Report on energy harvesting through mechanical vibration

ENERGY HARVESTING THROUGH

ENERGY HARVESTING THROUGH MECHANICAL VIBRATION

SHAMBHU KUMAR

R

(M.Tech 3

DEPARTMENT OF MECHANICAL ENGINEERING

MOTILAL NEHRU NATIONAL INSTITUTE OF

ALLAHABAD, U.P

SEPTEMBER 3

SUBMITTED TO: - COLLOQUIUM TEAM


COLLOQUIUM


By

SHAMBHU KUMAR

Reg. No. 2014DN06

(M.Tech 3rd semester- Design)


NEHRU NATIONAL INSTITUTE OFTECHNOLOGY

ALLAHABAD, U.P – 211004 SEPTEMBER 30, 2015

Committee in charge

Prof. A.

Dr. R.

Dr. J. C.



TECHNOLOGY

Committee in charge A. D. Bhatt

K. Patel

C. Mohanta


ii


iii

DECLARATION

I Shambhu Kumar hereby declare that this Colloquium report is wholly my own work and

has not been submitted anywhere else for academic credit, either by myself or another

person.

I understand what plagiarism implies and declare that this report embodies my own ideas,

words, phrases, arguments, graphics, figures, results and organization except where reference

is explicitly made to another work.

I understand further that any unethical academic behaviour, which includes plagiarism, is

seen in a serious light by MNNIT Allahabad and is punishable by disciplinary action as

stipulated by the institute’s rules and regulations.

Name –Shambhu Kumar

Registration number-2014DN06

Signature:................................

Date:..................................


iv

ACKNOWLEDGEMENTS

I take this opportunity to express my deep sense of gratitude to my thesis supervisor,

Dr. R.K. Patel, Assistant Professor, in the Department of Mechanical Engineering, Motilal

Nehru National Institute of Technology, Allahabad for his constant guidance and help during

the course of work. I shall always cherish my association with them for their constant

encouragement and freedom to thought and action that rendered to me throughout the

Colloquium.

I would also like to acknowledge the useful resources of the MNNIT Central Library.

Shambhu Kumar


v

Abstract

Energy harvesting through mechanical vibration have emerged as an important research area

and continues to grow at rapid pace. A wide range of applications are targeted for the

harvesters, including distributed wireless sensor nodes for structural health monitoring,

embedded and implanted sensor nodes for medical applications, recharging the battery of

large systems, monitoring the tyre pressure in automobiles and running security system in

household conditions. Several transduction mechanisms exist for transformation of

mechanical energy of mechanical vibrations into electric energy. Principle of vibration

energy harvesters is in most cases mass-spring-damper system with one degree of freedom.

Considering physical principles used to transform kinetic energy into electrical energy, there

are four transduction mechanisms: electrostatic, piezoelectric, electromagnetic and

magnetostrictive (magnetoelectric).

One latest and good example of energy-harvester device is “Mechanical motion rectifier”. It

is based on electromagnetic principle and the key component is a unique motion mechanism,

which is called “mechanical motion rectifier (MMR)”, to convert the oscillatory vibration

into unidirectional rotation of the generator. The prototype achieved over 60% efficiency at

high frequency, much better than the conventional regenerative shock absorbers in oscillatory

motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock

absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on

a smooth paved road. The motion rectifier based design can also be used for other

applications of vibration energy harvesting such as from tall buildings or long bridges.

One another good example is harvesting vibration energy by a triple-cantilever based on

triboelectric nanogenerator. Triboelectric nanogenerators (TENG), a unique technology for

harvesting ambient mechanical energy based on triboelectric effect, have been proven to be a

cost-effective, simple and robust approach for self-powered systems. TENG produces an

open-circuit voltage up to 101 V and a short-circuit current of 55.7 μA with a peak power

density of 252.3 mW/m2.


