Power Generation & Vibration Reduction by Floating Slab using Recycled Loudspeakers

Research Support Scheme FCE-CSE

Power Generation & Vibration Reduction
by Floating Slab using Recycled Loudspeakers
2012 JAN-JUN
Team No.2
Supervisor: Dr Chung-fai NG
Members: Lam Cheung
Choi Yun Sing
Iu Pui Hoi
Kam Tsz Yan Joanna
Lau Shiu Long
Ting Kam Tung

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Contents
Title
P.1


Acknowledgement
P.1


Introduction
P.1


Objective
P.2


Theory
P.2


Current application of vibration to electricity
P.5


Construction of model
P.8


Methodology
P.13


Results and Analysis
P.15
Vibration Reduction
P.15
Power Generation
P.27
Natural frequency
P.33
Electrical System Vibration Frequency
P.35


Challenges, Errors and Improvements
P.42


Comparison between our designs and
P.44
Current applications



Conclusion
P.47


References
P.48



Copyright 2011-12 FCE Research Support Scheme Team No.2
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Title
Power generation by floating slab using recycled loud speaker

Acknowledgement
We would like to express our great appreciation to Dr C. F. Ng for his valuable and constructive
suggestions during the planning and development of this research work. His patient guidance and
encouragement have been very much appreciated. We would also like to thank Ms Emily Fung, the
technician of noise laboratory, who assists us of manipulating the equipment in the laboratory.







Special thanks should be extended to the staff of Industrial Centre of the Hong Kong Polytechnic
University for their help in processing the raw materials.

Introduction
Most of the Mass Transit Railway lines are constructed beneath or close to business and residential
buildings, occupants of those buildings always complain and protest against vibration and noise
created by passing trains. In many areas, the noise level may even reach 100dB. To reduce the impact
on neighbouring buildings and minimize residents' complaints, the floating slab track (FST) system
was introduced. The system has already been used in railway projects to reduce vibration and noise
problems e.g. in West Rail Line and Tsing Ma Bridge.

Also, there are usually intense vibration and noise generated by some recreational facilities, e.g.
dancing floor. It is believed the mechanical energy can be collected and utilized, instead of simply
wasted or released into the surrounding.

On the other hand, we also concern about the solid waste pollution. According to Environment
Protection Department, there is 70000 ton e-waste produced every year, and increasing 2% annually.
With the consideration of the e-waste produced in Hong Kong, we try to utilize vibration to generate
electricity by recycled loud speaker to collect dissipated energy.


Copyright 2011-12 FCE Research Support Scheme Team No.2 1
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Objective
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To convert the dissipated energy into useful energy for "energy recycling"
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To absorb the vibration and reduce noise at floating slab track or dancing floor
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To promote the recycling of old electrical appliances
Theory
The basic theory of our design is to converting vibration from the floating slab track (FST) into an
electric current.

The principle of the sound generation by loudspeaker is that electrical energy causes a diaphragm to
move by turning into mechanical energy. The most common type of loudspeaker is called dynamic
loudspeakers. It uses a diaphragm or cone, connected to a rigid basket via a flexible suspension. An
electrical signal applied to the voice coil can produce a magnetic field, making it a variable
electromagnet. The coil and the magnetic system interact with each other. This generates a
mechanical force that causes the coil and thus the attached diaphragm to move forth and back, under
the control of amplifier.

And this principle can be reversed, i.e. If the diaphragm of loudspeaker vibrates, it generates
electricity. The figure below in the noise laboratory shows a little vibration can light a LED flashlight
with 8 bulbs.



Copyright 2011-12 FCE Research Support Scheme Team No.2 2
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Our design is proposed to test the efficiency of electricity generation and vibration reduction. When
the train is passing across the FST, the floating slab is pressed by the weight of train. Similarly, when
a person is dancing on the vibrating system, the platform of the system is pressed by the weight of
human body. This triggers the vibration of the slab. Our group is planning to construct a similar
model to take relevant data. Those data include vibration amplitude and frequency, electricity
generation, sound level, etc.



