encipher 2012
TRANSCRIPT
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Encipher2012
Published by Society of Electrical and Electronic Engineers (SEEE)
Encipher | 2012
EDITORIAL
No one can whistle a symphony; it takes an orchestra to play it. Certainly,
each individual in our publishing team have been a part of a great
orchestra to play all the harmonies of ENCIPHER. They undoubtedly deserve a
wholehearted appreciation for every instrument they lifted and every note
they played. From the collection of articles and advertisements to working on
designing and editing, each one of us have struggled to bring the best to our
readers.
In the department of electrical and electronics engineering at Kathmandu
university, it is not just the classroom lectures or the textbooks that students
learn. The most important lesson they learn is to contribute their knowledge
of technology for the betterment of their society. ENCIPHER is such a platform
which allows the students to do so.
This year there have been slight alterations to the magazine, the layout has
been exemplified beautifully and the reports printed in a more standard form.
This is an attempt to make the magazine more attractive and readable. The
superficial changes, however, in the appearance of the magazine are relatively
unimportant when compared to the most important factor in any magazine,
the contributions. As in previous years, this issue of ENCIPHER is the collection
of contribution from the students and the faculty members in their field of
study. But we were especially glad to be receiving article from national and
international sectors like Nepal Telecom and National University of Singapore.
There are obstacles in the life of a magazine - from planning, through
production, till publication, the main one being the inevitable problem of
finance. We would therefore like to thank our national and international
sponsors who have turned this issue into a reality.
This magazine is also uploaded in the website www.ku.edu.np/ee/seee.
For editorial queries, write to us at [email protected]
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EDITOR-IN-CHIEF
MANAGING EDITOR
EDITORS
GRAPHICS ANDDESIGNING
MARKETING EXECUTIVES
CONTRIBUTORS
SPECIAL THANKS
ACHYUT DEVKOTA
ABHILASHA BHUJU
AMAR SHRESTHA
NIRAB SHRESTHA
MANJIL SHAKYA
SAURAV BHATTARAI
AASTHA BHATTARAI
SHILPA MANANDHAR
SHASHI RAJ PANDEY
KASTUV MANI TULADHAR
DIPU MANANDHAR
ARQOOT MANANDHAR
SANGRILA PHUYAL
SAROJ MAHARJAN
PRASHANSA SHRESTHA
SIRISH SHRESTHA
Encipher | 2012
Table of Contents
Message from Head of Department
Message from SEEE President
Application of linear Analysis for Stability Study of a Rural Power System
Audio Notice Board Service
Next step in Cellular Services
-Long Term Evolution
Gallium-Nitride Power Semiconductor Technology for
Future Energy Conversion Applications
MIMO in Wireless Communication
Single-phase Shunt Active Power Filter
-Modeling and Control
Gasification Technology for Rural Electrification in Nepal
- Efforts at Kathmandu University
Impacts of the Prepaid meter system on
energy consumption
5 inventions taking shape in 2012
ZigBee for Home Automation
GOOGLE- The journey from garage to Android
Visible Light Communication
Issues of Liquid Biofuels
HYDROPOWER
-Development and Challenges in Nepal
Practical Audio Processing Circuitry
WIMAX- at your service
Wireless Energy Transfer
Interview
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8
9
12
13
15
18
19
22
24
25
27
29
31
33
35
36
38
40
41
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Encipher | 2012
Message from Head of Department
Engineering student's role is not only to pursue academic excellence but also to be self
motivated and lifelong learners, critical thinkers, and productive members of an ever-
changing global society.
To reach the greater heights students natural talents and abilities need to be identified and
nurtured. They need a platform to think, express their ideas and exhibit their skills. They need
to communicate their ideas in writing and express themselves in creative ways.
Through ENCHIPER our Electrical and Electronics Engineering students can flow their mind. To
produce such a quality magazine with hard work, dedication and teamwork is praise worthy.
Albert Einstein, who once said, “Imagination is more important than knowledge. For while
knowledge defines all we currently know and understand, imagination points to all us might yet
discover and create.”
Once again I congratulate The ENCHIPER team and SEEE for publishing yet another edition of
ENCHIPER 2012 and I wish you best of luck for your effort and wish you to work continuously in
producing this magazine with more in-depth knowledge, new ideas and making it as an
international standard in the years to come.
With warm regards,
Brijesh Adhikary
Graduate Program Coordinator
Department of Electrical and Electronics Engineering
Kathmandu University
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Encipher | 2012
Message from SEEE President
Technically speaking, Encipher is to decode the messages into cipher so as to make the
message hard to read and understand. But our magazine Encipher is not to proselytize the
knowledge and information but to build a common pulpit for knowledge sharing, revealing new
ideas, communicating new technologies and protruding creativity and innovation. This magazine
has provided each and every individual a chance to show his/her talent as being a writer, a
researcher, a graphics designer, an editor, a moderator or as a good reader who can provide us
healthy comments for the improvement of the magazine.
It has once again endorsed the capability and determination of each and every members of SEEE
along with Department of Electrical and Electronic Engineering who have contributed sincerely
for the publication of the Encipher 2012. The success of this magazine has made us raise our
head to dignify the unity and potential of the department for the enlighten of the horizon of
information.
We would like to express our sincere gratitude to the members of Encipher magazine, our
department members and the financial partners who facilitated us achieve this milestone. We
appreciate every comment ameliorating the magazine for our future publications.
With warm regards
Dhurba Bhattarai
President
Society of Electrical and Electronic Engineers (SEEE)
Kathmandu University
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Encipher | 2012
APPLICATION OF LINEAR ANALYSIS FOR
STABILITY STUDY OF A RURAL POWER SYSTEM
Abstract-This article presents a preliminary study of stability of a rural
power system. Linear analysis based on eigenvalue is used as a tool for the
study. A rural power system has been simulated using SIMPOW simulation
tool. Eigenvalues have been computed and the stability of the system is
predicted. The movement of eigenvalues with the change in the system
control parameters has been demonstrated.
1. INTRODUCTION
Electrification of rural and remote areas is a challenge for
the developing nation like Nepal. Renewable sources like
Micro hydro, wind turbine, photovoltaic system etc. are
being installed to meet the electrical demand in the rural
communities. As the installations of distributed generations
are growing up there is a need of interconnection of these
sources to form a local grid. Thus assessment of the system
stability of the interconnected generators for rural power
system becomes essential.
Linear analysis is a useful tool to study whether a power
system is stable or not, as it enables the determination of
the eigenvalues of the system. A complex power system can
be linearized about an equilibrium point in order to get
useful information on the small signal performance of the
system. The state-space approach using eigenvalue
techniques is an effective method for analysis of such
complex systems.
Results of linearization of a power system dynamics around
an operating point is expressed in state-space form
where x is (nX1) vector of state variables, and A is an (nXn)
matrix of real constant coefficients [2]. The characteristics
equation is given by:
det(A- I) = 0
The values of λ that satisfy the characteristics equation are
called eigenvalues. Eigenvalues can be real or complex. The
locations of the eigenvalues in the complex plane give
information about oscillatory behavior of the system. The
stability of a system is determined by the eigenvalues as
follows:
(a) A real eigenvalue corresponds to a non-oscillatory
mode. A negative real eigenvalue represents a
decaying mode. The larger its magnitude, the faster
is the decay. A positive real eigenvalue represents
aperiodic instability [1].
(b) Complex eigenvalues occur in conjugate pairs, and
each pair corresponds to an oscillatory mode. The
real component of the eigenvalues gives the
damping; the imaginary component gives the
frequency of oscillation. A negative real part
represents a damped oscillation whereas a positive
real part represents oscillation of increasing
amplitude
λ
[1].
For a complex pair of eigenvalues:
The frequency of oscillation in Hz is given by:
=
This represents the actual or damped frequency. The damping ratio
is given by:
The damping ratio determines the rate of decay of the amplitude of
the oscillation. The time constant of the amplitude of the decay is
1/| |, [1]. In practice damping is considered satisfactory if the
damping ratio 0.05 [2].
2. SYSTEM DESCRIPTION
The rural power system considered for the study is a case with four
micro hydro powers connected to form a local gird. The
interconnected system is as shown in the figure-1 below. It consists
of eight buses with four synchronous generators of 0.4MW,
0.5MW, 0.64MW and 0.7MW. The system also has 4 transformers,
one each with generators and four loads of 0.3MW (L5), 0.6MW
(L6), 0.5MW (L7) and 0.5MW (L8) respectively at buses 5, 6, 7 and
8. The system has a fundamental frequency 50Hz and system
voltage 230V.
All the synchronous generators are driven by cross flow hydro
turbines. Each turbine is equipped with a turbine governor which
controls the speed or the output power according to a preset
power-frequency characteristic. The generators power is fed into
the transmission network via a step-up transformer. The DC
excitation (or field current), required to produce the magnetic field
inside the generator, is provided by the exciter. The excitation
current, and consequently the generator's terminal voltage is
controlled by an automatic voltage regulator (AVR) [2]. Figure-2
below shows the block diagram showing voltage and speed control
at each power generation unit.
ƒ
ζ
ζ
σ
≥
Figure-1: Single line diagram of the rural power system
Figure-2: Block diagram of control system at each synchronous generator [2]
Shailendra Kumar Jha
DoEEE, Kathmandu University
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2p
Application of Linear Analysis
for Stability Study of a Rural
Power System
Everyone is a genius at least once a year. The real geniuses simply have their bright ideas closer together.—Georg Christoph Lichtenberg
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Encipher | 2012
The AVR regulates the generator terminal voltage by
controlling the amount of current supplied to the generator
field winding by the exciter. The regulator used in the system is
a proportional controller as shown in the figure-3 below.
Figure-3: Proportional regulator [3]
For stable operation, the turbine must have a power–speed
characteristic such that as the speed increases the mechanical
input power reduces. Similarly, a decrease in speed should
result in an increase in the mechanical power. This will restore
the balance between the electrical output power and
mechanical input power [2]. The turbine model used in the
system is the classical turbine model. The figure-4 below
shows the block diagram of the classical turbine model
considered.
Each turbine is equipped with a governing system to provide a
means by which the turbine can be started, run up to the
operating speed and operate on load with the required power
output. The governor considered for the system is an
approximate speed governing model as shown in the figure-5
below.
The task of the turbine governor is to set a characteristic which
has a small droop. Such a characteristic is necessary to achieve
stable operation of the turbine. Physically droop can be
interpreted as the percentage change in speed required to
move the valves from fully open to fully closed. K = 1/ is the
effective gain of the governing system [2].
The linear analysis has been performed as follows: (i) Eigen
value computation, (ii) Mode shape computation, (iii) Data
scanning
All the eigenvalues of the system were computed and the
values with the electromechanical modes in the range form
0.2Hz to 2Hz were listed as given in the table-1 below.
Figure-4: Classical turbine model [3]
Figure-5: Approximate speed governing model [3]
ρ
ρ
3. ANALYSIS AND RESULT
Eigen value computation
Table-1 : List of Complex eigen values
The graphical representation of the eigenvalues is shown in the
figure-6 below.
All the eigenvalues computed has negative real part, which shows
that the system is stable. Also damping ratio 0.05 for all the
eigenvalues, thus the system has satisfactory damping.
The mode shape analysis plays an important role in power system
stability analysis, especially for determining the influence of
individual oscillatory modes on swings of rotors of individual
generators. The output of model analysis is expressed either in
terms of kinetic energy magnitude and angle or in terms of phasor
diagram. By studying the output an oscillation of eigenvalues
mode can be identified. The graphical representation of the modal
analysis for the complex eigenvalues no. 21 of the system is shown
in the figure-7 below.
The result for mode shape for eigenvalue number 21with respect
to generator power shows the case of inter area mode where
generator G3 is the most dominating mass and is oscillating against
all other generators G1, G2 and G4. For all other cases too, the
mode shapes shows inter area oscillations, but the dominating
generator is different for different frequencies.
Figure 6: Position of Eigen values
Figure 7: Mode shape analysis for eigenvalue number 21
ζ≥
Mode shape computation
Eigenvalue
nos.
Damping
(1/s)
Oscillating
Frequency
(Hz)
Damping
ratio
(%)
5 -21.2 5.4 96.9
15 -19.4 1.9 99.5
17 -19.5 2.2 99.4
19 -19.5 2.1 99.4
21 -5.2 1.1 97.8
23 -4.3 1.2 96.1
25 -4.0 1.2 95.9
43 -0.3 0.055 98.6
48 -0.08 0.006 99.7
Even if you’re on the right track, you’ll get run over if you just sit there.—Will Rogers
Application of Linear Analysis
for Stability Study of a Rural
Power System
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Encipher | 2012
Data Scanning
Data scanning shows how an eigenvalue moves when a
control parameter of the system is varied. For this system,
figure-8 below shows how the eigenvalues moves when the
regulator gain KA for generator G3 varies from 100 to 500 in
steps of 50.
At KA =400 the system is stable. As depicted in the figure the
system is stable for all values of KA. For all the eigenvalues
with the increase of regulator gain KA the system becomes
more stable.
Figure-9 below shows the data scanning for generator G3
varying governor gain K. The system is stable for gain K=20
for all the eigenvalues. When the gain K is increased the
system becomes more stable for most of the eigenvalues. If
gain K is decreased the system stability decreases.
The following conclusions were drawn from the linear
analysis:
All the eigenvalues computed has negative real part,
which shows that the system is stable. Also damping
ratio 0.05 for all the eigenvalues, thus the system
has satisfactory damping.
Modal analysis shows that generator G3 has the
largest out swing and is oscillating against all other
generators for most of the cases.
For all the eigenvalues with the increase of regulator
gain KP the system becomes more stable.
Figure 8: Data scanning for generator G3
varying regulator gain KA
Figure 9: Data scanning for generator G3
varying governor gain K
·
·
·
≥
· The system is stable for gain K=20 for all the eigenvalues.
