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Josh Feshari and Sergio MateoJames Madison University

5/5/2016

2016Applicability of Piezoelectric Energy Harvesting on JMU’s Campus

Applicability of Piezoelectric Energy Harvesting on JMU’s

CampusBy Sergio Mateo & Josh Feshari

James Madison UniversityMay 5, 2016

Under the faculty guidance of Tony D. Chen, Ph.D.

Submitted by:

Sergio Mateo

(Signature)

Josh Feshari

(Signature)

Accepted by:

Dr. Tony Chen Tony Chen(Signature)

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AbstractThe goal of this project was to visualize and understand the potential

impacts of a piezoelectric energy harvesting system. There are a lot of potential impacts this system could have that haven't been tapped into fully by society. Effect on the environment, energy efficiency, and economic impact to society were the main areas of focus when conducting this project. Environmentally the system could reduce pollution because of its clean way of producing energy and offer many alternatives to fossil fuel consumption thus reducing the carbon footprint. The system produces voltage and thus energy (within a proper circuit) from deforming piezoelectric materials; this is a system not needing any external energy resource but produces high grade energy as electricity. Understanding that it is beneficial for the environment and has untapped potential energy uses this system would have a very positive impact on a society's economy. Implementing the piezoelectric energy harvesting system could reduce bills for power and those savings can be put towards investing in more sustainable technologies.

The study began with simple testing of functionality of the piezoelectric generators and then circuits were built to produce the most power output. Circuits created were connected to a battery and from different amounts of pressure/ force being applied to the connected generators they would charge the battery to full capacity. This battery once charged would be able to charge other devices such as a cell phone or other electronics at a bus stop or be utilized in a car. Although the study was small scale the data collected would then allow for assumptions and estimations to model out the impact on a bigger scale such as the James Madison Campus or a small city.

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Table of Contents

Abstract 2

Table of Contents 3

I. Introduction 4

II. History 5

III. Piezoelectricity Concept 7

IV. Methods 9a. Piezoelectric Constant g33 9b. DaqLab 11c. Rectifying Circuit 13d. Mat Construction 14

V. Data Collection and Reduction 16VI. Environmental Impact 19VII. Business Potential 21VIII. Conclusions 22IX. Acknowledgements 23X. References 24

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I. IntroductionFossil fuels are a finite resource and yet comprise over three quarters

of the global energy consumption. They are not only finite but they also produce greenhouse gas emissions when used as a fuel source. This has led to the world searching for a more sustainable solution to the global demand for energy. The answer is in the renewable sector of energy production and more specifically the modern renewables such as solar, wind, geothermal, hydropower, etc. The energy is used primarily for electrical power generation but also is utilized for industrial, residential/ commercial, and transportation purposes also. The technology and ideology is available today to fix the problem, issues with efficiency and differences in regulation globally are the main factors delaying the growth of sustainable practices. A sustainable answer is available to decrease reliance on fossil fuels and increase reliance on modern renewables and its piezoelectric energy harvesting. This study will focus on proving the piezoelectric theory and analyzing the benefits of implementation of a piezoelectric energy harvesting system. Materials will be gathered for construction of a mat to measure energy generated based on foot and vehicle traffic on James Madison’s campus. Once a circuit is properly configured that rectifies a proper output of electric voltage and current the mat will be tested. Recommendations for implementation will be made based on environmental impacts and economic potential will be made suing results from testing. Conclusions will be drawn on the applicability of implementation of a large-scale piezoelectric energy harvesting system on James Madison’s campus.

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II. HistoryIn the middle of the 1800s, Carolus Linnaeus and Franz Aepinus

observed that certain materials generate electrical charges when exposed to temperature changes. Jacques and Pierre Curie further researched these materials, primarily crystals and ceramics, as they initiated Piezoelectricity as a research field in crystal physics in the late 1800s [1]. Through their research, they found that tension and compression result in electric voltages of opposite polarity and that these voltages were directly proportionate to the applied force. These characteristics, recognized as the piezoelectric effect, were especially evident in crystalline minerals such as tourmaline, quartz, and topaz.

