ENERGY HARVESTING THROUGH THE PIEZOELECTRIC EFFECT AT
SPORTS VENUES
By
Julius Evans
A Project Presented to
The Faculty of Humboldt State University
In Partial Fulfillment of the Requirements for the Degree
Master of Business Administration
Committee Membership
Telesky, Carol, Ph. D., Committee Chair
Sleeth-Keppler, David, Ph. D., Committee Member
Sleeth-Keppler, David, Ph. D., Graduate Coordinator
July 2015
ii
ABSTRACT
ENERGY HARVESTING THROUGH THE PIEZOELECTRIC EFFECT AT SPORTS VENUES
Julius Evans
This paper examines the significance of piezoelectric energy harvesting in sports
venues and its role in influencing pro-environmental behavior in society. By
implementing piezoelectric technology, venues have the ability to harness mass amounts
of kinetic energy which would otherwise be lost to the environment. This has the
potential to be an alternate source of energy harvesting. Furthermore, utilizing the sports
industry with major social influence and appeal, could be a driver in sustainable
development.
The research will explore the kinetic energy and electrical charge generated from
the various human components of a sporting event and its significance in monetary
savings for the venue. Further research will also explore the potential of implementing a
sustainable technology in the sports industry to further pro-environmental behavior.
iii
ACKNOWLEDGEMENTS
This paper is based on research conducted on the usage of piezoelectric energy
harvesting in sports venues and its effect on the relationship of sustainability and sports. I
would like to pay special thankfulness and appreciation to the persons who made this
research possible through their continuous support and assistance.
To the faculty of the HSU School of Business and MBA Program, my educational
experience at Humboldt State University has expanded my vision of the world and I will
be forever grateful for my time here. Especially to my advisor, Dr. Carol Telesky, whose
continuous advice and encouragement throughout the semester, made this research
possible. To Dr. Kate Lancaster, whose enthusiasm and passion for sustainability is
contagious. Her insights on environmental and societal issues has completely changed my
way of thinking, and made me a better person because of it. I’d also like to express my
gratitude to my undergraduate advisor Dr. Quoc Pham, who continuously challenged me
and gave me the ability to push beyond my self-imposed limits.
I would also like to thank all my former coaches and players of the HSU Football
Program, as well the administrative staff of the HSU Athletic Department. The
opportunity to pursue my graduate education, while living out my dream as a college
athlete, is more than I can ask for. The morals and life lessons I’ve learned through
collegiate athletics is something I’ll carry with me forever.
Lastly, this journey would not have been made possible without the wonderful
support system I have at home. I would like to express my heart-felt gratitude to my
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family for the endless love, support, concern and strength all these years, especially in
trying times last year. My heart-felt thanks.
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TABLE OF CONTENTS
ABSTRACT ........................................................................................................................ ii
ACKNOWLEDGEMENTS ............................................................................................... iii
LIST OF TABLES ............................................................................................................ vii
INTRODUCTION .............................................................................................................. 1
Research Questions ......................................................................................................... 3
What is Piezoelectricity? ................................................................................................ 3
How Much Energy Can Be Harvested? .......................................................................... 6
Materials/Effect ............................................................................................................ 10
Cost ............................................................................................................................... 12
Sports and Sustainability .............................................................................................. 13
METHODOLOGY ........................................................................................................... 17
ANALYSIS ....................................................................................................................... 18
Kinetic Force of the Athlete .......................................................................................... 18
Kinetic Force of Walking Subject (Pavegen) ............................................................... 24
Energy Generated From Athletes ................................................................................. 26
Energy Generated From Fans (Foot Traffic) ................................................................ 26
Stadium Energy Savings ............................................................................................... 28
Savings on Light Fixtures (LED vs. HID) .................................................................... 29
Product Costs ................................................................................................................ 30
DISCUSSION ................................................................................................................... 32
LIMITATIONS ................................................................................................................. 35
vi
FUTURE RESEARCH ..................................................................................................... 36
CONCLUSION ................................................................................................................. 37
REFERENCES ................................................................................................................. 39
vii
LIST OF TABLES
Table 1: Power Consumption of Various Communicators ................................................. 7
Table 2: Force Exerted of NFL Athlete According to Various Literature ........................ 21
Table 3: Number of Steps per Game Estimate .................................................................. 23
Table 4: TransSafety Data on Average Walking Speed .................................................... 25
Table 5: Piezo Energy Harvesting From Foot Traffic...................................................... 28
1
INTRODUCTION
Given the global environmental problems that currently plague our planet, the
need for sustainable solutions has never been more critical. These conditions are only
expected to persist, which makes it our responsibility to not only implement more
innovative and sustainable technologies (Safian, 2012), but bring forth the common
understanding of responsibility in regards to our environment (Savery & Gilbert, 2011).
Energy efficient technologies are being introduced to the building sector to
harness as much “green energy” as possible. The building sector proves to be one of the
most detrimental sectors to the environment and is responsible for 48 percent of all
energy consumption. Despite long-term monetary savings, these technologies usually fail
during implementation due to high capital costs (Lovins & Boyd, 2011). They also lack
social influence and urgency that will allow individuals to partake in more pro-
environmental behavior.
Implementing sustainable technologies within the sports industry may be the key
that drives and maintains sustainable development. Sports has the ability to influence and
unite individuals at an international level (Savery & Gilbert, 2011). By emphasizing
sustainability on a platform of this magnitude, it can be seen as an educational hub for
sustainable living.
A sports venue can largely benefit from the implementation of sustainable
technologies. This paper explores an innovative, more cost efficient form of energy
harvesting called Piezoelectricity. Energy harvesting via the piezoelectric effect is
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different in that it does not rely on our planet’s resources like other technologies, but
from the mechanical stress applied by human movement. These high-activity areas
produce large amounts of vibration and kinetic energy from the thousands of fans that
attend the game, and the very athletes that entertain us through sport.
By installing piezoelectric transducers in sporting venues, natural energy can be
harnessed that is created by the consistent footfall of the thousands of fans, the roar
created by fans during a sporting event, and the powerful amount of force generated by a
professional athlete. Sustainable technologies, such as Piezoelectricity, can yield long-
term monetary savings for the venue, and may be a driving force in leading both the
building sector and society towards sustainable development.
Piezoelectric Energy Harvesting is an innovative step in the direction of energy
harvesting, hence not much research and literature has been done in this field till now.
The remainder of this paper is structured as follows: the research questions which
are the basis of this paper, some background on what piezoelectricity is and its
applications, how much kinetic energy can be generated, background on the materials and
effect, the costs associated with implementing transducers, the benefit of implementing a
sustainable technology in the sports industry, the results of the energy yielded from
piezoelectricity, discussion of the findings, limitations of the study, recommendations,
and a conclusion.
