NON-CONVENTIONAL ENERGY RESOURCES - saurabh ...

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Assignment # 01

For B. Tech. Final Year (EC + CSE + CE)

NON-CONVENTIONAL ENERGY RESOURCES Last Date of Submission : November 15, 2008

GENERAL INSTRUCTIONS

1. Each Question No. corresponds to individual student of that Roll No. in the

NCER Class.

2. Do mention the question and the following items on the first page of the

report as illustrated in ‘SAMPLE’.

Name :

Branch :

Class Roll No :

UPTU Roll No :

3. The answer must not be less than 6 pages including neat and clean

illustrations.

4. The font must be either “Times New Roman” or “Palatino Linotype” with 12

point size and 1.5 spacing.

5. The size of each figure must not be greater than 12 cm x 8 cm and the captions

of each figure must be given.

6. The marks allocations are as follows:

Adequacy of the material : 03 Marks

Organization of the material : 03 Marks

Illustrations : 04 Marks

TOTAL : 10 Marks

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7. Late submission of the assignment is not allowed in any case.

8. The hard copy is to be submitted to S.M. Tripathi or to Dr. K.G. Upadhayay.

9. The soft copy in MS Word format is to be submitted to

[email protected] mentioning NCER : Class Roll No., Name, Branch

in the subject line, e.g.,

NCER : 23, Rajesh Kumar Singh, EC

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SAMPLE

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ASSIGNMENT NO # 01

Name :

Branch :

Class Roll No :

UPTU Roll No :

QUESTION

What is Power Electronics? State the importance of Power Electronics? Also

mention some of its applications?

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I. POWER ELECTRONICS : An Introduction

Power Electronics deals with conversion and control of electric power using power

semiconductor devices that operate as high speed electronic switches. Power

electronics involves the study of electronic circuits intended to control the flow of

electrical energy. These circuits handle power flow at levels much higher than the

individual device ratings. Modern devices include diode, thyristor, triac, GTO

thyristor, power MOSFET and IGBT. The level of power may be from several watts

to kilowatts and megawatts compared to typical micro-watts to milli-watts level that

is handled by Signal Electronics.

Figure 1. Power electronics : an introduction

The traditional power engineers find it difficult to comprehend how such tiny

devices can handle so large power and so fast in comparison with electromechanical

circuit breakers, transformers and other bulky apparatus in power system. A power

electronic apparatus can be looked upon as a high efficiency switching mode power

amplifier, where the efficiency may approach as high as 98 to 99%. While switching

large voltage and current so fast (high dv/dt and di/dt) and at high switching

frequency at the command of microchip based signal electronics, the equipment

generates severe EMI (electromagnetic interference) and harmonics that create

difficult problems in the environment. Although the name power electronics starts

with “POWER”, and some people mistakenly indentify it with power engineering;

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power electronics is, infact, far distant from the traditional power area based on

50/60 Hz. Basically, the name “POWER ELECTRONICS” comes from

“ELECTRONICS” that handles high power. Some people define power electronics

as “enabling technology” or power processing apparatus that normally remains

hidden from the public eye and, therefore, general public is not familiar with power

electronics, unlike, for example, with computers. Truly specking power electronics

has now established itself more important than computers in modern industrialized

society. Power electronics is essentially a hybrid-high tech area that embraces

multiple disciplines. The area of motor drives (or motion control) is usually

amalgamated with power electronics, because the complexity and characteristics in

motion control are mainly due to power electronics that control the machines. In

recent years, a new hybrid discipline called MECHATRONICS has emerged that

blends power electronics with signal electronics, machine drives, and mechanical

systems.

Figure 2. Power electronics applications

The area of power electronics (including machine drives) has gone through

dynamic technology evolution during the last three decades, because of relentless

R&D that have resulted many inventions in power semiconductor devices, converter

topologies, PWM techniques, analytical and simulation techniques, advanced control

and estimation methods, digital signal processors, and ASIC (application specific

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integrated circuit) chips. It has now grown as a vast complex and interdisciplinary

technology. The excitement and R&D challenges in power electronics have attracted

large segment of researchers from traditional power, electrical machines, and control

engineering communities over the number of years, and most of them now take

pride in identifying themselves as power electronic engineers. The dramatic cost and

size reduction of power electronic apparatus, along with performance improvement

in recent years, is promoting widespread applications of power electronics in

industrial, commercial, residential, transportation, aerospace, utility and military

environments. It is interesting to note that according to the estimate of EPRI (Electric

power research institute in U.S.A.), roughly 60% of electricity consumed in USA is

now flowing through power electronics, and sooner or later, this figure will increase

to 100%.

