This is the slides for a talk I have given at Sensors expo & conference 2017 in San Jose, CA, on vibrations energy harvesting. The talk discussed approaches in VEH, transduction mechanisms, common mechanical structures, design challenges and how to tackle them, in addition to a short survey on some VEHs and associated circuitry.

1. Vibration Energy Harvesting:
Between Theory and Reality
Karim El-Rayes, MASc., BSEE.
Research Associate & PhD. Candidate
University of Waterloo
Canada

2. Our journey through VEH wonderland 
• Brief history of energy harvesting.
• Scales and Types of energy harvesting.
• Background on mechanical vibrations.
• Mechanical structures for VEH.
• Transduction mechanisms for VEH.
• Constraints: Resonance, Bandwidth and Nonlinearity.
• Techniques to harvest more power.
• Energy harvesting flow.
• Tuning your energy harvester.
• Case studies.
2

3. What is Energy Harvesting?
It is the process of scavenging energy from any physical
phenomenon in the surrounding environment and
converting it into usable electric power.
Input
conditioning
(optional)
Transducer
Output
conditioning
Energy
Storage
Input from
Physical
phenomenon
Output
power
Energy Harvester
3

4. 8642
1821
1831
1880
1891
1995
1839
1887
1954
Electromagnetic Induction
Michael Faraday
Piezoelectricity
Pierre & Jacques
Curie Electrical Resonant
Transformer Circuit,
AKA: Tesla Coil
Nicola Tesla
Mass-on-Spring
Electromagnetic
Vibrations
Energy Harvester
C.B. William
& R.B. Yates
Seebeck
Thermoelectric effect
Thomas Johann
Seebeck
Photovoltaic Cell
Edmond
Becquerel Wind Turbine
James Blyth
Radioisotope
Thermoelectric
Generator,
AKA: RTG
K. Jordan
& J. Birden
4

5. Scales of Energy Harvesting
• Macro energy harvesting: the output feeds
the electric grid (e.g. solar and wind).
• Micro energy harvesting: very low output,
useful for portable and inaccessible devices.
5

6. Types of Energy Harvesting
Solar
 Macro & Micro
Vibration & Motion
 Micro
Wind
 Macro
Thermal
 Micro
6

7. What is “Vibration Energy Harvesting”?
It is the technology of scavenging waste kinetic
energy due to natural or man-made activity
from the surrounding environment and
converting it to usable electrical energy.
7

8. Background on Mechanical Vibration
Vibrations are periodic motion of an object, such that the
motion repeats itself at time interval T. The vibration profile of
an object is defined in terms of the amplitude xo and frequency
 of the harmonic motion it performs :
x(t) = xo sin( t)
1st Cycle 2nd Cycle
Time (seconds)
Displacement(meters)
T = 1/f
xo
8

9. Mechanical Structures for VEH
𝒎 𝒙 + 𝒄 𝒙 + 𝒌𝒙 = −𝒎 𝒚
Mass
Spring stiffness “k”Spring
damping “C”
Unloaded beam
Loaded beam
Beam Length
Static
body or
Wall
Force
applied on
the beam
𝒌 =
𝟑𝑬𝑰
𝑳 𝟑
𝑓𝑜 =
1
2π
𝑘
𝑚
Cantilever Beam Structure Mass-on-Spring Structure
9

10. Transduction Mechanisms for VEH
Electromagnetic
Output
Piezoelectric
Piezoelectric
material
Output
Electrostatic
10

11. Sources of Vibration
Can you guess the frequency range where kinetic
energy is abundant within?
1. <1  200 Hz.
2. 500 Hz  1 KHz.
3. 1 KHz  5 KHz.
4. Above 5 KHz.
11

12. Sources of Vibration
Source of Vibration Frequency (Hz)
Walking 0.6 – 2.5
Ground vibration (man-made) 0 – 200
Human motion 0.6 – 5
Vehicles bouncing 1 – 10
Golden Gate Bridge 0.262
High-rise buildings < 1
12

13. How to Choose a VEH?
• Center frequency (Resonance).
• Harvesting Bandwidth (3dB bandwidth).
• Amplitude.
• Output power.
• Physical profile (form-factor).
13