3
Research Questions
Can piezoelectric transducers harvest enough energy to make a significant impact
in reducing energy costs in sports venues?
If so, can piezoelectric technology in the sports industry help be a catalyst for
sustainable development amongst society?
What is Piezoelectricity?
The piezoelectric effect is the “ability of certain materials to generate an electrical
charge in response to applied mechanical stress” (Nanomotion Corporation, 2008-2015).
Examples of these materials include crystalline structures such as Quartz, Rochelle salt,
Topaz, Tourmaline, Cane Sugar, Berlinite (AlPO4), Bone, Tendon, Silk, Enamel, Dentin,
Barium Titanate (BaTiO3), Lead Titanate (PbTiO3), Potassium Niobate (KNbO3) and
Lithium Niobate (LiNbO3). These materials are unique in that they carry a natural
piezoelectric effect, meaning that when mechanical stress is applied, an electrical charge
is generated. Normally, when mechanical stress is not induced, piezoelectric crystals are
neutral meaning their electrical charges are perfectly balanced. If a piezoelectric crystal is
agitated, the natural balance of positive and negative atoms is upset, causing net electrical
charges to appear on the opposite, outer faces of the piezoelectric material (Woodford,
2014). Piezoelectric material also has a reversal effect, meaning that materials generate
mechanic stress when an electrical charge is applied.
4
Of the studies done, the output voltage of a single piezoelectric crystal is usually
under the category of the micro scale energy harvesting scheme. Generally associated
with low power consumer devices. It is enough to be stored in lithium batteries or
capacitors and able to power small electronics (Dikshit, et al., 2010). Engineers are
currently conducting studies on the various structures of the piezoelectric component to
yield maximum output voltage, studies that involve which type of crystals to utilize, the
type of circuit that should be used at the output terminals, and various placements of
piezoelectric transducers, in hopes of bringing piezoelectric solution to the macro-level
(Dikshit, et al., 2010).
Common uses of the piezoelectric technology can be found in standard consumer
products as well as innovative products that utilize mechanical stress applied by human
movement. Examples of the piezoelectric effect are listed below:
Power Generating Sidewalk (Pavegen Systems)
Pavegen Systems, a technology company based out of London, recently
introduced a Pavegen Tile, which is a piezoelectric tile that harvests the kinetic energy
created by a footstep. These tiles are being laid underneath pavements in high traffic
areas such as airports, schools, and train stations. The consistent footfall yields sufficient
wattage to power LED lighting, cell phone charging stations and ad displays around the
tile. Their 17.1 by 23.6 inch tiles can produce an average of 7 watts per step (Alexander,
2012). One of the indirect benefits of the Pavegen tiles is the ability to educate the
interested public on energy harvesting and conservation, which could go far beyond the
direct benefit of monetary savings.
5
Power Generating Boots or Shoes (Military)
The United States Defense Advanced Research Project Agency (DARPA)
recently introduced an innovative project called the “Heel-Strike Unit” in which a
piezoelectric transducer is put into a soldier’s boots to harness electrical energy via the
mechanical stress of a simple step. The benefit to military soldiers from this technology is
that they have access to an electrical charge which otherwise, wouldn’t be present in a
secluded setting (Howells, 2009). It should be noted the Heel-Strike Unit has not made it
out of testing yet due to the concern of comfort level of having transducers in an active
soldier’s sock.
People Powered Dance Clubs (Club Watt)
Dance clubs in Europe, particularly “Club Watt” in Rotterdam, Netherlands, are
beginning to power their nightclub by the use of piezoelectric crystals underneath the
dance floor. The kinetic energy produced by a bulk of party-goers dancing, generates an
enormous amount of electrical energy which the Club utilizes to power the variable lights
and amplified music that make them go. The priority of this project was not only to
implement sustainability into the structure of the organization, but to communicate the
message of sustainability to the audience.
Standard Appliances and Equipment
Piezoelectric transducers can also be found in standard appliances or equipment.
A piezoelectric transducer converts an electrical charge to rapid mechanical vibrations in
ultrasound equipment. A transducer in a microphone converts the vibration from sound
waves into an electrical charge which is then amplified. In a quartz watch or clock,
6
electrical energy from a battery is fed to the piezoelectric crystal which causes the hand
oscillate and is controlled by a motor. In spark lighters, stoves, or barbeques, pressing the
switch applies pressure to the piezoelectric crystal which generates a mechanical shock
and creates the spark.
So there is plenty of equipment we use every day which utilizes the piezoelectric
effect as well as many up and coming products that have the potential to bring
piezoelectric technology mainstream.
How Much Energy Can Be Harvested?
As humans, we are known to be walking light bulbs; we have the ability to create
all kinds of energy that are otherwise lost into the environment. We create thermal energy
from our body heat, sound energy through voice, and kinetic energy through our
movements. For this study, I will be looking at kinetic energy and how much energy can
be generated from the mechanical stress applied by the human components of a sporting
event.
Kinetic Energy Generated from Athletes
In the Pavegen Systems study, the Piezoelectric tiles produce an average of 7
watts per footfall from a 150 pound, walking person (Alexander, 2012), which is strong
enough to power LED lighting and small electronics. Table 1 shows a comparison of the
power consumption by various electronic communicators in both stand-by and active
mode.
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Table 1: Power Consumption of Various Communicators
Products Battery Voltage (V) Stand-By Mode (W) Active Mode (W)
Cellular Phone Lithium Ion Battery
(3.6)
0.042 1.7
Two-Way
Communicator
3-AA Batteries (4.5) 0.158 0.675
Pagers 1-AA Batteries (1.5) 0.023 0.03
However, the force applied is variable in that it is dependent on the force and
kinetic energy produced of that step. The linear kinematic equations for force and
potential kinetic energy are as followed.
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 ∗ 𝐴𝐴𝐹𝐹𝐹𝐹𝐹𝐹𝐴𝐴𝑀𝑀𝐹𝐹𝑀𝑀𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴
𝐾𝐾𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴𝐴𝐴𝐹𝐹 𝐸𝐸𝐴𝐴𝐹𝐹𝐹𝐹𝐸𝐸𝐸𝐸 =12𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 ∗ 𝑉𝑉𝐹𝐹𝐴𝐴𝐹𝐹𝐹𝐹𝐴𝐴𝐴𝐴𝐸𝐸2
The amount of force and kinetic energy generated by a subject is dependent on the
subjects mass and speed (Birnbaum, 1999). If piezoelectric transducers were input
underneath athletic surfaces, the combination of consistent footfall generated by multiple
professional athletes on an athletic field during an event, along with the force generated
by those athletes who are not walking, but sprinting, running, jumping and accelerating,
would generate an aggressive amount of kinetic energy that can be harnessed into
renewable energy. A number of studies have been done to quantify the amount of force
8
generated by an athlete in competition, and all yield around 3.5 to 7 times their body
mass (Birnbaum, 1999).