vi

TABLE OF CONTENTS:-

ABSTRACT ………………………………………………………………………………… ii

DECLARATION …………………………………………………………………………… iii

ACKNOWLEDGEMENTS ………………………………………………………………. IV

TABLE OF CONTENT ……………………………………………………………………. VI

LIST OF FIGURE ………………………………………………………………………… VII

1. CHAPTER 1: Introduction

1.1 General ………………………………………………………………. 1

1.2 Necessity of energy harvesting ………………………………… 1

1.3 Source of vibrational energy harvester ………………………. 2

2. CHAPTER 2: Common vibration energy harvesting technique

2.1 Common technique ……………………………………. 5

2.2 Electromagnetic Harvesters ……………………………. 6

2.3 Electrostatic Harvesters ……………………………. 9

2.4 Piezoelectric Harvesters ……………………………….. 13

2.5 Magnetostrictive Harvesters …………………………… 17

2.6 Comparisons of different transduction mechanisms of kinetic energy

harvesters ………………………………………………………… 19

3. CHAPTER 3: Mechanical Motion Rectifier

3.1 Introduction of MMR …………………………………….. 20

3.2 Principle of MMR ……………………………………….. 22

3.3 Design of Highly-Compact Motion Rectifier Based Harvester …. 24

3.4 Experiment and Results ……………………………….. 26


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3.5 Conclusion of MMR ……………….. ………. 27

4. CHAPTER 4: Harvesting vibration energy by a triple-cantilever based

triboelectric Nanogenerator(TENG)

4.1 Introduction of TENG ……………………………28

4.2 Design & characterization of TENG ………….. 29

4.3 Design & characterization of TENG ………….. 30

5. CHAPTER 5: Conclusion and Future Work

5.1 Conclusion ……………………………….. ….. 32

5.2 Future Work ………………………………….. 32

REFRENCES ………………………………………………………. 33


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LIST OF FIGURES

Figure 2.1: Schematic diagram of electromagnetic energy harvester .................................6

Figure 2.2: Electromagnetic induction Faraday’s law .................................................7

Figure 2.3:Circuit Representation of Electromagnetic generator ..........................................8

Figure 2.4: Circuit representation for an electrostatic generator......................................11

Figure 2.5: Electrostatic generators: (a) in-plane overlap; (b) in-plane gap closing; and (c)

out-of plane gap closing………………………………………………………. 12

Figure 2.6: Piezoelectric Generator (a) mode 33 (b) mode 31 ……………………………………………….14

Figure 2.7: Circuit representation for an piezoelectric generator………………………. 15

Figure 2.8: Magnetostrictive Model …………………………………………………….17

Figure 2.8: Magnetostrictive Model …………………………………………………….18

Figure 3.1: MMR Setup in vehicle Chevrolet Suburban SUV.................................................. 21

Figure 3.2: Traditional design of a rack-pinion based regenerative shock absorber...................23

Figure 3.3: Principle of “motion rectifier” for oscillating motion............................................. 23

Figure 3.4: Electrical analogy for “motion rectifier” …………………………… .......................24

Figure 3.5: sample and 3D view of MMR........................................................................... 25

Figure 3.6: components of MMR .......................................................................................... 25

Figure 3.7: Damping loops for different external electrical loads under vibration input of 1.5 Hz and

5mm amplitude…………………………………………………………………………………………………………………………….26

Figure 3.8:Damping loops for different input frequencies with electrical load Ri +Re= 106.6 Ω .. 26

Figure 4.1 triboelectric Nanogenerator (TANG)………………………………………… 28

Figure 4.2 Photograph of typical cantilever beam ……………………………………… 29

Figure 4.3 A cycle of electricity generation process for illustrating the mechanism of the

Triple-cantilever based TENG ……………………………………………………………………………….. 30

Figure 4.3 Open-circuit voltage (VOC) at vibration frequencies of 3.5 Hz (a), 3.7 Hz (b), and 4.0 Hz

(c) and rectified short-circuit current (ISC) at vibration frequencies of 3.5 Hz (d), 3.7 Hz (e), and 4.0 Hz

(f). The insets of (c) and (f) are enlarged views of half cycles of the VOC and ISC at 4.0 Hz,

respectively ………………………………………………………………………………………………………………………… 31


ix


1

CHAPTER 1: Introduction

1.1 General “Top Problems of Humanity for Next 50 Years will be energy” –by Richard Smalley

(Noble laureate)

Energy harvesting is an active field of research aimed at powering low power wireless systems,

self-powered sensors and micro-systems and recharging existing batteries. Renewable energy

can be harvested by generating electrical energy from solar, thermal or kinetic energy present

within or around the system. Solar cells are excellent energy harvester under direct sunlight, but

are limited in application under dim day light condition, in the night and where light has no

access, such as in embedded systems. Thermal energy can be converted into electrical energy

using seeback effect, but this approach produces energy in the range of a few µW only. Kinetic

energy harvester converts kinetic energy present in the environment into electrical energy. It has

already been demonstrated by several groups that the ambient kinetic energy can be easily

converted into electrical energy in the µW range. Kinetic energy is typically present in the form

of vibration, random displacement of forces and is typically converted into electrical energy

using electromagnetic, electrostatic and piezoelectric energy transduction method.

