Category: Renewable Energy Objective Questions

Biomass Energy Objective Questions on “Biomass Conversion Technologies – 2″.

1. What are the two main products of anaerobic digestion?
a) Biogas and bio-fertilizer
b) Waste water
c) Producer gas
d) Syngas

Answer: a
Clarification: The two main products of anaerobic digestion are biogas and bio-fertilizer. Wastewater is the input to the anaerobic digester. Producer gas is produced during pyrolysis.

2. Which of the following organic compounds are present in biogas?
a) Butane gas and carbon dioxide
b) Methane gas and carbon dioxide
c) Nitrogen
d) Sodium

Answer: b
Clarification: Methane gas and carbon dioxide are present in biogas. Butane is not present in biogas. Nitrogen and sodium are not organic compounds.

3. Which of the following are considered as contaminant gases in biogas?
a) Chlorine
b) Fluorine
c) Nitrogen, hydrogen and carbon monoxide
d) Methane gas and carbon dioxide

Answer: c
Clarification: Nitrogen, hydrogen and carbon monoxide are the contaminant gases present in biogas. Methane gas and carbon dioxide constitute the fuel present in biogas. Chlorine and fluorine are not present in biogas.

4. Which of the following products of anaerobic digestion consists of organic humus and nutrients?
a) Biogas
b) Chlorine
c) Top soil
d) Bio-fertilizer

Answer: d
Clarification: Bio-fertilizer is a product of anaerobic digestion consisting of organic humus and nutrients for plantation. Top soil and chlorine are not products of anaerobic digestion. Biogas does not consist of organic humus.

5. Which of the following are used to store manure?
a) Silos and cellars
b) Plastic bottles
c) Glass bottles
d) Tin cans

Answer: a
Clarification: Silos and cellars are used to store manure. Manure bags are specifically designed to store manure. Plastic bottles, glass bottles and tin cans are not used to store manure.

6. What are the three methods of pre-treatment of influent for anaerobic digestion?
a) Galvanization, pyrolysis and pre-heating
b) Mechanical treatment, pre-heating and thermal treatment
c) Galvanization, pyrolysis and thermal treatment
d) Pyrolysis, thermal treatment and pre-heating

Answer: b
Clarification: Mechanical treatment, pre-heating and thermal treatment are the three different pre-treatment techniques of anaerobic digestion. Galvanization is a process to prevent corrosion of metals. Pyrolysis is a thermo-chemical process and not a bio-chemical process.

7. Thermo-chemical processes have higher efficiencies than bio-chemical processes.
a) True
b) False

Answer: a
Clarification: Thermo-chemical processes do have higher efficiencies than bio-chemical processes. In fact, they also have quicker reaction times and superior ability to decompose most organic compounds.

8. Which of the following is best suited to decompose lignin?
a) Anerobic digestion
b) Fermentation
c) Thermo-chemical conversion techniques
d) Bio-chemical conversion techniques

Answer: c
Clarification: Thermo-chemical conversion techniques can decompose lignin. When compared with bio-chemical conversion techniques, they have superior ability to decompose most organic compounds. Anaerobic digestion and fermentation are bio-chemical processes.

9. Which of the following are types of pyrolysis?
a) Flash and ablative
b) Intermediate and anaerobic digestion
c) Anaerobic digestion and fermentation
d) Fermentation and intermediate

Answer: a
Clarification: Flash and ablative are types of pyrolysis. Anaerobic digestion and fermentation are bio-chemical processes and are not types of pyrolysis.

10. Bio-oil has double the heating value of conventional fuel oil.
a) True
b) False

Answer: b
Clarification: Bio-oil has half the heating value of conventional fuel oil. It is produced after condensing the hot vapors in fast pyrolysis.