Numerous studies in biomechanics have proved that running, let alone a
professional athlete running, produces more force than an individual walking. A leverage
point in the amount of force generated is how quickly that force is applied (Hart, 2011).
Peter Weyand, a sports science professor from Southern Methodist University, conducted
a study on Olympic sprinter Usain Bolt and compared the amount of time Usain Bolt’s
foot was on the ground compared to that of an average person running. An average
person’s foot is on the ground for about .12 seconds, while Usain Bolt’s foot is on the
ground for .08 seconds, a 33 percent difference which can have a multiplying effect on
the amount of force generated (Hart, 2011). An Olympic athlete maximizes the output of
each individual step and can apply more than 1,000 pounds of force compared to 500
pounds of that of an average person sprinting (Hart, 2011).
Another study conducted by the American Association for Physics Teachers,
compared standing, walking and running on a force plate and recorded the comparisons
through wave frequency charts. The study concluded that running generates more force
than walking because there is no period when both feet are on the ground, the feet spend
a shorter fraction of time on the ground, as well as a shorter time on the ground each
stride (Cross, 1999). This results in a greater variation of force generated in a shorter
time unit, yielding a greater total force per step and total, given a time series.
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Vibrational Energy Generated from Crowd Noise
Sports facilities are now being renovated and built to amplify crowd noise, not to
harvest sound energy, but as a competitive advantage to the home team and strengthen
fan experience (Reed, 2014). FirstEnergy Stadium, home of the Cleveland Browns,
invested $120 million in physical and technical improvements in hopes of keeping sound
within the stadium. In most sports, fans take pride in being consistently loud and
disruptive, creating a “home-field advantage”. In 2011, Century Link Field in Seattle,
Washington generated 137.6 decibels of noise at one point which was enough to produce
a small earthquake (Memmott, 2013). Piezoelectric transducers can be input around the
stadium to collect the sound energy created by the roar of the fans which will vibrate the
piezoelectric crystal generating an electrical charge. Studies have been done on
harvesting the ear-piercing sounds of aerospace and jet engines and how it could be used
to power some appliances on the aircraft itself. Meggit Sensing Systems has introduced a
piezoceramic product to capture the high resonant frequency of engines, in which the
output is to be used for on-board appliances (Meggit Sensing Systems, 2015).
As it relates to stadium energy, the vibrations generated from crowd noise have
potential to generate energy, but on a miniscule scale. A recent study was done on the
crowd noise measured at Wembley Stadium (100,000 people at 120 dB) in London and
the potential to cook an egg. They estimated the need for 175 watts of energy which
required up to 142 dB of consistent sound. At 80 dB per person standing 1 meter away,
they estimated they would need 1.6 million people (standing 1 feet away from the egg) to
successfully boil the egg (Laursen, 2011), which would not be feasible. So the vibrational
10
energy in crowd noise will have a miniscule impact in piezoelectric energy harvesting
and will not be included in our calculations.
Kinetic Energy Generated from Fan Footfall
As mentioned earlier, Pavegen Systems produces energy harvesting tiles that can
harness an average of 7 watts per step from an average weighted, walking person.
Pavegen tiles are being installed in high traffic areas like airports, train stations and
schools. Considering that events in sports facilities can reach up to 100,000 people
depending on the sport, the facility generates a lot of traffic and kinetic energy in and
around it.
Materials/Effect
Regardless of the energy output from a transducer, the materials and how they
affect the playing surface for the athlete may be a question of more importance.
The installation would only be feasible underneath an artificial surface. One that can be
easily removed for renovation and maintenance that limits shock absorbance. This is not
the case with a natural grass field. However, according the 5-year study done by
FieldTurf, there has been a dramatic shift in playing surface material that have begun
making the switch from natural grass to artificial turf (FieldTurf, 2015), of the main
reasons being that artificial turf is easier to maintain, less susceptible to bad weather, and
less damaging to the field itself (FieldTurf, 2015)
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The contents and materials of artificial turf are simple. Along with synthetic grass,
two materials are spread throughout the turf: recycled rubber and silica sand (SiO2), also
known as Quartz (Rodriguez, Artificial Grass Infill Options, 2015). As mentioned earlier,
Quartz is one of the materials that naturally harvests an electrical charge from mechanical
stress. The granulated rubber and quartz infill in artificial grass, provides abrasion, slip
resistance, and durability (FieldTurf, 2015) but people are failing to realize the natural
electric charge that is being generated just by taking a step onto artificial turf.
Other playing surfaces have the ability to harness mechanical stress as well. Hardwood
flooring, as the surfaces used for basketball and volleyball, do not contain a layer of
quartz like artificial turf, but can still harness vibrational energy through maple flooring.
While, information on the makeup of maple wood flooring and its shock absorbance is
limited, there are other applications that utilize maple wood flooring as a piezoelectric
surface. As mentioned before, “Club Watt” introduced the world’s first human powered
dance floor. Their primary surfaces on the piezoelectric floorings are glass and maple
wood.
Another question to be addressed is if this technology and renovations to the turf
would affect player performance or safety. This is the “million dollar question”, literally.
This is a billion dollar sports industry in which owners invest millions of dollars in their
players and the last thing they would want to see is their players get injured or have it
downgrade their performance. This is difficult to test since we have nothing to compare
the injury rate of artificial turf with transducers with artificial turf without any. An
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alternative would possibly be to look at the injury rate of artificial turf against natural
grass since piezoelectric transducers cannot be installed under natural grass. The
FieldTurf study found that artificial turf is significantly safer than that of natural grass in
terms of injury prevention (FieldTurf, 2015). The study documented 1,164 injuries on
artificial turf to 2,377 on natural grass with 50% of games played on each surface
(FieldTurf, 2015). Artificial grass can also yield better performance. With the game being
played on a flat surface like turf with short cut synthetic grass, the game is played faster
and at a higher level, but still limiting injury rate.
Cost
The costs of the product is critical in determining the value of the overall project.