14. Hitting the Resonance
“Resonance occurs when a system is able to store and easily
transfer energy between two or more different storage
modes (such as kinetic energy and potential energy in the case
of a pendulum). However, there are some losses from cycle to
cycle, called damping. When damping is small, the resonant
frequency is approximately equal to the natural frequency of the
system”
Wikipedia
14

15. Hitting the Resonance (cont.)
Source:
https://www.boundless.com/physics/
15

16. Bandwidth: The Wider The Better
The harvesting
bandwidth is defined as
the range of frequencies
where output power is
higher than or equal
half of the maximum
power achieved at
resonance.
Source:
http://www.sengpielaudio.com/calculator-cutoffFrequencies.htm
16

17. Checkpoint
• The lower resonance frequency (below 200
Hz) the more kinetic energy you can harvest.
• The wider the bandwidth the more energy
you can harvest.
17

18. Nonlinearity: Life isn’t fair
Due to the material characteristics, either in the
mass-on-spring or cantilever beam structures,
the mechanical oscillator can behave nonlinearly
with frequency.
18

19. Hard vs. Soft Nonlinearity
Source:
The Impact of Chaos on Science and Society
Softening Nonlinearity
Source:
https://www.hindawi.com/journals/sv/2014/543793/fig4/
Hardening Nonlinearity
19

20. Practical Issues with Nonlinearity
• 3dB bandwidth looks
“deformed”, the system
doesn’t have proper ½
power boundary
frequencies.
• Center frequency not
necessarily at the peak i.e.
less energy harvested.
Frequency Response of the FDH
Source: Prototypes of FDH, El-Rayes et. al.
20

21. More Power:
Array of Energy Harvesters
If vibrations in the
environment of interest
hops between multiple
frequencies then an
array of VEHs, each VEH
will be tuned to a certain
center frequency. This
way you can harvest
more energy.
VEH #1
fc1
VEH #2
fc2
VEH #n
fcn
+
+
+ Output
21

22. More Power:
Multi-Frequency Energy Harvesters
A VEH can have two center
frequencies (or multiple),
while not necessarily
maximum power or similar
bandwidth are achieved at
all center frequencies of
but it allows to harvest
more energy using the
same device at multiple
frequencies.
Multi-frequency VEH output power verses frequency
Source: Zhenlong Xu et. al.
22

23. Energy Harvesting Flow (cont.):
Power Management Perspective
Transducer
Voltage
Boosting
Rectification
Energy Storage
circuitry
Voltage
Regulation
(optional)
Energy Storage To the
Load
Signal Conditioning Power Management
Energy Source
23

24. Energy Harvesting Flow (cont.):
Power Management Perspective
• Rectification: full-bridge diode rectifier, H-bridge
rectifier.
• Voltage Boosting: DC-DC converter, Voltage
multiplier, Step-up transformer.
• Energy storage: Rechargeable Battery vs. Super
capacitor.
• Energy management: PMIC and LDO.
• Optimum load for maximum power transfer.
24

25. Rectification
 Full-wave diode rectifier bridge
Source: Wikipedia
Full-wave MOSFET rectifier H-bridge 
Source: Yilmaz et. Al.
25

26. Voltage Boosting
Cockcroft Voltage Multiplier
Source: Wikipedia
DC-DC Boost Converter
Source: Wikipedia
Charge Pump DC-DC Converter
Source: Maxim Integrated
Step-up Transformer
Source: Wikipedia
26

27. Energy Storage Circuitry
Supercapacitor Charging Circuit 
Source:
http://www.edn.com/design/power-management/
4422103/Fast-charging-a-supercapacitor-from-energy-harvesters
 Battery Charging Circuit
Source: P. Gambier et. El.
27

28. Tunability for VEHs
Tuning the VEH center frequency and 3dB
harvesting bandwidth can be done:
• Mechanically.
• Magnetically.
• Electronically.
Where a combination of the three methods can
be used to harvest more energy.
28