When the slab vibrates, the vibration is transferred into the loudspeaker diaphragm. An electric
current is induced from the vibration of diaphragm and thus the voice coil. The electricity is first
transmitted to the controller and then directed to the electrical appliance or storage system.

Hooke's Law
It states that the applied force is directly proportional to the extension of a material, provided that the
elastic limit is not exceed.
F = kx
where x is the displacement of the spring's end from its equilibrium position,


k is the force constant or elastic constant

f =
(f is the frequency of the spring balance)


Resonance
When the driving frequency is equal to the natural frequency of the driven system, the amplitude of
the motion is maximum and hence maximum power is transferred to the system from the oscillator.
In our design, we need to consider the frequency of the material of floating slab and also the
frequency of the loudspeaker. The reason is to ensure resonant frequency is developed so as to
produce maximum power.

The frequency of the floating slab depends on its stiffness and mass, where
F /


Copyright 2011-12 FCE Research Support Scheme Team No.2 3
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Electromagnetic induction
Electromagnetic induction is the production of electric current across a conductor moving through
a magnetic field. In our design, we make use of the reverse property of the loudspeaker to generate
electricity (a normal loudspeaker converts electrical energy to mechanical energy).

According to Faraday's law of electromagnetic induction, electromotive force (EMF) produced
around a closed path is proportional to the rate of change of the magnetic flux through
any surface bounded by that path. For Lenz's law, an induced EMF always gives rise to a current
whose magnetic field opposes the original change in magnetic flux, together we get the formula

= - dB / dt
where B is the magnetic flux

The reverse property indicates that when a force (from the floating slab) is applied to vibrate the
diaphragm of the loudspeaker inside the magnetic field, induced e.m.f. will be formed and flowed in
the coil and hence electricity is generated.

= NBA sin


Copyright 2011-12 FCE Research Support Scheme Team No.2 4
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Current application of vibration to electricity

1. Sustainable Dance Floor (SDF)
Sustainable Dance Floor was developed by Sustainable Dance
Club, which was launched in the market in 2008 as the world's
first energy generating floor. It is now used as eye catcher for
sustainable innovation at many events and exhibitions, ranging
from a pavilion for renewable energy at the Winter Olympics to
use in a club and to use in a campaign to present in a show.

The source of energy of SDF are dancing and moving people. The energy produced by movement or
jumping i.e. kinetic energy is converted into electrical energy that is used to make the dance floor
react to the public in an interactive way, such as lighting up of different color. This also means that
the floor is basically a large touch screen providing information on the location and movement of the
people on the floor. The electricity can also be fed back to the electricity grid or used to power local
systems such as LED-lights.

To create electricity, the floor will compress 10mm when
being stepped on. This compression is great enough to
activate the internal generator of the module that will
produce up to 25 Watt of output per module. The Dance
Floor Modules are 75x75x20cm large and are allowed for
a large amount of possible sizes, shapes and designs of
the setup. The size can be varied to suit different clients.

The SDF can directly power other equipments. However, there are some restrains. Every module
produces up to 25W of power. To power up other appliances, more modules may require. Thus, the
SDF has an optional battery system and a power inlet connecting to the external grid. Electrical
energy produced by the dance floor modules will be used firstly. If it is insufficient, power from
stored energy in the battery or from the external grid will be drawn.



Copyright 2011-12 FCE Research Support Scheme Team No.2 5
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
2. The Pavegen Tiles
The Pavegen Tiles, invented by Lawrence Kembell-Cook, the director of UK Company, Pavegen
Systems, can generate green electricity by the foot power of the pedestrians on a street. The energy
can be stored and used for a variety of applications. The tiles make use of the dynamo technology
and collect the kinetic energy produced by walking over these green tiles. The top surface of the
flooring unit is made from 100% recyclable rubber while
recycled aluminium composes the internal components. The
system is designed to replace the existing flooring. Every time a
passerby steps on the slab, 5% of the energy contributed is used
to illuminate the tile to alert him about his share, whereas, the
rest of the energy is stored within the Lithium Polymer batteries
to power the surrounding street lamps and even the digital
displays. Each tile tends to generate 2.1watts of sustainable
energy per hour.