When the gain K is increased the system becomes more
stable for most of the cases.
The article presented how the stability of a power system can be
predicted using eigenvalues study. It also shows how the
characteristics of eigenvalues changes with the decreases or
increase of control parameters of the system. Although the study
was carried out on the rural power system, linear analysis is
equally applicable for large power systems. The system modeling
has been done with introducing basic components of the system
only, thus better predication can be done by detail modeling of the
system.
1. Kundur P., “Power System Stability and Control”, The EPRI
Power System Engineering Series, 1994.
2. Machowski J.,Bialek W. J., and Bumby R. J, 'Power System
Dynamics Stability and Control”, John Wiley & Sons, Ltd,2008
3. SIMPOW simulation software User Manual 11.0, STRI
2010.
4. CONCLUSION
REFERENCES
Application of Linear Analysis
for Stability Study of a Rural
Power System
“Adversity reveals genius, prosperity conceals it.” — Horace
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Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
It might seem quite impossible to believe. The development
of technology leads to the increase in expenditure of Service.
Notice Board Service which is best known as Voice Mail
Service (VMS) Notice Board Service technically or Audio
Notice Board Service. It's a very new technology.
This technology can be helpful in school, college, education
centre, Training centre, ministries etc where one can record
the information and listen to it many times or multiple users
can listen to it again and again at the same time in all of 75
districts of Nepal without the aid of additional manpower.
During the process the customer has to pay the bill for the
local call only and no the distance charge.
Don't you still believe!
Please dial and listen to yourself to the
news of Radio Nepal or dial and listen to
or dial and listen to
Ujjyalo News Network Khabar.
Everyone may have to know about when does the office
opens or when does it closes, if the office opens in the
closing days too, how to save electricity, water etc and many
other time safety measures.Many of the schools, higher
secondary schools may implement Audio Notice Board
Service to aware the students, teachers and parents about
the syllabus, new session etc.Similarly, social service centre,
some active ministries of Nepalese government has been
using these technologies for example Employees Provident
Fund use Audio Notice Board Service to convey the
information. Further, such Fund has been publishing such
news in one line sentence and one can know which is related
to the particular account by dialing the account number. This
practice has added a milestone to the application of new
technology.
The information which could be important to ordinary
people or limited group of communities like students,
players, musicians, music lovers, art lovers, consumers,
tourists, visitors, etc can be transmitted through Audio Voice
Board Service, and this service has been or can be made
available to the people in the future.
While opening the Narayanhiti Museum, the days in which
the museum would remain open or on which particular days
it remains closed or it would remain close twice a week or
any such information could be provided using Audio Notice
Board Service, the people coming from distant places
wouldn't have to return empty hand.
If such Audio Notice Service are made available, people
coming to watch the games at Dasrath Stadium, wouldn't
have to be depressed even if any match had been called off
or been postponed due to some reasons, further one can
know about which game is happening when and at what
time. So if such facilities are provided to the people, it would
1618-0707-00000
1618-707-77777
onlinekhabar.com 1618-0707-55566
develop overall sports of the nation.
Similarly, the drama lovers, music lovers, or literature lovers can
know at what time which presenter is presenting, which of the
art is free or payable. For example a show by famous artists Hari
Bhansa Acharya and Madan Krishna Shrestha is being shown or
any most view shows is being shown by the television or being
broadcasted by the radio but people don't know at what time is
the shows is being broadcasted. Thus such information could be
imparted to the general public.
A country like Nepal where load shedding is very prominent, Audio
Notice Service Technology could play a very important role. Due to
lack of educated and active communities it's importance has
further increased. Nepal Electricity, willingly or by force
continuously supply or cut off the electricity supply. Thus the
information of the time table on which day at what time there will
be supply or cut off of the supply could be made available to the
general customer using various Audio Notice Service (Currently 7
groups), by dialing to the respective group numbers. Also the time
table changes periodically according to the need of the electricity
in the nation so, if such information is transmitted to the people,
they would be hugely benefited.
Similarly, people are greatly affected due to problems regarding
the drinking water supply as they don't know on which particular
days is the supply continuous and on which days not.
Nepal khanepani sansthan and Kathmandu Upatyaka Khanepani
Limited is divided into four or five groups.So if the information
could be pre informed to the consumers, they could have utilized
the drinking resources well without any difficulties.
The notices published through Health Ministries time to time
regarding the various vaccines against the disease, measures to
control such disease or methods of preventions, place where
blood donation are carried out. Audio Notice Service could play
significant role in making people aware.
During the advertisement of Audio Notice Board Service Number,
particular number could be addressed so that people could dial
the number and take the benefit of such facilities. Many students
nowadays are going abroad for their future studies, and many of
them are unaware of such facilities, if Audio NBS Audio Notice
Service could be made available to them, they could be made well
informed. Let's hope respective nikayas would use such technology
to impart the information in small time to all the people in the
future.
Audio Notice Board Service
Audio Notice Board Service
Nabin Lal Shrestha
PSTN Directorate, Gwarko, Lalitpur
“If such Audio Notice Service are made
available, people coming to watch the
games at Dasrath Stadium, wouldn't have
to be depressed even if any match had
been called off or been postponed due to
some reasons”
“Show me the man you honor, and I will know what kind of man you are.” — Thomas Carlyle
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Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Recent Developments are growing in the field of Mobile
Communications and Nepal does not remain untouched
in this area. At present we have already experienced 2G and
features of 3G. Now telecom operators are talking about 4G
which can offer high speed internet, supportvarious
multimedia services on a common platform.Second
generation of wireless technology was widely dominated by
GSM(Global System for Mobile Communication) in voice
communication but it could not provide high data rate. So, to
overcome this problem GPRS(General Packet Radio Service)
was introduced which could provide high data speed, but still
could not satisfy the need of high speed internet. With the
introduction of 3G (WCDMA-WideBand Code Division
Multiple Access) both voice and high speed data have been
supported. At present with the significant increase in number
of mobile terminals and enormous amount of data from online
gaming, file sharing, video conferencing and VoIP it has almost
become difficult to handle with the existing networks. But
now it is possible to realize all our crazy data hunger
with the release of the new3GPP (Third Generation
Partnership Project)standard 'LTE' as a
high performance radio interface evolution for the UMTS
(Universal Mobile Telecommunication System).
LTE has not yet been deployed in our country with only few
sites that has been planned by Nepal Telecom. But,serious
talks have been going on among vendors like ZTE, Huawei and
customers like NCELL, NT for its soon deployment.
It may come into mind of many technical and non-technical
individuals what LTE is? How is its system Architecture? What
are the benefits offered? So, these are very basic questions
that have been answered in this article.
( i s a s t a n d a r d f o r
wirelesscommunication of high-speed data for mobile phones
and data terminals. Cellular long term evolution (LTE) is the
next step forward in cellular 3G services. LTE technology based
on a 3GPP standard provides a downlink speed of up to 100
megabits persecond (Mbps) and an uplink speed of up to 50
Mbps. With multiple antennas, speeds can reach more than
320 Mbps on thedownlink.
Key features of LTE
· Higher data rate
· High spectral efficiency
· Very low latency
· Support MIMO(Multiple Input Multiple Output) for
enhancing capacity and system coverage
· Provides cost effective and smooth migration path
What is LTE
LT E L o n g Te r m E v o l u t i o n )
from earlier 3GPP radio interfaces and architecture.
· Reasonable system and terminal complexity.
System Architecture of LTE:-
This below picture depicts the architecture of LTE Network end
N o d e B i n 3 G i s t e r m e d a s e N o d e B i n LT E
(eNodeB=RNC+NodeB)
Core Network Consists of:
o MME (Mobility Management Entity)
o S-GW (Serving gateway)
o P-GW (PDN Gateway)
LTE Equipments from Customer End
Examples:
Iphone 5, Samsung Galaxy S3 LTE, Samsung LTE stick
o Rich voice o Video telephony o SMS/MMS
o Mobile TV o Video on Demand
o Music
o Communities o Gaming
o Photo/video sharing
·
·
·
·
·
Benefits offered by LTE:
Person to person communications
Content Delivery
Social Networking
Next Step In Cellular Services-Long Term Evolution
Next Step In Cellular Services
-Long Term Evolution
Ananda Gachhadar
DoEEE, Kathmandu University
“He was a man, he always performed his promises.” — Zebulon Pike
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Encipher | 2012
·
·····
Business Services
Scenario of LTE throughout the world
o High speed access
o Email
o Video Conferencing
The subscription numbers of LTE users throughout the world
has been growing rapidly and is believed to grow in the
upcoming years. In third quarter of 2012, the world added
13 million of LTE users, 20 million of GSM/EDGE users and
65 million of WCDMA/HSPA users. LTE is currently being
deployed and built out in all regions and will reach around
1.6 billion subscriptions in 2018.
The Asia Pacific market continues to see a massive increase
in subscriptions. Markets like japan and Korea will take up
LTE subscriptions very early whereas China will add
substantial LTE subscriptions in the later years.
This figure depicts the number of mobile subscriptions (in
millions) for different standards from year 2009 till 2018. LTE
is currently commercially deployed in:
Europe: TeliaSonera
North America: Verizon and AT&T
Japan: NTT DOCOMO
Hong Kong: CSL
Korea: SK Telecom
M-Commerce
Challenges for LTE handheld devices:
·o Banking
o Mobile Payment
o Mobile Advertising
The main concern with LTE devices is power. Since, LTE
devices are faster, provides high speed data and various
multimedia services with enormous features, power
consumption may be very high because of which battery
may drain within few hours.Typically more than 50 percent
of the power in any mobile phone is used by the power
amplifier and the transmission of high-speed data
reqstructions per second—but these new techniques,to
implement LTE, will have to process several billion
instructions per second, at low power.
References
[1] D, Tom, Why LTE Matters? , freescale semiconductor Inc.
[2] http://www.telecomlead.com/news/world-added-13-
million-lte-users-20-million-gsmedge-and-65-million-wcdmahspa-
in-q3-ericsson/
[3] S, Alexander, LTE, Wimax and 4G presentation, Department
of Computer Science Institute for System Architecture, Chair for
Computer Networks
Next Step In Cellular Services
-Long Term Evolution
“Don’t let your will roar when your power only whispers.” — Thomas Fuller
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Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Gallium Nitride (GaN) will become the promising technology
for future high-voltage and high-current semiconductor
devices for various power electronic energy conversion
applications, including various-speed motion control, solid-
state lighting, electric vehicle drives, wind and solar power
converters, uninterruptible power supplies, etc. The
performance merit (which is the on-state specific resistance,
versus the breakdown voltage rating ) of a fully-
developed GaN power devices will be two times better than
the Silicon Carbide (SiC) counterpart, and at least fifteen times
far better than the current silicon power semiconductor
technology.
Figure 1 shows the demanding trend in world power
semiconductor devices. The new driving force for its growth
will be on the green energy sector, where energy-saving
devices, electric vehicle inverters, photovoltaic system and
smart/micro-grids are the suitable applications.
The overall technology-evolutional process on power energy
conversion starts from the material innovation. A more
advanced material provides much better intrinsic properties
which determine the device behaviours and characteristics,
and ultimately its system performance. Table 1 shows the
comparison between GaN and other semiconductor
materials used for power semiconductor. What worth to
take note are the bandgap values, the electron mobility and
the breakdown field. The bandgap value affects the device
leakage current,and thus a larger bandgap is preferred. The
electron mobility affects the carrier transport and thus the
current conductivity. As to the breakdown field, it
determines the device voltage sustainable ratings. For the
power semiconductor devices used for energy conversion
application, the voltage ratings can reach a few kilo-
volts.Figure 2 shows the graphical comparison on the
performance merits among these materials. What can be
seen is that, the performance merit limit lines are moving
R Von,sp BR
I. Introduction
Fig.1 World power semiconductor market in
terms of sales values
towards the right-hand side lower corner by the advancement of
better materials.
Unlike the silicon carbide counterpart, gallium nitride devices does
not made on the GaN wafer, but on the epitaxy layer on top of the
silicon wafer. GaN is compatible with silicon substrates and this
creates the feasibility in forming a large-area epitaxysubstrate for
GaN device fabrication with low cost benefit. The use of silicon as
foundation substrate also provides an opportunity in silicon CMOS
circuit integration with GaN power devices. The second advantage
of using the epitaxy configuration is on the formation of the two-
dimensional electronic gas (2-DEG), which serves as a good
conduction channel for on-state current. The 2-DEG formation is
owing to the effect called polarisation. Such an effect bypasses the
difficulties currently faced by the SiC device development where a
good MOS chhanel with high electron mobility is required for the
on-state current conduction.Figure 3 shows the polarisation by the
spontaneous and piezoelectric causes, and their induced sheet
charge density can be calculated by some semiconductor
equations.
Fig.2 Comparison on the performance merits among silicon, silicon carbide and
gallium nitride devices
Fig.3 The AlGaN-GaN interface polarisation: (left) device epitaxy structure; (middle)
spontaneous polarisation due to uneven molecular bonds at the interface; (right)
piezoelectric polarisation due to uneven tensile strain at the interface and band
diagram
Both the net spontaneous and piezoelectric polarization effects
have the same sign. The piezoelectric effect is non-linear with the
Al Ga N mole fraction increasing, while the spontaneous effect
shows more linear behaviour with increasing. Furthermore, the
polarization charge density induced spontaneous effect is a little
larger than the other one which indicates both effects have
important influence on 2DEG.
x x1- x
x
Gallium-Nitride Power Semiconductor Technology for
Future Energy Conversion Applications
Gallium-Nitride Power
Semiconductor Technology
for Future Energy
Conversion ApplicationsYung C. Liang, Ph.D, P.Eng
National University of Singapore
“No act of kindness, however small, is ever wasted.” — Aesop
15
Figure 4 shows the induced charges at the Al Ga N/GaN
heterostructures with a partially relaxed Al Ga N layer. The
polarisation charge forms the 2-DEG layer right underneath
the AlGaN/GaN interface.