1.2 Necessity of energy harvesting

Among many other advantages the primary reasons for the use of energy harvesting are:

Convenience: Nowadays energy harvesting is essential because of the future scarcity of the

natural mineral resources. Energy harvesting is done from those natural resources which are

inexhaustible. So that it is more convenient than wall plugs and batteries which are costly and

need replacements.


2

Back up energy source: It can also be used as the backup of the primary sources. Therefore, it

will increase the system’s reliability and prevent power interruption. Moreover, this energy

sources are considered as free form of energy in comparison with fossil fuel. If the energy

harvester is designed and installed properly then it will be available throughout the lifetime of

the application.

Mobility: Advanced low power VLSI design and CMOS fabrication have reduced power

requirement for wireless sensor nodes to the point that the self powered nodded are feasible.

Harvesting energy form ambient vibrations, wind, heat or light could enable smart device to be

functional for an indefinite period.

Environmentally Friendly: Energy harvesting aims to eliminate the dependence on batteries

which contains heavy metals that are toxic to living organisms. Furthermore, this technology

promises to reduce the dependence on nonrenewable energy sources.

Production cost: Business costs for consumers would be reduced in terms of the

packaging, development, disposal, longevity, and reuse of those products. For

instance, in the use of a cell phone, the cost of a chemical battery and charger would be saved

by replacing energy harvester device.

1.3 Source of Vibrational Energy Harvester

Vibration energy available in a wide variety of sources can be conveniently used for potential

powering of wireless sensors and low power devices. Such as escalators, bridges, rotor blades,

windmill blades, pumps and one of great resources are automobiles.

According to “Indian Motor Vehicles knowIndia.net” following data are given:-

India was the sixth largest motor vehicle/car manufacturer in the world in 2013.Indian auto

manufacturers produced a record 23.4 million motor vehicles in 201 41 5 (Apr Mar).3.22

million passenger vehicles rolled out from Indian auto plants in 201 41 5.


3

Table –I: Motor vehicle available in INDIA year wise.

Domestic Motor Vehicle Sales

2014-15 (In Millions)

Passenger Vehicles

2.60

Commercial Vehicles

.61

Two -wheelers

16.0

Three-wheelers

.53

Total 3.74 + 16.0 = 19.00

Year

Total numbers of Vehicle sales (In Millions

2013-14

3 + 14.36 = 17.36

2010-11

1.49+5.016 = 6.506

2009-10

1.211+4.123=5.334

2008-09

4.36+5.25 =9.61

“On the basis of above observation more than 19 million vehicles (Passenger Vehicle ,

Commercial Vehicle , Three wheeler) running on the road and suppose average 100 W electricity

produce by each vehicle that means it is equivalent to 1900 MW electricity will be produce ,

which is great energy”.


4

Table II: Sources of energy available in the surrounding which can be trapped for generating

electricity.


5

CHAPTER 2: Common vibration energy harvesting

techniques

2.1 Common technique

Vibration energy harvesting has become important as devices like sensors are getting smaller and

more efficient, requiring less power and has acquired a requirement to have their own powering

device. Additionally some batteries has to be made very small and if an alternative charging

device can be made, which will charge the battery constantly, it decreases the trouble of less

storage capacity.

