Smart-roads: Piezoelectric Transducers For Energy Harvesting

Umesh RVijaykumar M H

Sreedharkumar S R

Guided by: Dr. Venkatesh Vadde

PES Institute of Technology - ECE

Contents

• Background and motivation• Goals and deliverables• Summary of Achievements• Observations and calculations• Challenge encountered• Applications of PEH Systems• Limitations in PEH system• Conclusions

PES Institute of Technology - ECE

PES Institute of Technology - ECE

Background & Motivation

• Electricity demand far surpasses supply, and any sources of energy harvesting are very desirable

• Human actions, Kinetic energy of vehicles and ambient vibration are present every where in the environment they can be converted into useful energy

• Piezoelectric transducers are used as sensors in many applications• Piezoelectricity can be used as an energy harvesting mechanism• Motivation behind piezoelectric energy harvesting is to power mobile

devices without batteries, to control low power embedded systems etc.• Piezo-energy harvesting (PEH) from moving vehicles can power many

kinds of systems– Road warnings– Ad-billboards– Street lamps control– Traffic lights

PES Institute of Technology - ECE

Goals & deliverables

• A practical characterization of PEH-potential from commonly available piezoelectric transducer elements

• An interface circuit to condition the voltage and store the energy generated

• Quantification of energy storage potential (practically seen) in controlled & random experiments

• Demo of smart road applications powered by the harvested energy from the PEH setup

PES Institute of Technology - ECE

Summary of Achievements

• Using simple, inexpensive piezo-transducers we demonstrated energy harvesting and storage

• Designed a bridge rectifier circuit array to maximize the pulsed voltage output

• Optimized a sensor mounting mechanism for best voltage generation

• Demonstrated scaling of PEH systems from 4 discs to 16 discs all the way to 104 discs

• Discovered that vibrational mode of PEH is more effective than compressive mode

• Designed a suitable voltage regulation circuit to stabilize the pulsed voltage output of the PEH system

Study on piezoelectric elements

• Soft cushion needed under discs for producing bending stress and hence better yield

• Stacking the discs is not useful as the ceramic used in the disc is brittle. Also there are chances of shorting of the terminals.

• Using a single piezo-disc, for a normal finger pressure we could produce about 15µC of charge

• These discs when placed on vibrating materials, produce higher energy.

PES Institute of Technology - ECE

Block Diagram

PES Institute of Technology - ECE

Strain

Rectifier Filter Regulator

Battery Storage

Low power Embedded Systems

[Road warnings, Traffic lights control, Ad boards]

PiezoelectricTransducers

[Piezo element]

Waveforms at various stage

Waveforms observed

Interface Circuit

List of tasks completed

• Selection of piezoelectric transducers among available transducers• Suitable arrangement to bring out a soft cushion effect for discs• An experimental setup with 1,2,4,8 and 16 piezo-discs to show the

scaling• Quantization of charge stored on capacitor• A better interface circuit to produce constant 5V output• A larger PEH system with 104 piezo-discs to charge a Ni-MH battery• Applications in smart roads using harvested energy

PES Institute of Technology - ECE

Soft cushion for better yield

Foam Tape or rubber

Piezo buzzerStrain

• This arrangement produces soft cushion effect for better deformation of the transducer.

• Also by this way large strain could be handled without breakage of ceramic in the discs.

PES Institute of Technology - ECE

Interface Circuit

PES Institute of Technology - ECE

Scaling with number of piezo-discs

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Scale(number of piezoelectric discs)

Time (s) to charge capacitor with no load

1 120

2 65

4 35

8 20

16 5

Tabulation of time to charge 100µF cap to 10V

Scaling with number of steps

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Tabulation of voltage at 100µFcapacitor vs. number of steps

No. of steps

Volta

ge (V

)

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Tabulation of energy stored in 100µFcapacitor vs. number of steps

No. of steps

Ener

gy s

tore

d (m

J)Energy stored in capacitor

Capacitor voltage vs. Regulated DC Output time

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Voltage(V) at 1000µF cap Time(s)

8 47

12 111

16 162

20 158

Voltage(V) at 100µF cap Time(s)

8 11

12 16

16 18

20 18

Time duration of 5V, 50µA Regulated DC output provided by MAX666 IC for various capacitor voltages

Larger PEH system

PES Institute of Technology - ECE

Challenges faced and solutions found

• Connecting discs in parallel results in deformation in other discs.Connecting discs in series adds up voltage but, when the strain is not

synchronized subtraction happens.Solution: Connecting rectifier for each piezo-disc.Now series combination does not work because when one of the disc

is not deformed it results in open circuit.Parallel connection works – Capacitor is charged when any of the disc

is deformed irrespective of synchronization.

• Voltage drop in rectifier diodes is considerable i.e. 0.6+0.6=1.2VSolution: Using diode 1N5817/18/19 results in voltage drop of just

0.15+0.15=0.3V

PES Institute of Technology - ECE

Challenges faced and solutions found

PES Institute of Technology - ECE

Challenges faced and solutions found

• Use of linear regulators like IC7805 leads to more power dissipationSolution: Using MAX666 IC , a micro power voltage regulator which is more

efficient and can produce a constant stable output for a particular duration

• Vibrations produce more energy, but to convert the strain of vehicles into vibrations at discs a complex setup is required

PES Institute of Technology - ECE

Applications

• Road lines and road signs illumination at night efficiently• Efficient road lamp switching to save power (Only when a

vehicle approaches light glows)• Approximate measure of weight of the vehicles• Measurement of speed of vehicles

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Limitations of current PEH system

• Piezoelectric transducers are high impedance (low current) sources of power

• PEH system to provide continuous output power requires higher density of vehicles which cannot be guaranteed

• The ceramic piezoelectric material is brittle• Rather than strain, vibrations produce more energy. To

achieve vibrations we need a complex setup

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Conclusions

• Developed a modular, scalable PEH mat that can be deployed on roads, corridors, elevators as smart solution

• Piezoelectric energy harvested is best suitable for low power, embedded, programmable applications

• PEH system works in any weather condition compared to solar energy which depends on weather

• Many smart road applications can be realized using piezoelectric energy harvesting:– Intelligent traffic control– Intelligent street lighting– Cautionary flash-signs

PES Institute of Technology - ECE

References

• http://www.piezocryst.com/piezoelectric_sensors.php• www.innowattech.co.il• http://en.wikipedia.org/wiki/

Energy_harvesting#Piezoelectric_energy_harvesting• www.designboom.com/technology/intelligent-interactive-highway-by-

studio-roosegaarde-heijmans/• http://www.americanpiezo.com/knowledge-center/piezo-theory.html• http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6145389• www.fusionteq.com/html/battery_101_-_the_basics.html

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Thank You