The GaN HEMT (High Electron Mobility Transistor) transistor
normally uses a Schottky gate to control the 2-DEG channel
for current interruption, as shown in figure 5. The Schottky
gate is also liable for early breakdown. More recently, works
on a staged MOS-gate and a trench MOS-gate to handle
both the 2DEG and gate regions for normally-off field
modulation were carried out. The gate extension in the
planar case serves as a field plate to shield the gate edge
and to ease the field crowding at high-voltage blocking
state. The field plate can be uneven in dielectric thickness
and multiple layers in order to achieve the best result in
field modulation in the drift region. The trench gate has a
GaN/AlGaN(AlN)/GaN sandwiched structure to form
multiple 2DEG region to boost up device conductivity.
Usually, polarisation charges at the interface, required for
accurate 2DEG simulations, can be computed
automatically by the built-in strain piezoelectric
x 1-x
x 1-x
Fig. 4 Bound net spontaneous (PSP), piezoelectric (PPE), and combined
polarization (PSP+PPE) induced sheet charge density as a function of Al
mole fraction for AlxGa1-xN/GaNheterostructures with a partially relaxed
AlxGa1-xN layer
II. The HEMT Structure and Operation
Fig. 5 TheGaN HEMT structures with (left) the Schottky gate and (right) the
trench gate and field plates.
polarization model in Sentaurus TCAD. Figure 6 shows the
internal field distribution and the leakage current of the GaN
HEMT device with 4 µm field plate next to the gate. From the
leakage current curve, it can be seen that the device will break
down at 2600 V.
The process to fabricate a normally-on GaN HEMT starts from a
GaNepitaxywafer, as shown in Fig. 7(a). Drain and source metal
deposition (Al, Pt, Ti and Au) and annealing are done the next.
The step requires high temperature process for ohmic contact.
Step (c) gives the passivation. Step (d) provides ion implantation
for inter-device isolation. Zn is a suitable candidate for such a
purpose. Step (e) provides the gate window opening, and
followed by step (f) the gate metal deposition. The contact is
Schottky. (g) gives the microscopy photo of the fabricated device
under the probing measurement.
Typical applications are in the high-power (10 – 30kW), high-
voltage (800 – 1200V) ranges for solar photovoltaic energy
system and electric vehicle drive system, as shown in Fig.8.Both
the configurations of the converter/inverter structure are similar,
i.e. in both the cases the power electronic circuit is consisting of
a DC/DC converter followed by an inverter. The only difference in
the HEV inverter is the brake chopper leg as shown.
III. Fabrication Processes
IV. The Power Electronic Applications
Fig. 7 A brief process flow for the fabrication of normally-on GaN HEMT device
This brake
chopper is used to provide electrical braking and dissipate the
kinetic energy extracted from the HEV motor-load combination.
The typical DC/DC converter shown here is a 4 leg two level
resonant DC/DC converter. These resonant converters if operated
at very high switching frequency (of the order MHz), can operate
at very high efficiency (of the order of 98% and so). However, the
typical high power silicon based MOSFET cannot be used for this
application.
Encipher | 2012
Gallium-Nitride Power
Semiconductor Technology
for Future Energy
Conversion Applications
“Man needs difficulties; they are necessary for health.” — Carl Jung
16
Encipher | 2012
A GaN based resonant DC/DC converter will be a suitable
candidate to form the DC/DC converter in typical high power
application. The inverter will also be operated with high carrier
frequency PWM (of the order of MHz) with the proposed GaN
based semiconductor switches. This process helps to reduce
the ripple in voltage as well as in current to make the device
operationsmoother and more energy efficient. Because of the
high-frequency operation the over-all system size is also
expected to go down by at least half of the present day
inverter-converter size.
V. Conclusion
The wide-bandgapAlGaN/GaNheterostructure
possesses unique characteristics that favours the
realisation of high-performance HEMT devices. Its
strong spontaneous and piezoelectric charge
polarisation in AlGaN/GaNheterostructure yields 2-
dimensional electron gas (2-DEG) with high mobility
>1800 cm2V-1s-1) and carrier density (>1019cm-3).
Such a 2-DEG high mobility channel bypasses the
hurdle which hinders the development of SiC MOSFET
power devices.
The suitable high-voltage power MOS-HEMT devices
on cost-effective Ga/Si platform can be developed for
power electronic inverters for solar photovoltaic
system and hybrid electric vehicle applications. The
voltage range is above 1200 V and the inverter power
rating is up to 30 kW. These are realistic power
electronic application to employ the GaN power MOS-
HEMT devices.
Fig. 8 Power electronic circuit configuration for the
photovoltaic energy conversation and the hybrid electric
vehicle traction application
Gallium-Nitride Power
Semiconductor Technology
for Future Energy
Conversion Applications
“Function in disaster; finish in style.” — Howard Penney
17
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Throughput and Channel capacity are of utmost importance while
considering the performance of a system. Channel capacity is the
maximum amount of information that can be sent over a channel
and throughput is the maximum successful data that can be
transmitted through a channel. Therefore, throughput can be
equal or less than the channel capacity. As the throughput value
comes closer to the channel capacity, the successful data
transmission rate increases and the system quality improves.
MIMO technique helps in bringing the throughput of a considered
system closer to its channel capacity.
Above figure shows a simple MIMO technology consisting of two
transmitting antennas and two receiving antennas. Each receiving
antenna sees different versions of transmitted signal and when
these versions are combined in a proper manner,
the outcome has a better quality (lower Bit Error Rate). This
reduces the effect of multipath fading.
Thus, MIMO technique greatly improves the performance of a
wireless system. Since, not much effort has been made in
establishing this technique in Nepal; it might be beneficial to
researchers to work in this field.
MIMO in Wireless Communication
MIMO in Wireless
Communication
Shilpa Manandhar
EE- IV Communication
Wireless communication refers to the transfer of information
between two or more points that are not physically
connected. Distances between the two points can be short
or as far as thousands or even millions of kilometers.
Different ways can be used to establish wireless
communication. Basically, antennas are used as transmitter
and receiver in wireless communications like cellular
telephones, satellite communications, radio broadcasting,
etc. Despite many advantages of wireless communication
there are many factors that affect the quality of wireless
communication systems.
In urban and indoor environments, there are many obstacles
between the clear line-of-sight (LOS) of transmitter and
receiver. Instead the signal is reflected along multiple paths
before finally being received. Each of these bounces can
introduce phase shifts, time delays, attenuations, and
distortions at the receivers. These destructively and
constructively interfere with one another at receiving
antenna degrading the quality of signal sent. Many
researches have been done to mitigate these problems. One
of the most prominent ways is to use MIMO techniques.
MIMO (Multiple Input and Multiple Output) is a technique in
which multiple antennas are used both at the receiver and
the transmitter for better communication performance.
In 1996, Greg Raleigh and Gerard J. Foschini refined new
approaches to MIMO technology, considering a
configuration where multiple transmit antennas are co-
located at one transmitter to improve the link throughput
effectively.
It has been said that MIMO offers significant increase in data
throughput and quality without additional bandwidth or
increased transmit power. It achieves this goal by spreading
the same total transmit power over the antennas to achieve
an array gain that improves the spectral efficiency (more bits
per second per hertz of bandwidth) or to achieve a diversity
gain that improves the link reliability. It mitigates the
problem of multipath fading.MIMO technology is applicable
in many areas. The IEEE 802.16e standard incorporates
MIMO. MIMO is also planned to be used in Mobile radio
telephone standards such as recent 3GPP and 3GPP2. In
3GPP, High-Speed Packet Access plus (HSPA+) and Long Term
Evolution (LTE) standards take MIMO into account. WiMAX is
one of such standards that use MIMO technology.
Fig: MIMO technology
“Beware the barrenness of a busy life.” — Socrates
18
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
methodology for higher harmonic currents in three-phase network
and its' realization with micro-controller-based control is realized
[6, 7].
PWM control is preferable in comparison with other control
methods since semiconductor switches operate in one frequency
and current is easily filtered [1,7,8]
Shunt active power filter compensates current harmonics by
injecting equal-but-opposite harmonic compensating current. It
operates as a current source injecting the harmonic components
generated by the load but phase shifted by 180⁰. This principle is
applicable to any type of load considered a harmonic source.
Moreover, with an appropriate control scheme, the active power
filter can also compensate the load power factor. In this way, the
power distribution system sees the non linear load and the active
power filter as an ideal resistor. The current compensation
characteristic of the shunt active power filter is shown in Fig.1[9].
It's necessary to know the value of d co-ordinate of current since
the current is synchronized under 90º with network voltage, and
value of d coordinate is proportional to the amplitude of an active
current. Calculation of active filter-current sums up higher
harmonic currents and fundamental harmonic current in
synchronous coordinates:
(1)
Where i - current in abc coordinate; i i currents in
synchronous reference frame. In digital processing of signals, this
method is known as decomposition of a signal on rotating
coordinates.
2. Working Principle:
3. Calculation of higher order load- current harmonics using SRF.
Fig. Compensation characteristics of a shunt active
power filter
a d q,
Single-phase Shunt Active Power Filter
-Modeling and Control
Single-phase Shunt Active
Power Filter-Modeling and
Control
Abstract - This paper presents a pulse-width modulated voltage source
inverter (PWM-VSI) based shunt active power filter for harmonics
cancellation to improve the power quality in electrical systems. The control
system is based on the Park Goreva (abc-dq) transformation, derived to be
applied in single-phase systems. The control scheme calculates the current
reference waveform for the inverter, maintains the dc voltage constant, and
generates the inverter gating signals. This method is also known as
synchronous reference frame (SRF). In this case, transformation from a; b; c
axes to d-q synchronous reference frame is done. Simulation of the filter is
carried out in Matlab Simulink for 1KW load power in 220V/50Hz network.
Simulation results are given to show the behavior of the system, used for
harmonics cancellation. Fast Fourier transformation (FFT) is realized in
Matlab Simulink to show the spectrum of load current before filtration and
spectrum of source current after filtration.
Single-phase Shunt Active Power Filter, power quality, abc-dq
transformation, FFT
Key words:
1. Introduction
There are various methods for elimination of the higher
harmonics, but most often passive and active filters are used
[1]. Passive filters consist of reactive elements (reactors and
capacitors). Decrease in voltage and current harmonics
components can be provided by means of the resonant LC-
filters. These harmonics are present at current fed by
nonlinear element, for example rectifier [2]. Each resonant
branch of the filter shunts a corresponding current
harmonics, without allowing it to pass through the network.
However, such sort of filters has number of drawbacks -
incomplete compensation of higher harmonics, necessity of
selection of parameters such as C and L for achievement of
high efficiency of the filter e.t.c [3].
Several literatures present different control systems for
active filter. In [4] the active filter with the inductive storage
element on a basis of four quadrant converter is described.
Integrator with reset is core component to control the pulse
width of the converter. It is necessary to notice that
compensation is carried out on cycles (on the period) and in
order to receive full compensating current, given method
doesn't require current reference for the control of the
converter current.
The method is characterized by high precision (accuracy),
simplicity of realization of control circuitry and the improved
dynamic characteristics of a filtration. Spectral frequency
active filtering is another method where the form of
network current is predicted and it can be presented in a
discrete frequency spectrum [5]. Micro-controller-based
control is another method of control [6].Calculation
)cos()sin( 00 titii qda ××+××= ww
Sujan Adhikari Professor Y.K. Rozanov
Lecturer, DoEEE, KU Department of Electrical and Electronic Apparatuses, Moscow Power Eng. Institute
“The end of man is action, and not thought, though it be of the noblest.” — Thomas Carlyle
19
In this method, signal which is to be transformed, is
multiplied by oscillations of two generators (heterodynes),
with the frequency equal to frequency of that harmonics
which is necessary to be allocated. Oscillations of
heterodynes are shifted on a phase with respect to each
other by 90 degrees- sin( .n.t) and cos ( .n.t).The result
of each multiplication contains constant and periodic
components. If s (t) represents an input signal as a sum of
cosines with any phases and amplitude then
(2)
Where –
From time average of the given expression, it is seen that the
integral from the second sum will give zero, because
cos( .m.t+ ),m=n+k is periodic function. Thus, if a signal
is multiplied by cosine, and then let it pass through the low
pass filter (LPF), then 1/2 A(n)cos
Output of LPF is half of imaginary component of nth
harmonics in input signal. Because of both real and
imaginary part of a signal of nth harmonic, we can restore
initial harmonic component by simply multiplying real and
imaginary parts by corresponding oscillations of
heterodynes.
Further the signal is multiplied by coefficient (K) and is sent
to PI-regulator. After calculating the difference between d
and q components of load currents and filter currents, the
result is given as input of PI regulator. d and q components
of voltage is obtained at the output of PI- regulator. Vector
diagram for dq co-ordinates is shown in fig 3.
w w0 0
0
φ - phase difference between harmonics of a
signal and oscillation of heterodyne. The required harmonic
is n, and oscillation frequency of a heterodyne is equal to
ω n.
φ (Fig 2) is obtained (half
of the real component of nth harmonics in input signal).
Similarly finding an imaginary part:
k
0
k
ω φk
Fig. 2 Allocation of third harmonic current
Fig. 3 vector diagram for dq transformation
Where,
i – Projection of a third harmonic current vector on d-axis.
i – Projection of a third harmonic current vector on q-axis.
U – Projection of a third harmonic voltage vector on d-axis.
U – Projection of a third harmonic voltage vector on q-axis.
Fig. 4 control system schema with PI-regulator
d
q
d
q
d
d
q
q
The component of voltage U of active filter creates a component
of a current of the active filter i . The component of voltage of the
active filter U creates a component of a current of the active
filter i
Tracking load current is carried out by means of two proportional-
integrated regulators "PI" where converter current and load
current are fed in synchronous reference frame dq. It is necessary
to consider that a current across filter L will shift on 90 with
voltage across L because of which control path along q determines
d- voltage component and control path on q determines d-voltage
component. As an output of PI-regulator we’ll get voltage
components in dq co-ordinates (fig 4).