11. What are the three types of hydrothermal processing of biomass?
a) Hydrothermal liquefaction, hydrothermal gasification and ablate pyrolysis
b) Hydrothermal liquefaction, hydrothermal gasification and fast pyrolysis
c) Hydrothermal liquefaction, hydrothermal gasification and hydrothermal carbonisation
d) Intermediate pyrolysis, hydrothermal gasification and ablate pyrolysis

Answer: c
Clarification: Hydrothermal liquefaction, hydrothermal gasification and hydrothermal carbonisation are the three types of hydrothermal processes. Intermediate, fast and ablate are the types of pyrolysis.

12. Which of the following is the mildest hydrothermal process?
a) Hydrothermal gasification
b) Hydrothermal liquefaction
c) Ablate
d) Hydrothermal carbonisation

Answer: d
Clarification: Hydrothermal carbonisation is the mildest of the three hydrothermal processes. Ablate is not a hydrothermal process. It is a type of pyrolysis.

13. Which of the following hydrothermal processes produces syngas?
a) Hydrothermal gasification
b) Hydrothermal liquefaction
c) Fermentation
d) Hydrothermal carbonisation

Answer: a
Clarification: Hydrothermal gasification or supercritical water gasification (SCWG) occurs temperatures greater than 375 degree Celsius and pressure above 200 bar. It produces syngas. Fermentation is not a type of hydrothermal process. It is a bio-chemical process.

14. Hydrothermal liquefaction produces _________
a) syngas
b) bio-crude
c) bio-oil
d) producer gas

Answer: c
Clarification: Hydrothermal liquefaction produces bio-crude which can be distillated to obtain petroleum products. Bio-oil is produced in fast pyrolysis. Producer gas is produced in pyrolysis and syngas is produced in hydrothermal gasification.

15. Which of the following produces a solid hydro-char?
a) Catalytic liquefaction
b) Carbonisation
c) Hydrothermal gasification
d) Hydrothermal carbonisation

Answer: d
Clarification: Hydrothermal carbonisation occurs at temperatures between 180 and 250 degree Celsius and pressures between 20 and 40 bar. It produces a solid hydro-char with properties similar to a low rank coal.

Solar Energy Multiple Choice Questions on “Sun, Earth Radiation Spectrums – 1”.

1. What is solar radiation?
a) Energy radiated from the sun in all directions
b) Energy radiated from earth in all directions
c) Radiation travelling in space
d) Energy radiated from sun that travels in ether
Answer: a
Clarification: Solar radiation is the energy radiated from sun in all directions. Energy radiated from earth is not solar radiation. Any random radiation traveling in space is called cosmic rays.

2. What are three relevant bands of solar radiation?
a) UV, infrared and far infrared
b) UV, visible and infrared
c) Ultrasonic, infrared and visible
d) UV, ultrasonic and near infrared
Answer: b
Clarification: The three relevant bands of solar radiation are ultraviolet (UV), infrared and visible bands. Far infrared and near infrared are components of infrared. Ultrasonic is related to sound waves.

3. Which two bands of solar radiation are majority in the total solar radiation reaching earth?
a) UV and visible
b) Visible and ultrasonic
c) Visible and infrared
d) Infrared and UV
Answer: c
Clarification: Infrared and UV are the major components of the total solar radiation reaching earth. Infrared radiation makes up 49.4% and visible light makes up 42.3%. Only 8% of the total radiation is in the UV band.

4. Which of the following affects the amount of solar radiation received by a location or water body?
a) Shape of the water body
b) Time at night
c) Rotational speed of earth
d) Altitude and latitude
Answer: d
Clarification: A variety of factors affect the amount of solar radiation received by a location or water body. Some of them are altitude and latitude of the location, cloud cover over the location and the time of day. No solar radiation is received at night. Rotational speed of earth is constant and doesn’t affect the amount of solar radiation received.

5. What is direct solar radiation?
a) Solar radiation directly received by earth’s surface from sun
b) Cosmic radiation directly received by earth’s surface
c) Solar radiation received by earth’s surface after reflection
d) Cosmic radiation received by earth’s surface after reflection
Answer: a
Clarification: Direct solar radiation is solar radiation directly received by earth’s surface from sun. It is called direct because no scattering or reflection occurs. Cosmic radiation is not same solar radiation.

