Category: Renewable Energy Objective Questions

Wind Energy Question Paper on “Wind Energy Storage – 2″.

1. What is depth of discharge?
a) Percentage of the battery that is discharged during a cycle
b) Percentage of the battery that is discharged
c) Amount of charge discharged from a battery during a cycle
d) Amount of charge discharged from a battery
Answer: a
Clarification: Depth of discharge (DoD) is the percentage of the battery that is discharged during a cycle. It has a wider use because it indicates a percentage instead of an absolute value. Indicating the absolute value of the charge discharged is not practical as it is unique for every battery and cannot be generalized.

2. What is charge-to-discharge ratio?
a) Time taken to charge the device
b) Ratio of time taken to charge the device relative to the time taken to discharge the device
c) Ratio of the amount of charge during charging cycle to the amount of charge during discharge cycle
d) Time taken to discharge the device
Answer: b
Clarification: Charge-to-discharge ratio is the ratio of time taken to charge the device relative to the time taken to discharge the device. For instance, if a device takes 2 times longer to charge than to discharge, it has a charge-to-discharge ratio of 2:1.

3. What is memory effect?
a) Electro-hydrogen generation
b) Pumped storage
c) Remembering a charging level
d) Electric grid
Answer: c
Clarification: Memory effect is mainly used to describe rechargeable batteries. If they are not fully charged for long periods of time then they ‘remember’ that charging level. Thus, they lose some of their capacity. The other options are storage techniques of wind energy.

4. Which of the following have large power (>50MW) and storage capacities (>100MWh)?
a) Memory effect
b) Battery energy storage (BES) and flow battery energy storage
c) Super capacitor energy storage and flywheel energy storage
d) Pumped hydro-electric storage and underground pumped hydro-electric storage
Answer: d
Clarification: Pumped hydro-electric storage (PHES) and underground pumped hydro-electric storage (UPHES) are grouped under the category of large power (>50MW) and storage capacity (>100MWh). Compressed air energy storage (CAES) is another example of this category. Memory effect is a parameter used to describe a rechargeable battery.

5. Efficiency of pumped hydro-electric storage is in the range of _________
a) 50% — 80%
b) 80% — 120%
c) 10% — 20%
d) 45% — 50%
Answer: a
Clarification: Efficiency of pumped hydro-electric storage is in the range of 50% — 80%. It has large power (>50MW) and storage capacity (>100MWh). The efficiency is further being improved using variable speed machines.

6. How does pumped hydro-electric storage work?
a) Pumps water from higher level to a lower level
b) Pumps water from lower level to higher level
c) Uses electrical energy present in the water
d) Uses nuclear energy present in the water molecules
Answer: b
Clarification: PHES uses the gravitational potential energy of water to generate electricity. During off-peak hours, water is pumped from a reservoir at a lower level to a reservoir at a higher level and stored. When required, the water falls from the higher level and rotates turbines connected to an electrical generator.

7. Which of the following is an application of pumped hydro-electric storage?
a) Energy source
b) Frequency regulation only in pumping mode
c) Frequency regulation in both pumping and generation modes
d) Absorbs power to increase the net expenses
Answer: c
Clarification: Pumped hydro-electric storage is used for frequency regulation in both pumping and generation modes. In fact, it absorbs power in a more cost-effective manner and boosts efficiency upto 3%.

8. What is a major disadvantage with pumped hydro-electric system?
a) No dependence on geographical locations
b) Small scale construction for effective functioning
c) Low initial costs of construction
d) Depends on specific geographical locations for the construction of the two reservoirs
Answer: d
Clarification: A major disadvantage with PHES is its dependence on specific geographical locations for the construction of the two reservoirs. It also demands that the two reservoirs be located in close proximity to reduce costs. This increases the initial costs of construction considerably.

9. Which of the following best indicates the flow diagram of storage mode in compressed air energy storage?
a) Power from grid → motor → compressor → storage
b) Power from grid → motor → storage → compressor
c) Power from grid → compressor → motor → storage
d) Motor → power from grid → compressor → storage
Answer: a
Clarification: In CAES, power is drawn from the grid during off-peak hours to run a motor which in turn drives a compressor. Air passed into the compressor is then compressed and stored.