Although the tiles are currently being used in some high traffic areas, they are currently
not available for consumer purchase. So no official price has been announced, but
Pavegen employees have been reported as saying the titles could cost as little as $76 in
the future (Morales, 2013). It is important to note this does not however include the costs
of installation, labor, logistics, loss of productivity due to down time of bad tiles, or the
costs of a complete field or stadium renovation project. These indirect costs associated
with the technology are critical when determining of these tiles could be a financially
realistic source of energy. With the dimensions given of 1 tile being 17.1” x 23.6” an
estimate can be determined which will be discussed in the results section.
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Sports and Sustainability
While the point of interest of the facility remains the direct benefits of saving
overall costs, the indirect benefits of implementing sustainable technology, like
piezoelectricity, in a facility has major triple bottom line benefits.
The relationship of sustainability and sports has gone much unnoticed to the public
perception. There is a lack of environmental awareness and understanding that exists in
the way we see how competitive sports are played. Sports can be viewed as “the
encouragement of human effort in harmony with the natural environment” (Savery &
Gilbert, 2011, p. 4). They have always relied on taking advantage of nature’s clean air,
available water and land. Yet today, the health of the environment continues to decline,
while the sports industry has become a multi-trillion dollar industry. For sports, the
reliance on a healthy environment has gone unrealized to the public and has a direct
impact on the future of sport.
The organizations themselves have slowly begun to start building awareness. In
2007, Sports Illustrated released a cover story on climate change noting that it is “time
for our teams and athletes to take the lead, galvanize attention and influence behavior”
(Wolff, 2007). Since then, non-profit organizations have partnered with sports
organizations and athletes to communicate the connection between their environmental
passion and experience and the need to take action. Major League Baseball has begun the
MLB Greening Program, voicing their concern over environmental responsibility along
with the vocal and social support of their athletes (Hershkowitz, 2015). The National
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Football League partnered with the National Resources Defense Council to help share
information about better practices at NFL facilities, reducing their environmental impacts
(Smarter Business: Greening The Games, n.d.). The National Basketball Association
started NBA Green and NBA Green Week in which organizations voice environmental
awareness and athletes participate in “green” events (NBA Green, 2015).
Paired with the potential of an international stage, a sporting event has the ability to
appeal to a large audience as well. Events like the World Cup, which attracted nearly half
the planet to watch at least 1 game this past year (Klein, 2014), or the Olympics that had
4.7 billion viewers or 70% of the world’s population (Hui, 2008), can be stages to
showcase sustainable technologies. Events as such not only draw enormous publicity, but
cut cultural and national boundaries and uniting countries across a shared interest. The
2008 International Olympic Committee reports that The Beijing Olympics had 204
countries participating and even more watching (2008). A global sporting event like the
Olympics could be utilized as a catalyst in reducing the indifferences that exists across
countries and highlight the commonalities of how our actions affect the environment in
which we all depend on.
While organizations are beginning to take notice and build awareness, the gap
remains between awareness and behavior, and it is much more complex than we thought.
To bridge this gap, we must understand the theories of behavior and what influences it to
make sustainability, simply, a way of life to the public. Conceptualizing behavioral
theories and utilizing the factors that drive consumer behavior, marketers can develop an
15
engagement strategy and framework to facilitate pro-environmental behavior within
society. More of which will be discussed in the discussion section of this paper.
Despite the attempt to build awareness to the public, there still seems to be a lack of
major initiatives taken to address the venue itself. The building sector is responsible for
almost half (48 percent) of all energy consumption (Lovins & Boyd, 2011) and cases can
be made against not only the environmental damage but rising direct costs of energy
consumption. Cowboys Stadium in Dallas, Texas can consume up to 10 Megawatts of
energy during an event, while the country of Liberia has the capacity to pump less than a
third as much power into its national grid (Breech, 2013). By implementing sustainable
technologies into their venues, organizations can yield direct savings and have a bigger
impact on reducing the very carbon footprint that harms the future of their sport.
However, delivering sustainable initiatives and technology into stadium venues and
infrastructure can be a challenge itself. Organizations tend to stick to the norm or what
has worked for them in the past and initiating something outside of their comfort zone,
can be viewed as risky. Kristen Henson, former Senior Sustainability Advisor for the
Olympic Delivery Authority’s Delivery Partner for the London 2012 Olympic Games,
mapped out delivery mechanisms and processes as to how organizations can integrate
sustainability into the construction of their venue (Henson, 2011). Organizations must
first set a high-level strategy highlighting the long-term benefits of the structure. This
could include the capital outlay and long-term return of the technology to bypass the
perception of high initial costs. Collaborating between organizations on related
sustainability strategies can be beneficial as well. For the London 2012 Olympics the
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Olympic Delivery Authority (ODA) and the London Organizing Committee of the
Olympic and Paralympic Games (LOCOG) had complimentary sustainability strategies
(Henson, 2011) that developed a cohesive and collaborative partnership. Next
organizations must set a clear vision and targets. Without a broad definition of what
sustainability is, organizations need to establish a cohesive vision for sustainability and
its goals. This was clear and common across the Olympic and Winter Olympic games in
South Africa 2010, London 2012 and Vancouver 2010. Each had a clear vision relating
sustainability to their host cities as well as establishing quantitative measures and Key
Performance Indicators to measure and track their sustainable goals (Henson, 2011). That
being said, organizations must establish an auditable structure to monitor their
performance and continuous improvement. The Vancouver 2010 games established a
Sustainability Management and Reporting System to track and measure performance.
Annual sustainability reports consisting of their goals and methods of improvement, were
published and available to the public (Henson, 2011). Finally, organizations must develop
a team structure emphasizing and prioritizing sustainability across all parts of the team.
Establishing an organic structure that facilitates communication, creativity and innovation
can be beneficial in the delivery process of sustainability. By utilizing the delivery
mechanisms mentioned above, sports organizations can initiate a more sustainable
mindset when constructing or renovating not only stadium infrastructure, but internal
policies and principles of the building too.
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METHODOLOGY
This analysis is centralized around how much energy can be generated and
converted to monetary savings from the mechanical stress applied by human components
during a sports event. By installing piezoelectric transducers underneath the surfaces and
around the venue, usable energy from the powerful force generated by athletes and the
high frequency footfall and noise of fans could be captured, which would otherwise be
lost to the environment. The output yield of footfall would be comparable to the Pavegen
Systems experiment of a rate of 7 watts per footfall generated by a walking 150 pound
subject. Using linear kinematic calculations, a force per step rate of the component will
be calculated determining a total amount of energy generated for the duration of the
event. This will be converted to an amount of monetary savings and compared to the
amount of energy consumed during the day of an event. Product costs will also be
examined to determine the most cost-efficient use of these tiles.