29. Mechanical Tuning
• Change the proof-mass: higher mass  lower resonance
frequency
• Change mechanical stiffness: higher stiffness  higher
resonance frequency.
• Change cantilever beam length: changing the length will
reflect on the mass  change in center frequency.
• Change cantilever beam material: change in stiffness 
change in center frequency.
29

30. Magnetic Tuning
Magnetic field between two magnetic materials acts as a
“virtual” mechanical spring.
Mann et al. design
fo = 5.12 Hz
Output power = 200 mW
Zhenlong Xu et. al.
Multi frequency hybrid VEH
(Piezoelectric+Magnetic)
fo = 22.8 Hz & 25.8 Hz
Output Power = 1.2mW & 2.57 mW
30

31. Electronic Tuning: FDH As An Example
FDH Voltage – Frequency
response for resistive load,
fc = 11.6 Hz, BW = 6 Hz
FDH Voltage – Frequency
response for 0.1uf capacitive load,
fc = 11.6 Hz, BW = 6.23 Hz
FDH Voltage – Frequency
response for 1000uf capacitive load,
fc = 10.52 Hz, BW = 5.88 Hz
FDH Voltage – Frequency
response for open loop,
fc = 11.95 Hz, BW = 5.8 Hz
31

32. VEH
Case Studies & Designs

33. Electromagnetic VEH Designs
 Wang et al.
fo = 48.58 and 146.72 Hz
Output power = 104 nW
Amirtharajah et al. 
fo = 94 Hz
Output power = 400 μW
33

34. Electromagnetic VEH Designs
Haroun et. al.
fo = 3.33 Hz
Output power = 113.3 μW
Moss et. al.
fo = 5.4 Hz
Output power = 33 μW
Halim et. al.
fo = 51 Hz
Output power = 110 μW
Choi et. al. 
fo = 20 Hz
Output power = 9.03 μW
34

35. Electromagnetic and Hybrid VEH Designs
(cont.)
Sari et al.
fo = 3.5 – 4.5 kHz
Output power = 0.4 μW
 Challa et al.
fo = 21.6 Hz
Output power = 332 μW
Minami et al.
fo = 5 Hz
Output power = 1.2 μW
Qui et al.
fo = 27.5 Hz
Output power = 16.47 μW
35

36. Electrostatic VEH Designs (cont.)
Boisseau et al.
fo = 50 Hz
Output power = 160 μW
Despesse et al.
fo = 50 Hz
Output power = 1052 μW
Tashiro et al. 
fo = 6 Hz
Output power = 36 μW
 Designed for
pacemakers
36

37. Field Disruption Energy Harvester
Side view of the FDH Top view of the FDHEl-Rayes et al. FDH
fo = 11.95 Hz
Output power = 21 µW
37

38. • The FDH generates electricity when the steel ball
is excited under external vibration, resulting in a
“disruption” to the stationary magnetic field from
the four magnets mounted on the side walls.
• This version of the FDH is capable of generating
21 µW at center frequency of 11.6 Hz and
bandwidth of 6 Hz.
Field Disruption Energy Harvester (cont.)
38

39. Newer version of the FDH can harvest center
frequency 7.19 Hz, with a harvesting bandwidth
3.32 Hz and output power up to 154 µW.
Field Disruption Energy Harvester (cont.)
39

40. Challenges In front of VEHs
New
materials
Magnetic
materials,
Electrets,
Piezoelectrics…
etc
Fabrication
Technology
MEMS,
Polymers, IC
technology
Form
Factor
meso vs. micro
scale, MEMS
(again).
40

41. Summary of VEHs
Parameter Electromagnetic Piezoelectric Electrostatic
Voltage Low
mV  <1V
Very High
V  10x V
High
10V  100x V
Current High
10x µA  100x mA
Low
nA  100x µA
Very Low
nA  µA
Power High
100x µW  <1W
Low
nW  100x µW
Very Low
10x nW  100x µW
Center Frequency Low
< 100 Hz
Low  High
1 Hz  5 KHz
Low
< 100 Hz
41

