = 0.58 μW                                     (ΔT = 10 K, 10‐couple device)

• Meso‐scale prototype designed, p yp gbuilt, & characterized in duct

• Prms = 1.1 mW,  optimal conditions

Thank you! Any questions?

CylindricalCylindricalCylindricalTHERMOELECTRIC

Cylindrical ObstacleCylindrical Obstacle

FinFin

Cylindrical Obstacle

Fin

AIR FLOW

StandStandStand

AIR FLOW

VIBRATION

1.3 cm

Acknowledgements: California Energy Commission, Siemens, CITRIS, Berkeley Manufacturing Institute, Berkeley Wireless Research Center