However, vibration energy harvesting can be of many types, depending on the availability and

environment of the vibrational energy. Some of the types are discussed below:


6

2.2 Electromagnetic Harvesters

Fig. 2.1: Schematic diagram of electromagnetic energy harvester

It is based on Faraday’s law of electromagnetic induction. Electromagnetic induction was

discovered by Michael Faraday in 1831. Faraday’s law state that an electrical current will be

induced in any closed circuit when the magnetic flux through a surface bonded by the conductor

change. This applied whether the field itself changes in strength or the conductor is move

through it. In an electromagnetic generator, permanent magnets are use to produce strong

magnetic field or the coil is used as a conductor. Either the permanent magnet or the coil is fixed

to the frame while the other is attached to the inertial mass. The relative displacement caused by

the vibration makes the transduction mechanism work and generate the mechanical energy. The

induced voltage is also known as electromotive force (e.m.f), across the coil is proportional to

the strength of magnetic field, the velocity of relative motion and number of turns of the coil. An

electromagnetic generator is characterized by high output current level at expenses of low

voltage.


7

Fig. 2.2: Electromagnetic induction Faraday’s law

According to faraday law : - Emf = - ɸ

-------- (1)

Where ɸ=BA=Magnetic flux, B=External magnetic field, A=area of coil.

For a coil moving through a perpendicular constant magnetic field, the maximum open circuit

voltage across the coil (Voc) is:-

Voc = -

- ------------------ (2)

Where N=Number of turns in the coil, l=length of winding, x=relative velocity between magnet

and coil.

Magnetic field varies with distance apart from the magnet the induced emf can be given by:-

e.m.f = −

.

----------------------- (3)

Here (dB/dx) is gradient magnetic flux density.


8

Both expression (2) & (3) can be expressed as

e.m.f =

----------------------------------------------- (4)

= Electromagnetic coupling factor = − = -NA

Circuit representation of electromagnetic generator:-

Applying Kirchhoff’s voltage law in above circuit, we get:-

e.m.f + i. (RL +Rc) + Lc

=0 --------------------------------------------- (5)

Comparison from dynamic model, we get damping coefficient induced from electromagnetic

transduction, be:-

be =

( ) -------------------------------- (6)

Fig. 2.3


9

For micro-generator that works at low resonant frequencies ,the inductive impedance of coil

much lower than its resistive impedance .Hence inductive impedance can be ignored and written

as :-

be =

( ) ------------------------------------------- (7)

Electrically induced damping factor given as:

ζe =

( ) --------------------------------------------- (8)

One of the most effective ways of achieving this for energy harvesting by use of permanent

magnet and coil.

Well suited for micro-generator that works at resonant frequency.

Do not require smart materials.

No need external voltage source to start generating.

Output voltage is low ~0.1v.

Difficult to manufacture in micro scale.

Difficult to integrate with MEMS (Micro-Electro-Mechanical system) fabrication process.

Bulky size.

2.2 Electrostatic Harvesters

The basis of electrostatic generator is the variable capacitor. According to “Roundy Model”

variation in capacitance causes either voltage or charge increases. The variable capacitance


10

structure is driven by mechanical vibrations. The capacitance varies between maximum and

minimum values. If the charge on the capacitor is constrained, charge will move from the

capacitor to a storage device or to the load as the capacitance decreases. Thus, mechanical

energy is converted to electrical energy.

The electrostatic energy stored within the capacitor is given by:-

E=1/2 *Q*V = 1/2 * C * V2 = (1/2C)*Q2 ------------------------------------------------------- (9)

Where Q= Charged stored, V= Voltage across the capacitor, C=Capacitance)

C = εr. εo.

----------------------------------------------- (10)

εr = Relative permittivity of dielectric between the plates,

εo = Permittivity of free space .

Circuit representation of electrostatic generator: -

A simplified circuit for an electrostatic generator using charge-constrained conversion is shown

in Fig. 4. Vin is a pre-charged reservoir, which could be a capacitor or a rechargeable battery.

Cv is a variable capacitor, which is one of the three types mentioned above. Cpar is the parasitic

capacitance associated with the variable capacitor structure and any interconnections, which

limits the maximum voltage. CL is the storage capacitor or any kind of load.

ENERGY HARVESTING THROUGH

Fig. 2.4:- Circuit representation for an electrostatic generator

The maximum voltage across the load is given by:

Electrostatic generators can be classified into three types, i.e. in

varies the overlap area between electrode fingers, in

gap between electrode fingers and out

two large electrode plates.