Given the lack of literature and research specific to this field, conservative
estimates were determined based on statistics and various studies.
Further analysis of the impact of piezoelectricity and its relationship to
sustainable sport and influencing pro-environmental behavior will be given in the
discussion section.
For the sake of this study, the sporting event of a football game was analyzed.
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ANALYSIS
Kinetic Force of the Athlete
With respect to directional and applied force, the sport of football varies across
different positions. For example, vertical force assumptions can be better applied to those
of skill positions (receivers, defensive backs, running backs, linebackers) where more
steps are taken without the disruption of physical contact. The vertical force applied by
the lineman position will vary on the concurrent forces applied from different directions,
since they will experience more change of direction and sudden contact. In which case,
the concurrent forces of both athletes are dependent on both the magnitude of each force
and the angle of application (Hamilton, Weimar, & Luttgens, 2012). For the sake of this
experiment, linear kinematic equations will be used to determine conservative estimates
of the vertical force applied by the footfall of a professional football player during
competition. Newton’s second law of motion may be expressed in equation form as:
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 ∗ 𝐴𝐴𝐹𝐹𝐹𝐹𝐹𝐹𝐴𝐴𝐹𝐹𝐹𝐹𝑀𝑀𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴
A recent Scripps Howard study found that the average weight of a professional
football player is 248 pounds, or 112.49 kilograms (Hargrove, 2006). The conventional
standard value of gravitational acceleration on Earth is 9.80 𝑚𝑚/𝑀𝑀𝐹𝐹𝐹𝐹2. So the calculation
for the mass of a professional football player with regards to the Earth’s gravitational
attraction is as follows:
19
112.49𝑘𝑘𝐸𝐸 ∗ 9.8𝑚𝑚𝑀𝑀𝐹𝐹𝐹𝐹2
= 1,102.41 𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀
Next, the acceleration of the athlete must be determined, which is the rate of
change in velocity of the athlete. Before the play, the athlete has an initial velocity of
0 𝑓𝑓𝐴𝐴/𝑀𝑀𝐹𝐹𝐹𝐹 and when the snap signals the beginning of the play, the athlete’s velocity
begins to change by increasing. This rate of change in velocity is the athlete’s
acceleration (Hamilton, Weimar, & Luttgens, 2012). Acceleration is expressed in
equation form as:
𝑀𝑀� =𝑣𝑣𝑓𝑓 − 𝑣𝑣𝑖𝑖
𝐴𝐴
The athlete’s acceleration is dependent on the physical attributes of the athlete,
type of play, and position. For this study, the 2015 NFL Scouting Combine’s 40-yard
dash data will be used in determining the conservative estimate. The 40 yard dash is a
quantitative measure used to determine player speed by running 40 yards as fast as
possible starting from a stand-still (0𝑓𝑓𝐴𝐴/𝑀𝑀𝐹𝐹𝐹𝐹), which would signify the beginning of a
play. According to ESPN NFL DraftTracker the average 40 yard dash time of all 313
athletes that participated in the 2015 NFL Scouting Combine was 4.81 seconds (2014
NFL Combine Results, 2014). However, one can assume professional athletes reach their
top speed before the 40-yard marker, at which point they maintain maximum velocity
until the finish. An article published in the National Strength and Conditioning
Association Journal, breaks down the acceleration rate of sprinters during the 40 yard
dash and found that athletes reach maximum velocity, or an acceleration of 0 𝑓𝑓𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠2
, at
27.34 yards (McFarlane, 1993). To determine an athlete’s velocity at that point, we must
20
determine a conservative estimate. The average velocity of 24.97 feet per second can be
determined from the previous data. However, we can assume a higher max velocity since
the athletes instantaneous speed varies in that he will accelerate until he reaches his top
speed (Gage, 2010). For this particular experiment, the assumption will be made that the
athlete will have a maximum velocity of 28 feet per second at 27.34 yards.
Given the previously determined 4.81 40-yard dash time and 27.34 yard marker at which
maximum velocity occurs, the time interval over which the change in velocity occurred
can be calculated at 3.28 seconds. The calculation is as followed:
27.34 𝐸𝐸𝑦𝑦𝑀𝑀40 𝐸𝐸𝑦𝑦𝑀𝑀
∗ 4.81𝑀𝑀 = 3.28𝑀𝑀
So the athlete can run from the initial starting velocity of 0 feet per second to 28
feet per seconds in 3.28 seconds and continues to maintain that velocity to the 40 yard
finish marker. The acceleration rate at which the athlete can reach top speed can now be
calculated as:
𝑀𝑀� =28 𝑓𝑓𝐴𝐴𝑀𝑀 − 0 𝑓𝑓𝐴𝐴𝑀𝑀
3.28𝑀𝑀= 8.52
𝑓𝑓𝐴𝐴𝑀𝑀2
Given the previously calculated mass of a professional football player and the
acceleration rate at which they run, we can now calculate the kinetic force per step the
athlete exerts while running the 40-yard dash.
1,102.41𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀 ∗ 8.52𝑓𝑓𝐴𝐴𝑀𝑀2
= 9,397.27 𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀 𝑝𝑝𝐹𝐹𝐹𝐹 𝑀𝑀𝐴𝐴𝐹𝐹𝑝𝑝
However, the sport of football is a game of athleticism and change of direction,
and athletes may not mimic 40 yard dash sprint mechanics into their sport play. The data
21
calculated above assumes that a professional athlete can generate a force 8.5 times their
body weight, which may not happen with every step. The Saucony Shoe Company
reports that a force of up to 7 times the athlete’s body weight can be exerted when
running (Birnbaum, 1999). An article published by the Z-Tech Shoe Company reports
that the maximum force exerted by a step can equal up to three-and-a-half times the
runners body weight (Birnbaum, 1999). However, the articles listed conducted their
experiment with a jogging individual rather than one that is sprinting which simulates
that of an NFL athlete in competition. Below is a table showing how the force varies
across different literature.
Table 2: Force Exerted of NFL Athlete According to Various Literature
Source Mass of
Athlete
Multiple Force
Exerted
40-Yard Dash Calculation 1,102.41N 8.5 9,397.27N
The Science Behind the Shoes. Saucony, Inc. 1,102.41N 7.0 7,716.89N
The History. Z-Coil Shoes for Pain Relief. Z-
Tech, Inc.
1,102.41N 3.5 3858.44N
Average 6,990.87N
For this experiment, the average of 6,990.87 Newtons per step will be used as the
conservative estimate in determining the total kinetic force that can be harvested into
clean energy. This number will be used in later calculations in determining the wattage
yielded in a game, using the wattage yield rate of the Pavegen tile experiment.