Following World War I, Joseph Valasek discovered the ferroelectric phenomenon. Ferroelectric materials exhibit multiple phases across a temperature range that allows the individual polarization to change through the use of an electrical field [1]. This means that below certain temperatures, ferroelectric materials possess a spontaneous polarization or electric dipole moment that can be reoriented of reversed fully. This lead to the discovery that ceramic materials modified by additives, such as sintering metallic oxide powders, resulted in their ability to store electrical energy in electrical fields (dielectric constant) increasing 100 times higher than common ceramics [1]. This class of materials were called ferroelectrics and made to show improvements in piezoelectric properties. These discoveries lead to the

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further research in the field and the development of multiple piezoelectric ceramic with performance improvements and piezoelectric devices.

Between 1940 and 1965, there were a number of successful materials manufactured. The first being the mixed oxide compound barium titanate BaTiO3. Because barium titanate was easy to fabricate and could be molded at a low cost, it became the focus of studies with other materials soon to follow in 1945 [1]. With the fabrication of these materials, successful results were produced. Results in that period include:

Perovskite crystal structures with electrical-mechanical activity Developing families with metallic impurities to get specific

properties such as dielectric constants, material feel, durability, and piezoelectric constants

The development of the Lead Ziconate titante family

Early challenges for piezoelectric materials was a high failure rate in the field. Piezoelectric sensors were prone to breaking relatively easily when outside of the optimal resonance unless dampening measures were taken. Other challenges with piezoelectric materials includes matching impedance coupling of an energy source and the transfer from a transducer to the recovering electronic. But in recent years, power requirements of small electronic compounds have reduced making piezoelectric sensors a more applicable option considering advances in material manufacturing. This means that piezoelectric sensors are an ideal alternative for low energy consuming products such as low light fixtures and ac motors.

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III. Piezoelectric ConceptThe formation of an electric output from a mechanical deformation

input is the piezoelectric theory and can work in reverse, an electrical impulse as an input can cause a mechanical stress as an output [2]. Piezoelectric sensors produce an electrical charge from a deformation in shape meaning the voltage produced is directly proportional to strain or force exerted on the sensor. This effect is used in a wide variety of apparatuses and has a limitless potential when it comes to energy harvesting [2]. It is used is a vast array of devices from electronic frequency generation to quartz in modern wristwatches.

The piezoelectric material is a combination of four elements interacting in a way that allow for this effect to be possible. The chemical formula for the piezoelectric element used in this study is Lead Zirconate Titanate (PbZr0.52Ti0.48O3) an intermetallic inorganic compound comprised of Lead (Pb), Zirconium (Zr), and Titanium (Ti) metals, and Oxygen (O) a gas [1]. This compound that is insoluble in all solvents does not only produce the piezoelectric effect but also is ferroelectric meaning it has spontaneous electric polarization [1]. This property allows the polarization to reverse in the presence of an electric field as illustrated in Figure 1, which is why the piezoelectric effect works in both directions as seen in the figure below.

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Figure 1 The image above shows the two different inputs and outputs for the piezoelectric effect using the Lead Zirconate Titanate material. This phenomenon is caused by the ferroelectric property of the compound.

Works very similar to a photovoltaic array or cell just a mechanical input instead of a solar one. The piezoelectric effect works with frequency and vibration appliances as well and is being researched for more potential. This element allowed for the data collection used to test our hypothesis.

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IV. Methods

IV-a. Piezoelectric Constant g33

Using a digital multi-meter and balls of a known mass, a table (as seen in Figure 2) was constructed which shows the relationship between difference forces and the voltage generated on a single piezoelectric harvesting sensor. In gathering data, 10 trials were completed on each mass quantity. The distance of the drop was also held constant throughout each

trial.

Figure 2 Table shows the different voltages recorded with consistent forces applied Listed is data for a wooden ball along with, three different sized metal ball.

After each trial was completed at varying weights, the data points were inserted into a graph to find the linear characteristic line. With the insertion of each point, the linear equation was calculated using Excel as shown in Figure 3. The slope of the equation shows the relationship between the voltage and force exerted. This value was used as the Open Circuit value in the g33 calculations completed later on.

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Figure 3 The slope shows the linear relationship between the Force generated and the Voltage. It also enables us to calculate the g33 constant for our piezoelectric material.  

For the g33 Constant calculation, the contact area between the weight and sensor had to be found. The reason being because the weight used does not come into contact with the entire surface area of the sensor [2]. To calculate the contact area, playdoh as shown in Figure 4 was used. The playdoh was used to see the indentation of the ball when dropped on a flat surface. Taking the radius from the indent, the contact area was calculated

usingA=π r2 .