II. APPLICATIONS OF POWER ELECTRONICS

It is most essential to discuss applications of power electronics before discussing the

importance, challenges and technology evolution. Figure 1 summarizes the general

applications of power electronics. Let us now discuss several application examples

briefly in order to make our ideas clear.

(A). Three Phase UPS System with 50/60 Hz Line Backup

The utility power system is not very reliable. There may be interruption (or

blackout), brownout (or sag), or other power quality problems such as voltage

unbalance, waveform distortion, or frequency deviation. Critical loads such as

computers, telecommunication equipment, emergency lights, fire and security

systems, etc. demand reliable power supply. An UPS system, shown in Figure 3,

satisfies this requirement. The three phase critical UPS load can be supplied either

directly from the utility system, or by the battery backed inverter, as shown in

Figure 3. Electronic circuit breaker (CB), consisting of anti-parallel thyristors, can

help the transfer in sub-cycle period. In the system, the inverter normally supplies

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the load with the line circuit breaker remaining open. The system consists of three

phase diode rectifier, single-phase thyristor based battery charger, storage battery,

LC filter, PWM IGBT bridge inverter (shown with BJT), output LC filter, and circuit

breaker (CB). The inverter generates high quality 60 Hz power supply from the

inferior and unregulated line supply at the input. The thyristor Q is basically a

switch, which remains open in the normal condition. While the converter system

supplies the load, the battery gets trickle charging current from the charger that

boosts the supply dc voltage Vd by VR , as shown in the Figure 3.

Figure 3. Three-phase UPS system with 50/60 Hz line back-up

At utility power interruption, Q is turned on and the battery takes over the

supply to the inverter. When the line supply is restored, the battery supply is

withdrawn by turning off Q. If there is a problem in the inverter system, the load is

transferred to the ac line directly with a short interruption time (assuming the

interruption is permitted). Alternately, the line can be the primary source of power,

where the inverter system remains as the standby. The dc link can have a boost

chopper (single IGBT dc-dc converter) that will shape the line current sinusoidal at

unity power factor and maintain Vd at a desired level. For prolonged power

interruption, if battery storage is exhausted, an engine generator or fuel cell power

supply can take over.

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(B). Modern Bullet Train Drive in Japan

The high speed modern bullet train for railway transportation is a pride of Japan,

and it has gone through evolution over a period of more than 30 years. Figure 4

shows the modern drive system that has been added in some sections since 1999.

The overhead catenary has a single phase 25 kV, 60 Hz power supply that is

connected to the primary of a multi winding transformer on the vehicle. The lower

end of the primary is returned to ground (track) through the wheels. There are three

identical drive units in each carriage, which are fed by the stepped down

transformer secondary winding as shown. The 60 Hz power is rectified by a PWM

IGBT rectifier, and then converted to variable voltage variable frequency power by a

three phase three level inverter for speed control of four parallel connected identical

induction motors (275 kW each).

Figure 4. Modern bullet train drive system in Japan

The three level converter permits improved voltage sharing of IGBTs and

gives better PWM quality compared to traditional two level converter. Each machine

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is connected to an axle, and the characteristics of all the four machines along with

their wheel diameters are matched properly for parallel operation with equal load

sharing. The drive has vector (or field oriented) control in constant torque and field

weakning regions. In the regenerative braking mode of the four quadrant drive, the

inverter operates as rectifier and the rectifier operates as inverter, to pump braking

energy to the 60 Hz line. Sinusoidal PWM operation of the line side converter

permits sinusoidal line current at unity power factor, which can also compensates

the line voltage sag. The maximum speed of the train is around 180 miles/hour.

(C). Renewable Energy Systems

Renewable energy sources, such as wind and PV, are being emphasized recently, as

mentioned before. They are environmentally clean, safe and abundant in nature.

Figure 5 shows a simplified wind power generation system with a cage type

induction generator and two-sided PWM voltage-fed converter using IGBTs.

Figure 5. Wind power generation system with two-sided PWM converter

The variable speed wind turbine is coupled to the machine shaft. The variable

voltage variable frequency power output of the generator is converted to dc by the

PWM rectifier, and then pumped to the utility bus through the PWM inverter. The

machine excitation current is supplied by the rectifier that maintains the flux

constant.