22
The next step is determining an estimate as to how many active steps are taken
during a game of competition. According to SportsVU technology, which delivers
quantifiable data on player distance and speed, skill positions (receivers, defensive backs,
linebackers, running backs) run the most during a game at 1.25 miles per game (Rose,
2013). The skill positions account for half of the players on the field at one time, while
the rest usually are subject to concurrent forces and contact and stay within a close
distance to the area of the initial snap. That being said, it can be assumed that the average
distance a player runs in a game will be less than 1.25 miles a game. For this study, the
average distance an NFL football player runs for the duration of the contest will be 0.85
miles per game. Given that 22 players are on the field each play, the total distance run in
a game can be calculated as 18.7 miles.
The number of steps the athlete takes during competition then needs to be
determined. World renowned strength and conditioning coach Michael Boyle, states that
an athlete with a normal stride length will measure out at about 7.5 feet so the 40-yard
dash should be run with 17 steps by the athlete (Boyle, 2014). Although the frequency of
steps varies with the size and biomechanics of the athlete, the assumption will be made
that it takes the average athlete 17 steps to run the 40 yard dash. With 44 40 yard
increments in a mile, it is calculated that the athlete yields 748 sprinting steps per mile.
At a total distance run of 18.7 miles per game, the total number of steps during a game by
all athletes can be calculated at 13,987.60 steps. The calculations are shown below.
23
Table 3: Number of Steps per Game Estimate
Driver Frequency
Miles Per Game Per Player 0.85 miles
# of Players On The Field Per Play 22
Total Miles Run In A Game By Athletes 18.70 miles
Steps In A 40-Yard Dash 17
Yards To Mile Factor 1,760 yards
40 Yard Increments (Mile) 44
Sprinting Steps per Mile 748
# of Action Steps In A Game 13,987.60 steps
The estimated total force yielded in a football game can now be determined
through the following calculation:
𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀 𝑝𝑝𝐹𝐹𝐹𝐹 𝑆𝑆𝐴𝐴𝐹𝐹𝑝𝑝 ∗ # 𝐹𝐹𝑓𝑓 𝑀𝑀𝐴𝐴𝐹𝐹𝑝𝑝𝑀𝑀 𝑝𝑝𝐹𝐹𝐹𝐹 𝐸𝐸𝑀𝑀𝑚𝑚𝐹𝐹 = 𝑇𝑇𝐹𝐹𝐴𝐴𝑀𝑀𝐴𝐴 𝐾𝐾𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴𝐴𝐴𝐹𝐹 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
6,990.87𝑁𝑁 ∗ 13,987.60 𝑀𝑀𝐴𝐴𝐹𝐹𝑝𝑝𝑀𝑀 = 97,785,451.98𝑁𝑁
So it is to be assumed that 97,785,451.98 Newtons of force is generated during a
professional football game. However, this number only accounts the force generated
during the active play. This number could be higher given activity before competition, as
well as steps taken in between plays, although the force per step generated outside of the
contest may not be as high.
24
Kinetic Force of Walking Subject (Pavegen)
Determining the force per step of a walking subject will be similar to how the
force per step was calculated for the athlete. After the force per step of a walking subject
is calculated, a rate can be determined and used to determine the amount of energy
yielded in contest by an athlete.
The 7 watts yielded per step stated by the Pavegen experiment was the output of
the step pressure exerted by a 150 pound man (68.04kg) (Alexander, 2012). With a
gravitational acceleration of 9.8 𝑚𝑚𝑠𝑠2
that mass of the Pavegen subject is 666.78 Newtons.
To determine the acceleration, an estimate of the average walking speed of a human must
be determined. The Road Engineering Journal conducted a study on the average walking
speeds of subjects variable on their age. Of the 7,123 pedestrians examined, 3,665 were
of the elderly population. The study found that the average walking speed of the elderly
population was 4.11 feet per second, while the remaining sample walked at a pace of 4.95
feet per second (Road Engineering Journal, 1997). The average start-up times were also
calculated for both populations with the elderly population taking 3.75 seconds to reach
their average speed of 4.11 feet per second, while it takes the remaining population 3.0
seconds to reach their average speed of 4.95 feet per second (1997). With the data the
TranSafety study provides, an expected value can be calculated using the weights of the
study size to determine an estimate for the acceleration of a walking subject. Below is a
table that shows the TranSafety data (1997) and the expected value that can be used to
continue the study.
25
Table 4: TransSafety Data on Average Walking Speed
Sample Sample
%
Avg.
Speed
(ft/s)
Expected Value
(Sample %
*Avg. Speed)
Start-
Up
Time (s)
Expected
Value
Elderly 3,665 51.45% 4.11 2.11 3.75 1.93
Remaining 3,458 48.55% 4.95 2.40 3 1.46
Sum 7,123 100% 4.52 3.39
With an average speed of 4.52 feet per seconds and an average start up time of
3.39 seconds to reach that speed, the acceleration rate can now be calculated at 1.33 𝑓𝑓𝑓𝑓𝑠𝑠2
.
The calculation can be expressed as:
𝑀𝑀� =𝑣𝑣𝑓𝑓 − 𝑣𝑣𝑓𝑓
𝐴𝐴=
4.52 𝑓𝑓𝐴𝐴𝑀𝑀 − 0 𝑓𝑓𝐴𝐴𝑀𝑀3.39𝑀𝑀
= 1.33𝑓𝑓𝐴𝐴𝑀𝑀2
Given the calculated mass and acceleration of the walking Pavegen subject, a
force per step value can now be calculated.
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 ∗ 𝐴𝐴𝐹𝐹𝐹𝐹𝐹𝐹𝐴𝐴𝐹𝐹𝐹𝐹𝑀𝑀𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴
889.68 𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀 = 666.78 𝑁𝑁𝐹𝐹𝑁𝑁𝐴𝐴𝐹𝐹𝐴𝐴𝑀𝑀 ∗ 1.33𝑓𝑓𝐴𝐴𝑀𝑀2
So the assumption can be made that a walking person exerts 889.68 Newtons of
force per step, which is the similar to the force of a walking step shown in the frequency
26
wave charts of Figure 4 at around 0.8 to 0.9kN or 800 to 900 Newtons. So it is safe to say
that 889.68 Newtons of force generates 7 watts of energy or 127.10 Newtons per watt.
