PRESENTATIONon

Energy-Harvesting Through Mechanical Vibration

Department of Mechanical Engineering Motilal Nehru National Institute of Technology Allahabad

Uttar Pradesh- 211004

SUBMITTED BY

SHAMBHU KUMAR

Reg. No- 2014DN06

SUBMITTED TO

COLLEQUIUM TEAM

Motivation 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 4 1 5 (Apr Mar). 3.22 million passenger vehicles rolled out from Indian auto plants in 201 4 1 5. According to “Indian Motor Vehicles knowIndia.net “ following data are given:-

“On the basis of above observation more than 19 millions 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”.

Domestic Motor Vehicle Sales

2014-15 (In Millions)

Passenger Vehicles 2.60

Commercial Vehicles .61

Two -wheelers 16.0

Three-wheelers .53Total 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

OUTLINE Introduction

Brief discussion of Mechanical Motion Rectifier

Brief discussion of Triboelectric Nanogenerator

Conclusion

References

INTRODUCTION

Taken from NiPS Energy Harvesting Summer SchoolAugust 1-5, 2011

Electromagnetic Harvesters It is based on Faraday’s law of electromagnetic induction which state that “an

electrical current will be induced in any closed circuit when the magnetic flux through a surface bonded by the conductor change”.

According to faraday law :- Emf = - (dɸ/dt) --------(1)

(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 = - NBl .(dx/dt) -------------------(2)

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

(figure - NiPS Energy Harvesting Summer School)

Electromagnetic Harvesters

Magnetic field varies with distance apart from the magnet the induced emf can be given by:- e.m.f = - N .A. (dB/dx).(dx/dt)(dB/dx = gradient magnetic flux density ) e.m.f = κ . (dx/dt) κ = Electromagnetic coupling factor = -NBl = -NA( dB/ dx). Applying Kirchhoff’s voltage law;- e.m.f + i.(RL +Rc) + Lc (di /dt) = 0

Damping coefficient induced from electromagnetic transduction ,be –

be = κ2 / (RL + Rc + j ω Lc )

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 = κ2 / (RL + Rc ) and electrically induced damping factor given as:

ζe = κ2 / 2mω (RL + Rc )

Electromagnetic Harvesters One of the most effective way 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.

SENSOR

Electrostatic Harvesters load is given it is based on varying vibration – dependent capacitance of variable

capacitor s (varacators).

Ambient vibrations induced displacement of charged plates of varacators and mechanical energy converted into electrical energy.

According to “Roundy Model” variation in capacitance cause either voltage or

charge increases .

The electrostatic energy stored within the capacitor is given by

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

(Q= Charged stored , V= Voltage across the capacitor , C=Capacitance) & (c = εr εo (A/d)) (ε Permittivity)

Maximum voltage across the

Figure from NiPS Energy Harvesting Summer School

Electrostatic Harvesters Parallel capacitor effectively constrained the voltage on the energy

harvesting capacitor.

Advantage of this principle of harvesting is ease of integration such devices into printed circuit board of MEMS(Micro-Electro-Mechanical system).

No need of smart materials.

High output voltage (2-10v).

Electrostatic generators require an initial polarizing voltage or charge.

High output impedance .

Low output current.

Figure-Tom J.Kazimiersiki.steve Beeby energy .

Piezoelectric Harvesters The piezoelectric effect was discovered by Pierre and Jacques Curie

in 1880.

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

(D=Electrical displacement (charge density) , ε=Dielectric constant ,d=Piezoelectric strain coefficient , E =Electric field, σ =Mechanical stress , € =Mechanical strain)

The voltage source (Voc ) open circuit voltage when electrical displacement is zero is given by :-

Voc = -(d/ ε ) .t. σ t=Thickness of piezoelectric material .

Figure-Energy harvesting system by Tom.J.Kazmie.

Piezoelectric Harvesters 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) c.) Polymer - Polyvinyledene fluoride (PVDF)

Magnetostrictive Harvesters Magnetostrictive energy harvesters use the “ Villari effect of

Magnetostrictive materials” such as Metglas 2605SC, TerfenolD /PZT/ Terfenol-D composite.

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

B = dm .σ + μ . H --------------(Villari effect) S = (σ/E) + dm .H --------------(Joule effect) The magnetic field strength , H, could calculate- H = IN

(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)

Fig - http://dx.doi.org/10.5772/50892

Magnetostrictive Harvesters Magnetostrictive materials to be used in actuator and sensor application

Ultra-high coupling coefficient >.9

No depolarization problem .

High flexibility.

Suited to high frequency vibration.

Difficult to integrate with MEMS fabrication process.

Non-linear effect.

Need of pick-up coil.

MECHANICAL MOTION RECTIFIER(MMR) MMR 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 convert the oscillatory vibration into unidirectional rotation of the generator .

Prototype MMR is to achieve more than 60% efficiency at high frequency ,which is much more better than conventional regenerative shock observer in oscillatory motion.

The model is capable of analyzing electrical and mechanical components at the same time.

MMR Shock absorber are installed between chassis and wheels to suppress the vibration.

MMRThe road test are done to demonstrate the feasibility of the MMR shock observer and it is observe that more than 15 watts of electricity which harvested while driving at 15 mph on a smooth road.

Scientist Zuo and Zhang ,They 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.

PRINCIPLE OF MMRIt is working on “motion rectifier” with two working mode : positive mode and negative mode .

Key components of “motion rectifier” are two one way roller clutch 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.

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 backlash , would be much smaller so that the impact forces would be much smaller ,in this way reliability would be improved.

Design of MMR

Design of MMRDesign 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.

EXPERIMENT AND RESULT OF MMR

The prototype was tested with the MTS 858 Mini Bionix II testing system and a dynamic signal analyzer (Hewlett Packard Model 35670A).

TRIBOELECTRIC NANOGENERATOR(TENG)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 .

Unambiguously demonstrating its feasibility of power portable electronics.

Using as sensor for environmental and infrastructure monitoring security.

TENG

Design and charachterization of TENGThe basic structure of the triple-cantilever based TENG in which three metal plate of beryllium-copper alloy foils are the three cantilevers .

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 ineach 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.

Design and charachterization of TENG

Fig : A cycle of electricity generation process for illustrating the mechanism of the triple-cantilever based TENG .

Fabrication of TENG.

BCAL(65x28x.2)With tip mass 12.29 g

2 BCAFs(45x28x.2)With spin coatedPDMS (32x28x.6)

Aqueous solution of hexamethylenetetramine and zinc nitrate hexahydrate with equal Concentrated used to growth of ZnO nanowire on BCAFs .

PDMS elastomer and cross-linker mixed in ratio 10:1(w/w) then cast on BCAF substrates . Uniform PDMS obtained by heating in a mechanical convection at 850c for 2 hours.

Mechanical convection oven 4h,850c

EXPERIMENT AND RESULTS

Fig . - 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.

CONCLUSION

REFRENCES