After the reverse transformation from dq to abc, voltage signals for
every harmonic are summed, scaled to the magnitude of voltage
across the capacitor and given for the pulse width modulation.
A single-phase shunt active filter with parameters given below is
simulated in Matlab Simulink.
Load power – 1kW
Nominal network voltage- 220V
Frequency of network voltage- 50Hz
Load contains single-phase thyristor bridge with R-L load on dc
side of it. Load current, current generated by active filter and
source-current is presented in fig. 5. Active power filter starts to
work after two periods of industrial frequency. It provides current
to the network equal in magnitude but opposite in phase after
sensing higher order current harmonics in the network from load.
As a result, an approximate sinusoidal current flows from the
source.
4. Simulation results
Encipher | 2012
Single-phase Shunt Active
Power Filter-Modeling and
Control
“I never make the mistake of arguing with people for whose opinions I have no respect.” — Edward
20
Fig. 5 Simulation results a) load current; b) current generated by
compensator; c) source current
Fig 6: Load current spectrum
Result of mathematical modeling shows that current drawn
by rectifier from the source is non-sinusoidal. Spectrum of
load current and source current during active filtration is
presented in fig 6 and 7 respectively. Harmonic currents are
seen in the load-current spectrum. Coefficient K is the ratio
of amplitude of nth harmonics to the amplitude of
fundamental harmonic in percentage. In load-current
spectrum , 33% of 3rd harmonics and 20% of 5 harmonics
is seen. In the same way, amplitude of 7 , 9 and 11
harmonics is also large. After filtration contents of higher
harmonic currents in the source reduces less than 2% (fig 7)
I
th
th th th
Fig 7:Source current spectrum after filtration
4. Conclusions
References
The Shunt Active power filter with SRF based-PI controller was
examined in this paper. Results of mathematical modeling has
shown the possibility of harmonics mitigation quickly and
efficiently.
[1] Y.K Rozanov., M.V Ryabchiski., A.A. Kvasnyuk, Power
Electronics, MPEI publishing house, Moscow 2007 [translated].
[2] I.I. Kartashev, .Power Quality Control, MPEI publishing house,
Moscow 2006 [translated].
[3] Adhikari S., “Single-phase Shunt Active Power Filter” – Thesis
of Bachelor's Degree Program under supervision of Prof. Rozanov
Y.K., Moscow Power Engineering Institute (Technical University),
June 2008.
[4] Unified constant-frequency integration control of active
power filters / Luowei Zhou and Keyue M. Smedley. – University
of California, 2002.
[5] Open loop and closed loop spectral frequency active
filtering./ Sebactien Mariethoz and Alfred C. Rufer// IEEE
transactions on power electronics, vol. 17, no. 4, July 2002.
[6] Active filters. ABB- 2002.
[7] Y.K. Rozanov., Fundametals of Power Electronics,
Energoatomizdat, ,1992 [translated].
[8] Adhikari S., “Power Quality Control Using Microcontroller-
based Control of Inactive Power Compensator,” Asia Pacific
Quality Organization[APQO], 16th International Conference on
Quality-2010, 18-20 September 2010, Kathmandu University,
Dhulikhel, Nepal, Conference Handbook. Page: 121.
[9] Luis A. Morán, Juan W. Dixon, José R. Espinoza, Rogel R.
Wallace “Using Active Power Filters to improve Power Quality”,
Chile.
Encipher | 2012
Single-phase Shunt Active
Power Filter-Modeling and
Control
“Real love is a permanently self-enlarging experience.” — M. Scott Peck
21
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
The syngas-engine systems with the accessories are getting
popular for electrification of rural villages in India. The gasifier
systems can be very promising alternatives for decentralized
electrical power in the places far away from the national grid
where sustainable biomass supply can be assured. Nepal can also
benefit from this small scale decentralized power generation
technology, particularly in remote rural Terai villages where
potential for microhydro power is almost nil.
In order to provide a low cost small scale biomass gasifier system
for rural electrification and agricultural mechanization in Nepal, a
project named as 'Gasifier-Engine Project' has been started at
Kathmandy University (KU). This project is funded by Norad
through Renewable Nepal Programme, which is a programme
managed by KU in collaboration with Sintef Energy Reseasrch,
Norway, for initiating industry based research and development in
renewable energy sector. Till date the 'Gasifier Engine Project' has
completed several activities in design and development of various
types of gasifier, and fuelling the syngas produced by the gasifier in
a diesel engine to run the engine in dual fuel mode (30% diesel
and 70% syngas).
Fig: KU Series II Gasifier
Fig: Computer Drawing of KU Series III gasifier
Gasification Technology for Rural Electrification in Nepal
- Efforts at Kathmandu University
Gasification Technology for
Rural Electrification in Nepal
- Efforts at Kathmandu
UniversityBivek Baral, PhD
DoME, KU
Gasification technology available in recent years has
been one of the most efficient energy conversion
devices for biomass. Gasification process is basically
the conversion of biomass into thermal energy which is
achieved by partial combustion of biomass (with limited
amount of oxygen) in the gasifier producing combustible gas
(also called syngas, which is a mixture of CO, H2 and CH4
along with tar) that is burned in secondary combustion
devices in the presence of excess air. The combustion
engines fuelled with syngas can be used as prime mover for
agricultural machineries and electric generators.
This technology has been employed around the world since
the late 18th century, firstly as fuel for 'gas lights' in the cities
like London and then later to fuel the internal combustion
engines. In ca. 1880, producer gas was used for the first time
to power an internal combustion engine. The raw materials
for the producer gas were both coal and biomass. Although,
gasifier found some use in fuelling various stationary as well
as automobiles in the early 1900s, the use soon were
diminished because of the more convenient and reliable
fossil fuelling. The use of gasifier system was restarted
during the Second World War due to the paucity of fossil
fuels. The development of gasification technology reached
its peak, which again after the end of the war, was gradually
forgotten. Most of the technological information about the
gasifier was either lost or was not effectively transferred to
the further generations. During the wartime in Europe there
were about a million vehicles fuelled with gasifier, which
greatly outnumbers the current gasifier use.
In recent years renewable energy sources including biomass
and biogas have been getting considerable attention,
particularly in the developing countries due to increase in
fossil fuel price and due to incentives for using those energy
resources through climate finance. In fact, for a country like
Nepal, biomass accounts for about 70% of primary energy
demand. The major motivation for the consideration of
biomass gasifier system is that it can be a viable alternative
for electricity generation in the remote rural areas of Nepal
where biomass supply based on agricultural and forestry
residue as well as waste biomass vegetation is in abundance.
The operation can be sustainable if the production of
biomass is in the same rate as it is consumed. For small
decentralized power generation intended for a rural
community, this can be possible.
Another attraction for using such system for decentralized
power generation is that the energy revenue stays within the
community. In other words, people get financial incentives
by producing or harvesting and selling the biomass to the
operator of the gasifier plant.
“Success is nothing more than a few simple disciplines, practiced every day.” — Jim Rohn
22
The current activities of the project are focused in developing a commercial gasifier (KU Series III), which features: better
maintainability with accessibility of the reactor hearth for cleaning and preventive maintenance; better gas cleaning and cooling
system; automatic grate agitation and ash disposal mechanism; proper drying of biomass in the gasifier, and, proper water
treatment system in the package. This model will be promoted for several upcoming biomass based rural electrification in remote
Terai villages of Nepal.
Several activities are also being carried out to develop a producer gas engine which can run entirely on syngas without requiring
any other fossil fuel. This engine will be based on a small sized production (5-10 kW) diesel engine. The engine will be converted
into spark ignition gas engine with high compression ratio. This enables low cost conversion of existing diesel engines which in
turn avoids the import of expensive gas engines from India and abroad.
The future activities of the project includes establishment of a biomass gasifier based demo power plant with an ultimate goal to
generate electricity in KU Central Campus by renewable energy resources.
Encipher | 2012
Gasification Technology for
Rural Electrification in Nepal
- Efforts at Kathmandu
University
“God bears with the wicked, but not forever.” — Miguel de Cervantes
23
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Effect on consumption
Conclusion
To look at how consumption trends change after installation of
prepaid meters one case of small town in Copperbelt province of
Zamabia is shown below. The seasonal peak in Zambia happens
between June and July.
There has been a significant reduction in the consumption of
energy as seen from the table. By introducing prepaid meter 40%
of power is saved. This is because of the more careful utilization of
energy by client. It is clear to see the benefits using prepaid meters
as this guarantee the 100% used in kWh paid for. The display in the
meter always gives clients the credit left and proper uses of the
energy. A lot of money is saved as there is no need of meter
reading personnel. Since the payment is up-front, it reduces the
financial risk by improving the cash flows and necessitates an
improved revenue management system.All meter are protected
against fraud with an internal contact. The systems are easy to use
and no expensive training is needed. The meter warns the users
before the electric energy reaches zero and they will have enough
time to buy new credit.Nepal is facing acute power shortage. This
kind of scheme is very useful in the context of Nepal.
Impacts of the Prepaid meter system on
energy consumption
Impacts of the Prepaid meter
system on energy
consumptionMichelo Daisydaria Muleya
Brijesh Adhikary
Electricity is the backbone of a countries economy as it
drives the countries industries. Therefore the concept
of future networks (smart grids) aims to increase the
reliability, quality and security of the power supply. Smart
metering technology promises to radically change the way
traditional electricity markets operate. Most utilities in the
world however are still using mechanical meters to bill their
customers.As opposed to the mechanical meter which
requires physical meter reading, a smart meter measures the
energy consumption data from the remote location and
monitor continuously.
There are growing trends in smart metering with most
electricity utilities and companies are replacing the existing
mechanical meters with smart/prepaid meters. Smart
meters however require additional infrastructure such as
Home Area Networks (HANs) to operate. Therefore these
meters are more expensive to install and operates. Prepaid
meter on the other hand offers a cheaper alternative.
Prepaid meters are called semi smart meters as they can
only handle one way communication unlike fully smart
meters which can communicate both ways with utility and
clients.
A pre-payment metering system is a system where a
customer purchases energy before using it. With the prepaid
meter system the customer purchases electricity energy
from a vending station. A voucher is given upon payment
and on the voucher; the digit code is then keyed into the
meter. The new balance appears on the LED display. The LED
display informs the client when 75 percent of the credit
energy has been consumed. It will keep alerting the client
until all units run out. Once the units run out, the client is
automatically disconnected. Client need to purchase
additional units and charge the meter for further use. This
allows client to use the energy in responsible and efficient
use.
The Pre payment meters have certain advantages over the
traditional meter
No meter reading
No bills delivery
No accrued debts
No billing problems
Clients can be aware and control the monthly usage
of electricity
Energy theft is avoided
User friendly
Advantages of Pre payment meter system
Month Consumption (MW)
February 871.373
March 990.598
April 968.123
May 991.117
June 882.017
July 748.905
August 594.886
“Prepaid meters are protected against
fraud with an internal contact. They are
easy to use and no expensive training is
needed”
“Cleverness is not wisdom.” — Euripides
24
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution5 inventions taking shape in 2012
5 inventions taking shape in
2012
Sirish Shrestha
EE-IV Power and Control
Transparent Touchpad Laptops
Intel (amongst others) are now creating transparent touch pads and laptops. The concept is
simple: replace the palm rest and touch pad on a notebook with a transparent strip with
integrated touch pad. When open the touch pad area should work just like a glass covered
touch pad. Intel also includes palm detection that disables the mouse cursor if it detects
that you're resting your hands on the transparent strip. Close the clamshell and the
transparent touch pad will act as a capacitive window to your display. With some support in
Windows 8 Intel claims you'll be able to do things like view your calendar, read emails, even
browse the web through this little window.
Both sides of the transparent strip support capacitive touch so you'll still be able to interact with
your machine when closed. Nikiski is still just a concept PC but it's now functional. Intel owns
the patent on the design, but as is normally the case with these concepts it's unclear when
we'll see something like it in the market. Make the design thin enough and I definitely see
potential though. It'd be nice to still have access to some of your data even when your
notebook is closed.
Google Glass
This almost cliche looking piece of futuristic hardware
has the potential to become as ubiquitous as cell phones
or laptops. the device is designed to be a stand-alone device
rather than an Android phone peripheral: while Project Glass can
connect to a smart phone via Wi-Fi or Bluetooth 4.0, "it
communicates directly with the cloud". There is also a front-
facing camera and a flash, although it's not a multi-megapixel
monster, and the most recent prototype's screen isn't
transparent.Fuel-Cell Powered MacBooks
Apple is no stranger to user related innovation and change –
they’re always a head of the game. Well, this time they’re
looking into using hydrogen fuel cells to power portable
electronics. Using this energy method could significantly reduce
the size, weight and cost of the fuel cell system. Apple’s
reasoning for investigating this option is because they believe
that the “country’s continuing reliance on fossil fuels has forced
the government to maintain complicated political and military
relationships with unstable governments” such as the Middle
East.
Using this type of energy to power portable electronics is
environmentally friendly because it is a source of renewable
energy, and would allow our devices to stay charged for days and
weeks on end! Of course, there are challenges associated with
this idea and Apple is currently in the first phase of exploration.
noting that hydrogen and associated fuels could allow such
devices to operate "for days or even weeks without refueling."
But the company also notes there are challenges in creating
hydrogen fuel cell systems that are portable and cost-effective.
Concept Fujitsu Lifebook
Wouldn’t it be nice to just have one place to store our digital
camera, laptop and smartphone? The new Fujitsu Lifebook
(also called Lifebook 2013) is a laptop which stores our
smartphone, tablet and digital camera all in one laptop. The
idea is to provides an affordable laptop that can sync and
update all devices simultaneously from the same place.
