Deakin University: Power Generating Shoe Design from Walking Motion

This project report details the design of shoes capable of generating power from the motion of walking. The introduction highlights the need for energy harvesting devices and the limitations of existing methods, particularly in terms of metabolic cost and power output. The project aims to investigate electrical energy harvesting from foot motion, study piezoelectric power generation theory, and model an energy harvester to determine its efficiency. The literature review explores existing research on energy harvesting from human motion, focusing on piezoelectric energy harvesters embedded in shoes. The methodology includes the design of a sandwich structure featuring a thin layer for high compatibility with the shoe, the use of piezoelectric materials, and the application of mechanical energy to generate electricity. The report covers the theory behind piezoelectric power generation, the mechanical framework of the shoe design, and a SIMULINK model for the generator. It presents plots and results, followed by a conclusion and analysis of the results, discussing the feasibility and potential of the designed shoe for energy harvesting. The report also includes references to relevant research papers and studies.

Shoes design which can generate power
from the walking motion

Contents
1. Introduction........................................................................................................................................2
2. Aim and Objectives.............................................................................................................................3
3. Literature Review................................................................................................................................3
4. Harvesting of Electrical Energy............................................................................................................7
5. Producing Electricity While Walking.................................................................................................22
6. GENERATOR OF PIEZOELECTRIC POWER THEORY.............................................................................27
7. MECHANICAL FRAMEWORK.............................................................................................................29
8. GENERATOR OF PIEZOELECTRIC POWER SIMULINK MODELING......................................................30
A. Mechanical Energy:.......................................................................................................................30
9. PLOTS AND RESULTS.........................................................................................................................33
10. CONCLUSION AND ANALYSIS OF RESULT......................................................................................41
A. References.....................................................................................................................................42
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1. INTRODUCTION
Much research finds devices which can produce electricity. Much research is in the
energy harvesting field. They developed the devices during their daily tasks with less client
effort. While carrying the harvester, no foregoing study has focused on the metabolic cost. They
must determine the energetic effects. No energy harvester has the capability to produce
electricity less than 5W when the device carrying costs are high. Maintain a user effort to
produce electricity less than 5W. It is at an equal level or smaller than conventional power
generation methods.
In most vehicles, there is limited battery power, so they are not used for long trips. It is mainly
used for short trips. For charging batteries the builder of the vehicle uses an engine which uses
biodegradable fuels in high range vehicles. The requirement is that the extension must be high
and problems around surroundings must be very low. Electrical energy must be produced from
piezoelectric materials. Piezoelectric materials produce electric potentials must be the same as
that of forces. It is used for censoring and also used as actuators. The main use of piezoelectric
material is Sonar sound navigation in the year 1971. These attributes make the material for the
sensor which can be used to produce electricity. These materials convert electrical energy into
mechanical energy. Development of piezoelectric generator is difficult due to less sources such
as result is the appropriate power sensors. It leads to the final result such less energy, heavy
voltage, increased impedance etc. The result had been appropriate for sensors and other less
energy consuming products. The energy production in piezoelectric stacks must be illustrated by
scientists such as chok kea wboonchuay and pearson.
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Piezoelectric power harvesting generatorProcessing
Storage of Energy or on-board devices supply
Figure 1: Harvester of the piezoelectric structure framework (ozdemir, 2019)
In fig1. The picture represents the piezoelectric power harvesting model (ozdemir, 2019). The
mechanical energy in the system must be converted into electrical energy by energy harvested
block. The final result is voltage variation and it is corrected. The direct current to direct current
converter tries the present phase so the device for piezoelectric had fewer source features.
Onboard devices are devices that are attached on the motherboard. Primary memory, internal
disk drive and processor are the examples for onboard devices. Then the power is used in
onboard devices or for storing source.