10. Which of the following best indicates the flow diagram of power generation mode in compressed air energy storage?
a) Storage → LPT → HPT → generator
b) Storage → HPT → LPT → generator
c) Storage → LPT → generator → HPT
d) HPT → Storage →LPT → generator
Answer: b
Clarification: In CAES, the compressed air is first sent from the storage tank to a high pressure turbine (HPT) which is in turn connected to a lower pressure turbine (LPT). Finally, the LPT is connected to an electric generator.

11. Which of the following are used for large scale battery energy storage?
a) Li-ion batteries
b) Capacitors
c) Lead acid
d) Reservoirs
Answer: c
Clarification: Lead acid (LA) is used for large scale BES. Nickel-cadmium (NiCd) and sodium-sulphur (NaS) are also commonly used BES. Capacitors are not batteries. Li-ion is an upcoming technology and hasn’t been established as the industry standard yet. However, it is likely to take over the industry in the next decade.

12. How does a flow battery energy storage work?
a) Electrolyte tanks → pumps → electrodes → current
b) Electrolyte tanks → pumps → current → electrodes
c) Electrolyte tanks → current → electrodes → pumps
d) Electrolyte tanks → electrodes → current → pumps
Answer: a
Clarification: FBES operate in a similar way. Two charged electrolytes are pumped to the cell stack where a chemical reaction occurs, allowing current to be obtained from the device when required. This current is then harnessed by sending it to a load.

13. The central shaft in a flywheel energy storage device rotates on two magnetic bearings.
a) False
b) True
Answer: b
Clarification: A flywheel energy storage (FES) consists of a central shaft. The shaft holds a rotor and a flywheel. The central shaft rotates on two magnetic bearings which considerably reduces friction losses. The entire setup is placed in vacuum to prevent drag losses.

14. Flywheels are used in uninterrupted power supply (UPS).
a) True
b) False
Answer: a
Clarification: The entire setup is mechanical, it can be repeatedly charged and discharged without much damage to the setup itself. Thus, flywheels are used in uninterrupted power supplies (UPS).

15. Capacitors do not suffer from ________
a) dielectric breakdown
b) material dependence
c) excess electric potential
d) memory effect
Answer: d
Clarification: Capacitors store energy in the form of electric potential. They do not suffer memory effect as the energy is stored between two conducting plates. However, they do suffer from dielectric breakdown when excess electric potential is applied.

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Geothermal Energy Multiple Choice Questions on “Geothermal Energy in India”.

1. Which of the following organisations deals with geothermal energy locations in India?
a) Geological Survey of India
b) Geological Society of India
c) Forestry Department
d) Ministry of external affairs
Answer: a
Clarification: Geological Survey of India (GSI) is the government organisations that deals with various geothermal energy locations in India. It was founded in 1851 and works under the Ministry of Mines Organisation. It is the second oldest survey in India after Survey of India.

2. Which of the following is the most promising geothermal locations in India?
a) Sohana
b) Puga valley
c) Gurgaon
d) Patna
Answer: b
Clarification: Puga valley is the most promising geothermal locations in India. Gurgaon and Patna are not geothermal locations. Sohana is not the most promising one.

3. What is the estimated potential for geothermal energy in India?
a) 1000MW
b) 1MW
c) 10000MW
d) 100MW
Answer: c
Clarification: The exploration and study of geothermal fields in India started in 1970. The estimated potential for geothermal energy in India is 10000MW. Amongst all the other locations, Puga valley is the most promising one.

4. Which of the following are geothermal provinces in India?
a) Telangana
b) Coimbatore
c) Manipur
d) Godavari
Answer: d
Clarification: Godavari is one of the seven geothermal provinces in India. Most of the provinces are located in northern and central part of Indian sub-continent.

5. Where is the volcanic arc in India?
a) Andaman and Nicobar Islands
b) Lakshadweep Islands
c) Godavari
d) Puga valley
Answer: a
Clarification: The volcanic arc is in Andaman and Nicobar Islands. It is actually a barren land. There are no geothermal provinces in Lakshadweep Islands. Puga valley and Godavari are not prone to volcanoes.

6. Which of the following geothermal sites is in Gujarat?
a) Tattapani
b) Cambay Garden
c) Surajkund
d) Manikaran
Answer: b
Clarification: Cambay Garden is located in Gujarat. Today, Cambay is known as Khambat. It is a town in Khambat Taluka, Anand district.