The design for the Lifebook was developed by Prashant
Chandra after winning a competition Fujitsu was holding.
The Lifebook allows all the parts and devices to work
together with computer without having to worry about USB
plugs and cords. For example, the digital camera slot on the
front of the Lifebook allows for instant connectivity,
enabling you to download all your photos straight to the
computer. You can also charge your camera this way.
Another interesting part of the design is that the Lifebook
doesn’t come with a keyboard because it is also a tablet.
The tablet, once slotted in place becomes a keyboard when
needed or a second display screen.
“If there is no struggle, there is no progress.” — Frederick Douglass
25
Encipher | 2012
Sony Cyber-shot RX 100
Digital cameras have been getting smaller and more capable every year, but that
trend took a huge leap forward in 2012 with the Sony RX100, which bridges the
gap between point-and-shoots and pro-quality digital SLRs. Sony’s innovative
design allow the camera to take flawless photos even though it’s 20% slimmer
than average digital SLR—small enough to fit in pocket.
• 1" Exmor CMOS sensor
• 20.9 million effective pixels
• 28-100mm (equiv), f/1.8-4.9 Carl Zeiss Vario-Sonnar
T* lens
with 'Advanced Aspherical' element
• ISO 125-6400 (ISO 80 and 100 expansion, up to
25,600 using
multi-frame noise-reduction)
• Rear control dial and customizable front
'Control Ring'
• 10fps continuous shooting in 'Speed Priority'
mode
• 13 Picture Effects with 27 variations
• 1080 60p video (AVCHD) with MP4 option
5 inventions taking shape in
2012
In three words I can sum up everything I’ve learned about life. It goes on.” — Robert Frost
26
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
• End devices: An end device can be RFD. And RFD operates
within limited set of IEEE 802.15.4 Mac layer, enabling to consume
less power. End device can be connected to the router or
coordinator. It operates at low duty cycle power, meaning it
consumes power only when transmitting power. End device
performs function such as Join or Leave network, transfer
application packets.
·• Zigbee trust center (ZTC): the trust center is the device that
provide security management, security key distribution and device
authentication.
·• Zigbee gateway: It is used to connect the Zigbee network to
another network such as LAN, by performing protocol conversion
ZigBee for Home Automation
ZigBee for Home Automation
Abhilasha Bhuju
EE- IV Communication
Home automation is to be able to turn on a light across
the room or unlocking the front door as you pull into
the driveway. It is also to be able to turn on your home
sprinkler system with your cell phone or logging in from your
computer at work to view your home security cameras.
Home automation uses technology to make your everyday
tasks in the home simpler, safer, or less expensive. It includes
anything that gives you remote or automatic control of the
electronics inside it.
Usually IR remote controls or WiFi (WLAN) are used for such
systems. The major drawback of IR remotes is the necessity
of line of sight for communication and that they are non-
interchangeable among devices. For WiFi, the unwanted
consumption of electricity in standby mode and its
complexity are the downside factors.
To try to put them under a single standardized control
interface that can interconnect into a network, one of the
most promising protocols is ZigBee, a software layer based
on the IEEE 802.15.4 standard.
ZigBee is a wireless communication standard based on a
standard network architecture using an OSI model through
an IEEE 802.15.4-2006 IP layer.
Although ZigBee networks can be configured in star, peer-to-
peer and mesh topologies, it is the mesh network from
which ZigBee was named. A ZigBee mesh provides multiple
pathways from device to device and eliminates a single point
of failure. If nodes go down or are removed, ZigBee devices
can "zig" and "zag" through the network to their destination
like a bumblebee.
A Zigbee network consists of the nodes (devices). A node
consists of microcontrollers, transceiver and antenna. A
ZigBee node uses stack profile, which are develop by
software. The node can be use for the variety of applications
–for example lighting control, smoke detector and home
security monitoring. Therefor the node can support multiple
subunits and each subunit has an application object that
describes the subunit function. The node can operate either
a full function device (FFD) or reduced-function devices
(RFD). An FFD can perform all the tasks that are defined by
the ZigBee standard, and operate in the full set of the IEEE
802.15.4 MAC layer. An RFD performs only a limited number
of tasks.
• Coordinator (ZC): organizes the network and maintains
routing tables, starts network, permits devices to join and
leave the network, holds the list of neighbors and router
• Routers: A router is FFD. A router uses tree or mesh
topologies to expand network coverage. The function of the
router is to find the best route to the destination.
What is ZigBee?
Zigbee Network
“Love and work… work and love, that’s all there is.” — Sigmund Freud
27
Advantages of ZigBee
Conclusion
· Power saving, as a result of the short working period, low power consumption of communication, and standby mode
· Reliability: Collision avoidance is adopted, with a special time slot allocated for those communications that need fixed
bandwidth so that competition and conflict are avoided when transmitting data. The MAC layer adopts completely
confirmed data transmission, that is, every data packet sent must wait for the confirmation from the receiver
· Low cost of the modules, and the ZigBee protocol is patent fee free
· Short time delay, typically 30 ms for device searching, 15 ms for standby to activation, and 15 ms for channel access of
active devices
· Large network capacity: One ZigBee network contains one master device and maximum 254 slave devices. There can be
as many as 100 ZigBee networks within one area
· Safety: ZigBee provides a data integrity check and authentication function. AES-128 is adopted and at the same time each
application can flexibly determine its safety property.
The main disadvantages of ZigBee include short range, low complexity, and low data speed. Due to their high cost, GSM and GPRS
are normally used in concentrators to transmit data to the main station, or in high end multi-function meters. ZigBee is used
mainly in the concentrators, data collectors, repeaters, and meters installed in the urban distribution AMR systems and
prepayment systems. Because of the good real time capability of RF, meters are often equipped with a remote control function.
Home automation is the biggest market for ZigBee-enabled devices. ZigBee wireless technology shall prove to become a vital
element of such communication systems as in HAN, providing the robustness and reliability, low cost, security and ease-of-
deployment required to make it all work together and deliver tangible benefits. We can be assured that, this cost-effective and
easy-to-use home network shall potentially assist in developing a whole new ecosystem of interconnected home appliances, light
and climate control systems, and security and sensor sub-networks.. In conclusion, Zigbee will help to squeeze this world into a
single touch control and will soon revolutionize the field of wireless technology and rule the world.
Encipher | 2012
ZigBee for Home Automation
“If you do not change direction, you may end up where you are heading.” — Lao Tzu
28
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Now, with more than 50% share of the total search market,
Google provides search results for numerous search engines on
the web. Google has become all-important to both search engines
and search engine optimization specialists alike.
The other search engines have a tendency to mimic any
algorithmic changes made by Google. Likewise, search engine
optimization specialists continually study the changes as well in
order to provide their clients with the best search engine rankings.
In 2000, Google began selling advertisements associated with
search keywords. The ads were text-based to maintain an
uncluttered page design and to maximize page loading speed.
Keywords were sold based on a combination of price bid and click-
throughs, with bidding starting at $.05 per click.
Since 2001, Google has acquired several small companies, often
consisting of innovative teams and products. One of the earlier
companies that Google bought was Pyra labs; they were the
creators of blogger, a weblog publishing platform, first launched in
1999. This acquisition led to many premium features becoming
free. In early 2006, Google acquired Upstartle, a company
responsible for the online collaborative word processor, Writely.
The technology in this product was combined with Google
Spreadsheets to become Google docs.
Then on October 9, 2006, Google announced that it would buy the
popular online video site YouTube for $1.65 billion and maintain
YouTube as a separate brand, rather than merging it with Google
Video. Meanwhile, Google Video signed an agreement with Sony
BMG and the Warner music group, for both companies to deliver
music videos to the site. The deal was finalized by November 13.
On October 31, 2006, Google announced that it had purchased
JotSpot, a company that helped pioneer the market for
collaborative, web-based business software to bolster its position
in the online document arena. Google also acquired PeakStream
Technologies. On May 22 2012, Google acquired Motorola Mobility
for $12.5 billion.
-The journey from garage to Android
GOOGLE-The journey from garage toAndroid
Prazun DaniEE- III Communication
Google, the most cosmopolitan word known by web
users after Facebook, is actually the mathematical
term for a 1 followed by 100 zeros, Googol.
Google's play on the term reflects the company's mission to
“organize immense amount of information available on the
web.”
Google, the leading search engine worldwide, was founded
in 1998 by Stanford University graduates Larry Page and
Sergei Brin. While at Stanford in 1996, they began
developing a search engine they eventually entitled BackRub
which was designed to look at the connecting links between
web pages in order to determine a site's authority. In 1998,
Page and Brin set up their first data center in Page's dorm.
With the encouragement of fellow Stanford alum David Filo,
who started Yahoo a few years earlier, Page and Brin decided
to start a company and started looking for investors to back
them.
Andy Bechtolsheim, one of the founders of Sun
Microsystems, invested $100,000 in the company after
receiving a demo of their search technology. Eventually the
fund rose over $1M and Google, Inc. was established on
September 7, 1998 in a friend's garage in Menlo Park,
California where Page and Brin hired their first employee,
Craig Silverstein, who was later to become Google's Director
of Technology. In their beginnings, Google served over
10,000 queries a day and quickly gained a reputation as a
trustworthy source of information. By 1999, it was serving
500,000 queries a day and the company moved from the
unassuming four walls of a garage to the now mega
Googleplex headquarters in Mountain View, California.
Google achieved praise and publicity as news spread rapidly
through online and offline media as well as their receipt of
numerous awards and recommendations. Their audience
continued to grow along with their reputation for
effectiveness, relevance, speed, reliability and simple design.
In 2000, Google replaced Yahoo's own internal search engine
as the provider of supplementary search results on Yahoo.
“Don’t judge each day by the harvest you reap but by the seeds that you plant.” — Robert Louis Stevenson
29
Encipher | 2012
Android, a Linux-based mobile operating system developed and distributed by Google in conjunction with the Open Handset
Alliance, was initially developed by Android Inc. before its purchase by Google in 2005. And at the end of 2010, it had become the
world's leading Smartphone platform. It had a worldwide Smartphone market share of 59% at the beginning of 2012. As of late
2012; there were 500 million devices activated and 1.3 million activations per day.
Both Android and Android phone manufacturers have been the target of numerous patent lawsuits. On August 12, 2010, Oracle
sued Google over claimed infringement of copyrights and patents related to the Java programming language. Google has
publicly expressed its dislike for the current patent landscape in the United States, accusing Apple, Oracle and Microsoft of
trying to take down Android through patent litigation, rather than innovating and competing with better products and
services.Hence, the journey of Google from garage to android is a milestone in history and we must be proud that we have been
blessed with the most advance mobile operating system in our hand and we are living in the era of smartphones.
Google releases the Android code as open source under the Apache license. The Android open source (AOSP), lead by Google, is
tasked with the maintenance and further development of Android. Additionally, Android has a large community of developers
writing applications that extend the functionality of devices, written primarily in a customized version of java and available for
download through Google play or third-party sites.
In September 2012, there were more than 675,000 apps available for Android, and the estimated number of applications
downloaded from Google Play was 25 billion. The user interface using single- and multi-touch inputs like swiping, tapping,
pinching and reverse pinching to manipulate on-screen objects is designed to be immediate and provides a fluid touch interface.
Internal hardware such as accelerometers, gyroscopes and proximity sensors are used by some applications to respond to
additional user actions. We have seen a number of updates to its base operating system since its original release. These
updates typically fix bugs and add new features. Since April 2009, each Android version has been developed under a codename
based on a dessert or sweets. These versions have been released yet ; Cupcake(v1.5), Donut(v1.6), Éclair(v2.1),
Froyo(v2.2),Gingerbread(v2.3.x), Honeycomb(v3.0.x), Ice Cream Sandwich(v4.0.x), and Jelly Bean (v4.1).The most recent update
to the Android OS was Jelly Bean v4.1, which was announced in June 2012. Android has an active community of developers and
enthusiasts who use the Android source code to develop and distribute their own modified versions of the operating system.
Applications are usually developed in the Java C or C++ language using the Android Software Development Kit, but other
development tools such as android SDK are available for free.
GOOGLE-The journey from garage toAndroid
“Never allow a person to tell you no who doesn’t have the power to say yes.” — Eleanor Roosevelt
30
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
The requirement of ubiquitous communication, security of data,
environmental factors including energy saving and interference
less communication has motivated VLC to thrive in.
The potential application of VLC includes:
· Navigation and high-speed connectivity in the indoors
· ITS and Advertising in the outdoors.
Field experiments and demonstrations for VLC system has also
been conducted. It includes:
· A sound communication system (analog system) It is used
for amusement. In Yokohama National Gallery, there is an
exhibition of illumination synchronized with music
sounds, which are transmitted through the lights by VLC
to the audience,
· A sound communication system (digital system)
Music sounds are transmitted through visible lights (RGB)
independently i.e. R: Drum, G: Bass, B: Piano. Even Music
sounds can be controlled through their combination. i.e B:
Piano only, R and G: Drum and Bass, White(RGB): Drum, Bass,
Piano altogether.
Fig: Indoor Application of VLC
Fig: Outdoor Application of VLC
Visible Light Communication
Visible Light Communication
Aastha BhattaraiEE- IV Communication
Visible Light Communication (VLC) is a fast-growing
technology that provides data communication using
low-cost LEDs and photodiodes. The history of VLC
dates back to 1880, with Graham Bell's experiment on
Photophone, in which VLC technique was used for voice
communication for a distance of 200m.
This communication system uses lighting source LED'S as
transmitter and photodiodes as receiver. The system is of
multi-use, one for lighting and the other for communication.
The communication is done using common LED light which is
aesthetically pleasing. Basically, we can communicate in the
frequency range between 400 THz to 800 THz and the data
rates may reach up to 500 Mbps in VLC.