42. Corporates in the VEH business
42
Company Technology
MicroGen Piezoelectric
Lord MicroStrain
Magnetic,
Piezoelectric
Perpetuum Magnetic
Bionic Power Magnetic
PI Cermaic Piezoelectric
EnOcean Solar, Thermal, RF
Smart Material Piezoelectric
Company Technology
Meggitt smart
sensing Piezoelectric
KCF Technologies Thermal
AdaptivEnergy Piezoelectric
Micropelt Thermal
Perpetua Thermal
PowerCast RF
Flexous Piezoelectric

43. Thanks for your time 
Questions?
Karim El-Rayes® 2017
kelrayes@uwaterloo.ca
43

44. References
• “Prototypes of Field Disruption Energy Harvester”, K. El-Rayes,
E. Abdel-Rahman, R. Mansour, and E. El-Saadany.
• “Piezoelectric, solar and thermal energy harvesting for hybrid
low-power generator systems with thin-film batteries”, P.
Gambier, S. R. Anton, N. Kong, A. Erturk, and D. J. Inman.
• “Passive Full-Wave MOSFET Rectification for Electromagnetic
Energy Harvesters”, M. Yilmaz, B. A. Tunkar, S. Park, K. Elrayes,
M. A.E. Mahmoud, E. Abdel-Rahman, and M. Yavuz.
44

45. References (cont.)
• “A Novel Tunable Multi-Frequency Hybrid Vibration Energy
Harvester Using Piezoelectric and Electromagnetic Conversion
Mechanisms”, Z. Xu, X. Shan, D. Chen and T. Xie.
• “Investigations of a nonlinear energy harvester with a bistable
potential well”, B.P. Mann, B.A. Owens.
• “Self-powered signal processing using vibration-based power
generation”, R. Amirtharajah, A.P. Chandrakasan.
• “An electromagnetic micro power generator for wideband
environmental vibrations”, I. Sari, T. Balkan, H. Kulah.
45

46. • “Design, fabrication and performance of a new vibration-
based electromagnetic micro power generator”, P. Wang, X.
Dai, D. Fang, X. Zhao.
• “A non-resonant, frequency up-converted electromagnetic
energy harvester from human-body-induced vibration for
hand-held smart system applications”, M. A. Halim and J. Y.
Park.
• “Micro electromagnetic vibration energy harvester based on
free/impact motion for low frequency–large amplitude
operation”, A. Haroun, I. Yamada and S. Warisawa.
References (cont.)
46

47. • “Vibration energy harvesting using a spherical permanent
magnet”, S. D. Moss, G. A. Hart, S. K. Burke; S. C. Galea and G.
P. Carman.
• “Low Frequency Vibration Energy Harvester Using Spherical
Permanent Magnet with Non-uniform Mass Distribution”, Y.
Choi, S. Ju, S. H. Chae, S. Jun, S. M. Park, S. Lee, H. W. Lee and
Chang-Hyeon Ji.
• “Development of enhanced piezoelectric energy harvester
induced by human motion”, Y. Minami and E. Nakamachi.
References (cont.)
47

48. • “A coupled piezoelectric–electromagnetic energy harvesting
technique for achieving increased power output through
damping matching”, V. R. Challa, M. G. Prasad and F. T. Fisher.
• “Magnetoelectric and electromagnetic composite vibration
energy harvester for wireless sensor networks”, J. Qiu, H.
Chen, Y. Wen and P. Li.
• “Cantilever-based electret energy harvesters”, S. Boisseau, G.
Despesse, T. Ricart, E. Defay and A. Sylvestre.
References (cont.)
48

49. • “High damping electrostatic system for vibration energy
scavenging”, G. Despesse, J. J. Chaillout , T. Jager, J. M. Léger,
A. Vassilev , S. Basrour, B. Charlot.
• “Development of an electrostatic generator for a cardiac
pacemaker that harnesses the ventricular wall motion”,
R. Tashiro, N. Kabei, K. Katayama, E. Tsuboi, K. Tsuchiya.
• Vibrations Based Energy Harvesting, K. El-Rayes, E. Abdel-
Rahman: http://www.vlsiegypt.com/home/?p=845 &
http://www.vlsiegypt.com/home/?p=1677
References (cont.)
49