7. Where is the geothermal plant in Chhattisgarh?
a) Puga
b) Cambay Garden
c) Balrampur
d) Manikaran
Answer: c
Clarification: The geothermal plant is located in Balrampur district in Chhattisgarh. It is one of the recently established plants. The other options are not areas in the state of Chhattisgarh.

8. The reservoir rock in Puga valley is made up of ________
a) sulphite
b) nitrogen
c) carbon
d) granite
Answer: d
Clarification: The geothermal reservoir in Puga valley is made up of granite. Hot springs with a temperature range between 30 – 84 degree Celsius are found.

9. Which of the following is a potential site for binary cycle power plant?
a) Tatapani
b) Gurgaon
c) Godavari
d) Hyderabad
Answer: a
Clarification: Puga, Tatapani and Manikaran are potential sites for binary cycle power plants. Gurgaon and Hyderabad are not geothermal sites.

10. What is the temperature range of the reservoir at Puga valley?
a) 30 – 84 degree Celsius
b) 160 – 220 degree Celsius
c) 100 – 120 degree Celsius
d) 30 – 50 degree Celsius
Answer: b
Clarification: The temperature range of the reservoir at Puga valley is 160 – 220 degree Celsius. Also, the reservoir rock is made up of granite. The temperature of hot springs are in the range of 30 – 84 degree Celsius.

11. What is the thermal temperature gradient in Tatapani?
a) 1 degree Celsius/km
b) 10 degree Celsius/km
c) 60 – 100 degree Celsius/km
d) 110 – 150 degree Celsius/km
Answer: c
Clarification: The temperature gradient in Tatapani is 110 – 150 degree Celsius/km. Tatapani is a geothermal site located in Chhattishgarh. Arsenic and sulphur deposits are commonly found here.

12. What is the temperature gradient in Manikaran?
a) 50 degree Celsius/km
b) 10 degree Celsius/km
c) 70 – 100 degree Celsius/km
d) 90 – 110 degree Celsius/km
Answer: d
Clarification: The temperature gradient in Manikaran is 90 – 110 degree Celsius/km. Manikaran is a geothermal site located in Himachal Pradesh. The temperature range of hot springs is between 34 – 90 degree Celsius.

13. Which of the following states hosts the West Coast geothermal site?
a) Maharashtra
b) Assam
c) Bihar
d) Kerala
Answer: a
Clarification: Maharashtra hosts the West Coast geothermal site. Assam and Bihar are located in the eastern and central parts of Indian sub-continent. The West Coast does not stretch till Kerala.

14. The geothermal site in Godavari consists of Gondwana sediments.
a) False
b) True
Answer: b
Clarification: The geothermal site in Godavari consists of Gondwana sediments. The temperature range of the reservoir is between 100 and 150 degree Celsius.

15. Extraction of dissolved heavy metals and native elements is another use of geothermal site.
a) True
b) False
Answer: a
Clarification: Extraction of dissolved heavy metals and native elements is another use of geothermal site. Native elements like sulphur are commonly found in many geothermal sites like Puga. Heavy metals like mercury and silver are found in West Coast and Surguja.

Education & Learning Series – Geothermal Energy.

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Renewable Energy Questions and Answers for Freshers on “Salient Features of Non-Conventional Energy Sources”.

1. ______ energy sources provide energy in dilute form.
a) Non-Renewable
b) Conventional
c) Nuclear
d) Renewable
Answer: d
Clarification: Renewable Energy sources are generally unreliable and dilute. These resources are not available constantly. The efficiency of conversion of these energy sources is low, so a large land area is required to concentrate the energy.

2. Non-Conventional Energy sources have a high gestation period.
a) True
b) False
Answer: b
Clarification: Non-conventional energy sources require lower time for setting up the power plant as compared to conventional energy sources. Solar power plants and wind power plants have gestation period of 15 months and 1.5 years respectively. On the other hand, thermal power plants have a gestation period of 5-6 years.

