S.
No. Description Marks
Q1 StateSeebeckEffectandPeltierEffect. 2
The Seebeck effect is a phenomenon in which a temperature difference between
twodissimilar electrical conductors or semiconductors produces a voltage difference
between thetwo substances. If the pair is connected through an electrical circuit, direct
current (DC) flowsthroughthat circuit.
A-1
The Peltier effect is the reverse phenomenon of the Seebeck effect; the electrical
currentflowingthroughthejunctionconnectingtwomaterialswillemitorabsorbheatperunitt
imeatthejunction to balancethedifferencein thechemical potential of thetwomaterials.
What is the maximum energy conversionefficiencyofawindturbinefora 2
Q2 givensweptarea?
Powercoefficientandtipspeedratioofdifferentwindconvertersdesigns.Thetheoreticalmax
imumefficiencyofa windturbineis givenbythe BetzLimit andis around59percent.
AA-2
Betz's law shows that as air flows through a certain area, and as wind speed slows
from losingenergy to extraction from a turbine, the airflow must distribute to a wider
area. As a result,geometrylimits anyturbineefficiencyto a maximumof59.3%.
Q3. Howmuch ofour dailyCO2 emissions can wind avoid? 2
Wind energy does not emit any greenhouse gases and has an extremely good
energybalance. The calculations on just how much CO2 could be saved by wind
energy is based onan assumption for the carbon intensity of the global electricity
sector, i.e. the typical amountof CO2 emitted by producing one kWh of power.
Individual countries’ emissions differsubstantially, but here we use the IEA’s estimate
of 600g/kWh as an average value for thecarbondioxide reductionto be obtainedfrom
A-3 wind generation.
The most ambitious scenario by the Global Wind Energy Council (GWEC) show that,
withgrowth rates much lower than the 30% the wind sector has experienced over the
past decade,global wind energy capacity could increase from 121GW at the end of
2008 to over 1,000GWby 2020 and 2,400 GW by 2030. This would result in annual
CO2 savings of more than 1.5billiontons in 2020and3.2 billon tons in 2030.
Q4. Classifyrotors employedforwindgeneration. 2
A-4 Refer to class notes
DescribetheworkingofaThermo-electricgenerator.Deriveanexpressionfor
Q5. 7
itspoweroutput.
A-5 Refer to class notes
What is the basic difference between thermoelectric andthermionic conversion
7
Q6. systems? Also, explain the workingofthermoelectricgenerators.
A-6 Refer to class notes
Describe the principle of operation and constructionaldetails of a basic thermionic
7
Q7. generator. Explain the workingofthermoelectric generator.
, A-7 Refer to class notes
Describemainconsiderationsinselectingasiteforwind
Q8. 7
farm.Discussmeritsariddemeritsofwindenergy.
A-8 Refer to class notes
Explain the working of horizontal axis two blade windmillswithsuitable diagram. 7
Q9.
A-9 Refer to class notes
What is the basic principle of wind energy conversion?
Q10. Whatmethodsareusedtoovercomethefluctuatingpowergenerationof awindmill? 7
The windmill works on the principle of converting kinetic energy of the wind to
mechanical energy.
Wind turbines are designed to yield Maximum output at a wind speed of 15m/s if the
wind speed is more the excess energy is wasted. But the rotor is to be protected from
damage. This done by power control mechanism.
The important method use in power control is as follows:
Pitch Control :-
The power output of the turbine is constantly checked by an electronic measuring
unit.
When the power output become to high, it a actuate the blade pitch mechanism
Which turns the rotor blades out of the wind this reduce the power output.
When the wind velocity reduce and the power output falls, the blade is turned
back to the original position &the power again increases.
A-10
Passive Stall control :
In this control blade fixed at a fixed angle. When the wind speed increases, it
creates turbulence on the side opposite to the facing wind reduce the angle of
attack.
This will reduce the lift force developed & hence reduce the power output.
It is much sampler method than the pitch control method but it less accurate.
Yaw Control :-
This is another method in which the turbine is rotated about a vertical axis facing
or away from the wind.
This method is used only in small wind turbines power plant 1 KW or less.
Describe the basic principle of wind energy conversion and derive the expression
for power developed due to wind.
The power in the wind
The wind systems that exist over the earth’s surface are a result of variations in air
pressure.These are in turn due to the variations in solar heating. Warm air rises and
cooler air rushesin to take its place. Wind is merely the movement of air from one place
to another. There areglobal wind patterns related to large scale solar heating of different
regions of the earth’ssurface and seasonal variations in solar incidence. There are also
localized wind patternsdue the effects of temperature differences between land and seas,
No. Description Marks
Q1 StateSeebeckEffectandPeltierEffect. 2
The Seebeck effect is a phenomenon in which a temperature difference between
twodissimilar electrical conductors or semiconductors produces a voltage difference
between thetwo substances. If the pair is connected through an electrical circuit, direct
current (DC) flowsthroughthat circuit.