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Figure 4 Shows screenshots of the experimental procedure with the playdoh with the contact area indicated by the yellow circle. From the indent indicated was used in the area calculation.

This process was completed to find the contact area for all of the weights because each had vary contact areas. Averages across the different areas were used in the g33 equations for the most accurate results.

IV-b. DaqLab

DaqLab® is a computer program that is able to record a variety of data entries simultaneously over time via Omega OM-DaqPro-5300 data logger. DaqLab was used to calculate Voltage & Current vs Time over a 1-minute period with constant motion on a single sensor set (two sensors per set). The Program is able to show the changing values by taking one data point per second as shown in Figure 5.

Figure 5 Depicts the relationship between Voltage and Current against time. As shown through the graph, the peaks and trough of both lines alternate. The peak of the voltage aligns with the trough of the current and vice versa.

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With the voltage and current values, the power generated can be found over the same 1-minute interval as shown in Figure 6. From the equation P = I × V, the power at each second is calculated in Watts. In recording the data, the force exerted on the sensors varied depending on the steps taken. There were standard steps, hard stomps, and quick shuffles taken within the minute in that order as shown in Figure 7. Averages from the data below were used in the per person and daily energy production calculations.

Figure 6 Graph shows the graphed power calculations from the Current and Voltage values. It was from this data that the average watts generated per step was taken. The averages were only of the values above zero because values at zero were instances where no steps were taken.

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Figure 7 Shows the steps isolated from one another. The steps circled in red were regular steps, the steps circled in yellow were stomps, and the steps circled in purple are quick shuffles.

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IV-c. Rectifying circuitDesign of the circuit as shown in Figure 8 was based on research of the

piezoelectric element utilized in this study. The circuit needed for a piezoelectric element/ sensor was called a rectifying circuit meaning it converted an input of AC voltage into an output of useable DC voltage, and also turned all the negative current to positive current. Once this was established the pieces that fit into the rectifying circuit were collected. For the circuit to work there needs to be an input, four zenith diodes, a capacitor, and a battery (or LED). The circuit configuration can be seen in the schematic below.

Figure 8 The schematic depicts the rectifying circuit used in this study. The squiggly line to the left is the piezoelectric element, the segmented lines with triangles are the four zenith diodes, the segment with the parallel lines is the capacitor, and the positive and negative signs along with the rectangle at the end are the battery.

Once all the pieces to the circuit were gathered it was assembled on a breadboard in series the same way the schematic depicts it above. The circuit was then tested using one piezoelectric element. The piezoelectric elements were then paired two at a time in parallel and each pair was tested for functionality. After seeing conclusive evidence the circuit was operating correctly the pairs of piezoelectric elements were put together in series in

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sections as can be seen in the matt construction and then tested again at each stage of production of the matt.

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IV-d. Mat ConstructionIn constructing the mat, the first step was creating piezo sensor sets.

Each set consisted of two individual piezo sensors with a positive and ground wire. Each set was soldered together, the positive of the two being linked and the negative being linked separately. Following soldering, each set was tested to confirm its functionality and reduce error. The sets were aligned to be soldered onto copper wires. Copper was chosen because it had the lowest variable resistance of the options available. The positive line from each set was soldered onto one copper line and the negative line from the set was connected to another, separate copper line. The connections were made using Rosin-Core material as shown in Figure 9.

Figure 9 Above is the Piezo-sensor sets soldered to individual copper lines. The lines were kept isolated from one another to prevent a short circuit in later testing.

With four positive and ground line sets made, implementing them to a mat followed. The base of the mat was made of particleboard. Particleboard was used because it is easy to cut, reshape, and is a durable material. Five smaller individual particleboards were placed on top of the base, each separated by a half inch and secured with wood glue. This was done to have

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a level mat once the copper lines with the piezo sensors were attached as shown in Figure 10. The lines were set in the half-inch gaps, and the sensors were secured on the individual particleboards. Roughly, ten sensor sets were attached to the lines with five sets on each side. The sensors were secured using electrical tape and glue.

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Figure 10 Shown are the sensor sets in line with the particleboards. Gaps were left on each side of the individual boards to allow for the copper lines to pass through the mat with no exposure.

Once the lines were implemented, the final step in the construction was covering the sensors with a rubber mat. This was done to protect the sensors and to cover the individual lines as shown in Figure 11 below. The circuit was purposely left out of the mat to leave both the mat and circuit open for alterations.