3. Based on the following options, choose the correct option.
Statement I: Non-Conventional energy is available in nature free of cost.
Statement II: Non-Conventional energy is exhaustible in nature.
a) Statement I and Statement II are correct and Statement II is the correct explanation
of Statement I
b) Statement I and Statement II are correct and Statement II is not the correct
explanation of Statement I
c) Statement I is true and Statement II is false
d) Statement II is true and Statement I is false
Answer: c
Clarification: Most of the renewable energy sources such as wind and solar energy are available in nature free of cost. They are inexhaustible and cannot be depleted by human activity.

4. The availability of Renewable energy sources is _____
a) uncertain
b) constant
c) high
d) regular
Answer: a
Clarification: Renewable energy sources i.e. wind energy, solar energy, wave energy, tidal energy, etc are intermittent in nature. Most of them are non-dispatchable due to their variable nature.

5. The cost of harnessing energy from Non-Conventional Energy sources is low.
a) True
b) False
Answer: b
Clarification: Non-conventional energy plants employ expensive equipment. This increases the cost of harnessing energy from them.

6. Which of the following statements is not true about Renewable Energy?
a) They do not cause pollution
b) Their transportation is difficult
c) They cause ecological imbalance
d) They have a low gestation period
Answer: c
Clarification: Non Renewable energy sources such as fossil fuels cause emission of greenhouse gases which disturb the ecological balance. Renewable energy sources, on the other hand, do not cause ecological imbalance.

7. Renewable energy-based power plants have ______
a) negligible fuel cost
b) low energy availability
c) negligible production capacity
d) fuel storage tanks
Answer: a
Clarification: Renewable energy-based plants require negligible to no fuel for their operation. That’s why they cause negligible pollution.

8. Renewable energy plants require ________than traditional generators.
a) more fuel
b) less maintenance
c) higher operating cost
d) more uranium
Answer: b
Clarification: Renewable energy plants require very little maintenance after installation. They require very fewer operating costs as compared to traditional fossil fuel generators. They need negligible amount of fuel for operation. They do not employ uranium.

9.Most of the Renewable energy sources are ________
a) location-specific
b) universally available
c) highly efficient
d) polluting
Answer: a
Clarification: One of the major limitations of renewable sources is that they are location specific. States without rivers can’t have hydropower dams, and states with wind speed less than 23km/hr at 50 m height can’t have wind energy plants. Renewable energy sources are not universally available due to their location specificness. They have low efficiency due to their dilute nature. Most of the Renewable energy sources do not require any fuel and hence cause minimum to low pollution.

10. The storage of renewable energy sources is expensive.
a) True
b) False
Answer: a
Clarification: Due to their intermittent nature, renewable energy sources are needed to be stored. Currently, the storage systems of renewable energy are expensive.

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Solar Energy Multiple Choice Questions on “Solar Radiation Geometry – 2”.

1. Which of the following best describes the motion of sun from autumnal equinox to winter solstice?
a) Earth is above the plane of the sun
b) Earth is below the plane of the sun
c) Earth’s center lies on the plane of the sun
d) Earth first escalates above the plane and then transcends below the plane of sun
Answer: a
Clarification: Earth is above the plane of the sun during its motion from autumnal equinox and winter solstice. Equinox occurs when the earth’s center lies on the plane of the sun. However, it doesn’t always lie on the plane of the sun throughout the year.

2. What is sun’s declination angle during earth’s motion from autumnal equinox to winter solstice?
a) Greater than 90 degrees
b) Less than 0 degrees
c) Greater than 0 degrees
d) Between 60 and 90 degrees
Answer: b
Clarification: Sun’s declination angle during earth’s motion from autumnal equinox to winter solstice to vernal equinox is less than 0 degrees. This is because the earth is above the plane of the sun.

3. During which of the following periods is the earth below the plane of sun?
a) Vernal equinox to winter solstice
b) Winter solstice to vernal equinox
c) Vernal equinox to summer solstice
d) Summer solstice to winter solstice
Answer: c
Clarification: The earth is below the plane of sun during its motion from vernal equinox to summer solstice and back to autumnal equinox. The earth is above the sun’s plane during its motion from winter solstice to vernal equinox.

4. What is the sun’s declination during earth’s motion from vernal equinox to summer solstice?
a) Greater than 50 degrees
b) Between 0 and 30 degrees
c) Greater than 0 degrees
d) Less than 0 degrees
Answer: d
Clarification: The sun’s declination angle during earth’s motion from vernal equinox to summer solstice is less than 0 degrees. This is because the earth is below the plane of the sun.