6. What is indirect solar radiation?
a) Solar radiation directly received by earth’s surface from sun
b) Solar radiation received by earth’s surface after scattering
c) Cosmic radiation directly received by earth’s surface
d) Cosmic radiation received by earth’s surface after reflection
Answer: b
Clarification: Indirect solar radiation is solar radiation received by earth’s surface after scattering or reflection. It is called indirect because the incident radiation is not directly received by earth’s surface. Every cosmic radiation need be radiation from sun.

7. What type of radiation does earth emit?
a) UV
b) Visible
c) Infrared
d) Longitudinal
Answer: c
Clarification: Earth emits infrared radiation. This is typically called as outgoing long-wave radiation (OLR) of wavelength between 3 and 100um. They are also called as thermal radiation.

8. What is the electromagnetic spectrum?
a) Radiation spectrum consisting only of UV and visible rays
b) All rays falling in the category of infrared and UV rays
c) All rays falling in the category of gamma and x-rays
d) Radiation spectrum encompassing all types of radiation
Answer: d
Clarification: As the name suggests, electromagnetic spectrum is a term used to define all types of existing radiation. It ranges from gamma rays to radio waves. Solar radiation received by earth is just a small part of the spectrum.

9. Which of the following type of UV radiation inhibits photosynthetic reaction in phytoplankton?
a) UV-A
b) UV-C
c) Infrared
d) Gamma rays
Answer: a
Clarification: UV-A and UV-B radiation inhibit photosynthetic reaction in phytoplankton. Infrared and gamma rays are not the types of UV radiation.

10. Which of the following is responsible for thermal energy?
a) UV
b) Infrared
c) Gamma
d) UV-A
Answer: b
Clarification: Infrared radiation is responsible for thermal and heat energy. They lie on the opposite side of the spectrum from ultraviolet light. This radiation has a wavelength greater than 700nm.

11. How do infrared radiation cause heat?
a) By exciting neutrons of the substance that absorb them
b) By de-exciting electrons of the substance that absorb them
c) By exciting electrons of the substance that absorb them
d) By exciting protons of the substance that absorb them
Answer: c
Clarification: Infrared radiation cause heat by exciting electrons. When they are absorbed by substances, they interact and excite electrons by transferring energy. This leads to heat as the atom (or electron) is said to be in excited state.

12. Why are surfaces of water bodies warmer than the depths?
a) Because water does not absorb UV radiation
b) Because water does not absorb thermal radiation
c) Because water absorbs visible radiation
d) Because water absorbs thermal radiation
Answer: d
Clarification: Surfaces of water bodies are warmer than the depths. This is because most of the infrared radiation is absorbed in the first meter of the water’s surface. Hence, they don’t make it to the depths.

13. What is photosynthetically active radiation (PAR)?
a) Radiation best suited for photosynthesis
b) All radiation in which photosynthesis occurs
c) Radiation in which photosynthesis does not occur
d) Radiation which deactivates the ongoing photosynthesis
Answer: a
Clarification: Photosynthetically active radiation (PAR) is the radiation best suited for photosynthesis. It is basically wavelength range in which photosynthesis occurs with ease. This range is between 400nm and 700nm – visible range.

14. UV-A, UV-B and UV-C are three wavelength ranges of ultraviolet radiation.
a) True
b) False
Answer: a
Clarification: UV-A, UV-B and UV-C are three wavelength ranges of ultraviolet radiation. These wavelengths can directly affect the DNA of water inhabitants as well as harmful photochemicals.

15. Energy of the wavelength increases with frequency and decreases with the size of wavelength.
a) True
b) False
Answer: a
Clarification: Energy of the wavelength increases with frequency and decreases with the size of wavelength. The more energy a wavelength has, the easier it is to disrupt the molecule that absorbs it.

Solar Energy,
social networks below and stay

Solar Energy Multiple Choice Questions on “Solar Industrial Heating Systems”.