11

Circuit representation for an electrostatic generator

The maximum voltage across the load is given by:

Electrostatic generators can be classified into three types, i.e. in-plane overlap (Fig.

varies the overlap area between electrode fingers, in-plane gap closing (Fig. b) which varies the

gap between electrode fingers and out-of-plane gap closing (Fig. c) which varies the gap between

plane overlap (Fig. a) which

) which varies the

) which varies the gap between


12

Fig. 2.5- Electrostatic generators: (a) in-plane overlap; (b) in-plane gap closing; and (c) out-of

plane gap closing


13

These three types can be operated either in charge-constrained or voltage constrained cycles.

Generally, generators working in voltage-constrained cycles provide more energy than

generators in charge-constrained cycles. However, by incorporating a capacitor in parallel with

the energy harvesting capacitor, the energy from the charge-constrained system can approach

that of the voltage-constrained system as the parallel capacitance approaches infinity. This

parallel capacitor effectively constrains the voltage on the energy harvesting capacitor.

An electrostatic generator can be easily realized in MEMS version. Since the fabrication process

of electrostatic generators is similar to that of VLSI, electrostatic generators can be assembled

with VLSI without difficulties. Unfortunately, electrostatic generators require an initial

polarizing voltage or charge. The output impedance of the devices is often very high, which

makes them less suitable as a power supply. However, they can be used to charge a battery, in

which case, electrostatic generators can use electrets to provide the initial charge.

2.3 Piezoelectric Harvesters

Piezoelectric materials are generating electric charge when a mechanical load is applied.

Mechanical energy is in the form of pressure or force into electric energy and vice versa.

The constitutive equation for a piezoelectric material is given by-

D = ε. E + d. σ ------------------------------------- (Direct effect) ---------- (11)

€ = (σ/Y) + d. E -------------------------------------- (Converse effect) -------- (12)


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Piezoelectric generators typically work in either 33 mode (Fig. a) or 31 mode (Fig. b). In the 33

mode, a force is applied in the same direction as the poling direction, such as the compression of

a piezoelectric block that has electrodes on its top and bottom surfaces. In the 31 mode, a lateral

force is applied in the direction perpendicular to the poling direction, an example of which is a

bending beam that has electrodes on its top and bottom surfaces. Generally, the 31 mode has

been the most commonly used coupling mode although the 31 mode has a lower coupling

coefficient than the 33 mode. Common energy harvesting structures such as cantilevers or

double-clamped beam typically work in the 31 mode because the lateral stress on the beam

surface is easily coupled to piezoelectric materials deposited onto the beam.

Fig. 2.6


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Circuit representation of Piezoelectric generator: -

Figure .7 shows a circuit representation of a piezoelectric generator with a resistive load, RL. C is

the capacitance between two electrodes and Rs is the resistance of the piezoelectric material. The

voltage source, VOC, is the open circuit voltage resulting from Eq. (12) when the electrical

displacement is zero. It is given by

Voc = -

ε. . --------------------------------- (13)

Here t is the thickness of the piezoelectric material.

An expression for the piezoelectric damping coefficient is ,[2]

Fig . 7


16

Energy harvesting device employing piezoelectric conversion mechanism typically consist of

cantilever beam coated with piezoelectric material and mass placed on the tip of beam.

Piezoelectric require no external voltage source.

Compact dimension allow for MEMS integration.

Voltage relatively high (2-10V).

Poor mechanical properties.

Poor coupling in piezo thin film.

Piezoelectric materials -

a.) Naturally occurring crystal – Berlinite (AlPO4), Cane sugar, Quartz, Rochelle salt

b.) Man-made ceramics - Barium titanate (BaTiO3), Lead titanate (PbTiO3), Lead

Zirconium titanate (PZT) , Lithium niobate (LiNbO3)


17

c.) Polymer - Polyvinyledene fluoride (PVDF)

2.4 Magnetostrictive Harvesters

Magnetostrictive materials are also used to extract electrical energy from ambient vibration.

These materials deform when placed in a magnetic field and it can induce changes in magnetic

field when it is strained. Magnetostrictive materials are generally used in piezoelectric-

magnetostrictive composites. Such composites were originally used in magnetic field sensors and

have recently been adopted in energy harvesting. Magnetostrictive energy harvesters use the

“Villari effect of Magnetostrictive materials” such as Metglas 2605SC reported Wang and Yuan

[46]. Huang et al.[45] reported two energy harvesting devices based on a

TerfenolD/PZT/Terfenol-D composite. Their device produced 1.2 mW of power when excited at

5 m s−2 at 30 Hz.