5. How is latitude of a location on earth defined?
a) Angle between line joining the location to earth’s center and earth’s equatorial plane
b) Angle between line joining the location to earth’s center and the meridian plane
c) Angle subtended by sun on earth
d) Angle between sun’s rays extended to earth’s center and earth’s equatorial plane
Answer: a
Clarification: Latitude of a location on earth is defined by the angle between line joining the location to earth’s center and earth’s equatorial plane. Sun’s declination angle is the angle between sun’s rays extended to earth’s center and earth’s equatorial plane.

6. The lines joining North and South pole of earth are called _____
a) latitudes
b) longitudes
c) equator
d) semicircle lines
Answer: b
Clarification: The lines joining North and South pole of earth are called lines of longitudes. They are semicircular because they run along the curved surface of earth.

7. When does the autumnal equinox occur?
a) January
b) August
c) September
d) December
Answer: c
Clarification: Autumnal equinox occurs in the month of September. Specifically, it occurs either on 22^nd September or on 23^rd September. Winter solstice occurs in December.

8. When does the vernal equinox occur?
a) January
b) December
c) September
d) March
Answer: d
Clarification: Vernal equinox occurs in the month of March. Specifically, it occurs on 20^th or 21^st March. September is the month of autumnal equinox.

9. Solar radiation spectrum is close to _____
a) that of a black body
b) that of a white body
c) that of Jupiter
d) that of phase response
Answer: a
Clarification: Solar radiation spectrum is close to that of a black body. The temperature is about 5800K. Phase response is talks about the delay of a (an electronic) system with frequency. Though it is not related to solar radiation, it is used to analyse many solar energy harvesting systems.

10. Which of the following indicates the position of any point on earth?
a) Rectangular co-ordinate system
b) Latitudes, longitudes
c) Radial co-ordinate system
d) Spherical co-ordinate system
Answer: b
Clarification: Latitudes and longitudes are used to indicate the position of any point on the surface of the earth. Usage of spherical co-ordinate system depends on the application. Moreover, earth is not entirely spherical.

11. What is the range of sun’s declination angle throughout the year?
a) Between 0 and 90 degrees
b) Between 0 and 23.5 degrees
c) Between -23.5 and 23.5 degrees
d) Between -23.5 and 0 degrees
Answer: c
Clarification: Sun’s declination angle lies in the range of -23.5 and 23.5 degrees. It is positive when the earth is below the sun and negative when the earth is above the sun.

12. What the hour angle?
a) Angle between ray of the sun when extended to the earth’s center and the equatorial plane
b) Angle between line joining the location to earth’s center and earth’s equatorial plane
c) Angle through which the turns to bring the meridian of a point in line with sun’s rays
d) Angle through which the turns to bring the meridian of a point directly in line with sun’s rays
Answer: d
Clarification: Hour angle is the angle through which the turns to bring the meridian of a point directly in line with sun’s rays. Declination angle is angle between ray of the sun when extended to the earth’s center and the equatorial plane. Latitude is angle between line joining the location to earth’s center and earth’s equatorial plane.

13. Altitude angle is the _______
a) vertical angle between projection of sun’s rays on the horizontal plane of earth’s surface
b) horizontal angle between projection of sun’s rays on the horizontal plane of earth’s surface
c) vertical angle between projection of sun’s rays on the vertical plane normal to earth’s surface
d) horizontal angle between projection of sun’s rays on the vertical plane normal to earth’s surface
Answer: a
Clarification: Altitude angle is the vertical angle between projection of sun’s rays on the horizontal plane of earth’s surface. It is important to note that the angle is between the project of sun’s rays on the horizontal plane and not the ray its.

14. Hour angle is a measure of time of day with respect to solar noon.
a) True
b) False
Answer: a
Clarification: Hour angle is a measure of time of day with respect to solar noon. At noon, the hour angle is 0 degrees and rotates at 15 degree per hour.

15. The altitude angle is maximum at noon.
a) True
b) False
Answer: a
Clarification: The altitude angle talks about how high the sun appears in the sky. It is maximum at noon. It is zero at sunrise and sunset and is 90 degrees (maximum) at noon.

