1. Name-Anshuman Samantray
7th semester
Electrical Engineering
College of Engineering and Technology

2. PATTERN OF EXPLANATION
1. Introduction
2. What is piezoelectric effect?
3. What is a crystal?
4. How piezoelectricity works?
5. What are piezoelectric generators?
6. What are the advantages of piezoelectric generators?
7. What is piezoelectric car?
8. Diagrammatic presentation of piezoelectric car.
9. Operation of piezoelectric car.
10. Advantages of piezoelectric car.
11. Disadvantages of piezoelectric car.

3. INTRODUCTION
 The battery range for many electric vehicles is limited,
meaning that such methods of transportation can only
be used for short trips.
 In extended range vehicles manufacturers provide an
internal combustion engine that uses conventional
fuels to recharge batteries in motion & hence extend
their range.
 But in order to reduce environmental pollution, a
piezoelectric energy assisted car, using piezoelectric
effect for charging the batteries in motion, can be
taken as a better alternative.

4. HISTORY
 Piezoelectricity was discovered in 1880 by two brothers,
Pierre and Paul-Jacques Curie ,who found that when a
certain type of crystals, including Quartz, Tourmaline And
Rochelle salt were compressed along certain axes, a voltage
was produced on the surface of the crystals. This effect is
known as piezoelectric effect.
White Quartz Rochelle Salt

5. What is a crystal?
 A class of material arranged in a definite geometrical
pattern in three dimensions (table salt and sugar are
common examples)
 Quartz Crystal is silicon and oxygen arranged in a
crystalline structure (SiO2).
 SiO2 is also found abundantly in nature in a non-
crystalline structure (“amorphous”) as sand.

6. A method for predicting the behavior of a
crystal: The unit cell
+ Represents silicon atom
- Represents oxygen atom
Not actually correct, but this method allows
a good understanding of quartz crystals

7. The unit cell of crystal silicon dioxide
-
+ +
- -
+
As we can see that there is no inversion centre & hence a
quartz crystal shows piezoelectric effect………

8. How piezoelectricity works
 Normally, the charges in a piezoelectric
crystal are exactly balanced, even if
they're not symmetrically arranged.
 The effects of the charges exactly cancel
out, leaving no net charge on the crystal
faces. (More specifically, the electric
dipole moments—vector lines
separating opposite charges—exactly
cancel one another out.)
 If you squeeze the crystal , you force the
charges out of balance.
 Now the effects of the charges (their
dipole moments) no longer cancel one
another out and net positive and negative
charges appear on opposite crystal faces.
By squeezing the crystal, you've produced
a voltage across its opposite faces—and
that's piezoelectricity!

9. The Piezoelectric Effect
Crystal material at rest: No forces applied,
so net current flow is 0
Crystal
+-+-+-
Current Meter
=0
Charges cancel +-+-+-
each other, so
no current flow

10. The Piezoelectric Effect
Crystal material with forces applied
in direction of arrows………..
Crystal
-----
Force
Current Meter
+++++ deflects in +
direction
Due to properties of symmetry,
charges are net + on one side &
net - on the opposite side: crystal gets
thinner and longer

11. The Piezoelectric Effect
Changing the direction of the
applied force………..
Crystal
++++
Force Current Meter
deflects in -
direction
-----
…. Changes the direction of
current flow, and the crystal gets
shorter and fatter.

12. The electromechanical nature of piezoelectric material
 In general, if you deform a piezo crystal by applying a force,
you will get charge separation: Think of a simple battery.
 Taking it one step further, what would happen to the
crystal if you applied an electrical force that results in the
exact same current flow from the proceeding circuit?

13. The electromechanical effect
Now, replace the current meter with a power source capable
of supplying the same current indicated by the meter….
Crystal
switch
+-+-+-
charges cancel power source
+-+-+-
…. With the switch open, the crystal material is now at rest again:
the positive charges cancel the negative charges.

14. The electromechanical effect
When the switch is closed, and we apply the exact amount
of power to get the same current that was detected when the crystal
was squeezed , then the crystal should deform by the same amount!!
Crystal
++++
+ side
power source
(battery)
----- - side
…. and, the crystal should get shorter and fatter.

15. The electromechanical effect
What will happen if you switched the battery around??
Crystal
-----
- side
power source
(battery)
+++++
+ side
…. the crystal should get longer and skinnier.

16. PIEZOELECTRIC GENERATORS
 Piezoelectric generator is nothing but a piezoelectric
crystal sandwiched between two metallic electrodes.
So when a mechanical pressure/stress is applied on the
crystal , an emf is generated across the metallic plates
provided.

17. IMPORTANCE
 The converse effect is also possible i.e. when the emf is
applied along certain electrical axes in the crystal ,this
crystal produces mechanical vibrations. This effect,
known as converse piezoelectric effect, is used in
many practical devices such as buzzers , Ultrasonic
filters & sonar for producing Ultrasonic waves.

18. IMPORTANCE
 This effect is implemented in a variety of practical
devices such as microphones, phonograph pick-ups
and wave filters in telephone communications systems
and electric power generation etc.

19. PIEZOELECTRIC CAR
 Each of these piezoelectric car tires
is equipped with an array of highly
bendable PZT benders covering
most of the inner surface .The
output due to deformation of tires,
which is an AC waveform has to be
converted into DC signal by a
rectifier before it can be cached in a
capacitor . Each row of benders,
running across the width of tire is
taken as one generator & is rectified
separately with all PZT lines
connected in parallel.
 At any given time only three or four
rows , depending on the length of AN ARRANGEMENT OF
the contact patch , generate power. PZT BENDERS IN A TIRE

20.  Since rectifiers provide very high resistance for reverse
flow of current the remaining PZT benders behave as
disconnected & hence inverse piezoelectric effect can
not occur.
 The following curve shows Voltage and Power across a
1000Ω load at various rotations per minute.

21.  Power is extracted from the tire-wheel system using a
commutator-like assembly i.e. one that continuously
maintains the electrical contact between the chassis
and the wheel while allowing the latter to spin freely .
Such a setup permits the extraction of tire-generated
power to run on-board electronics.
 The energy obtained in this method depends on two
factors –tire surface area , rpm at 100 km/h. So greater
the surface area more will be the output.
 If a huge amount of power can be extracted so as to
charge the batteries of an all-electric engine then no
fossil fuel will be required to provide power reducing
the pollution . Such a concept vehicle is named as
P-Eco.

22. DIAGRAMATIC PRESENTATION OF A PIEZO-CAR
Piezoelectric generator

23. ADVANTAGES
 1. Reduces environmental pollution.
 2. By using Lead Zirconate piezoelectric crystals, we
can generate until 10000 volts by small deformations of
the tire.
 3. It helps increase a car’s efficiency.

24. IMPROVEMENTS
 However piezoelectric materials’ output has only been
sufficient for low-energy-consumption gadgets. To
obtain high-power output, a large area of tires’ inner
surface must be filled with PZT benders.
 Since PZT elements have limited flexibility ,high
deformation areas of the tire such as sidewalls could
not be covered . So a more flexible polyvinylidene
fluoride is being developed for increasing power
output.