Figure 11 Shows the completed exposed board. The rubber mat was secured on top of this set up in testing and data collection.

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V. Data Collection and Reduction The piezoelectric harvesting sensor used in the experiment and for

data collection is made up multiple thin layers of piezoelectric material [4]. These materials are mechanically connected in series and electronically connected in parallel. When force is applied to the stack, there is a voltage generated called the open circuit voltage as shown in Equation 1 below:

V psg=g33×t ×F

A (1)

In Equation 1, g33 is the piezoelectric constant for the material for when force is applied in the same direction the material is poled, in this case being vertical [4]. A is the surface area of the piezoelectric material, but only the area of the material coming into contact with the force applied. t is the total thickness of the piezoelectric material while F is the force applied to the stack.

m=g33 tA

(2)

Using data collected, the Open Circuit Voltage equation can be adjusted. Instead of using the open circuit voltage recorded directly from the digital multi-meter, the Vpsg is replaced with the slope (listed as m in Equation 2) of the graphed data points. The slope is used because it shows the direct linear relationship between the different forces applied and voltages generated:

2.6656 VN

=g33 (0.00051m )1.14×10−4m2

(3)

With the data in hand, the values are input into Equation 3 above and the g33 constant is found. But this piezoelectric constant calculated in the

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way is only for the material used. To compare this materials piezoelectric capabilities to others, it would again have to be multiplied by the thickness. The reason being because other piezoelectric materials constants are rated in relation to the entire area of the material. In doing so, the values below are generated in Equations 4 and 5 below:

0.59584 v−mN

× (0.00051m )=3.04×10−4 (4)

g33=3.04×10−4 V−m2

N (5)

Equation 6 below is the energy harvested per person on one piezoelectric sensor set, comprised of four sensors. Energy is the average Watts generated per step. The average Watts per step being generated from the data collected from Figure 6. Continuous movement is the time over the course of a day that that the mat would be generating energy with little to no interruption over an 8-hour period.

Energy Harvesting Potential ( per person )

¿Energy× Steps onMatPerson

×Sensor Sets×Continuous Movement (6)

Inserting the 0.037 average milli-watts generated the 1.5 average numbers of steps taken on the mat per person, the 20 sensor sets and the time of continuous movement the following value is calculated. The 2 hours of continuous movement was calculated by assuming there is constant traffic on the mat during 15-minute class intermissions in the building. In an 8-hour day, the total energy harvested per person can be calculated from Equation 7 below.

E=(0.037 mWStep−Sensor set )×(1.5 Steps onMatPerson )×20 senser sets×2hrs

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¿2.22mW−hrsPerson (7)

Equation 8 can be employed to find the energy harvested per day, the total number of people engaging the mat is multiplied by the energy harvested per person. The 4,500 people per day is an assumed number for the total of people. This number also accounts for people that may step on the mat multiple times a day.

Energy Harvesting Potential ( per day )=mW−hrsperson

× Personsday (8)

Inserting the values calculated in Equation 8 gives us a total of 9.9 Watt hours per day as shown in Equation 9 below.

E=2.22mW−hrsperson

×4500 Personsday

=9,900 mW−hrsday

∨9.9 W−hrsday (9)

The 9.9 Watthours per day is an estimated total given the single step power generations. This also assumes that the same force is being applied to every sensor set resulting in the same wattage being generated at each set across the mat.

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VI. Environmental ImpactsGlobal energy demands have skyrocketed in the past several decades

due to population growth and increased industrialization. Fossil fuels are finite and envelope over seventy-five percent of global energy demands as seen in the figure below. Renewable energy is going to have to increase in its percentage of the energy share of the globe or fossil fuels will run out. The renewable energy sector is a mixture of modern renewables and traditional biomass. Piezoelectricity falls under the modern renewable portion and has an opportunity to increase exponentially in the coming decade.