2. AIM AND OBJECTIVES
The objectives of this research work are
To investigate the electrical energy harvesting from foot motion
To study the theory of the piezoelectric power generation
To model an energy harvester to find out the harvester efficiency
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3. LITERATURE REVIEW
The use of a human motion for mechanical energy is a great technique for getting sustainable and
clean electrical energy for powering sensors that can be worn. These sensors are used for a wide
range of tasks including gait analysis, activity recognition, and health monitoring among others.
The paper discusses a harvester of piezoelectric energy gotten from shoes during a human
motion to achieve parasitic mechanical energy. The specially designed harvester utilizes a
sandwich structure featuring a slim level of thickness so that it has high compatibility with the
shoe. Also, excellent durable and high performance are considered. The harvester offers a mean
power out of 1mW when walking at about 1 Hz frequency. Additionally, the harvester is
integrated with a circuit for power management towards supplying direct current electricity. The
direct current supply of power is tried by using a wireless transmitter simulation such that every
two to three steps will activate it so that it is active for 5ms every period, implying a 50mW
average power. This study shows how feasible it is to use harvesters based on piezoelectric
energy to drive sensors that can be worn.
There are various ways energy can be generated. However, one of the under-utilized
methods for the production of energy is mechanical energy. There have been few cases where
individuals could move an item and its reaction will generate energy to drive a small object. In
recent times, there have been a lot of innovations in terms of developing products that humans
could wear. Some of such items include smartwatches and other items with sensors. The sensor
can read some parameters of the body such as pulse and use it to interpret the current state of the
individual. The fact humans can wear these gadgets while carrying out their daily activities such
as running and walking has provided a great opportunity for mechanical energy to be exploited.
As opposed to stopping your daily activities and using mechanical energy to drive a fan that
could be easily powered by electricity or battery, you could instead, continue to do your daily
activities, while generating adequate power for some of the devices you wear.
A major activity human carries out on a daily basis is walking. Despite the presence of
cars and every other type of transportation medium, there is yet to be any indoor means of
transportation that can completely eliminate walking. This is coupled with the fact that walking
is encouraged as a means of exercise for health purposes. Considering the inevitable nature of
walking, this study has decided to leverage on it to create a harvester that can harvest mechanical
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energy when an individual is walking. The aim is to be able to use such energy to drive a device
that a person wears regularly. Figure 1 below shows the illustration of the different components
of the finished product.
Figure 1(a) shows the harvester’s sandwich structure
Figure 1(b) shows the film of the multiple layer PVDF
Figure 1(c) shows the force as applied with the foot for driving the top plate to move upwards
and downwards in a circular manner
Figure 1(d) shows the parameter of the design.
A method for optimization is used for the harvester’s design (Zhao and You, 2014). Furthermore,
the value parameter ranges, constraint conditions, and objective function will be determined.
When the top plate gets to its lowest spot, the tension of both the force of resistance F3 and the
film of the multiple layer PVFD F1 on the top plate developed by the film of the PVDF reaches
its highest. It is possible for the tension F1 to be written as:
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Where ɛ1 connotes normal strain and δ1 connotes normal stress. To make the description simpler,
the friction between the 2 wavy surfaces and film of the PVDF are ignored. The force of
resistance F1 can be gotten from a fourth equation.
Figure 2 below shows the force of resistance F3 against the top plate that the film of the PVDF
produces.
The amount of charges the film of the PVDF produced within the time the top plates goes down
to its lowest spot is the same as the number of charges that will be produced within the time the
top plates goes upward to its starting point.