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III. IMPORTANCE OF POWER ELECTRONICS

The applications of power electronics discussed so far have possibly demonstrated

adequately the importance of power electronics. Modern solid-state power electronic

apparatus has very high efficiency compared to old and traditional motor-generator

(M-G) sets, saturable-core magnetic amplifiers, mercury-arc converters, and gas tube

electronics. The equipment is static, free from audio noise, and has low cost, small

size, high reliability, and long life. The device switching frequency in the apparatus

is normally high that reduces the size of passive components, such as filters and

transformers. Power electronics is very important in modern power processing

plants (such as UPS, HVDC, SVC, FACTS, etc.), as discussed before. Power

electronics based control has established more importance than hydraulic and

pneumatic controls in industrial systems. Power electronics in motion control

systems gives high industrial productivity with improved product quality. In

modern automated industrial environment, power electronics and computers work

closely, where the former can be looked upon as a brawn (or muscle), and the latter

is the brain. In a modern automobile plant, for example, power electronic controlled

robots are routinely used for assembling, material handling, and painting. In the

highly automated industrial environment, it appears that two technologies will be

most dominant: power electronics with motion control and computers. It is no

wonder that power electronics is now spreading fast from the industrially advanced

nations to developing countries of the world. There is another important role of

power electronics. Power electronics is now playing an increasingly important role

in energy conservation and environmental pollution control trends of the 21st

century.

Let us now expand our understanding of energy saving by power electronics

with some specific example applications. Rheostatic control of power is well-known

and yet common in many developing countries. Rheostatic speed control of dc

motor drive in a subway train or tram car is still common in many parts of the

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world. Replacing rheostat by switching mode dc-dc converter saves large amount of

energy. Variable speed operation of the motor with the help of power electronics at

full throttle opening is highly efficient, and can save up to 30% energy at light load.

Again, most of the machines operate at light load most of the time. Motor-converter

efficiency at light load can be improved by reduced flux operation (flux

programming efficiency optimization), instead of operating with the rated flux. Flux

programming at light load increases copper loss, but decreases iron loss. However,

the total loss is reduced. Power electronics based high frequency fluorescent lamps

can be three to four times more efficient than incandescent lamps. These lamps have

additional advantages, such as long life, soothing light, and easy dimming

capability. It is interesting to see that incandescent lamps are recently being widely

replaced by compact fluorescent lamps. Another large and potentially growing area

of power electronics applications is electric and hybrid vehicles, which have been

discussed before.

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ASSIGNMENT

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[1]. Write short notes on classification of energy resources? What are the advantages

of use of renewable sources of energy?

[2]. Explain the basic principle of MHD generation and discuss about seeding

process and working fluids for both open loop and closed loop operations.

An MHD generator has plate area of 0.30 m2 ; distance between plates 0.4 m ; flux

density 2.0 wb/m2 ; average gas velocity 1000 m/sec and gaseous conductivity of 10

mho/m. Calculate open circuited voltage and maximum power output.

[3]. Name different types of winds. Explain how they are being produced. What is

the basic principle of wind energy conversion?

[4]. Explain flat plate collector with the help of diagram. Discuss about fluids used

for heat transfer medium. Write applications of flat plate collector.

[5]. Derive the expression for power developed due to wind? Write notes on

a. Savonius Rotor

b. Darrius Rotor

c. Applications of wind energy

d. Site selection criteria for wind power generation

[6]. Explain heat energy extraction and other factors involved with solar pond with

the help of diagram.

[7]. Explain the difference between a geothermal power plant and thermal power

plant? Discuss various sources of geothermal energy in detail.

[8]. Give classification of wind turbines on the basis of axis of rotation? Draw the

schematic diagram of a wind turbine and explain the functions of its main

components.

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[9]. Discuss Claud and Anderson cycle systems for ocean thermal energy conversion

and limitations associated with OTEC.

Also determine the overall efficiency of an OTEC plant if surface warm water

temperature is 27oC and deep cool water temperature is 5oC. Assume relative

efficiency factor of the plant is 55%.

[10]. Explain heat energy extraction and other factors involved with solar pond with

the help of diagram.

[11]. Name different types of winds. Explain how they are being produced. What is

the basic principle of wind energy conversion?

[12]. Write notes on the following

a. Power crisis in India

b. Hot dry rocks (HDR)

c. Solar collectors

d. Liquid dominated system

e. Efficiency of OTEC

f. HAWT generator unit

g. Space heating

[13]. Explain distributed collector system (DCS). Mention the main features of the

sub-systems for the DCS.