Energy Generated From Athletes
Assuming the pre-determined number of 6,990.87 Newtons per step is generated
by a professional athlete, and the rate of 127.10 Newtons is required to generate 1 watt of
electricity, a per-step rate of the athlete can now be determined. The equation yields a
rate of 55 watts per step as shown below:
6,990.87𝑁𝑁𝑀𝑀𝐴𝐴𝐹𝐹𝑝𝑝
∗𝑁𝑁𝑀𝑀𝐴𝐴𝐴𝐴
127.10𝑁𝑁=
55 𝑁𝑁𝑀𝑀𝐴𝐴𝐴𝐴𝑀𝑀𝑀𝑀𝐴𝐴𝐹𝐹𝑝𝑝
So the assumption can be made that about 55 watts are generated from every step
of an athlete in competition. Since the number of steps in a game were already given at
13,987.60 steps, one can expect 769,371.46 watts or 769.37 kilowatts total generated by
the athletes during a football game.
Energy Generated From Fans (Foot Traffic)
An alternative to harvesting kinetic energy through footfall may be through the
fans that attend the game. If sporting venues were to lay down strips of piezoelectric tiles
across the stadium entrances, consistent force can be harvested as fans enter and exit the
stadium. This could be a more cost efficient way for energy harvesting as it requires less
tiles than that of a whole athletic playing surface, and more consistent footfall or steps.
27
To determine the amount of energy generated from fan footfall, the number of fans that
attend a game has to be determined first. According to Stadiums of Pro Football the
average stadium capacity of all 32 professional football sports venues was 69,652 (2014),
with an average attendance rate of 96.66% (NFL Attendance, 2014). So it can be said that
67,323.11 fans attend each professional football game.
Next, an estimate must be made on the number of steps a fan will take on the
piezoelectric tile strip. The dimensions of the Pavegen tiles are 17.1 by 23.6 inches
(Pavegen Systems, 2015). Recent studies report that the stride length for the average
human being is approximately 2.5 feet long (The Walking Site, 2015). Assuming each
fan enters and exits that stadium at a walking pace, it’s safe to say that each fan will step
on the 23.6 inch tile strip at least twice during the day of the event. With about 67,323.11
fans in attendance per game, we can assume a total of 134,646.23 steps on the tiles that
day. Using Pavegen’s rate of about 7 watts per step per the average weighted human
being, the energy generated from fan footfall during an event is about 942,523.60 watts
or 942.52 kilowatts. But it is important to note that the calculated energy yield is of a
single strip of tiles. This number is variable in that multiple strips would produce a much
greater energy yield.
28
Table 5: Piezo Energy Harvesting From Foot Traffic
Driver Frequency
Average Stadium Capacity 2014 69,651.81 people
Average Attendance Rate 2014 96.66%
Fan Attendance for an NFL Game 67,323.11 people
Steps per Fan (Entrance and Exit) 2 steps
Total Steps on Piezo Strip per Game 134,646.23 steps
Energy Produced @ 7 watts per step 942,523.60 watts
Kilowatts 942.52 kW
Despite the aggressive amount of force generated by a professional athlete, the
fans in total generate more energy than the professional athlete during an event. This is in
large part due to the number of steps taken by the fans is about 9.5 times more than the
steps of professional athletes during competition.
Stadium Energy Savings
So if sports venues were to implement piezoelectric transducers underneath sports
surfaces and around stadium entrances, they can expect a total of about 1,711,895.06
watts or 1,711.90 kilowatts. How much will this save stadium operations in terms of
energy usage and monetary value?
29
As previously mentioned, a recent article published in the Wall Street Journal
found that on game day, Cowboys Stadium in Dallas, Texas can consume up to 10
Megawatts of energy during an event, while the country of Liberia has the capacity to
pump less than a third as much power into its national grid (Breech, 2013). Including pre
and post event operations, total game day operations amount to about 8 hours of energy
usage. With piezoelectric energy harvesting, stadiums can save about 2.14% of stadium
energy consumption on game day. Assuming $.1034 kWh cost, which, according to U.S.
Energy Information Administration for 2014 was the average cost for the commercial
sector (Electric Power Monthly, 2015), piezoelectric energy harvesting can save stadiums
about $177.01 on game day.
Savings on Light Fixtures (LED vs. HID)
Light fixtures continue to be the greatest factor of energy consumption in sports
venues. Most venues are still operating on High Intensity Discharge (HID) lighting which
can be costly, both monetarily and environmentally. If venues were to replace their
current light fixtures with LED powered bulbs to illuminate the field, it could be fully
powered by renewable energy from piezoelectric energy harvesting.
University of Phoenix Stadium in Glendale, Arizona is the first NFL stadium to
light their field using only LED’s and saw a 75% savings in the switch alone (Sweetnam,
2015). LED lighting draw about 310 kWh while compared to HID lighting which
requires 1240 kWh (Sweetnam, 2015). Games, with exception to Monday night “prime-
time” games, start at 1:05pm local time but remain on for the night during post game
30
operations and clean-up. Assuming stadium lights remain on for around 5 hours, total
LED light usage for duration of the event would be 1,550 kilowatts compared to 6,200
kilowatts using HID lights. Using the energy harvested from the kinetic force of athletes
and fans (2371.66kW), stadiums can fully power the LED lighting to light the field
yielding a savings percentage of 110.44% versus 27.61% using HID lighting.
Product Costs
As previously mentioned, failed implementation of sustainable technology is
usually associated with high capital costs (Lovins & Boyd, 2011). So assessing product
costs of this technology is crucial to brining this technology mainstream. The dimensions
of a football field are 360’ by 160’ or 4320 inches by 1920 inches. So considering the
dimensions, an organization would need about 20,553 tiles to cover the entire field. At
$76 dollars per tile, the total product costs would amount to about $1.5 million dollars.
Further costs associated with installation, labor, logistics, loss of productivity, or costs of
a complete field renovation project could be a subject of further research to assess the
total initial implementation costs. That being said, this kind of investment and renovation
to the field could take away the costs of daily field maintenance and labor that come with
a natural grass field.
The costs of capturing fan footfall is dependent on where the tiles are placed as
well as how many. To capture the highest frequency of fan footfall, piezoelectric tiles
could best be installed at fan entrance/exits. If tiles were to be put in different areas
31
around the venue, they may not capture the highest frequency of footfall given that fans
disperse into different areas of the venue.
32
DISCUSSION
The results of the calculations yield only a 2.14% savings in total energy costs
from piezoelectric transducers. This suggests a relatively minimal savings to the stadium
during game day operations. However, the energy generated could be used to assist in
powering LED lighting for the stadium, or other various stadium applications. As it
relates to other forms of sustainable technologies, piezoelectric transducer product costs
are significantly less. However, piezo technology is dependent on footfall frequency
which is only significant during game day operations. Macro-level harvesting techniques
like wind and solar are harvested year round on earth’s renewable resources, which result
in a higher and more consistent energy yield.