18

Fig. No- 8

Fig. no- 9

B = dm .σ + μ . H …………………….(Villari effect)……………………… (14)

S =

+ dm . H ………………….(Joule effect) ……………………… (15)

The magnetic field strength, H, could calculate -

H = . ...……………………………………………….. (16)

Here, B=Magnetic displacement /flux density , dm-Magnetostrictive constant , σ – Stress , Permeability ,

H – Magnetic field strength, S – Strain ,E-Young’s modulus, I= Current ,N=Number of coil turns.


19

2.5 Comparisons of different transduction mechanisms of kinetic energy

harvesters

Type Advantages Disadvantages

Electromagnetic • No external voltage source

• No mechanical constraints

needed

• High output current

• Difficult to integrate with

MEMS fabrication process

• Poor performance in

micro-scale

• Low output voltage

Piezoelectric • Simple structure

• No external voltage source

• Compatible with MEMS

• High output voltage

• No mechanical constraints

needed

• Thin films have poor

coupling

• Poor mechanical properties

• High output impedance

• Charge leakage

• Low output current

Electrostatic • Easy to integrate with

MEMS

fabrication process

• High output voltage

• Mechanical constraints

needed

• External voltage source or

pre-charged electret needed

• High output impedance

• Low output current


20

Magnetostrictive • Ultra-high coupling

coefficient

• High flexibility

• Non-linear effect

• May need bias magnets

• Difficult to integrate with

MEMS fabrication process


21

CHAPTER 3: Mechanical motion rectifier (MMR)

3.1 Introduction of MMR

Mechanical motion rectifier is energy harvesting shock absorber which is able recover the

energy otherwise dissipated in suspension vibration while simultaneously suppress the

vibration induced by road roughness. It can work as a controllable damper as well as an

energy generator. A mechanical motion rectifier (MMR) is a device which converts the

oscillatory vibration into unidirectional rotation of the generator. Prototype MMR is to

achieve more than 60% efficiency at high frequency, which is much better than

conventional regenerative shock observer in oscillatory motion. The model is capable of

analyzing electrical and mechanical components at the same time. Shock absorber is

installed between chassis and wheels to suppress the vibration.

Figure -3.1 MMR Setup in vehicle Chevrolet Suburban SUV. [9]


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The road test is done to demonstrate the feasibility of the MMR shock observer and it is

observed that more than 15 watts of electricity which harvested while driving at 15 mph

on a smooth road. Zuo and Zhang et.al,[1] observe that 100 to 400 watts of energy

harvesting potential exist in the suspension of typical passenger vehicle travelling 60 mph

on the good roads and more energy available for trucks or on the rough roads. The

motion rectifier based design can also be used for other application of vibration energy

harvesting such as from tall building, long bridge or ocean vehicles. It can significantly

improve the reliability by reducing impact forces and increase efficiency by decreasing

the influence of friction. he main contribution of this paper is an innovative concept of

“mechanical motion rectifier”, which can convert bidirectional motion into unidirectional

motion. It is not a substitute of electrical voltage rectifier. It can significantly improve the

reliability by reducing impact forces and increase efficiency by decreasing the influences of

friction. It also enables the electrical generator to rotate unidirectional at relative steady speed

with higher energy efficiency. The second contribution is a circuit based modeling to analyze the

system’s dynamic properties both in electrical domain and mechanical domains. The third

contribution of this paper is simulation, lab experiments, and road tests to verify the concept

and advantages of mechanical motion rectifier based vibration energy harvester.

3.2 Principle of MMR

Shock absorbers are installed between chassis and wheels to suppress the vibration, mainly

induced by road roughness, to ensure ride comfort and road handling. Conventional rotational

regenerative shock absorbers translate the suspension oscillatory vibration into bidirectional

rotation, using a mechanism like ball screw or rack pinion gears. Figure 3.2 shows one such an

implementation, where the rotary motion is changed by 90 degree with a pair of bevel gears for

retrofit.


23

Fig. 3.2 - Traditional design of a rack-pinion based regenerative shock absorber [9]

It is working on “motion rectifier” with two working mode: positive mode and negative mode. Key components of “motion rectifier” are two one way roller clutches that transmit rotation

only in one direction and dive the motion in two different routes. As a result, shaft of the motor

and planetary gear will always move in one direction. It converts the irregular reciprocating

vibration into the unidirectional rotation.