Using a white light-emitting diode, researchers have
succeeded in transmitting data over a distance of up to five
meters of empty space. The data are directly transferred by
modulating, via the power supply, the amount of light
emitted by the LED -which can be modulated at such a
frequency that data transfer rates of up to 500 Mbps are
possible. The resulting changes in brightness remain
imperceptible to the human eye. The receiver is a photo
detector which converts the light signals into electrical
pulses. The photo detector without lens limits the
communication distance. Thus the receiving photodiode is
accompanied with lens for long distance communication.
The reception this way is not perfect as the LED has to be
precisely in front of the diode or only the photo detector
that is positioned directly within the light cone is able to
receive the data. Thus, for the communication to occur,
there are arrays of photodiode that is capable of receiving
the signal even when the LED are not exactly in front of the
LED.
Wireless data transport by means of light has paved the way
for new applications in homes as well as in industries and
transportation.
Fig: VLC Communication technique
Fig: Array of photo diode for better VLC performance
“It’s fine to celebrate success but it is more important to heed the lessons of failure.” — Bill Gates
31
·
·
Visible light ID system (digital system)
i. Merchandise information distribution system- where product ID is identified by the visible light receiver on the cart,
ii. Information distribution system from a traffic light,
iii. Indoor navigation system-that includes the location identification of a room by the use of different lights used in a room.
This positioning system can be used even in the underground subway station, shopping mall etc, where GPS is not accurately
used.
High-speed data transmission system (digital system)
VLC is the best system for an ecological and human health, and can use the established retro-system including the lighting facility
as well as power line system. This system is also free from the current radio regulation. Visible Light ID System (which is already
standardized by JEITA: Japan Electronics and Information Technology Industries Association) is good for “Indoor Navigation
system” as well as “Indoor Traffic-research system linked with POS/Client data”.
Thus, in VLC, we send what we see hence it is secured as it is impossible to "tap" the data transported in the light beam. The use
of visible light is totally harmless and besides this it can be used in the restricted areas like aircraft, spaceship and hospitals.
Hence, it is a good technology with least cost and high potential.
http://www.impressrd.jp/photonics/files/u7/C-7ke.pdf
http://ieee802.org/802_tutorials/2008-03/15-08-0114-02-0000-VLC_Tutorial_MCO_Samsung-VLCC-Oxford_2008-03-17.pdf
http://www.siemens.com/innovation/en/news/2010/500-megabits-second-with-white-led-light.htm
References:
Visible Light Communication
Encipher | 2012
“All life is an experiment. The more experiments you make the better.” — Ralph Waldo Emerson
32
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
At present, bioethanol is produced from crops like sugarcane and
corn. These crops are cultivated and also used as food and feed
crops worldwide. Latin America is the main producer now and if
the trend continues, the bioethanol trade will flow from Latin
American countries to Asia, North America, and Europe and from
Africa and East Asian countries to Europe. Biodiesel is produced
from oil rich crops like soybean, rapeseed and palm. These also are
the cultivated food crops. Good yield of these crops need intensive
farming. New sources for biofuels are also being considered.
Bioethanol can be produced from more abundant biomass known
as lignocellulose, however the process is more complicated.
Similarly, biodiesel can be produced from non-edible oil as well as
algae.
The technology for first-generation biofuels including the
bioethanol from sugar rich crops (corn and sugarcane) and
biodiesel from oil rich crops (soybean and rapeseed) is well
established and is already commercial. In contrast, the technology
for second-generation biofuels including bioethanol from
lignocelluloses and biodiesel from algae is not fully mature.
Although the technology is developing fast and several test plants
have been established, major breakthroughs will be needed if they
are to be commercially viable before another decade.
The most prominent of the biofuel issues is related to its use of
land that is also used for growing food and feed for animals.
Several reports point towards the growing production of biofuels
for the recent global rise in food prices. It is evident that the use of
conventional food/feed crops alternatively for biofuel has a
negative impact on food security. The first generation biofuels
directly competes with the food and feed for its feedstock. Once
the technology matures, the focus may shift towards cellulosic
sources, including grasses and wood.
Even in the case of second generation biofuels, whose feedstock
differ from that of food and feed, meeting the massive demand
means a larger part of land must be set aside for the dedicated
energy crop cultivation. This again indirectly competes with the
food crop production. In addition to this, in many countries where
water is a scarce resource, the extensive use of water for
cultivation of energy crops directly competes with the water usage
for irrigating conventional agricultural crops. This issue is even
fiercely debated in poorer countries where still food security is a
dominating concern for people and government.
How advanced is the technology?
Food, feed or fuel?
Issues of liquid biofuels
Issues of liquid biofuels
Asst. Prof Madhav Prasad PandeyDoEEE, KU
Availability of energy is closely related to the social and
economic development of a country. It is proven by the
fact that developed countries consume massive amount of
energy compared to the developing and underdeveloped
countries. In recent decades, the world is facing a combined
effect of rapidly increasing population, ever increasing
demand of energy, depleting fossil fuel reserves and
environmental concerns due to GHGs (Greenhouse gases).
For about 2.7 billion people around the world, solid biomass
is still the main source of energy. Recent years have seen a
strong renewed interest in liquid biofuels. Several countries
are promoting biofuels with one or more of the following
intentions: energy security, rural development and reducing
negative impacts on environment due to fossil fuels. Liquid
biofuels are considered very promising particularly in
reducing the impacts of greenhouse gases. They are being
developed as direct substitution for liquid petroleum widely
used as transport fuels.
Energy policy of many countries promoting biofuels gives
preference to its domestic production. However, many of the
potential impacts are likely to affect other countries, through
global markets for food and forest products. Several
technical and socio-economic issues concerning it are in hot
discussion in different forums. Although most of the issues
are global in nature, the regional concerns include the
conflict of land and water use in Africa, effect on
deforestation, land use in Asia and sustainability, expansion
and small integration in Latin America.
According to the Food and Agriculture Organization (FAO), all
fuels derived from biomass (that is, matter of biological
origin) are biofuels. They can be of different type (solid,
liquid, and gas) and origin (forest, agriculture, and municipal
waste). Liquid biofuels include bioethanol, biomethanol,
bioETBE and bioMTBE (which all can be called biogasoline),
biodiesel and biodimethylether. Among all these, bioethanol
and biodiesel are the two primary candidates. Bioethanol is
the ethanol produced from biomass and biodiesel is methyl-
ester produced from vegetable oil.
What are the biofuels under consideration?
“Liquid biofuels are considered very
promising particularly in reducing the
impacts of greenhouse gases. and are
being developed as direct substitution
for liquid petroleum widely used as
transport fuels”
“We should take care not to make the intellect our god; it has, of course, powerful muscles, but no personality.” — Albert Einstein
33
Are they really clean?
Are they commercially competitive?
Global warming is a serious concern now. Continued
warming of the atmosphere is expected to have severe
consequences, including climate change. The use of fossil
fuels is the major source of greenhouse gas emissions in
most countries. Biofuels are considered one of the most
important developments towards reduction of GHG
emission. Estimation of the greenhouse gas balance of a
biofuel feedstock requires examination of the entire
production chain, including emissions from cultivation,
extraction, transport, processing, distribution, and
combustion. An estimate of fossil energy ratio of liquid
biofuel feedstock is one measure to show how clean the
biofuels are. Studies show that most of the biofuel feedstock
have low fossil energy ratios than as generally thought.
Bioethanol from corn has the lowest fossil energy ratio.
When emissions from land conversion are included it is even
worse. Sometimes, use of biofuels can even generate greater
emissions than fossil fuels.
Although these estimates may not be exact, the message is
clear: when a complete lifecycle is considered, biofuels are
not as clean as they are perceived. Another environmental
concerns related to biofuel production is the deforestation
and land clearing that comes with increasing capacity and
expansion. In addition to direct land conversion, there are
possible indirect land clearing by displaced farmers and
ranchers.
The cost of liquid biofuel production is determined by the
cost of the biomass feedstock and the cost of its conversion
into liquid biofuels. The feedstock costs are, in turn,
determined by the cost of growing, harvesting, and
transporting the feedstock. The conversion cost includes the
capital and operational costs associated with processing.
Except for production from lignocelluloses, feedstock costs
account for the major share of total production costs for
liquid biofuels. The cost breakdown of biofuel production,
thus largely depends on the feedstock type. Cost comparison
with liquid fossil fuels must also take in account the energy
contents of the fuels. Biodiesel has similar energy content
with fossil diesel while ethanol has only half of the energy
content compared to gasoline. Since the yields of the
biofuels are diverse, and the feedstock costs for the first
generation biofuels are fluctuating, biofuel costs are also not
stable.
In the past several years, the costs of liquid biofuels have
always been higher than the cost of their fossil fuel
alternatives. Bioethanol from sugarcane is cheaper than that
produced from corn, but still is slightly expensive than the
gasoline in general. Biodiesel production from palm oil is
only slightly expensive than fossil diesel while biodiesel from
soybean and rapeseed oil are far more costly. Under very specific
circumstances, including the target set by each nation and the
subsidies, liquid biofuels may be an economically viable alternative
to fossil fuels. However, without such policies, it seems likely that
the biofuel production from current feedstock is not economically
viable now or in the near future.
In many developing countries biofuel production is associated with
better natural resource management and poverty reduction. This
is thought as means of increasing the income of the rural poor and
improving their livelihood. However, bioenergy production in large
scale causes land concentration and as a result, many small
farmers will lose their land to bioethanol or biodiesel companies.
Since oil processors and investors often receive most of the profits
from biofuels, small scale farmers do not benefit much from it.
Although it is accepted that large plantations may bring amenities
including housing, water and electricity to the reach of rural poor,
it is often debated that whether it will reach to the marginalized
and the neediest ones.
Biofuel produced from biomass may be a very good solution on
reducing dependence on fossil fuels, improving energy security
and mitigating climate change effects. However, its sustainability
issue must be addressed. There must be some regulation on
sharing the feedstock that cis also used for food and feed. Second
generation biofuels that utilize non-edible feedstock are better
alternative. Still, a sustainable way for land use must be found.
Feedstock that can be grown on low quality lands with minimal
care must be promoted. Biofuels from waste treatment are other
alternatives. For countries like Nepal, small scale plants that
involve local people and require least transportation of feedstock
are certainly recommendable.
Do they improve livelihood of rural people?
So, what should be the approach?
Encipher | 2012
Issues of liquid biofuels
“God bears with the wicked, but not forever.” — Miguel de Cervantes
34
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Kulekhani III, 60MW Upper Trishuli 3'A', 32MW Rahughat are
under construction. Besides, there are more than 2000 micro
hydro power projects spread in various districts of Nepal.
So far only about 1.5% economically feasible hydropower potential
is developed. Nepal has a huge opportunity for hydropower
development. There are plenty of rivers with high head and
discharge. The hydropower plants of storage type, run off type,
peaking pondage and pump storage can be constructed.
Economically, hydropower is the most attractive sector of
investment with high internal rate of return (IRR). Nepal can export
power if the resources are utilized at is full phase. Various micro
hydro power stations can be made in the rural part in collaboration
with various donor agencies working in the sector of renewable
source of energy.Hydropowers under IPP (independent power
producer) sell their power to NEA under negotiated price.
In spite of its huge opportunity, there are lots of challenges in the
sector of hydropower. The challenges are directly related to
technical, economical, social, environmental as well as political
problem in Nepal. The geographical condition is one of the major
problems for construction. The electromechanical parts imported
from abroad do not suit Nepalese sediment condition causing
inefficient power production and corrosion. Hydropower needs huge
investment so there is lack of investors. Along with economic
problem hydropower has face the social problem. The local people
expectations are increased with arrival of hydropower of which all
cannot be addressed. They may create problem in the project.
Environmental issues are also to be addressed while constructing
hydropower stations for long term running. Environmental matter
should be taken seriously as it directly affects the life of the project.
The political problem is the worst among all. The hydropower sector
could not remain untouched by politics. Unstable government, lack
of security, corruption, and political disturbances are the major
problem of hydropower development in Nepal. We all should take
lesson from Arun III Project where World Bank had withdrawn its
investment. Additionally, making Power purchase agreement (PPA)
with authority and not constructing the project has also been great
problem in Nepal. NEA should discourage such practice and should
check and balance the situation.
20MW Chilime hydropower has proved that hydropower can be
produced with internal investment and Nepalese manpower. The
habit of depending on other should be left. If the hydropower sector
is taken to the top priority of development then Nepal can get rid of
load shedding and may be able to export power within a decade. For
this everyone should realize their responsibility and work for the
hydropower development for better tomorrow.
[1] Hydropower development and its sustainability with respect to
Sedimentation in Nepal.Sangroula DP.Journal of institute of
Engineering Vol.7
Opportunities and challenges
Reference
HYDROPOWER
Development and Challenges in Nepal
HYDROPOWERDevelopment andChallenges in Nepal
Ashim PokharelEE II
Nepal is the country with the immense potential of
hydropower. Estimated theoretical power potential is
approximately 83,000MW however, the economical feasible
potential has been evaluated at approximately 43,000MW
out of which about 700MW has been harnessed. Ministry of
Energy, Nepal electricity Authority (NEA) and private sector
are working together for the development of hydropower.
According to NEA, the annual peak power demand is
946.10MW out of which 651MW is produced in rainy season
and 321MW is produced in dry season and cause the
nightmare of load shedding in the country. And the worst of
all is NEA purchase power at high rate from India and sell in
low rate. Various projects are under construction and let us
hope the power crisis fades soon in the country.
The 500 KW Pharping Power Plant which was commissioned
in 1911 is the first hydropower installation in Nepal. In 1936,
the 640 KW Sundarijal Hydropower Plant was commissioned
and in 1965, the 2.4 MW Panauti Hydropower plant was
installed.
