This document describes an elective on energy harvesting that will discuss harnessing renewable energy from the environment, including an overview of energy harvesting, applications, and a hands-on activity where students will characterize solar panels and use the energy to power loads like LEDs, motors, and buzzers. Students will also design a scenario to power a 3 room apartment using solar energy under constraints set by the owner.

1. Energy Harvesting Elective
Are the Environmental Energy Going to Waste?
Harness Renewable Energy from the
Environment
Presenter: Mr. Tan Yen Kheng
(g0600108@nus.edu.sg)
Department of Electrical & Computer Engineering
Cordially invited Raffles Junior College for the presentation

2. Present Energy Crisis
Global warming results from excessive fuel burning
Pollution caused by burning and oil spill
Depleting in fossil fuels supply
Surge in oil price due to growing demand
Economy intact with energy supply

3. Sources of Energy
Sources of electricity in the U.S. recorded in 2005
Fossil fuel generation is the largest energy source
Cited from Wikipedia, the free encyclopedia, “Electricity generation”, >http://en.wikipedia.org/wiki/Electricity_generation<

4. Sources of Energy (cont’d)
Renewable energy source Nonrenewable energy source
Renewable energy source Nonrenewable energy source
Renewable energy source Nonrenewable energy source
Renewable energy source Nonrenewable energy source
Renewable energy source Nonrenewable energy source
Cited from National Energy Education Development Project (NEED), “Scientific Forms of Energy”,
>http://www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html<

5. Transformation of Energy
How do we achieve the goal of providing energy to the consumer at a
specified location?
converting energy from primary form (e.g. chemical energy contained in
coal) to a suitable secondary form (electrical energy)
transporting energy in the secondary form (electrical) from the place of
conversion to the point of consumption, and
finally converting it back to a suitable form (mechanical) at the point of
consumption for final usage
Transmission & distribution
Power Electric Final energy
Primary energy Power station
electronics machines usage
Fossil fuel
Controlled Electric Drive
Power
Steam Electric Electric Mechanical
Nuclear electronic
turbine generator machine load
converter
Solar heat
Thermal Mechanical Electrical Electrical Mechanical
constant v & f variable v & f

6. Transformation of Energy
Energy in electrical form is most versatile and
universally useful:
instant availability
easy transmit-ability
easy controllability
For these reasons:
centralized electric power generating stations are built
transmission and distribution networks have been developed
to convert, transmit and deliver energy to the point of
consumption

7. Motivation of Energy Harvesting
“The pervasiveness and near-invisibility of computing will be helped
along by new technologies such as … inductively powered computers that
rely on heat and motion from their environment to run without batteries.”
Bill Gates in ‘The Economist’, Dec. 2002.
“The $170 million initiative is part of an over $1 billion research
blueprint, to generate new breakthroughs, grow top R&D talent and pursue
a new research area - clean energy.”
article in ‘Strait times Newspaper’, Mar. 2007.
Goal: To investigate various energy harvesting technologies that can
power mobile low-power electronic devices

8. Overview of Energy Harvesting
What is energy harvesting?
Gather energy from ambient environment and convert into
usable electrical energy
Importance of energy harvesting
Need for endless energy supply to electronic systems
To reduce dependency on batteries
Accelerated interest for powering ubiquitously deployed
sensor networks and mobile electronic products
To conserve energy consumption and promote
environmental friendliness

9. Overview of Energy Harvesting
Advantages
Boundless supply ⇒ Self-sustainable
Ample energy solution ⇒ Unlimited usage
Readily available, anywhere, everywhere
⇒ Mobility and promote truly autonomous
Green and clean
⇒ Environmental friendliness
Eliminate the problems that arise from replacement
/recharging of batteries
Suitable for numerous deployment at unreachable location

10. Characteristics of Batteries
1000
Continuous Power Density (µW)/cm3
Lithium
100 Alkaline
10
Zinc air
Lithium rechargeable
1 NiMH
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Lifespan (Years)

11. Forms of Energy
KINETIC ENERGY POTENTIAL ENERGY
Electrical Energy is the movement of Chemical Energy is energy stored in the
electrical charges. bonds of atoms and molecules.
Radiant Energy is electromagnetic energy Mechanical Energy is energy stored in
that travels in transverse waves which includes objects by the application of a force.
visible light, x-rays, radio waves, etc. Solar
energy is an example of radiant energy. Nuclear Energy is energy stored in the
nucleus of an atom––the energy that holds
Thermal Energy or heat, is the internal the nucleus together.
energy in substances – the vibration and
movement of the atoms and molecules within Gravitational Energy is the energy of
substances. position or place.
Motion Energy is the movement of objects
from one place to another.
Sound is the movement of energy through
substances in longitudinal waves.