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[15]. Derive the expression for power developed due to wind? Write notes on

a. Savonius Rotor

b. Darrius Rotor

c. Applications of wind energy

d. Site selection criteria for wind power generation

[16]. Explain the heat extraction in form of hot water from the earth’s interior with

the help of neat diagram. Also discuss different methods involved in process to

recover heat energy from hot dry rocks.

[17]. What do you mean by dry steam, wet steam and hot water geothermal systems?

Discuss the field of application of these systems. What are the difficulties in the large

scale utilization of geothermal energy?




c. Solar collectors




g. Space heating

[19]. Discuss the limitations in the construction of barrages for tidal power projects.

Explain basic tidal power schemes.

[20]. Give classification of wind turbines on the basis of axis of rotation? Draw the

schematic diagram of a wind turbine and explain the functions of its main

components.

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[21]. Explain open and closed cycle MHD generation systems with the help of

diagrams. What are the advantages of MHD power generator?



[23]. Explain distributed collector system (DCS). Mention the main features of the

sub-systems for the DCS.

[24]. Discuss the limitations in the construction of barrages for tidal power projects.

Explain basic tidal power schemes.

[25]. Describe the principle of solar photovoltaic energy conversion and hence

explain the operation of a solar cell. Also discuss the solar photovoltaic power plant.

[26]. Discuss various types of solar thermal power plants. Write short notes on

a. Central receiver with heliostat fields

b. Solar cooking

c. Solar chimney

d. Solar thermal storage

[27]. Discuss the working of

a. Thermo-syphon type water heater system

b. Circulating pump type water heater system

[28]. Show the origin and distribution of geothermal energy with the help of

diagram. Discuss advantages and disadvantages associated with this. Discuss the

following—

a. Hydrothermal Energy

b. Petro-thermal Energy

c. Geo-pressured Energy

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[29]. What is the basic difference between thermoelectric and thermionic conversion

system? Explain the working of thermoelectric generator.

[30]. Explain the heat extraction in form of hot water from the earth’s interior with

the help of neat diagram. Also discuss different methods involved in process to

recover heat energy from hot dry rocks.

[31]. Write short notes on classification of energy resources? What are the

advantages of use of renewable sources of energy?

[32]. Draw schematic diagram of an MHD power generating system having heat

recovery steam generator. Explain the functioning of the system. Also derive the

equations for the voltage and power output of MHD generator.




[34]. Discuss merits and demerits of various non-conventional energy sources? Also

mention their applications.

[35]. What do you mean by dry steam, wet steam and hot water geothermal systems?

Discuss the field of application of these systems. What are the difficulties in the large

scale utilization of geothermal energy?



b. Solar cooking

c. Solar chimney


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[37]. Describe the principle of solar photovoltaic energy conversion and hence

explain the operation of a solar cell. Also discuss the solar photovoltaic power plant.

[38]. Explain the difference between a geothermal power plant and thermal power

plant? Discuss various sources of geothermal energy in detail.

[39]. Define solar constant? Compare FLAT and all FOCUSING COLLECTORS.




[41]. Explain open and closed cycle MHD generation systems with the help of

diagrams. What are the advantages of MHD power generator?

[42]. Discuss the following in view to the wind energy conversion system

a. VAWT generator unit

b. Cut-in speed

c. Cut-out speed

Also explain the working of horizontal axis two blade wind mill with suitable

diagram.

[43]. Discuss merits and demerits of various non-conventional energy sources? Also

mention their applications.



following—




[45]. Define solar constant? Compare FLAT and all FOCUSING COLLECTORS.

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b. Cut-in speed

c. Cut-out speed

[47]. Discuss Claud and Anderson cycle systems for ocean thermal energy

conversion and limitations associated with OTEC.




[48]. What is the basic difference between thermoelectric and thermionic conversion

system? Explain the working of thermoelectric generator.




[50]. Name the components of a tidal power plant? Give the working of single basin

and double basin tidal power plants?

[51]. What is a photovoltaic cell? Explore the advantages and disadvantages of

‘Photovoltaic solar energy conversion’.



b. Solar cooking

c. Solar chimney


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c. Solar collectors




g. Space heating

[55]. Discuss Claud and Anderson cycle systems for ocean thermal energy

conversion and limitations associated with OTEC.











b. Cut-in speed

c. Cut-out speed

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following—




[59]. What is a photovoltaic cell? Explore the advantages and disadvantages of

‘Photovoltaic solar energy conversion’.



[61]. Name the components of a tidal power plant? Give the working of single basin

and double basin tidal power plants?




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