Figure 3.3 Principle of “motion rectifier” for oscillating motion [9]

MMR with two roller clutch can be analogy to full-wave voltage rectifier using a centre

tapped transformer and two diodes. The system inertia is equivalent to the electrical

smoothing capacitor in series with electrical load. When the direction of the motion

changes, the relative velocity between the driving part and driven part, which caused by


24

backlash, would be much smaller so that the impact forces would be much smaller ,in this

way reliability would be improved.

Figure 3.4 Electrical analogy for “motion rectifier” [9]

3.3 Design of Highly-Compact Motion Rectifier Based Harvester

Design of MMR is very compact in comparison of existing other design. In this design

they using pair of rack and pinion, one shaft and three bevel gears .Two roller clutches

are mounted between the shaft and the two larger bevel gears, which are always engaged

with the small bevel gear .When rack moves up and down, the pinion and shaft rotate

clock wise and counterclockwise directions. Due to the engagement of one-way roller

clutches at instant time only one large bevel gear will be engaged and be driven by the

shaft; another large bevel gear disengaged with from the shaft by the roller clutch. The

assembly of the pinion, shaft, and bevel gears will be mounted to one cylinder, and

another cylinder covers outside and to guide the linear motion. Similar as roller bearings,

the roller clutches can’t hold large thrust in the axial direction, so two thrust bearings are

designed to support the thrust forces on the two larger bevel gears. In order to reduce the

friction between the inner and outer cylinders, we insert Teflon rings between the two

cylinders. The rack is preloaded and guided by a roller in the place opposite to the pinion.

The enclosed construction of the shock absorber prevents dirt from hurting gears inside.


25

Figure 3.5 sample and 3D view of MMR [9]

Figure 3.6 components of MMR [1]


26

3.4 Experiment and Results

Experiment Setup –

5.1. Experiment Setup The prototype was tested with the MTS 858 Mini Bionix II

testing system and a dynamic signal analyzer (Hewlett Packard Model 35670A).

Figure 3.7 Damping loops for different external electrical loads under vibration input of 1.5 Hz and

5mm amplitude.

Figure 3.8 Damping loops for different input frequencies with electrical load Ri +Re= 106.6 Ω


27

3.5 Conclusion of MMR

“Motion rectifier” based design of electromagnetic energy harvester for enhanced

efficiency and reliability for potential application of vibration energy harvesting from vehicle

suspensions. “Motion rectifier” can transfer the oscillatory motion of vehicle suspension into

unidirectional motion of the electrical generator, thus enabling the generator operating in a

relatively steady speed with higher efficiency. In such a design, the motion inertia will act as a

filtering capacitor to temporarily storage the energy and smooth the rotation, which can decrease

the influences of backlash impact and static friction.


28

CHAPTER 4: Harvesting vibration energy by a triple-

cantilever based triboelectric Nanogenerator (TENG)

4.1 Introduction of TENG

Figure 4.1 triboelectric Nanogenerator (TANG) [7]

Triboelectric effect – “The triboelectric effect is phenomenon that material becomes

electric charged after it contacts a different material through friction.” It is based on

triple-cantilever TENG harvesting vibration energy with the assistance of nanowire

arrays fabricated onto the surface of beryllium-copper alloy foils. TENG produces an

open-circuit voltage up to 101 V and short circuit current reached up to 55.7 μA with

peak power density of 252.3 mW/m2 . Output power of single device with a size of 3.2

cm by 2.8 cm is high enough to simultaneously light up more than 40 commercial LED.


29

Unambiguously demonstrating its feasibility of power portable electronics. Using as

sensor for environmental and infrastructure monitoring security.

4.2 Design & characterization of TENG

Figure 4.2 Photograph of typical cantilever beam

The bottom surface of top cantilever and top surface of bottom cantilever are coated with

polydimethylsiloxane (PDMS) films and middle cantilever are covered by ZnO nanowire

array which layer copper will deposited. A mass is attached at end of its effectiveness of

vibration. Middle cantilever has two chances the contact the top and bottom cantilever in

each cycle of vibration. PDMS film can easily deformed to increase the effectiveness

contact area and nanowire array can deeply inserted into PDMS to increase the effective

contact area and thus leading to substantially higher electric output. A cycle of

electricity generation process illustrating mechanism of the TENG can be explained by

coupling between triboelectric effect and electrostatic effect.