The need for a more sustainable way to produce energy is an impending concern. Piezoelectric energy harvesting offers a viable solution because it’s a clean and green technology. Other than the production of the materials to make the sensors there is no emissions to the air or pollutants to the water associated with piezoelectric energy harvesting. One of James Madison University goals is to become a net zero greenhouse gas emitting school and community, and their efforts can be seen with green roofs and sustainable building practices around campus. This can be achieved by utilizing the piezoelectric technology. For instance all the impermeable

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surfaces on campus can be revitalized and serve a greater purpose than to just disturb runoff. On the James Madison campus there would be no disturbance to the current infrastructure because all impermeable surfaces that have foot or vehicle traffic on them can be utilized by incorporating a piezoelectric energy harvesting system beneath. Streetlights, caution signals, and other apparatuses requiring electricity around campus could be powered by campus operating like normal with the amount of student and faculty, foot and vehicle traffic each day.

Piezoelectricity is an opportunity to constantly generate electricity without using a fuel as an energy source to produce it. This allows for a significant reduction in use of fossil fuels thus reducing the amount of emissions to the air and water. No system has been developed that is large scale and can run sustainably on just renewable energy. Some fossil fuel energy will have to be utilized in any process, the goal is to substantially decrease that usage of fossil fuels until there is a viable solution that doesn’t include them. With reduction of emissions and clean power generation more and more benefits arise such as energy and cost savings.

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VII. Economic PotentialEconomic decisions are constantly being made especially at

Universities over their energy demands and usage. Any opportunity to save is taken into consideration and usually the more cost-effective route is chosen. Currently James Madison University receives most of its electric power from utility companies that produce their electricity predominantly from burning coal. This means James Madison University pays for most of its electrical power generation around campus. Utilizing a piezoelectric energy harvesting system would help the Universities’ campus in the following ways.

First this technology has the possibility to offer tax breaks similar to those offered by government agencies for photovoltaic solar arrays. The government tries to reward parties if they are being environmentally responsible by implementing green technologies. Not only is money saved by James Madison but also recognition is received from local, state, and/ or federal government agencies.

Second the potential to save money on utility bills because of piezoelectric system is generating energy and all that is unused charges a battery that can be stored for later. Not only would monthly billing prices decrease but also if enough energy was produced by the installed system there is a chance of selling power back to the grid. Receiving a monthly bill with earnings instead of having to pay a monthly bill increases income that the University can use in other areas of development.

Lastly, given both the benefits presented above, James Madison would have more money to spend on other university facilities. Tuition rates could be lowered allowing for more students to apply and also be able to attend school. Less money would be needed from donors and more projects could be underway such as the new convocation center and new D-hall. Not only would infrastructure benefit but education would as well with implementation of a piezoelectric system.

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Money is the root of most decisions especially ones made at the University level that affect the University. Implementation of a piezoelectric system may be expensive but the benefits are limitless. Environmentally friendly energy generation along with saving with the opportunity to make money is the best and most cost effective decision for a University trying to achieve net zero greenhouse gas emissions.

VIII.ConclusionsFrom the calculations completed, an estimated 9.9 Watthours per day

was generated from the piezoelectric generation mat. Though 9.9 Watthours isn’t very much, the potential is there. If materials that are more efficient were used and the piezoelectric mat is constructed on a larger scale, a higher production of power would be possible.

On a larger scale, piezoelectricity could be used for a multitude of uses. Lighting and power storage being the most feasible. Harnessing power into a battery would further open doors of applications in society. Piezoelectricity has the potential to indirectly save money and lessen the strain our energy needs have on the environment.

In furthering study into the applicability of piezoelectricity of JMU’s campus, there would be more research required. Along with improved materials, researching the largest amount of foot traffic would greatly benefit the power output. Roadway applications are also an option considering the increased voltage generated from a higher force from automobiles.

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IX. AcknowledgementsWe would like to thank Dr. Tony Chen for his guidance throughout the

entire course of this project. We would also like to thank the ISAT department and JMU Machine Workshop for assistance and advice. Without any of you, this project would not have been possible.

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X. References[1] “Dynamic Fracture of Piezoelectric Materials”, Chapter 2, 2014 Springer

International Publishing.[2] Sodano, H.A, Inman, D.J, & Virginia Polytechnic Institute and State

University. (2005). Journal of Intelligent Material Systems and Structures: Comparison of Piezoelectric Energy Harvesting Devices for Recharging Batteries.

[3] Energy Floors Limited (Sustainable Dance Club Subsidiary). Sustainable Energy Floors Information Leaflet

[4] Priya, S., & Inman, D. J. (Eds.). (2009). Energy Harvesting Technologies. New York, NY: Springer Science Business Media LLC. doi:10.1007/978-0-387-76464-1

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