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Solar Energy Multiple Choice Questions on “Solar Thermo-Mechanical Systems -1”.

1. Which of the following best describes the flow of energy in a solar thermo-mechanical system?
a) Solar → thermal → mechanical → electricity
b) Electricity → thermal → mechanical → solar
c) Mechanical → solar → electricity → thermal
d) Solar → electricity → thermal → mechanical
Answer: a
Clarification: In a solar thermo-mechanical system, the solar energy is first converted to thermal energy. Then this energy is used to drive mechanical systems thereby being converted to mechanical energy. This mechanical energy is further converted to usable forms like electricity.

2. What is a heat engine?
a) System that converts thermal energy to mechanical energy
b) System that converts thermal and chemical energy to mechanical energy
c) System that converts mechanical energy to thermal energy
d) System that converts mechanical energy to thermal and chemical energy
Answer: b
Clarification: A heat engine is an energy converting system. It converts in the heat or thermal energy and chemical energy to mechanical. This mechanical energy can be used to do mechanical work.

3. How does heat engine convert thermal and chemical energy to mechanical energy?
a) With the help of steam
b) By converting the input energy into electrical energy which is then used to drive mechanical systems
c) By bringing a working substance from a higher state temperature to a lower state temperature
d) By converting the input electrical energy to mechanical energy
Answer: c
Clarification: The heat engine convert thermal and chemical energy to mechanical energy. It does this by bringing a working substance from a higher state temperature to a lower state temperature. During this conversion, any form of energy being used is not converted to electrical energy.

4. Which of the following is/are examples of heat engines?
a) Fuel cell vehicles
b) Fuel cell energy power plants
c) Photovoltaics and concentrating mirrors
d) Rankine cycle and Brayton cycle
Answer: d
Clarification: Rankine cycle and Brayton cycle are examples of heat engines. Photovoltaics and concentrating mirrors are not heat engines. Fuel cells are another type of source that convert chemical energy to electrical energy.

5. Which of the following is a popular solar thermal power system?
a) Central receiver thermal electric power system
b) Photovoltaics
c) Concentrating mirrors
d) Solar reflectors
Answer: a
Clarification: Central receiver thermal electric power system is a popular solar thermal power system. Photovoltaics are not solar thermal power systems. They directly convert solar energy to electrical energy. Concentrating mirrors and solar reflectors are components of various solar thermal power systems.

6. Which of the following best describes the working of central receiver thermal power system?
a) Sunlight → heliostats absorb solar flux → central receiver → turbine system → electricity
b) Sunlight → heliostats reflect solar flux → central receiver → turbine system → electricity
c) Heliostats reflect solar flux → sunlight → turbine system → central receiver → electricity
d) Heliostats reflect solar flux → sunlight → central receiver → turbine system → electricity
Answer: b
Clarification: In a s central receiver thermal power system, the solar radiation from the incident sunlight is reflected by heliostats onto central receiver. The receiver consists of a boiler to boil the working fluid which is in turn used to drive the turbines to generate electricity.

7. What is the operating temperature of turbines in a central receiver thermal power system? Note that “C” stands for Celsius.
a) 10 – 100 degree C
b) 5000 degree C
c) 500 – 800 degree C
d) 200 – 500 degree C
Answer: c
Clarification: The typical operating temperature of the turbines in a central receiver thermal power system is between 500 – 800 degree C. The temperatures are so high because large concentrations of solar flux are reflected onto the central receiver by several arrays of heliostats (hundreds and sometimes even thousands).

8. Which of the following is a line focus collector used in a distributed power system?
a) Parabolic mirrors
b) Convex mirrors
c) Concave lenses
d) Linear fresnel reflector
Answer: d
Clarification: Linear fresnel reflector is a line focus collector. Parabolic mirrors and convex mirrors may reflect sunlight but they may not be line focused collector. Lenses are not used to collect sunlight in a distributed power system.

9. How is energy collected in a distributed power system?
a) Sunlight → line focused collectors → interconnecting pipes → heat engines → turbines → electricity
b) Line focused collectors → sunlight → interconnecting pipes → heat engines → turbines → electricity
c) Sunlight → line focused collectors → turbines → interconnecting pipes → heat engines → electricity
d) Interconnecting pipes → sunlight → line focused collectors → heat engines → turbines → electricity
Answer: a
Clarification: The solar radiation from the incident sunlight is collected by various line focused collectors. This energy is collected through pipes interconnecting the dispersed collector units and then supplied to the heat engines which in turn use the working substance to drive turbines and generate electricity.