12. Potential energy harvesters

13. Comparison of Energy Harvesting Sources
Energy source Power densities Notes
Cited from J.A. Paradiso, T. Starner, “Energy scavenging for mobile and wireless electronics”,
IEEE Pervasive Computing, vol.4, issue.1, pp.18 – 27, 2005

14. Lists of possible application areas
Potential applications
Remote area sensing
Detection of natural disasters
Industrial Automation
Condition-based maintenance of energy distribution system
equipment
Lifestyle Management
Body area network for health monitoring
Structure health monitoring
Buildings and bridge structure monitoring
Automotive Network
Vehicle navigation and safety system
Eco Management
Charging of Electronic devices, etc.

15. Thermal Energy Harvesting
Nextreme Thermal Solutions: http://www.nextreme.com/home.htm

16. Thermal Energy Harvesting (cont’d)
Wrist-watch-like thermal harvester to power oximeter
Thermoelectric conversion of human heat
Oximeter measures heart rate
and oxygen level in the blood

17. Thermal Energy Harvesting (cont’d)
Seiko’s Thermic wristwatch
Small thermal gradient provided by body heat over ambient
temperature
Hence body heat energy is converted into electrical energy and then
into mechanical energy

18. Vibration Energy Harvesting
Piezoelectric and Electromagnetic generators

19. Vibration Energy Harvesting (cont’d)
Stair-Case Vibrations from Running Up and Down Stairs
Convert vibrations from passing trains to provide continuous
light without the need for wiring into the grid
Harvest vibration energy from a wooden staircase to power
temperature sensor
Research work done in University
of California, Berkeley, USA

20. Vibration Energy Harvesting (cont’d)
Motion/Kinetic/Vibration Energy
Captures the kinetic energy of normal everyday motion – Human
or vehicular
Helping solve the military’s high-pain mobile power crisis
Transforming the way mobile devices are powered
M2E link: http://m2epower.com/index.htm

21. Vibration Energy Harvesting (cont’d)
Batteryless remote controller/lighting switch
Converts mechanical energy provided by human hand depressing
the piezoelectric transducer into regulated electrical energy to
power the RF transmitter
To power remote control of light switches within buildings in a
wireless manner
Piezoelectric
Transducer
RF transmitter and power
conditioning circuit

22. Motion Energy Harvesting
Knee-powered generator
Self-powered totaltotal knee replacement setup
Self-powered knee replacement components

23. Wind Energy Harvesting
A wind turbine obtains its power input by converting the force
of the wind into a torque (turning force) acting on the rotor
blades
The amount of energy which
the wind transfers to the rotor
depends on the density of the air,
the rotor area and the wind speed

24. Wind Energy Harvesting (cont’d)
Wind energy harvesting scheme implemented to power remote
area wind speed sensor

25. Solar Energy Harvesting
Develop a solar energy harvesting mechanism to power the
optical sensor used to detect vehicle speed
Solar-powered Wireless Optical Sensor for Vehicle Speed
Detection
Rechargeable battery
Power processing unit
and RF circuits
Solar panel
Optical sensor

26. Solar Energy Harvesting (cont’d)
Optical sensors
placed 2
meters apart
Vehicle
traveling
t t
speed = 1 2
Y = t2 – t1
2/Y
time
Calculation for speed:
Distance between the optical sensors = 2 meters
Total time taken by the car to travel 2 meters = 340ms
Speed = Distance/Time = 2m/340 ms = 5.88 m/s = 21.17 km/h
Actual traveling speed of the car = 20 km/h

27. Design considerations for energy
harvesting circuit
Typical block diagram of the energy harvesting circuit
More challenges and design considerations for the low-powered
power converter than other portions of the power processing
unit

28. Photovoltaic Technology
Do You Know ……
The sun generates an enormous amount of energy –
1,540,000,000,000,000,000 kWh/year
(1,540 Peta kWh/year)
This is 15,000 times as
much the electrical
consumption worldwide

29. Photovoltaic Technology (cont’d)
PV stands for Photovoltaic and is short for photovoltaic
solar energy
Photovoltaic solar cells or PV cells convert sunlight
directly into electrical energy
Solar cell’s energy conversion efficiency is the percentage
of power converted from absorbed light into electrical
energy
For example, solar cells of 1 m² surface area producing
120 watt of peak power (Wp) under Standard Test
Condition (STC) has efficiency of 12%

30. How Photovoltaic Works
Photovoltaic cells – silicon-based
A solar cell or a photovoltaic
cell is a device that can convert
light energy directly into
electrical energy by means
of photovoltaic effect
Two main functions:
1. Photo generation of charge
carriers in a light absorbing
material (electrons and holes)
2. Separation of these charge
carriers to maintain flow
i.e. produce electricity

31. How Photovoltaic Works (cont’d)
When solar energy photons hit the cell, its energy frees the
electron hole pair. The electric field generated in the depletion
zone pushes the electron to n-side where it is provided with a
conducting path to produce current
Flow of
Su Electrons
nl
ig
ht
N-Type Silicon
Junction Layer
P-Type Silicon