The 92 MW Kulekhani Hydropower Plant, (I and II)
commissioned in 1982, is the only project offering seasonal
water storage in Nepal. The 144 MW Kali-Gandaki-A
Hydropower Project, commissioned in 2003 is the biggest
hydropower project in Nepal so far. Most of the Hydropower
Plants in Nepal are owned by NEA, and most of the projects
were designed, constructed, and financed by international
consultants, contractors with the support from international
assistants. However, recently a few hydropower installations
took place from private sector also.
Local capacity is also getting competence on planning, design
and construction of hydropower projects. For example, the 20
MW Chilime Project and 3 MW Piluwa Project which were
commissioned in 2003, were designed, and constructed by
Nepalese experts. The projects fund was obtained from local
sources. These projects have improved the confidence of
Nepalese engineers and also demonstrated their capability to
build plants with domestic technical and financial resources.
Private hydropower developers also started financing in this
sector after 1992, when the government adopted new
hydropower policy and electricity act. In particular, Butwal
Power Company (BPC), Himal Power Limited (HPL), Bhote
Koshi Power Company (BKPC), Hydro solutions, Sanima
hydropower, National Hydropower Company (NHPC) and
other have already started generation. The total generation
capacity of the hydropower projects owned by the private
sectors is more than 120 MW. [1]39MW Duhabi Multi fuel,
14.4MW Hetauda are diesel power plants operating in the
country currently.
These power plants operate normally only under peak load
condition ie.after 5:00pm and shut at around 9:00 pm.
456MW Upper Tamakoshi, 30MW Chamelia, 14MW
Background
“People often say that motivation doesn’t last. Well, neither does bathing – that’s why we recommend it daily.” — Zig Ziglar
35
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
The internal configurations of microphones used for 99% of all
audio systems have one of three basic designs, which are often
used to organize microphones into distinct categories. These three
categories are dynamic microphones, condenser microphones, and
ribbon microphones.
A preamplifier is an electronic amplifier that prepares a small
electrical signal for further amplification or processing. The output
of MIC is fed to the preamp to increase gain, to change the tone
and lower the output impendence.
It is the connector which is used to connect analog audio signal
between two audio processing units. These connectors typically
have three contacts, although versions with two or four contacts
are also in common. Three-contact versions are known as TRS
connectors, where T stands for "tip", R stands for "ring" and S
stands for "sleeve". Similarly, two- and four-contact versions are
called TS and TRRS connectors respectively.
The 3.5 mm, 2.5 mm and 6.35mm sizes are also referred to as 1⁄8
in, 3⁄32 in and ¼ in respectively.
It is also termed an audio jack, phone jack, phone plug, and jack
plug.
Preamplifier
Phone connector
Fig : (a) 2.5 mm mono (TS), (b) 3.5 mm mono (TS), (c) 3.5mm stereo (TRS), (d) 3.5
mm 4-conductor (TRRS) and as 6.35 mm (TRS) phone connectors
Fig: 3.5 mm 4-conductor (TRRS)
Practical Audio Processing Circuitry
Practical Audio ProcessingCircuitry
Achyut DevkotaEE-IV Communication
An audio Processor is the circuit which takes an audio
input signal and generates an audio output that is
directly related to the input. Each channel of a modern
stereo audio system comprises a number of interconnection
circuit blocks, as indicated in figure 1. Here, input signals
from a radio tuner, a tape deck, mobile, i-pod or a phono
pre-amplifier are selected via Selecting switch (SW), and
then fed to the input of a power amplifier stage via a tone
control system and a volume control.
Signals of suitable amplitude are usually available directly
from the output of audio sources (i.e. tape, tuner, mobile, i-
pod etc) but not directly from the output of a microphone.
The output of microphone signal is first amplified using pre –
amp and then by equalizer circuit.
There are various types of micro phones available in market.
Some of them are: studio microphones for recording, PA
microphones for live sound, boom microphones for
broadcast or film shoots, instrument microphones which are
attached directly to guitars or horns, boundary microphones
for conference systems, lapel mics for seminars and business
meetings, and even headset microphones for telephone call
centers. The reason for this diversity is that while all
microphones perform the same basic function, they are
adapted to a wide variety of different environments and
uses.
Microphone
Figure : Diagram Single Channel Practical Audio Processing system
DynamicMicrophone
CondensorMicrophone
RibbonMicrophone
To the man who only has a hammer, everything he encounters begins to look like a nail.-Abraham Maslow
36
Tone Control Network
Volume Control
Audio Power amplifier
Tone control Network is the combination of various types of
filter circuit used in audio application. Thus user can alter a
system response according to their moods by changing filter
parameter. A circuit or device in an amplifier designed to
increase or decrease the amplification in a specific frequency
range without affecting other frequencies. There are two
types of tone controller: passive tone controller & active
tone controller. The tone controller without gain amplifier is
passive tone controller while one with gain amplifier is
Active tone controller. An active tone controller can easily be
made by wiring a passive tone control networks into the
negative feedback loop of an Op-amp, so that the system
gives an overall signal gain even if the controls are in flat
position. The ultimately (most sophisticated) type of tone
control system is the so called Graphic Equalizer. This
consists of a number of parallel connected, overlapping,
narrow-band, variable-response filter that cover the entire
audio spectrum, thus enabling an amplifier system's
spectrum response which precisely fulfills the individual's
need.Commonly available tone control IC: TDA4292 (stereo),
TDA4290, TDA1524 (stereo) etc.
The volume control in a hi-fi amp is a truly simple concept
which provides smooth increase in level. It is provided with
the potentiometer (pot) which must be logarithmic to match
the non-linear characteristics of our hearing. A linear pot
used for volume is quite unsatisfactory.
Take a 100k linear pot (VOL), and connect a 15k resistor (R)
as shown above. The output of the attenuation V/S the gain
plot had to be a straight line but is actually a far more
logarithmic than a standard log plot. For stereo, use a dual-
gang pot and treat both sections the same way. Different
values can be used for the pot, but keep the ratio between
6:1 to 10:1 between the value of VOL and R respectively.
While 6.7:1 is close to a real log curve, which still allows
excessive sensitivity at low levels. Higher ratios than 10:1 can
be used, but will cause excessive loading of the driving stage.
Audio power amplifier is the component that drives the
loudspeakers and it must have sufficient power to drive
them; without strain or clipping.
Fig: Circuit of the Log Pot Approximation
Figure :The Transfer Curve in dB
Most loudspeakers come with recommended power amplifier
ratings in watts. The power rating of an amplifier may be stated for
various loads whose units are measured in ohms. The most
common load impedances are 8 Ω, 4 Ω and 2 Ω (old vacuum tube
amplifier, load impedances are more likely to be 32 Ω, 16 Ω, 8 Ω
and may be 4 Ω). A large range of audio power amplifier ICs are
readily available. Some of these ICs house a single (mono)
amplifier, while others house a pair (a dual/stereo) of amplifiers.
LM 831 and TDA 2822 are dual types, and that only the LM380 and
LM384 have fully protected (short circuit proof) output stages.
High power audio amplifiers (typically 5-25 W) are used in theater,
vehicles, cinema hall and many more places to cover large area.
The basic types of high power audio amplifier ICs are LM377,
LM378, LM379, LM2879 and TDA 2004 which are dual (Stereo)
types and each house is a pair of independently accessible
amplifiers, while TDA 2005M is bridge type which houses a pair of
amplifier that are permanently wired in the bridge or power
boosting configuration.
A loudspeaker is an electro acoustic transducer that produces
sound in response to an electrical audio signal input.
The term "loudspeaker" may refer to individual transducers
(known as "drivers") or to complete speaker systems consisting of
an enclosure including one or more drivers. Individual electro-
dynamic drivers provide optimal performance within a limited
pitch range. Multiple drivers (e.g., subwoofers, woofers, mid-range
drivers, and tweeters) are generally combined into a complete
loudspeaker system to provide performance beyond their
constraint. A full-range driver is designed to have the widest
frequency response possible. These drivers are small, typically 3 to
8 inches (7.6 to 20 cm) in diameter to permit reasonable high
frequency response, and carefully designed to give low-distortion
output at low frequencies, though with reduced maximum output
level. In hi-fi speaker systems, the use of wide-range drive units
can avoid undesirable interactions between multiple drivers
caused by non-coincident driver location or crossover network
issues. Fans of wide-range driver hi-fi speaker systems claim a
coherence of sound due to the single source and results in
interference, and are likely due to the lack of crossover
components.
Note: see respective audio ICs datasheet for detail information.
Loudspeaker
Encipher | 2012
Practical Audio ProcessingCircuitry
You must be the change you wish to see in the world.—Gandhi
37
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Broadband Wireless Access (BWA) has emerged as a promising
solution for last mile access technology to provide high speed
internet access in the residential as well as small and medium sized
enterprise sectors. It uses radio waves to transmit and receive data
directly to and from the potential users whenever they want it. It is
a point-to-multipoint system which is made up of base station and
subscriber equipment. Instead of using the physical connection
between the base station and the subscriber, the base station uses
an outdoor antenna to send and receive high-speed data and
voice-to-subscriber equipment.
At this moment, cable and digital subscriber line (DSL)
technologies are providing broadband service in this sectors. But
the practical difficulties in deployment have prevented them from
reaching many potential broadband internet customers. Even
many urban and suburban locations may not be served by DSL
connectivity as it can only reach about three miles from the central
office switch. On the other side many older cable networks do not
have return channel which will prevent to offer internet access and
many commercial areas are often not covered by cable network.
But with BWA this difficulties can be overcome. Because of its
wireless nature, it can be faster to deploy, easier to scale and more
flexible, thereby giving it the potential to serve customers not
served or not satisfied by their wired broadband alternatives.
IEEE 802.16e standard for BWA and its associated industry
consortium, Worldwide Interoperability for Microwave Access
(WiMAX) forum promise to offer high data rate over large areas to
a large number of users where broadband is unavailable. This is
the first industry-wide standard that can be used for fixed as well
as mobile wireless access with substantially higher bandwidth than
most cellular networks. Wireless broadband systems have been in
use for many years, but the development of this standard enables
economy of scale that can bring down the cost of equipment,
ensure interoperability, and reduce investment risk for operators.
In practical terms, WiMAX would operate similarly to WiFi but at
higher speeds, over greater distances and for a greater number of
users. WiMAX could potentially erase the suburban and rural
blackout areas that currently have no broadband Internet access
because phone and cable companies have not yet run the
necessary wires to those remote locations. A WiMAX system
consists of two parts:
• A WiMAX tower, similar in concept to a cell-phone tower - A
single WiMAX tower can provide coverage to a very large area -- as
big as 3,000 square miles (~8,000 square km).
• A WiMAX receiver - The receiver and antenna could be a small
box or PCMCIA card, or they could be built into a laptop the way
WiFi access is today.
How does it work??
WiMAX-at your service
WiMAX-at your service
Amar Shrestha / Shashi Raj PandeyEE-IV Communication
It became a big fuss, when for the first time in the country,
Nepal Telecom (NT) launched WiMAX amidst a special
function in Kathmandu this November. While it is still under
the phase of active deployment over the country, the
operator announced that at present, the services were being
launched only for the corporate clients. Under this;
hospitals, educational institutions, business firms, diplomatic
missions and non-governmental organizations, can now
instantly subscribe to the high-speed internet service with
minimum speed of 256 kbps as stated. Individual users,
however, will have to wait for a month to subscribe to the
WiMAX service. So what is WiMAX all about?? Let's have
some insight about it.
WiMAX (Worldwide Interoperability for Microwave Access) is
a wireless communications standard designed to provide 30
to 40 megabit-per-second data rates, with the 2011 update
providing up to 1 Gbps for fixed stations. The name
"WiMAX" was created by the WiMAX Forum, which was
formed in June 2001 to promote conformity and
interoperability of the standard. The forum describes WiMAX
as "a standards-based technology enabling the delivery of
last mile wireless broadband access as an alternative to
cable and DSL".
Wireless technologies can be classified in different ways
depending on their range. Each wireless technology is
designed to serve a specific usage segment. The
requirements for each usage segment are based on a variety
of variables, including bandwidth needs, distance needs and
power.
There are following three major issues with existing Wireless
Networks.
• One of the primary concerns
about wireless data delivery is that, like the Internet over
wired services, QoS is inadequate. Lost packets, and
atmospheric interference are recurring problems for wireless
protocols.
• This has been another major issue with a
data transfer over a wireless network. Basic network security
mechanisms like the service set identifier (SSID) and
Wireless Equivalency Privacy (WEP). These measures may be
adequate for residences and small businesses but they are
inadequate for entities that require stronger security.
• Normally wireless network offers a
range of about 100 meters or less. Range is a function of
antenna design and power. Nowadays the range of wireless
is extended to tens of miles so this should not be an issue
any more
Quality of Service (QoS):
Security Risk:
Reachable Range:
intelligence without ambition is a bird without wings.Salvador Dali
38
A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection (for example, a T3 line). It
can also connect to another WiMAX tower using a line-of-sight, microwave link. This connection to a second tower (often referred
to as a backhaul), along with the ability of a single tower to cover up to 3,000 square miles, is what allows WiMAX to provide
coverage to remote rural areas.
What this points out is that WiMAX actually can provide two forms of wireless service:
There is the non-line-of-sight, WiFi sort of service, where a small antenna on your computer connects to the tower. In this
mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength transmissions are not as easily
disrupted by physical obstructions -- they are better able to diffract, or bend, around obstacles.
There is line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-
sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use
higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more
bandwidth.
WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65 square km of coverage, which is similar in
range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station would send data to
WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of
coverage). This is what allows WiMAX to achieve its maximum range.
In simple terms if we look at this, here's what would happen if you got WiMAX. An Internet service provider sets up a WiMAX base
station 10 miles from your home. You would buy a WiMAX-enabled computer or upgrade your old computer to add WiMAX capability.