A-1
The Peltier effect is the reverse phenomenon of the Seebeck effect; the electrical
currentflowingthroughthejunctionconnectingtwomaterialswillemitorabsorbheatperunitt
imeatthejunction to balancethedifferencein thechemical potential of thetwomaterials.
What is the maximum energy conversionefficiencyofawindturbinefora 2
Q2 givensweptarea?
Powercoefficientandtipspeedratioofdifferentwindconvertersdesigns.Thetheoreticalmax
imumefficiencyofa windturbineis givenbythe BetzLimit andis around59percent.
AA-2
Betz's law shows that as air flows through a certain area, and as wind speed slows
from losingenergy to extraction from a turbine, the airflow must distribute to a wider
area. As a result,geometrylimits anyturbineefficiencyto a maximumof59.3%.
Q3. Howmuch ofour dailyCO2 emissions can wind avoid? 2
Wind energy does not emit any greenhouse gases and has an extremely good
energybalance. The calculations on just how much CO2 could be saved by wind
energy is based onan assumption for the carbon intensity of the global electricity
sector, i.e. the typical amountof CO2 emitted by producing one kWh of power.
Individual countries’ emissions differsubstantially, but here we use the IEA’s estimate
of 600g/kWh as an average value for thecarbondioxide reductionto be obtainedfrom
A-3 wind generation.
The most ambitious scenario by the Global Wind Energy Council (GWEC) show that,
withgrowth rates much lower than the 30% the wind sector has experienced over the
past decade,global wind energy capacity could increase from 121GW at the end of
2008 to over 1,000GWby 2020 and 2,400 GW by 2030. This would result in annual
CO2 savings of more than 1.5billiontons in 2020and3.2 billon tons in 2030.
Q4. Classifyrotors employedforwindgeneration. 2
A-4 Refer to class notes
DescribetheworkingofaThermo-electricgenerator.Deriveanexpressionfor
Q5. 7
itspoweroutput.
A-5 Refer to class notes
What is the basic difference between thermoelectric andthermionic conversion
7
Q6. systems? Also, explain the workingofthermoelectricgenerators.
A-6 Refer to class notes
Describe the principle of operation and constructionaldetails of a basic thermionic
7
Q7. generator. Explain the workingofthermoelectric generator.
, A-7 Refer to class notes
Describemainconsiderationsinselectingasiteforwind
Q8. 7
farm.Discussmeritsariddemeritsofwindenergy.
A-8 Refer to class notes
Explain the working of horizontal axis two blade windmillswithsuitable diagram. 7
Q9.
A-9 Refer to class notes
What is the basic principle of wind energy conversion?
Q10. Whatmethodsareusedtoovercomethefluctuatingpowergenerationof awindmill? 7
The windmill works on the principle of converting kinetic energy of the wind to
mechanical energy.
Wind turbines are designed to yield Maximum output at a wind speed of 15m/s if the
wind speed is more the excess energy is wasted. But the rotor is to be protected from
damage. This done by power control mechanism.
The important method use in power control is as follows:
Pitch Control :-
The power output of the turbine is constantly checked by an electronic measuring
unit.
When the power output become to high, it a actuate the blade pitch mechanism
Which turns the rotor blades out of the wind this reduce the power output.
When the wind velocity reduce and the power output falls, the blade is turned
back to the original position &the power again increases.
A-10
Passive Stall control :
In this control blade fixed at a fixed angle. When the wind speed increases, it
creates turbulence on the side opposite to the facing wind reduce the angle of
attack.
This will reduce the lift force developed & hence reduce the power output.
It is much sampler method than the pitch control method but it less accurate.
Yaw Control :-
This is another method in which the turbine is rotated about a vertical axis facing
or away from the wind.
This method is used only in small wind turbines power plant 1 KW or less.
Describe the basic principle of wind energy conversion and derive the expression
for power developed due to wind.
The power in the wind
The wind systems that exist over the earth’s surface are a result of variations in air
pressure.These are in turn due to the variations in solar heating. Warm air rises and
cooler air rushesin to take its place. Wind is merely the movement of air from one place
to another. There areglobal wind patterns related to large scale solar heating of different
regions of the earth’ssurface and seasonal variations in solar incidence. There are also
localized wind patternsdue the effects of temperature differences between land and seas,
