ppt thickness

7/31/2019 Ppt Thickness

1/13

of a Piezoelectric Converterfor Energy Harvesting

M. Guizzetti1, V. Ferrari1, D. Marioli1 and T. Zawada2

1Dept. of Electronics for Automation, University of Brescia, Italy

erroperm ezoceram cs , egg , v s gaar , enmar

Presented at the COMSOL Conference 2009 Milan


2/13


3/13

Mechanoelectrical energy conversion

onvers on ec n ques

electromagnetic (inductive)

electrostatic (capacitive)

Direct piezoelectric effect: surface charge induced by a mechanical stress

Piezoelectric energy converter

unimorph cantilever shape (thick-film, MEMS technologies)

piezoelectric layer+ V

Thick ness Opt im iza t ion o f a Piezoe lec t r ic Conv er t e r fo r Energ y Harvest ing

mechanical substrate -2 / 1 2


4/13

Use of COMSOL

mprovemen o e conver e energy

Optimization of the dimensions

piezoelectric layer thickness

Application modes piezoelectric: mechanical / electrical behaviour

sinusoidal vertical acceleration application

generated charge / voltage

moving mesh: thickness change

a+ V

Q PZT+ + + ++ + + ++ + ++ + + +


-3 / 1 2


5/13

Geometry

lenght L = 27 mm;

width w= 3 mm;

steel

piezoelectric layer thickness tPZT = 60 m (poled along thickness)

t

L

piezoelectric layer

s ee


w

4 / 1 2


6/13

Mesh

appe mes

320 quad elements; 11808 degrees of freedom

2 elementslinearly spaced

4 elementslinearly spaced

20 elementsex onentiall s aced

Th ick n ess Op t im i zat ion of a Piezoelect r ic Co nv er t er fo r En er gy Har vest in g 5 / 1 2


7/13

Governing equations

ezoe ec r c ayer

strain-charge form11210

0070000

000502020

000205020

000202050

PasE

7000000

0700000

0110000

dTED

s

T

S = mechanical strain

T= mechanical stress [N/m2] E -1

11210

00055.25.2

0011000

CNd

d= piezoelectric coefficient [C/N]

D = electric displacement [C/m2]

E= electric field [V/m]

0

5000

0500

0050

T

= dielectric permittivity [F/m]

112

33000 mkg

Steel layer


s


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Subdomain and boundary conditions

Body load Fz = a

a = 0.1 g

=

Mechanical boundary conditions clamped end

Electrostatic boundary conditions

bottom surface: grounded floating potential dt = 0 ; dn = deltaThick upper sur ace: oa ng po en a

other surfaces: zero charge

Mesh boundary conditions bottom surface: clamped

vertical surfaces: normally clamped

fixed dn = 0GNDfixed

zero charge


upper sur ace: angen a y c ampe ,

normally displaced (deltaThick)

7 / 1 2


9/13

Solver parameters

arame r c segrega e so ver

group 1: moving mesh, static analysis

deltaThick:-50 m340 m

group : p ezoe ec r c var a es, requency response

frequency = 10 Hz

Th ick n ess Op t im i zat io n o f a Pi ezo el ect r ic Con v er t er fo r En er gy Har v est in g 8 / 1 2


10/13

Results tip displacement

ment[nm]

tipdisplace

100

10 100 1000

piezoelectric layer thickness [ m]

tPZT =

m

PZT rigidity > steel rigidity

tip displacement nPZTt

1tPZT = 400 m



11/13

Results electrical output

3.E-03

4.E-03

5.E-03

oltage[V]

6.E-13

7.E-13

8.E-13

[C]

voltage

charge

PZT rigidity > steel rigidity

0.E+00

0 100 200 300 400

piezoelectric layer thickness [ m]

3.E-13

1.4

]

voltage const

0.8

1.0

1.2

ricalenergy[fJ

Stored electrical energy

0.2

0.4

.

storedelect

QVE1

05.1

substrate

PZT

t

t


.

0 100 200 300 400piezoelectric layer thickness [ m]

1 0 / 1 2


12/13

Results influence of the geometry

eren geome r es Substratethickness

[m]

Width

[mm]

Length

[mm]

reference 200 3 27

geometry 1 300 3 27

geometry 2 200 6 27

geometry 3 200 3 10

geom 1

geom 2

Th ick n ess Op t im i zat io n of a Pi ezo el ect r ic Con v er t er f or En er gy Har v est in g 1 1 / 1 2

geom 3


13/13

Conclusions

FEM simulations used for optimizing the geometrical dimensions of apiezoelectric energy converter

Geometry with parametrized thickness

piezoelectric application mode

moving mesh application mode

The optimal tPZT/tsubstrate was found for maximizing the electrical energy

The optimal tPZT/tsubstrate value is independent from the converter

This model is a specific example of using moving mesh for device

Th ick n ess Op t im i zat io n of a Pi ezo el ect r ic Con v er t er f or En er gy Har v est in g 1 2 / 1 2

ppt thickness

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