piezoelectric energy harvesting

Mems Based Energy Harvesting

Guided byDr. M.R. BaijuProfessorDept. of ECECET

Presented byVISAKH.V

M4 AEI,ROLL NO:12

Energy Harvesting College of Engineering, Trivandrum

Overview


Characteristics of Various Vibration Sources

According to the study only the first 500 Hz of the spectra is important.

First, there is a sharp peak in magnitude at a fairly low frequency with a few higherfrequency harmonics.

Another observation is that the fundamental vibration frequency for almost allsources is between 70 and 125 Hz.


Vibration to Electricity Conversion Model

Figure: Generic vibration converter


Vibrations to Electricity Conversion Methods

There are mainly three main methods for converting the energy from vibrations toelectrical energy. They are

Electromagnetic Power Conversion

Elecrostatic Power Conversion

Piezoelectric Power Conversion




The constitutive equations for a piezoelectric material are given in equations ?? and ??.

δ =σ

Y+ dE (1)

D = εE + dσ (2)

where:δ is mechanical strainσ is mechanical stressY is the modulus of elasticity (Young’s Modulus)d is the piezoelectric strain coefficientE is the electric fieldD is the electrical displacement (charge density)ε is the dielectric constant of the piezoelectric material


WORK DONE AND RESULT

The work done for the thesis includes the following.

Familiarized Coventorware(Design and Analysis Software)

Design and Analysis of Cantilever Beam in Coventorware

Design an Analysis of Piezoresistor in Coventorware

Familiarized Mems+

Interfaced Mems+ with Matlab

Designed Mems Switch in Mems+

Analysed Mems Switch in Matlab

Designed Energy Harvester Structure in Mems+


Design and Analysis of Cantilever Beam


Figure: Solid Model of Cantilever Beam



Modes of Vibration

Mode 1

Mode 2



Mode 3

Mode 4



Mode 5

Mode 6



Pull in with Cosolve

Figure: Pull in Analysis Plot



Liftoff with Cosolve

Figure: Lift off Analysis Plot


Design and Analysis of Piezoresistor

Solid Model of Diaphragm

Figure: Solid Model of Diaphragm


Design and Analysis of Piezoresistor

A new MemPZR analysis is set up using the above model. And with a voltagedifference of 1V applied to the electrodes and a 0.2N of force appied , the resultingcurrents at the electrodes is obtained.

Patch voltage Patch Current % change in currentin1 1 1.462025E08 4.430218in2 1 1.332666E08 -4.809469out1 0 -1.462025E08 4.430218out2 0 -1.332666E08 -4.809469


Mems Switch

Mems Switch Model in Mems+

Figure: Mems Switch Model in Mems+


Mems Switch

Simulink Model

Figure: Simulink Model


Mems Switch

Pullin Voltage

Figure: Simulink Model


Energy Harvestor Circuit in Mems+

Materials Used

The piezoelectric energy harvesting structure process flow is designed in MEMS+. Thematerials used for the process are

Silicon (Proof Mass)

SiO2

AlN(Piezoelectric Material)

Al(Electrical Contact)



Process Flow

Silicon material is deposited over a substrate to define the proof mass layer andalso the anchor part.This layer has a height of 400 um.

The next step is the deposition of oxide layer over this layer. The oxide layer has athickness of about 0.5 um .

Then another layer of silicon is deposited over this layer with a thickness 5 um.

Then the piezoelectric material AlN is deposited over this layer with a thickness of1 um.

After etching , Aluminium is deposited to define the electrode contacts.



Mask Layouts

Figure: Mask for the first Silicon layer



Figure: Mask for the first SiO2layer



Figure: Mask for the Si layer



Figure: Mask for the AlN layer


Work to be Done

System level Analysis of Energy Harvester Circuit Using Matlab and Mems+

FEM Analysis of the EH circuit using Coventorware

Multiphysics Analysis of the circuit using Comsol


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piezoelectric energy harvesting

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