You would receive a special encryption code that would give you access to the base station. The base station would beam data from the
Internet to your computer (at speeds potentially higher than today's cable modems), for which you would pay the provider a monthly
fee. The cost for this service could be much lower than current high-speed Internet-subscription fees because the provider never had
to run cables. If you have a home network, things wouldn't change much. The WiMAX base station would send data to a WiMAX-
enabled router, which would then send the data to the different computers on your network. You could even combine WiFi with
WiMAX by having the router send the data to the computers via WiFi.
Encipher | 2012
WiMAX-at your service
Great minds discuss ideas; average minds discuss events; small minds discuss people.-Eleanor Roosevelt
39
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
The one of the component, current is defined as that factor of the
electric power which is proportional to the magnetic field. While the
other component voltage, is defined as that factor of the electric
power which is proportional to the electric field.
Wireless electricity transmission would completely replace high
voltage transmission line. It has more freedom of choice of receiver
and transmitter. The cost of transmission and distribution would be
less and also the power could be transmitted to the places where the
wired transmission is not possible. Loss of transmission is negligible
in the Wireless Power Transmission (WPT). Power is available at the
rectenna as long as the WPT is operating. The power failure due to
short circuit and fault on cables would never exist in the transmission
while power theft would be not possible at all.
The Capital Cost for practical implementation of WPT seems to be
very high and the other drawback of the concept is interference of
microwave with present communication systems.
1. Nikola Tesla, “The Transmission of Electrical Energy Without
Wires as a Means for Furthering Peace,” Electrical World and
Engineer.
2. Nikola Tesla, My Inventions, Ben Johnston, Ed., Austin, Hart
Brothers
http://cleantechindia.wordpress.com/2008/07/16/indiaselectricity
3. transmission-and-distribution-losses/
4. http://en.wikipedia.org/wiki/witricity
Pros and Cons
References:
Wireless Energy Transfer
Wireless Energy Transfer
Milan SilwalEE- III Power and Control
Wireless Energy Transfer or Wireless Power is the
transmission of electrical energy from a power source
to an electrical load without interconnecting manmade
conductors.
When an electric current passes through a circuit there is an
electric field in the dielectric surrounding the conductor;
magnetic field lines around the conductor and lines of electric
force acts radially about the conductor. In a direct current
circuit, the fields are constant. While in an alternating current
circuit, the fields alternate; i,e with every half wave of current
and voltage, the magnetic and the electric field starts at the
conductor and run outwards into space with the speed of light,
where these alternating fields impinge on another conductor a
voltage and a current are induced.
The process of wireless energy transmission can be simplified
by the example of energy transmission in a transformer.
Electromagnetic induction is proportional to the intensity of
the current and voltage in the conductor which produces the
fields and frequency. Higher the frequency, more intense is the
induction effect. Energy is transferred from a conductor that
produces the fields (the primary) to any conductor on which
the fields impinge (the secondary). Part of the energy of the
primary conductor passes inductively across space into
secondary conductor and part of the energy decreases rapidly
along the primary conductor. A high frequency current does
not pass for long distances along a conductor but rapidly
transfers its energy by induction to adjacent conductors.
Higher induction resulting from the higher frequency is the
explanation of the apparent difference in the propagation of
high frequency disturbances from the propagation of the low
frequency power of alternating current systems. The higher
the frequency the more preponderant becomes the inductive
effects that transfer energy from circuit to circuit across space.
The more rapidly the energy decreases and the current dies
out along the circuit.
In the electric circuit, where there are several conductors, the
electric fields of the conductor superimpose upon each other
and the resultant magnetic field lines and lines of electric force
are not concentric and radial. Between parallel conductors
they are conjugate of circles. Hence, neither the power
consumption in the conductor, and nor the magnetic and
electric fields, are proportional to the flow of energy through
the circuit. However, the product of the intensity of the
magnetic field and the intensity of the electric field is
proportional to the flow of energy and power. The power is
therefore resolved into a product of the two components i and
e, which are chosen proportional respectively to the intensity
of the magnetic fields and of the electric fields.
Generation
Discovery consists not in seeking new lands but in seeing with new eyes.Marcel Proust
40
Encipher | 2012
Next Step in Cellular Services- Long Term Evolution
Before it would have taken 1-1.5 years for the recruitment process
to complete after the notice had come. Now it only takes about 6
months to complete the process.
Well as an engineer, the job was quite straight forward. A
supervisor would give you a task and you had to work on it and
provide an output. And when you reach the management level,
the job doesn't really change if you are competent. You could do
the engineer's job and also take other responsibilities. Like when
you are an engineer, you only work in the engineer department.
But when you reach the management level, you also work in the
finance account, administration and even many other departments
of NEA.Basically you just install intercommunication and co-
ordination between these departments. According to the NEA's
recruitment policy, when you are recruited you can work in any of
its fields. For example, I currently work in the generation ,
operation and maintenance business group, but I can also work in
any other business group in the same position. There are no any
restrictions.
Well, the energy crisis in Nepal is quite known to the public and
the shareholders. Currently, well according to my forecast we will
have 12-15 hours of load shedding. We used to have even more
severe power cuts, but due to a 2-3 days rainfall at the end of
September the reservoirs at Kulekhani (one of only two storage
type projects) have filled, giving us some relief for the time being.
But even then due to increasing power demands, we will face
similar or more severe power cuts for the next 2-4 years.
We have short-term, midterm and long-term initiatives. But to
understand this, you'll also have to understand NEA's background.
NEA is a completely state owned electric utility company. We are
working on making it a shareholder company, but it hasn't been
implemented yet. So it is completely under government control,
and what we implement are all government policies. So we take
care of our business ventures as well as the government policies.
So we know, solving this crisis requires increased power
generation. On the short-term basis, we are currently importing
around 100 MW of power from India with a plan to increase this
figure to 200 MW after grid reinforcement and transmission line
reform and maintenance in the border areas.Another initiative
which is being implemented is the mobile diesel plant. This will be
kept at the load centers and dedicated feeders. With a total power
of 80MW brought about in phases of 30MW in 3 months and so
on. And as its tariff is very high, about Rs 30 per unit, it will be
provided only to the dedicated industrial customers.Another
initiative is to better reschedule the repair and maintenance of our
existing hydropower plants to run it efficiently.
What was your job here as an engineer, and what is it now as the
Assistant Manager?
So now lets talk about the present energy scenario in Nepal.
So what is the NEA's vision to solve this crisis?
Interview
- With Keshab Shrestha
Interview
So let's start off with your childhood and your academic
journey?
And you were an electrical engineer student ?why did you
choose this field in particular?
So you studied both in KU as well as in NIT, India. How
would you compare or differentiate the academia in these
two places?
Electrical students, those who want to stay in Nepal, are
always looking for a job in NEA. So how hard is it to get an
opportunity to work here in NEA, especially for KU
students?
Well, I was born in Tamghas, Gulmi and did all of schooling
there in Amrit High School, a reputed school in the region.
Then I did my I.sc from St.Xavier's College, Maitighar and
then got an Indian government seat to do be in India in NIT.
At around 1997, I graduated at around 2001,and then looked
for jobs a year. In that time, I taught in KEC(Kantipur
Engineering College) for 6 months until I was hired as an
engineer at NEA. Then in 2008, I took a leave from NEA to
complete my masters degree from Kathmandu university.
The thing is , I can't particularly point out the reason why. I
just coincidentally happened to be studying this and as I
continued in this field, I got more interested to do more. I
think I made a good choice.
There is not much difference actually. The actual difference
was only in myself during those times. When I went to India
for B.E, I wasn't that mature; due to that I feel I didn't really
take the best advantage of the academic atmosphere there.
But in time to do masters here at KU, I had worked for 4-5
years and was mature enough. And the atmosphere at KU
was also very freeing for those who had the desire to study
and I guess I was able to explore my potential there better
than my time in India.
Actually, it's not that hard at all. The NEA has given a great
platform to the electrical engineers of the country and is
thus highest recruit company. Well, the recruitment process
is quite similar to Civil Service but better and easier.
And recently, the management has taken an initiative to
make the recruitment process even cleaner and faster.
Current: Asst. Manageer at NEA
Past Engineer at Nepal Electricity
Authority
Education: Kathmandu University,
NIT, Silchar
Even if you’re on the right track, you’ll get run over if you just sit there.—Will Rogers
41
And also the existing diesel thermal power plants at Hetauda
(14.4MW) and Dugauli , Biratnagar (39MW) are under major
rehabitation by the original manufactures, scheduled to be
completed at around Poush 22.
Obviously, it is. As I had said earlier, to understand the loss,
we have to understand the structure of NEA. NEA doesn't
stand solely as it has shareholder, so all of them have
responsibilities. And also there are government
interventions. So NEA is not independent enough to act to
reduce losses, as all the initiatives have to be supported by
the government. It has become a socio-economic issue. And
also to reduce losses, NEA has to improve the operational
and financial efficiency. For example, the tariff increased by
20 percentage recently. And even if we generate electricity,
tariff is fixed under the directive of Electricity Tariff Fixation
Commission. This tariff had been stagnant for the last
decade, while everything around us has inflated in value.
And about how these losses are taking place, we have
technical and non-technical reasons. In the technical front,
NEA is in a satisfied situation. These can be reduced, but it
takes a large amount of fund. Similarly, non-technical losses
includes pilferage, using electricity without paying etc.
I guess you know what DSM is. It is the management of load
at the consumer end. If there is a deficit in the peak load,
then it decreases the deficit at peak load and increases it at
the off peak. I don't think it effectively increases or
decreases the deficit at peak load and increases or decreases
the energy consumption, but it only changes the time of
consumption. And yes, NEA has implemented it and in the
context, we are distributing CFL, and those LED lights which
reduce consumption to the customers through NEA
subsidies. Similarly, we have taken measures to correct
power factor in industrial consumers. So basically DSM it
cannot reduce consumption but only differ capacity
increment's capital investment by some time. Personally I'm
not a fan of DSM.
This is somewhat of a policy level question. Firstly, you should
not forget that NEA is not exactly an organization in the energy
sector to address all the problems and issues. It's just one of
the number of possible companies in the government's
hydropower policy. If you look at the power market, we have
generation, transmission and distribution. In the generation
front, NEA has to compete with other national and foreign
hydropower companies. I don't know if you have read it, but
Nepal's Hydropower Policy 2001 is a heaven for private sector
and foreign investor. But even with a good policy, we are
Is NEA at loss? If so, why and how ?
How feasible is DSM (Demand Site Management) in the
context of Nepal?
We all know what potential Nepal has in terms of
hydropower. But why are we still struggling with power
cut?
struggling due to a couple of reasons. Firstly, due to the long
insurgency period, the investors have become reluctant and
resistant. And as it requires huge investment but has a long gestation
period to get the profit, unlike the housing business, auto loan, etc.
We haven't had the expected amount of investment. So basically
these socio-political and socio-economic factor are the reasons.
For this I will have to continue with the previous answer.
Hydropower is capital intensive and time for return is long and its
opportunity as well as challenges but on the basis of policy level
itself, the investors are on the safe side. The policy is quite friendly
to the investor. Let me highlight some of the policies.
Electricity Act, 1992 protects foreign investor from confiscation,
expropriation and nationalization on discouraging thing is that the
environment policy is very rigid and time consuming, but even that
is being made flexible for hydropower projects of under 50MW.
And the policies are also liberal on royalty taxes, representation of
the foreign investments, visa governing law etc. And there is an
institutional mechanism in the hydropower development with
Traffic Fixation commission, DOED, and construction of Energy
Management and Research Institute in the policy. So, this should
invite Investors.
Well those two year were some of the most productive and
enjoyable time, and the freedom the KU provided me to explore
my potential to the fullest should be admired. And the MEEP
program that I studied under was a really great platform which was
under NOMA, now known as NORAD.
Well, I think it's a common procedure in any organization. And all I
hope is that there is a smooth transition in the leadership.
Well, I am really enjoying the assignment that I am getting in my
position. And being in the position. I always have the inner feeling
that I have to contribute something. This really motivates with my
work.
You know Electrical Engineering is a field with lots of challenges as
well as opportunities. And even if I did join this coincidently, over
the period of time I feel I have chosen the right field. While I was
studying in Norway, there were no one in more demand than the
Electrical and Power engineers. And with the power engineering
technology directed towards renewable energy , power
electronics, smart grid field, the electrical engineers do and will
have really good opportunities.
So far a capital investor, how feasible and profitable is an
investment on the hydropower front?
Now lets us change the topic, and get a lot un-technical, Tell us
about your time at KU?
I suppose you have knowledge about the change of VC from
Suresh Raj to Ram Kautha Makaju Shrestha , What are your
opinion about that?
How satisfies are you with your profession?
So finally what the suggestion would you give to the KU student
of your field?
Encipher | 2012
Interview
You can do anything, but not everything.—David Allen
42
Encipher | 2012
l = s±jw
PHOTO
CORNER
PHOTO
CORNER
Encipher | 2012
ACROSS
4. Microprocessor with peripheral devices
7. Common base configuration in BJT is used to provide
which type of gain?
9. The Apparatus which superpose the modulation on the
carrier current or a wave in a line
11. Turn a circuit on or off with this
14. Laws of Planetary motion is given by
16. Most semiconductor chips and transistors are created
with
18. Person responsible for breaking the German Enigma
code
19. Light Year is the unit of
20. Magnetic circuit connecting the limbs of a Transformer
DOWN
1. The most sophisticated device to change current into
voltage
2. A type of EEPROM
3. Unit of Flux Density
5. The visible luminous discharge along High Tension
Transmission line
6. Official mascot of the Linux Kernel
8. An object detection system which uses radio waves
10. Integration of Unit Step Function
12. In Object Oriented Programming language, the
mechanism of deriving a new class from an old one is
13. Known as 'Royal Water’
15. Has a function opposite to that of a Motor
17. Logic gate that gives high output if all inputs are high
CROSSWORD