A comparison was carried out between the suggested harvesters in this study and other
reported harvesters using PVDF energy that are embedded in shoes. It was discovered that the
suggested harvester has more benefits including excellent durability, high performance, and thin
geometrical form, due to the special sandwich structure design. The multiple-layer PVDF film
deformation is made to retain its elasticity and the highest deformation has close proximity to the
elastic limit of the PVDF. Hence, a tradeoff exists between durability and performance. The
mean harvester power, at 1Hz, reaches 1mW. This, at 1Hz, is approximately 1.1mW PVDF
insole power. Even though our design offers more durability and comfort, the design can be
further improved through the combination of the advantages of Prototypes 1 and 2 in future
research. The ribs and grooves of arc shape on top of the wavy surfaces that be manufactured
from harder material, such as polyurethane, to enhance the deformation of the PVDF film for
increased production of energy. The remaining plates parts are made from a flexible material so
that the shoe can be comfortably worn. Furthermore, adding to the layers of PVDF acts as a
different technique for performance enhancement
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A harvester for piezoelectric energy that can be embedded in a shoe was built in this
work (Ali and Ibrahim, 2012). Harvesting energy from human movement is possible when the
product is embedded inside the show. A test was carried out on the two different prototypes that
were developed. One of the prototypes was very comfortable to wear, while the other was able to
generate more power (Musirin and Sulaiman, 2015). The supply system for the direct current
power, such as a circuit for power management and a harvester, was utilized in collecting
mechanical energy from shoes for powering wearable sensors that required low energy to
function. An example of this type of sensor is the activity tracker (Turkmen and Celik, 2018).
Despite the harvester not being tipped to immediately replace the battery in all sensors that can
be worn, it can immediately play a great role in reducing battery-related problems. The study
presented a successful project that had the ability to harvest energy, which can be used to provide
energy for sensors that can be worn, from normal daily activities of individuals.
4. HARVESTING OF ELECTRICAL ENERGY
There are a lot of reasons why alternatives for the use of the battery is being considered.
Despite the increased technology in the production of batteries and the different types of batteries
available, there are still a number of limitations that the use of batteries portends. First of all,
batteries are not very reliable. This is because they could run down at that moment when you
need it the most. You will subsequently have to forfeit the functions of the device it is powering
till you are able to replace it. There is also the problem of environmental impact, where the
toxicity of its materials such as NiMH could be a matter of concern. There is also the issue of
cost, as the cost of buying, charging and replacing batteries could be reduced. This is in line with
about 60 percent mean yearly energy costs savings and 40% mean yearly cost of energy for
lighting saved by avoiding the use of the battery. It is based on these premises, that the use of
other ambient energy harvesting is also being considered as a great way to save cost,
environmental impact and enhance reliability (Batra and Alomari, n.d.).
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A wide range of sources for ambient energy has been identified. The identified sources
include the thermal and mechanical energy gotten from the body of animals and humans as well
as from natural sources of energy such as solar, wave, hydro and wind. Other sources of ambient
energy is mechanical excitation such as induced mechanical strains and stresses as well as
machine vibrations, energy from low-grade thermal such as heat energy lost from frictional
losses, heaters, boilers and furnace among other, light such as solar and artificial as well as
electromagnetic energy such as transformers, coil and inductors (Eliot, 2016). The diagram below
depicts the characteristics of these ambient sources of energy (Nishi et al., 2016).
Figure 1: Harvesting of energy and associated technologies such as rectenna,
thermoelectric, solar photovoltaic cell and vibrational micro generator, that can be potentially
applied in ICT equipment as well as assisting devices. (Gotten from Fujitsu Laboratories Ltd,
http://www.fujitsu.com/)
Even though it is most likely impossible to a particular source of power to be used to power
everything, it is great that there are many different options that can be chosen depending on the
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need and the characteristics of the energy source that fits the most. For instance, there are some
concepts that have been created in line with ambient energy harvesting. Some of them are:
 Storage battery for Solar heated thermal explained as the place where the accumulation of
solar heat takes place in storage for thermal energy
 Inductive coupling explained as a tested configuration that includes insulated wires of
copper that travel for a system on and parallel to the two transmission system sides’ right
of way.
 Human effort output is needed for the achievement of higher potential performance given
by the data in the table below. For every physical activity, the endurance of human is an
inverse mechanical output function.