10. The type of heat engine depends on _______
a) material of interconnecting pipes
b) type of collector
c) sunlight
d) photovoltaics
Answer: b
Clarification: The type of heat engine depends on the type collector, temperature of operation, cycle efficiency, working fluid, conversion efficiency, transport fluid, etc. Photovoltaics are not used in solar thermo-mechanical systems.

11. What is Carnot efficiency?
a) Rate of the temperature difference divided by rate of initial temperature change
b) Ratio of relative temperature between source and sink and the relative source temperature
c) Ratio of absolute temperature between source and sink and the absolute source temperature
d) Ratio of rate of the temperature difference and the absolute source temperature
Answer: c
Clarification: Carnot efficiency is ratio of absolute temperature between source and sink and the absolute source temperature. It can also be defined in terms of heat added to the source at some temperature and heat rejected by the fluid at some temperature.

12. Heat engine efficiency increases as the source temperature _______
a) decreases
b) remains the same
c) decrement rate increases
d) increases
Answer: d
Clarification: Heat engine efficiency increases as the source temperature increases. Also, the rate of increase of the source temperature should be greater at lower temperatures than at higher temperatures.

13. Distributed power system is a type of solar thermo-mechanical system.
a) True
b) False
Answer: a
Clarification: Distributed power system is a type of solar thermo-mechanical system. It works on the principle of collecting the incident solar radiation using multiple arrays of line focused reflectors distributed across a large area. These collectors are interconnected by pipes which transfer the energy to the mechanical system.

14. Heat engine efficiency increases with ________ sink temperature.
a) no change in
b) decrease in
c) increment in rate of increasing
d) increase in
Answer: b
Clarification: Heat engine efficiency increases with decrease in sink temperature. It should also be noted that the rate of decrement of sink temperature should be faster than the rate which the source temperature is increased.

15. Isothermal process is a process conducted at constant temperature.
a) True
b) False
Answer: a
Clarification: Isothermal process is a process conducted at constant temperature. Isobaric process is a process conducted at constant pressure.

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Biomass Energy Problems on “Solar Radiation on Inclined Plane Surface”.

1. When is the power density of the absorbing surface equal to the incident sunlight?
a) Absorbing surface and incident sunlight are perpendicular to each other
b) Absorbing surface and incident sunlight are parallel to each other
c) Absorbing surface and incident sunlight are inclined at an acute angle to each other
d) Absorbing surface and incident sunlight are inclined at an obtuse angle to each other

Answer: d
Clarification: Net power received from incident sunlight depends on two things – the power contained in the sunlight and the angle of the receiver with respect to the incident sunlight. Incident power equals the received power when the receiver is perpendicular to the incident sunlight.

2. For a fixed receiver, incident power density and received power density are always equal.
a) True
b) False

Answer: b
Clarification: For a fixed receiver, incident power density and received power density are not equal always. In fact, the net received power is often less than the incident power as the angle between the sun and the receiver changes continuously.

3. What is direct solar radiation?
a) Radiation scattered by molecules
b) Radiation reflected from an obstacle
c) Radiation traveling on a straight line from sun to earth
d) Sum of diffused and reflected radiation energies

Answer: c
Clarification: Direct solar radiation is that radiation which travels in a straight line from the sun. It travels to the earth without deviating from its path due to obstacles.

4. What is diffused solar radiation?
a) Sum of direct and reflected radiation energies
b) Radiation reflected from an obstacle
c) Radiation traveling on a straight line from sun to earth
d) Radiation scattered by molecules

Answer: d
Clarification: Diffused solar radiation is that radiation which has been scattered by molecules and particles in atmosphere. Though it deviates from its initial path, it does travel down to the earth.

5. Which of the following is tried to maximized in tilted receivers (panels)?
a) Direct radiation
b) Diffused radiation
c) Reflected radiation
d) Diffracted radiation

Answer: a
Clarification: Receivers are tilted to maximize the collection of direct solar radiation from the sun. The tilt tries to ensure that the receivers are perpendicular to the direct radiation. It accounts for the continuous change in angle between the sun and the receiver.

