ENERGY HARVESTING & STORAGE

1. Comparison of Energy Harvesting Systems for Wireless Sensor Networks

2. A Quantitative Investigation of Inertial Power Harvesting for Human-powered Devices

Hyeon Joo

OUTLINE

Power requirement Suitable scavenging energy source Energy conversion device

Vibration

POWER REQUIREMENT

Power requirement

Power requirement

Actuator and Communication consumes a large propor-tion of total power

SUITABLE SCAVENGING ENERGY SOURCE

Mechanical energy source

Steady state mechanical source Steady state: wind, flow, current..

Intermittent mechanical source Human activity(walking, typing.. 5.88J/2steps ) Vehicles passing

Vibration Energy depends on the amplitude and its freq. Mass of harvesting device relative to the vibrat-

ing mass

Mechanical energy source

Typically vibration is made up of a number of funda-mental freq. and their har-monic

ENERGY CONVERSION DE-VICES

Vibration

m: seismic massk: spring of stiffnessu(t): Position of casex(t): Position of the seismicb: Damping coefficient

Vibration

m: seismic massk: spring of stiffnessu(t): Position of casex(t): Position of the seismicb: Damping coefficient

Mx’’(t) + Bx’(t) + Kx(t) = - Mu’’(t)

Vibration

m: seismic massk: spring of stiffnessu(t): Position of casex(t): Position of the seismicb: Damping coefficient

2

2 2 2

( ) sin( )

( ) ( )

x t U tk bm m

Vibrationmx’’(t) + bx’(t) + kx(t) = - mu’’(t)

2 2

2

2

2

2

''( ) '( ) ( ) ''( )

( ) ( ) ( ) ( )

( ) ( )

( )( ) ( )

( ) ( )

b kx t x t x t u t

m mbS k

S X s X s X s S U sm m

SX s U s

bS kS

m mS j

jX j U j

b kj j

m m

2

2 2 2

( ) sin( )

( ) ( )

x t U tk bm m

2

2

2

2 2 2

( )( ) ( )

( )

( ) ( )

( ) sin( ) j t

U jk b

jm m

U jk bm m

U j U t e dt

Vibration

ωn : natural freq

2 2 3

2 2 2

/

( )

[1 ( ) ] [2 ( )]

n

nd

T

Tn n

k m

m YP

T : damping factor

ω =ωn => peak power (resonant)

ω : vibration freq

Vibration

ωn : natural freq

T : damping factor

ω : vibration freq

Increase the damping factorÞReducing the peak power,Þ but increase bw

2

4d

n T

mAP

2

4d

n T

mAP

Vibration

ωn : natural freq

T : damping factor

ω : vibration freq

Thus,1) fixed freq => low d.f.2) Various freq => high d.f.

2

4d

n T

mAP

2

4d

n T

mAP

Vibration

Harvested energy is proportional to the m

3

3

4

3

4 1

3 3

max

max

max

max

max

4

4

ne

ne

e n

m

e n

mAZP

m d

d AZP

Z d

P d A

d

P m A

Vibration

Piezoelectric conversion (pres-sure) Commonly used material: PZT, BaTiO3,

PVDF Electrostatic conversion

The formation of a parallel plate capaci-tor

Electromagnetic conversion Magnetic and coil

1

2E QV

Intermittent mechanical conv. Piezoelectric conversion

Electro-active polymers(EAP) conver-sion

Electromagnetic conversion

ANY QUESTIONS?

OUTLINE

Motivation Mobile device Energy harvesting model Data Analysis Power Estimation

Motivation

Human motion energy harvesting Electronic devices Realistic experiment 6 different parts of body

Mobile devices

Wearable deviceWearable device

Energy harvesting model

k: spring constantm:proof massd: damping coefficienty(t): generator displacementz(t): generator’s motionZmax: interval travel limit

Energy harvesting model

Loggers: 1GB SD

80HZ

Data Analysis

3-aixs accelerometers (X,Y,Z) Harvest energy from daily human ac-

tivities using free motion Only kinetic energy from human

body Zero-gravity for accuracy High-passed filtered with 0.05Hz cuf-

foff

Data Analysis

Data Analysis

Data Analysis

2

1

2

1 0 0

0

'

' ''

1''

z

z

z T T

z t t

T

t

d

d

average d

E Fdz

F Dz

dz dzE Dz dz D dt D z dt

dt dtD

P E z dtT T

ANY QUESTIONS?