1. Which of the following is/are applications of solar heating systems?
a) Pasteurisation and drying
b) Wetting
c) Rainfall
d) Battery and capacitor technology
Answer: a
Clarification: Pasteurisation and drying are applications of solar heating systems. Battery and capacitor technology are used to store energy from various sources like wind, sun, geothermal, etc. Wetting and raining are not applications of solar heating systems.

2. What is a solar heating system?
a) A system which uses heat to generate sunlight
b) A system which uses sunlight to generate heat
c) A system which uses earth’s heat to generate sunlight
d) A system which uses earth’s heat to generate electricity
Answer: b
Clarification: A solar heating system is a system which uses sunlight to generate heat. This heat can either be directly used or converted to other usable forms of energy like electricity. Geothermal energy is using earth’s heat to generate usable forms of energy.

3. What solar thermal technologies are useful for industrial processes?
a) Photovoltaics and solar air collectors
b) Solar air collectors and geothermal energy
c) Solar air collectors and solar water systems
d) Geothermal and photovoltaics
Answer: c
Clarification: Solar air collectors, solar water systems and solar concentrators are three well known solar thermal technologies used in industrial processes. Geothermal energy and photovoltaics are not solar thermal processes.

4. Which industry primarily uses solar air collectors?
a) Industries manufacturing plastic
b) Industries melting metals
c) Semiconductor industry
d) Food processing industry
Answer: d
Clarification: Food processing industry primarily uses solar air collectors. They replace traditional gas or oil-based drying in the industry. Melting metals requires extremely high temperatures that are not provided by solar air collectors.

5. How does using a solar air collector benefit food processing industry?
a) Reduce gas-or-oil-based drying and/or reduce food spoilage
b) Reduce food spoilage and increase gas-or-oil base drying
c) Increase food spoilage
d) Increase gas-or-oil-based drying and/or increase food spoilage
Answer: a
Clarification: Solar air collectors benefit food processing industry in many ways. They primarily reduce gas-or-oil-based drying and/or reduce food spoilage due to open air drying. Also, they can be built locally and their cost depends on local building materials and labour.

6. Which of the following is a conventional solar water system?
a) Solar air collectors
b) Flat-plate collectors
c) Parabolic dish collectors
d) Linear Fresnel collectors
Answer: b
Clarification: Conventional solar water systems consists of flat-plate collectors (FPC) or evacuated tube collectors (ETC). Solar air collectors are not solar water system.

7. Which application is best suited for a solar water system?
a) Food industry
b) Semiconductor industry
c) Residential applications
d) Liquid adsorption
Answer: c
Clarification: Solar water systems are best suited for residential applications and if required can be installed on rooftops to meet temperature demands upto 125 degree Celsius. Solar air collectors are mainly used in food industries.

8. Which of the following are types of solar concentrators?
a) Solar air collectors
b) Flat-plate collectors
c) Parabolic flat plate collectors
d) Linear Fresnel collectors
Answer: d
Clarification: Solar concentrators include parabolic dish collectors, linear Fresnel collectors and linear parabolic trough collectors. Solar air collectors are not a type of solar concentrators. There is no such thing as parabolic flat plate collector because the shape can either be parabolic or flat.

9. What is a solar cooling technology?
a) Sun’s thermal energy is transferred to a heat transfer fluid which passes through a heat exchanger
b) Sun’s thermal energy is transferred to a heat transfer solid which passes through a heat exchanger
c) Sun’s nuclear energy is transferred to a heat transfer fluid which passes through a cold exchanger
d) Sun’s thermal energy is transferred to a heat transfer fluid which passes through a cold exchanger
Answer: a
Clarification: A solar cooling technology is a system that transfers sun’s thermal energy to a heat transfer fluid (also called as working fluid). This fluid then passed through a heat exchanger where the heat is moved from one system to another thereby achieving cooling.

