1. Shendu Ma and Michael Mansour; Zixin Zhang and Mengbi Yao; Shih Wei Yan Daphne and Keong Loong Fuo
Department of Mechanical and Industrial Engineering, University of Toronto; Department of Energy and Resources Engineering, College of Engineering, Peking University; National University of Singapore
Energy Harvesting from Human Locomotion
Acknowledgments
Prof. Hani Naguib from U of T for sponsoring this project.
Prof. Hani Naguib and Prof. Pingchou Han from PKU strongly
providing technical instruction and suggestions. Prof. Michael
Munro and Prof. Kamran Behdinan for organizing and
communicating of the international capstone program. Ms.
Matthesa Gregg for help in logistic of all activities. Ms. Faezeh
Heydari for communication instructions.
Conclusions
• The potential of piezoelectricity as well as the still
developing triboelectricty are feasible and practical for
harvesting energy from human locomotion.
• Efficiency of such devices is closely related to the design
parameters.
• Mass production and manufacturing of such devices requires
more professional and detailed economic, societal,
environmental and regulation analysis.
Concept Generation and Selection
“The Black Box” Method:
Functional Decomposition:
Project Requirements
Problem:
• Solve the self-powering problem for biomedical micro-
devices such as a pacemaker, blood pressure monitor, insulin
pump etc.
• Not only complete a design for powering micro-devices, but
also provide feasible ideas in renewable energy generation
using human locomotion.
Scope:
• Target power generation in the range of 1-10 μV
• Mass production and manufacturing not included
Stakeholders:
• Client -- Prof. Hani Naguib
• Potential Users
• Researchers and developers in related field
• Engineers’ Society and other organizations
Functions:
• Must harvest energy from human locomotion
• Must convert other forms of energy in human locomotion
into electrical energy.
• Must allow other micro-devices to use the energy it
harvests.
• Must be able to store the unused energy it harvests.
Objectives:
Portable, Durable, Efficient, Accessible, and Low Cost:
Constraints:
• The design shall cost less than $50.
• The design shall be lightweight and weigh under 750g.
• The design shall not obstruct/interfere with regular motion
of carrier.
• The design shall be compliant with government and health
regulations, design procedures and local bylaw.
Final Design Concept
Basic Concept:
• V slider receives impact from foot strike in vertical direction
• H-sliders provide forces in horizontal direction
• Horizontal force delivered to comb clamper to evenly
deform the bimorphs
• Clamped bimorphs are supported at their mid-points
• Bimorphs deform symmetrically
• Fixed-to-guided end of bimorphs further extend its
deformation
Theoretical Background – The “Plucking” Method:
• Initial impact induces low frequency vibration of
mechanical energy transfer unit
• Mass and spring system amplifies vibration to higher
frequency
• Vibrating beams attached with piezoelectric elements
composite of secondary vibrating units
• Double-beam / single cantilever system amplifies impact
from the mechanical energy transfer unit into higher
frequency
• Optionally, permanent magnet couples increases vibration
frequency
• Increase efficiency from original PZT bimorphs up to 900%
Triboelectric Layer – Optional Attachment
• Currently under research stage, components not
commercially available.
• With the potential of increase power generation of 25% to
34% (power density addition of 313 W/m2)
Functional Unit and Analysis
Assumptions and Simplifications:
• Functional Unit: PZT Bimorph + fixed-to-guided beam
structure
• Dimension: 50mm by 50mm in size for the entire structure
• Load: at least 4 units are needed for the minimal power
generation, one person weighs 600N, load=100-200 N/unit
Design of Experiment (DOE)
• Control Factors (CFs):
• A: Square plate dimension (mm)
• B: Length of the beam (mm)
• C: Number of beams
• Noise: Vertical force on structure (N)
• Experiment Option: Taguchi Experiment
• Find optimal parameter settings
• No interaction between CFs and Noise
suspected
• DOE Matrix
Finite Element Analysis (only 1 pair of comparison sampled)
Experimental Results
Tabulated Results
• D=displacement response; E=electrical potential response;
σ=stress response
• Columns in white background represents responses with
Fz=100N
• Columns in black background represents responses with
Fz=200N
Main Effect Plots
Optimized Parameters for the Model:
• Plate dimension = 150mm x 150mm;
• Beam Length = 75mm;
• Beam Number = 4.