30

Fig 4.3 : A cycle of electricity generation process for illustrating the mechanism of the

triple-cantilever based TENG [4]

4.3 Experiment & Result

Electric output measurements were performed on a triple-cantilever based TENG device with effective

contact area of 3.2 cm × 2.8 cm, at triggering frequencies of 3.5 Hz, 3.7 Hz, and 4.0 Hz (Fig. 3). The open-

circuit voltages (VOC) at 3.5 Hz (Fig. 3(a)), 3.7 Hz (Fig. 3(b)), and 4.0 Hz (Fig. 3(c)) are about 89 V, 101 V,

and 81 V, respectively, indicating that the 3.7 Hz is the resonance frequency of the TENG. As shown in

the inset of Fig. 3(c), a positive voltage is generated due to the immediate charge separation on the

departure of the middle cantilever from the PDMS film on the bottom cantilever. Since the electrons

cannot flow back to screen the induced electric potential difference between the two electrodes under

the open-circuit condition, the voltage remains at a plateau until the next contact [10–14]. Moreover,

the peak values of the rectified short-circuit current (ISC) at 3.5 Hz (Fig. 3(d)), 3.7 Hz (Fig. 3(e)) and 4.0 Hz

(Fig. 3(f)) also reach up to 45.9 μA, 55.7 μA, and 44.5 μA, respectively.


31

Fig.4.4 Open-circuit voltage (VOC) at vibration frequencies of 3.5 Hz (a), 3.7 Hz (b), and 4.0 Hz (c) and

rectified short-circuit current (ISC) at vibration frequencies of 3.5 Hz (d), 3.7 Hz (e), and 4.0 Hz (f). The

insets of (c) and (f) are enlarged views of half cycles of the VOC and ISC at 4.0 Hz, respectively.


32

CHAPTER 5: Conclusion and Future Work

5.1 Conclusion

An overview of sources of ambient energy available for harvesting was presented. Description

of four vibration energy harvesting mechanisms was proposed with respect to pros and cons of

each technique. The aim of this technique is to make the energy harvester produce maximum

power output in the most effective way. “Motion rectifier” based design of electromagnetic

energy harvester for enhanced efficiency and reliability for potential application of vibration

energy harvesting from vehicle suspensions. The “motion rectifier” based design achieved a

mechanical efficiency of over 60% and no obvious backlash effect. It also harvested average

powers 40.4 Watts and 25.6 Watts on 30 and 93.4 external resistive loads under vibration of

RMS velocity 0.047m/s and we have also seen triple-cantilever based TENG for harvesting

vibration energy in ambient environments. This innovative structure provides the middle cantilever

with two chances to contact the top and bottom cantilevers in each cycle of the vibration, doubling the

vibration energy conversion efficiency.

5.2 Future Work

Mechanical vibration is great source of energy harvesting, we have seen at present time more

than 19 million automobiles are available in INDIA and it will be very large data in future.

Improvement is possible in efficiency as well as reliability. We can save 10-14% fuel by

recharging car battery and small electronics device. We can make more robust and regular

unidirectional rotational design.


33

REFERENCES

[1]. Energy Harvesting Technique by Shashank Priya. Daniel J. Inman.

[2]. Harvesting the Vibration Energy by Marek Matak*, Peter Šolek Institute of applied

mechanics and mechatronics, Slovak University of Technology, Bratislava, Slovakia.

[3.] Energy Harvesting Systems by Tom J. K a ´zmierski · Steve Beeby

[4.] Introduction to Vibration Energy Harvesting NiPS Energy Harvesting Summer School

August 1-5, 2011

[5.] http://iopscience.iop.org/0964-1726/19/10/105012

[6.] Electromagnetic energy harvesting from vibrations of multiple frequencies

Bin Yang1, Chengkuo Lee1 ,2, Wenfeng Xiang2, Jin Xie1, Johnny Han He1,Rama Krishna

Kotlanka1, Siew Ping Low2, 3 and Hanhua Feng.

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Yuan Lin2 , and Zhonglin Wang1,3