Pavegen Tiles can be applied in different ways
- Increased Pedestrian Safety
Pavegen Systems offer tactile paving slabs that generates energy at pedestrian crossings. The
lighting makes pedestrians more visible and increases the safety of its users with the Pavegen
slab that requires no grid connection.
- Powering street lighting, displays and signage
The system is particularly useful where grid connections are not feasible or where there is a
requirement for a low carbon solution.

- Generating energy from students
The tiles can be installed at schools, allowing thousand students to generate electricity every time
when they walk through the corridor to power lighting systems. It also enhance students'
awareness of sustainability in their daily lives.


Copyright 2011-12 FCE Research Support Scheme Team No.2 6
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
3.
Power Generation Device for Roadway Green Kinetic Energy
After receiving the counselling from ministry of Foreign Affairs, Yeu-Chun Green Energy
Technology Incorporated Co., Ltd. have cooperated with National Taipei University of Technology
on developing Power Generation Device for Roadway Green Kinetic Energy.

The device by Yeu-Chun is to use the car weight to compress the piston plates to transfer the energy
through hydraulic transmission method. The fluid compressed by the vehicles will help drive the
linear cylinder. The cylinder uses crankshaft-connecting rod system to convert the rectilinear motion
into rotation movement, and then drive the generator for power generation. The system fully
introduces mechanical transmission which helps reduce losses of power conversion and enhance
overall efficiency. The device is mainly divided into two parts. One is the piston plate; the other is
power generation device. The piston plate is composed of modules which are mainly by subsidence
installation on the road. For the power generation device, there is a potential storage that connects the
piston plate and power generation device. Due to the instability of traffic flow, a potential storage is
required to produce energy adjustment for the convenience of steady power output and combing into
mains electricity directly.

Furthermore, the device will be divided into two types. When there is bigger traffic flow, the power
can be directly generated out of piston plate for being run over by the vehicles. The other is when
there is discontinuous traffic flow, the fluid pressure can be temporality saved into potential energy
storage. The time difference between the vehicles regarded as output of energy buffer, to unleash
steady energy for power generation. When the device is installed on street, the capacity of power
generation is determined by car weight, paving length and traffic flow.

The traffic flow is the most important factor to consider for installation site, in which the downhill
paths and roads require deceleration driving will be major installation sites at initial stage, such as
the interchange down below the highway, downhill paths, falling slope of overpass, downhill path of
parking lot, roads require deceleration driving. The vehicles on these roads and paths require
deceleration driving originally. By having these devices installed will absorb and use the power of
road surface rendered by the vehicles for power generation and cause no additional energy loss to the
vehicles.


Copyright 2011-12 FCE Research Support Scheme Team No.2 7
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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Research Support Scheme Team No.2 (Dr. Chung-fai NG) Power Generation by Floating Slab using Recycled Loudspeaker
Construction of model
This part is illustrating the steps of constructing the model for experiment that generates electricity.
Pre-work
Silver plate
Track

This structure was used to simulate the real floating slab used in the track. The track was composed
of few wooden blocks. And the silver plate and the in the photo were used to stimulate the floating
slab in the railway.


This photo shows that the track is adjustable by utilizing the screw as shown

Design A

Diaphragm

Piston
In the initial stage, a piston was used. This photo
shows the orientation of the piston in the
loudspeaker box set. The piston will be moving up
and down in that hole of the loudspeaker box set.
Then the air pressure inside the loudspeaker will
change, thus the diaphragm of the loudspeaker will
vibrate and finally, electricity is generated




Copyright 2011-12 FCE Research Support Scheme Team No.2 8
Environment and Sustainable Development - Department of Civil and Structural Engineering - The Hong Kong Polytechnic University

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