32. Types of PV cells
Monocrystalline Silicon Cell
The principle advantage of mono-
crystalline cells are their high
efficiencies, typically around 15%,
higher costs than other technologies
Multicrystalline (Polycrystalline) Silicon Cell
Multicrystalline cells are cheaper
to produce than monocrystalline ones,
slightly less efficient, with average
efficiencies of around 12%

33. Types of PV cells
Amorphous (Non-Crystalline) Silicon
Composed of silicon atoms in a thin
homogenous layer. Amorphous
silicon can be deposited on a wide
range of substrates, both rigid and
flexible. Efficiency varies between
4% to 12%. Easy to manufacture,
low cost

34. Types of PV cells
Other Thin Films
Cadmium Telluride (CdTe) and
Copper Indium Diselenide
(CIGS: Cu(In,Ga)Se2 ) are now
being used for PV modules. Can
be manufactured by relatively
inexpensive industrial processes,
and offer higher module efficiencies
than amorphous silicon.

35. Factors Affecting PV Performance
Solar Isolation
Angle of Incidence and Orientation
Temperature
Spectrum of Light
Shadows
Dust, Dirt, Fungus, Birds

36. Factors Affecting PV Performance
Solar Isolation
State / City Latitude Longitude Year Average
Sydney 34°0’ S 151°0’ E 4.59
Singapore 1°17’ N 103°51’ E 4.61
Kuala Lumpur 3°7’ N 100°42’ E 4.70
Bangkok 13°45’ N 100°30’ E 4.27
New Delhi 28°42’ N 77°12’ E 5.10
Tokyo 35°45’ N 139°38’ E 4.00
Paris 48°52’ N 2°20’ E 3.34
London 51°32’ N 0°5’ W 2.61
Mexico City 19°23’ N 99°9’ W 5.49

37. Factors Affecting PV Performance
Angle of Incidence and Orientation
To optimise the effect of the solar radiation, the solar
cells need to be directed towards the sun
The electricity yield of a solar cell depends strongly on
its orientation and angle of inclination
Reflected rays
Sunlight
Harvested rays
Solar panel

38. Factors Affecting PV Performance
Temperature
Cell temperature increases, PV performance decreases

39. Factors Affecting PV Performance
Spectrum of Light
Solar cell respond differently to the different wavelengths or
colours of light
Light that is too high or low in
energy is not usable by a solar
cell to produce electricity

40. Factors Affecting PV Performance
Shadows
Shadow casts on solar cells
affect the output performance

41. Factors Affecting PV Performance
Dust, Dirt, Fungus, Birds
Spikes installed to
prevent birds resting
Fungus Growth

42. Conclusions
Discuss on the topic of Energy
Overview of Energy Harvesting
Illustrate some applications of EH in both academic and
industry
Learn about photovoltaic technology
Investigate on various factors that affect the PV
performance

43. Q&A
Thank you
for your attention!

44. Energy Harvesting Elective
Objectives of Elective
Getting to know Solar Energy Harvesting
Understand how power is harvested and transferred to
the load
Characteristic the performance of the solar panel
Design and implement solar energy harvesting in
practical application system

45. Energy Harvesting Activity (cont’d)
Basic configuration of the solar panel and the motor

46. Energy Harvesting Activity (cont’d)
Materials to be provided to each team include: -
2 x Solar Panels
1 x Solar Motor
3 x LEDs (Red, Yellow, Green)
1 x Buzzer
1 x Variable resistor
1 x Digital Multimeter
1 x Breadboard

47. Energy Harvesting Activity (cont’d)
Guidelines for the hand-on sessions
1. Characterize the solar panels
a) Measure the electrical Open-Circuit (O/C) voltage and Short-
Circuit (S/C) current
b) Connect the solar panel to the load resistance. Measure the
voltage across the load and the current in the circuit
c) Repeat steps 1.a) and 1.b) for different light intensity
d) Plot the I vs V and Power vs Resistances curves

48. Energy Harvesting Activity (cont’d)
Guidelines for the hand-on sessions
2. Use the solar panel to power the given loads i.e. LEDs,
motor and buzzer
a) Measure the voltage required by each load
b) Measure the current required by each load
c) Compute the power required by each load based on
Power = Voltage x Current

49. Energy Harvesting Activity (cont’d)
Guidelines for the hand-on sessions
3. Design Scenario
a) Imagine you are a contractor who is tasked to design
a three room apartment to run on sun energy
b) The design of the apartment must fulfilled the
following constrains by the owner
I. At least one ‘ON’ LED per room
II. At least one fan in one of the rooms
III. Place a door bell in the apartment
IV. Under bright light intensity
c) Draft out the circuit schematic drawing to verify that
your design is working

50. Q&A
Q&A