The results also indicate a greater difference in energy output from fans (942.52
kW) versus those generated by athletes (769.37 kW). Despite the higher amount of force
per step generated by the athlete, fans generate a higher total due to the higher frequency
of footfall. This looks to be the most cost effective use of piezoelectric tiles as well.
Installation of tiles solely for fan use yield a savings of 1.18% of game-day energy
consumption. Less tiles are needed to capture fan footfall while if installed underneath
sports surfaces would require installation across the whole playing surface. This would
subtract out the difficulty of maintenance and labor of attending to a tile if it were to be
underneath a surface. This would also dampen the possible shock absorbance if it were
underneath the surface of a playing field versus a tile installation on a walkway.
33
If a strip of piezoelectric tiles were to be installed for fan footfall, fans would
visually see their role in energy harvesting. Direct contact with this technology could be
the key in bridging the gap between awareness and pro-environmental behavior and is a
key factor in understanding behavior theory. Rajecki suggests that one of the root causes
of the gap is the lack of direct relationships and that “direct experiences have a stronger
influence on people’s behavior than indirect experiences” (Rajecki, 1982). This
indifference could be what sets piezoelectric technology apart from other sustainable
technologies. For example, in piezoelectric technology fans could visually and directly
realize that one of their steps creates an electrical charge. Macro-level technologies that
rely on earth’s renewable sources and not directly with the fans, might not necessarily
lead to more of a pro-environmental behavior.
As it relates to the energy output for a piezoelectric tile, one must consider the
higher level of frequency on a surface at a recreational facility versus a professional one.
In a more consistently active setting, energy savings will be greater and a higher
frequency of footfall from athletes. However, the feasibility of implementing sustainable
technologies are limited. Recreation centers can only make do with a small capital budget
and don’t have the means of significant public financing to cover the high capital costs of
implementation. When considering a recreational verse professional setting, one must
consider the magnitude of influence for sustainable technologies. The sports industry is
not like any other in that it unites countries internationally under one common interest.
Utilizing the opportunity to present sustainability on an international stage, as well as the
social influence of professional athletes promoting it, could catalyze how we instigate
34
green living within the public. This opportunity would not be present at the recreational
level.
Another benefit of implementing piezoelectric technology is the progress made
toward “smart cities” of the future. By releasing quantifiable data of energy savings and
footfall frequency, reachable goals and objectives can be established. Tracking in-time
energy data and making it available to the public through a wireless applications, could
be a step closer in influencing pro-environmental behavior. This kind of technology could
play a key part in not only sustainable practice around the facility, but in the community
as well.
35
LIMITATIONS
Given the lack of prior research in this topic, the biggest limitation with this study
is the reliance on assumptions and estimations. Data was compiled from different sources
and studies to determine conservative estimates that were not independently verified.
This study also did not account for the overall capital costs of the technology in full, only
of the product itself. This could be an area of future research, which could better shield
the perception of high initial capital costs associated with sustainable technologies.
This study also does not account for the product components itself. Different
components and materials of the piezoelectric transducer could generate a different
energy output, regardless of the variable force. Finally, this study was conducted from the
activity level of a professional football athlete. Results should vary given different sports
and physical activity.
36
FUTURE RESEARCH
The potential for this technology presents opportunities for future research. Future
research associated with this technology should examine shock absorbance of the tiles
that are underneath a playing surface. If the force of an athlete were to be taken, some
kinetic energy is most likely lost to the rubber content of the artificial turf. Researches
should asses how much is lost and its significance to the total energy savings.
Future research should also be done on the product itself. Research that involves
which type of crystals to utilize, the type of circuit that should be used at the output
terminals, and various placements of piezoelectric transducers should all be accounted
for. Various components of the product could help maximize energy output from a
footfall.
37
CONCLUSION
This study was conducted to assess the energy savings from piezoelectric energy
harvesting in sports venues and whether this technology could be a catalyst for
sustainable development in society. The study found that harvesting mechanical stress
from the human components of a sporting event generates 2.14% of savings off
electricity consumption from game-day operations.
Separate analysis showed energy output to be greater and more cost-efficient to
utilize kinetic energy from fans versus the active professional athlete. Although the
kinetic energy of the active athlete is much greater per step, there is a higher frequency of
footfall from the thousands of fans that fill the stadium. Given the perception of high
capital costs associated with implementing sustainable technology, this might be the best
means of initial implementation.
The energy savings does not show to be of significance to direct monetary savings
to the building. So the sports industry must emphasize the indirect benefits of
piezoelectric technology.
Piezoelectric technology gives the building sector, in sports specifically, an
alternate source of energy harvesting to reduce their detriment to worldwide energy
consumption. It also provides an opportunity to foster pro-environmental behavior within
its fans. Given the social influence and international stage of the sports industry, utilizing
and marketing piezoelectric technology during events could lead the public to more
sustainable lifestyles.
38
Piezoelectric technology gives the opportunity to reach fans that is different than
other sustainable technologies. By harnessing fan footfall, fans have the direct experience
that comes with their physical step creating electrical energy. As Rajecki (1982)
mentions, direct verses indirect experience of the public is one of the root factors to
understanding behavioral theory. This could bridge the gap in awareness and influencing
pro-environmental behavior which the sports industry has previously struggled with.
Further research is to be done given the lack of piezoelectric products on the
market, let alone in sports, but this research shows the indirect potential for this
technology and could be used as a building block to bring this technology mainstream.
39
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Birnbaum, S. (1999). Force on a Runner's Foot. (G. Elert, Editor) Retrieved November 15, 2014, from Hypertextbook: http://hypertextbook.com/facts/1999/SaraBirnbaum.shtml
Boyle, M. (2014, February 26). Archive for 40 yard dash. Strengthcoach.com. Retrieved March 16, 2015, from http://strengthcoachblog.com/tag/40-yard-dash/
Breech, J. (2013, September 17). Cowboys Stadium uses more electricity than Liberia . CBSSPORTSS.com. Retrieved February 6, 2015, from http://www.cbssports.com/nfl/eye-on-football/23703637/cowboys-stadium-uses-%20more-electricity-than-liberia
Cross, R. (1999, April). Standing, walking, running, and jumping on a force plate. American Association Journal for Physics Teachers, 67(4), 304-309. Retrieved November 15, 2014, from http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/6.%20StandingForcePlate.PDF
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