6. When receivers (panels) are laid horizontally, they usually collect _______
a) Direct radiation
b) Diffused radiation
c) Deflected radiation
d) Heat

Answer: b
Clarification: When solar receivers (panels) are laid horizontally, they usually collect diffused radiation. This is because diffused radiation is equally distributed throughout the sky and hence can easily be gathered.

7. More the tilt in receivers (panels), larger amounts of diffused radiation is collected.
a) False
b) True

Answer: a
Clarification: More the tilt in receivers, larger amounts of direct radiation is collected. As the tilt increases, the amount of diffused radiation received considerably reduces.

8. What is reflected solar radiation?
a) Sum of direct and reflected radiation energies
b) Radiation reflected from an atmospheric obstacle
c) Radiation traveling on a straight line from sun to earth
d) Radiation reflected from a non-atmospheric obstacle

Answer: d
Clarification: Reflected solar radiation is that sunlight/radiation that is reflected from a non-atmospheric obstacle. The obstacles could be trees, ground, light poles, cars, etc. They do not contribute significantly towards electricity generation from solar panels.

9. Reflected solar radiation is used in _______
a) Snowy regions
b) Temperate region
c) Equatorial region
d) Tropical region

Answer: a
Clarification: Generally, reflected solar radiation does contribute significantly towards electricity generation. However, energy from reflected radiation is harvested in snowy regions as fresh snow reflects about 80-90% of the incident radiation.

10. What is global insolation?
a) Direct radiation + diffused radiation
b) Diffused radiation – direct radiation
c) Direct radiation + diffused radiation + reflected radiation
d) Reflected radiation * direct radiation

Answer: c
Clarification: Global insolation or total insolation is the sum of the radiation received by earth from sun. It is nothing but the sum of direct radiation, diffused radiation and reflected radiation. This is used as a reference for the insolation at some tilt.

11. What is normal radiation?
a) Direct radiation
b) Sun’s radiation and striking surface are perpendicular to each other
c) Incident solar radiation and striking surface are perpendicular to each other
d) Global insolation – direct radiation

Answer: b
Clarification: Normal radiation describes the radiation that strikes a surface that is perpendicular to the sun’s radiation. It is not same as direct radiation as the it does not talk about the incident radiation. It may so happen that normal radiation and direct radiation may be the same at some tilt.

12. What is hour angle of the sun?
a) Angle of radiation with earth’s surface
b) Angle between the hands of sun dial
c) Angle made by the sun’s rays with moon’s surface
d) Orientation of earth with respect to sun

Answer: d
Clarification: Hour angle of sun is defined as the actual orientation of earth with respect to the sun. Mathematically, it is calculated by converting earth’s one rotation in degrees and dividing it by the time taken – 360/24 = 15 degrees/h.

13. What is solar intensity?
a) Amount of outgoing solar energy
b) Amount of incoming solar energy on a plane surface
c) Amount of outgoing solar energy on a plane surface per unit time
d) Amount of incoming solar energy on a plane surface per unit time per unit area

Answer: d
Clarification: Solar intensity is defined as the amount of incoming solar energy on a plane surface per unit time per unit area. It is a weighted average of the full radiation and is equal to 1367 Watt/square meter.

14. What is solar azimuth angle?
a) Orientation of earth with respect to sun
b) Orientation of moon with respect to sun
c) Angle of radiation with earth’s surface
d) Angular distance between zero azimuth and sun’s projection on ground

Answer: d
Clarification: Solar azimuth angle is defined as the angular distance between zero azimuth and the projection of the line of sight to sun on the ground. Zero azimuth is a line due north or due south. Azimuth angle is measured clockwise from zero azimuth.

15. Diffuse radiation models can be classified into ________ and __________
a) direct and reflective
b) adiabatic and isotropic
c) isotropic and anisotropic
d) anisotropic and adiabatic

Answer: c
Clarification: Diffuse radiation models can be classified into isotropic and anisotropic. Isotropic models of diffuse radiation model diffuse radiation intensity by assuming uniform distribution throughout the sky (medium). Anisotropic models include suitable modules that are used to represent regions of increased (varied) diffuse radiation.