ENERGY:
1. Kinetic Energy
2. Change in Elastic
Potential Energy
3. Change in Gravitational
Potential Energy
INPUT “The Black Box”
DESIGN
OUTPUT
MASS:
No mass input related to
function
INFORMATION:
1. When to start energy
harvesting
2. When to stop energy
harvesting
3. How much energy is
available to use
ENERGY:
Electrical Energy
MASS:
No mass output related to
function
INFORMATION:
1. Indicate when the design
is turned on for energy
harvesting.
2. Indicate when the design
is at rest.
3. Indicate how much
energy is harvested.
Energy
Harvesting
System
Convert Energy
from other forms
into electrical
energy
Supply power for
micro-devices
Store the energy it
harvested
Material or mechanism that
allows energy conversion
Allow micro-devices to access
the energy harvested
Energy is able to be stored
through material or
mechanism for a period of
time and allow instantaneous
consumption to start at
anytime
Figure 1. Final
Design Concept
Drawing: Foot strike
is applied directly
onto the V-slider.
PZT Bimorphs are
supported through
fixed-to-guided beam
to further amplify
human locomotion
frequency
Fig. 3. Illustration of
Triboelectric Layer:
This layer is
optionally placed on
top of the V-slider in
Fig. 1.
Triboelectric layer
further increases
energy harvesting
efficiency by power
generation from
friction.
Figure 2. Illustration of How the “Plucking” Method Amplifies Lower Frequency of Human
Locomotion to Higher Frequency of Power Input.
Left part is the common type of two-stage mass and spring amplification structure.
Right part is the optional cantilever plus magnet structure.
Figure 4. Functional Unit Drawing.
deff =d33 –Ad31
Figure 5. Governing Formulas for the Force
and Voltage conversion of the Piezoelectric
Bimorph Beam Structure and the Effective
Piezoelectric Coefficient.
Matrix Entry Factor A Factor B Factor C Noise
Detail
Square Plate
Dimension (mm)
Length of the
Beam (mm)
Number of
Beams
Vertical Force
(N)
Level 1 100 25 2 100
Level 2 125 50 4 200
Level 3 150 75 8 N/A
Figure 6. Displacement Responses for 4 Beam and 2 Beam Structures.
Figure 7. Electrical Potential Responses for 4 Beam and 2 Beam Structures.
Figure 8. Net Stress Distribution Responses for 4 Beam and 2 Beam Structures.
Run
Plate
Dimension
(mm*mm)
Beam
Length
(mm)
No.
of
Beam
D (mm) E (μV) σ (kPa) D (mm) E (μV) σ (kPa)
1 100 x 100 25 2 0.604 2.05 115.3 1.222 4.23 145.6
2 100 x 100 50 4 0.440 2.36 81.2 0.879 4.64 172.3
3 100 x 100 75 8 0.713 1.89 97.3 1.405 3.79 198.6
4 125 x 125 25 4 0.395 1.74 58.9 0.790 3.20 135.6
5 125 x 125 50 8 0.607 1.65 64.1 1.139 3.15 128.9
6 125 x 125 75 2 0.974 2.76 209.8 1.908 5.64 436.8
7 150 x 150 25 8 0.345 1.43 45.2 0.812 2.97 100.4
8 150 x 150 50 2 0.856 2.23 234.6 1.923 4.56 475.1
9 150 x 150 75 4 0.687 2.98 250.6 1.396 6.02 500.3
Figure 9-11. Main Effect Plots for
Means of Reponses in Displacement,
Electrical Potential and Net Stress
Corresponding to CF A, B, and C .
Conclusion is that Beam Length has
highest impact on performance while
plate dimension has smallest impact
on performance
Key Citations
• Wang Z L. Triboelectric nanogenerators as new energy technology for self-powered systems
and as active mechanical and chemical sensors[J]. ACS nano, 2013, 7(11): 9533-9557
• Wu T T, Wang S H, Yao W S, et al. Analysis of high efficiency piezoelectric floor on intelligent
buildings[C]//SICE Annual Conference 2010, Proceedings of. IEEE, 2010: 1777-1780.