Table 1: Basic density of ambient energy power sources
A major thermoelectric energy element is the fact there is a different in temperature available, as
well as the heat flow, form the hotter part to the colder part (Zhao and You, 2014). Finding the
difference in the arising temperature is easy from different sources of thermal energy (Ibrahim and
Abdelaal, 2013). For instance, heat as a result of the sun as well as releases of energy from thermal
processes including manufacturing processes and automobiles as well as the heat that results
from the activities of humans. It is possible for such heat to be utilized in the production of
electricity through the use of several transducers including photovoltaic cells, materials for phase
change (PCM) as well as thermoelectric couples.
Harvesting energy from heat from PCM requires high fusion heat so that it is possible for it to
solidify or melt when certain temperatures are achieved as well as being capable to release or
store high heat energy quantity gotten from the changing state. The PCM materials are of three
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types, they include: liquid – gas where the PCM transform to gas when it absorbs heat and
transforms back to liquid when heat is lost, solid-liquid where the PCM changes to liquid when it
absorbs heat and changes back to solid when heat is loss as well as the solid-solid PCM where
the materials transform from one structure of crystalline-based on its lattice configuration to
another when heat is absorbed and transform back to the former when heat is lost.
The PCM has potential smart and energy applications such as using clothes or fabric to
externally induce the temperature of the human body from the understanding of the
transportation of moisture, temperature, thermal comfort and temperature regulation through
layers of clothing. It also includes the regulations of temperature in buildings towards reducing
the effect of heat from rays of the sun.
It was observed that clothing that contains PCMs have thermal properties that are different from
conventional clothing since the clothing with PCMs has the ability to release and absorb latent
heat, as opposed to conventional clothing that uses on sensible heat. This technology has been
utilized in the creative of clothing limits for protecting heat dissipation from the body. For the
body temperature to be maintained there must exist a balance between heat loss and heat
production. For building, the need to maintain the internal temperature at a degree that is
comfortable to the inhabitants is important. As a result, people invest in heaters and ACs that
consume a lot of energy. However, the use of PCM for cooling of buildings is being considered
as a way of decreasing heat transmission that enters the building to be from 47 percent to 72
percent lower. The research that has been carried out along this line has worked effectively,
leading to a reduction in the temperature of the building compared to when they were not used. A
great advantage of this is that the thermoelectric devices does not need any part to be moving for
the production of energy. This is thus, making it a popular option in harvesting energy.
Energy harvesting for assistive and mobile applications
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Harvesting power
When two metals with different properties are connected and heated at different temperatures, a
potential difference is causing electrons to move. a process referred to as "Seebeck effect”. Tec a
transducer that converts heat power to voltage depending on the "Seebeck effect. Connect 33
thermocouples in series, to come up with a commercial generator can be connected in series to
produce commercial micro generators. Thermocouple materials are either n-type or p-type with
huge Seebeck coefficient that varies directly to temperature difference. To reduce heat, CMOS
process can be used, Yang et al (44). The increases the device power. Micro generators typically
produce 9.4W at a 15k temperature difference.
Using TEGs to harvest Human body heat.
Carbohydrates, fats, and proteins make up the human body. 15 -30% of power dissipated from
the body and lost to the surroundings. Human power depends on the level of body heat emission
that relies on human activity and posture as depicted in table 3.
Table 3. The power released from a person’s body in the form of heat when carrying out various
tasks (adapted from Reimer and Shapiro
Power (W)
Activity Total Sensible Latent
Sitting and resting 100 60 40
Writing or doing light work while sitting 120 65 55
Eating and sitting 170 75 95
Trekking at 1.5m/sec 305 100 205
Lifting or other strenuous tasks 465 165 300
Athletics 525 185 340
Data important as it informs the foundation upon that power harvesting technologies can be used
to power electronic devices. Above table indicates how the output from human effort can be used
to higher performance (ozdemir, 2019). Thus the higher the power emission the higher the
performance of the device. Fig. 6. Indicates how human skin temperatures vary with differing
room temperatures that range between 5-10 degrees Celsius. Some contend that TEC best for
harvesting body temperature due to its miniature size and weight that makes it easier to be
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