Shendu Ma and Michael Mansour; Zixin Zhang and Mengbi Yao; Shih Wei Yan Daphne and Keong Loong FuoDepartment 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

AcknowledgmentsProf. 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 RequirementsProblem:• 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 ConceptBasic 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 AnalysisAssumptions 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

DetailSquare 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.