10. Which of the following is an example of solar air heating/collection technology?
a) Drying food using hair dryer
b) Drying food under direct sun
c) Heating the food in oven
d) Grilling food in a barbeque
Answer: b
Clarification: Drying food under direct is one of the simplest and naturally occurring techniques of solar air heating. Drying food using hair dryer is not a solar air heating technology as electricity is used to run the hair dryer.

11. Which of the following groups are types of solar drying technology?
a) Indirect, direct and active, photovoltaic
b) Photovoltaic, direct and indirect, active
c) Indirect, direct and active, passive
d) Indirect, passive and active, direct
Answer: c
Clarification: Solar drying technology can broadly be grouped into indirect/ direct and active/passive technologies. Directly drying under the sun is an example of direct drying. Photovoltaic is not a solar drying technology.

12. Active solar drying systems control _______ by fans.
a) water flow rate
b) food flow rate
c) electricity
d) air flow rate
Answer: d
Clarification: Active solar drying systems control air flow rate by fans. They can reduce drying time by a third and are compact. However, they require more electricity to operate machines like fans.

13. Solar air collectors transfer sun’s thermal energy to air via ______
a) conduction
b) convection
c) Seebeck effect
d) Peltier effect
Answer: a
Clarification: Solar air collectors transfer sun’s thermal energy to air via conduction. Convection is the transfer of heat by movement of fluid between areas of different temperature. For this to happen, some region of air must first have a higher temperature which is achieved by conduction.

14. Solar concentrators are used for temperatures beyond 500 degree Celsius.
a) True
b) False
Answer: a
Clarification: Solar concentrators are used for temperatures beyond 500 degree Celsius. Such industrial applications include generation of electricity or melting metals.

15. Solar heat industrial systems are used for desalination.
a) True
b) False
Answer: a
Clarification: Solar heat industrial systems are used for desalination. They are thermally driven systems with operating temperatures around 110 degree Celsius. Desalination is the process of removing minerals from saline water.

Solar Energy,
social networks below and stay

Wind Energy Question Bank on “Wind Turbine Aerodynamics – 2”.

1. How is drag force experienced by the blade reduced in various modern blade designs?
a) Bending and tapering the blade
b) Using heavy metals
c) Twirling the blade
d) Increasing the length of the blade

Answer: a
Clarification: Turbine blades experience drag force. They are bent and tapered along their length to reduce the effect of drag force.

2. What is angle of attack?
a) Angle between downwind side and upwind side
b) Angle between the blade and the rotor
c) Angle between the direction of wind and pitch of the blade
d) Angle between the blade and the wind tower

Answer: c
Clarification: Angle of attack is the angle between the direction of the oncoming wind and the pitch of the blade. It is important to note that position of the pitch of the blade is with respect to the oncoming wind.

3. When plotting lift vs angle of attack, which of following best describes the shape of the curve?
a) Exponential
b) Cubic
c) Linear
d) Parabolic

Answer: d
Clarification: The shape of lift vs angle of attack curve is parabolic in nature. The value of lift attains a maxima when the angle is between 15-18 degrees.

4. There is no ideal angle of attack for best rotation.
a) True
b) False

Answer: b
Clarification: There is an ideal angle of attack that creates best rotation. It can be seen that the value of lift increases as the angle increases and then decreases as the angle crosses 20 degrees.

5. The speed at the tip of the blade is faster than its center.
a) True
b) False

Answer: a
Clarification: The speed of the tip of a rotating blade is faster than its center or root. This ensures a good tip-speed-ratio and provides high efficiency.

6. What is the angle by which the rotor blades are twisted?
a) 5-10 degrees
b) 15-45 degrees
c) 100-120 degrees
d) 10-20 degrees

Answer: d
Clarification: The rotor blades are twisted by an angle between 10-20 degrees from root to tip. This ensures that the angle of attack decreases from the region where the air is moving slowly near the root to the region where the air is moving much faster at the tip.

7. Which of the following blade designs further increases the efficiency of airfoil blades?
a) Twisting and tapering the blades
b) Reducing wind tower height
c) Increasing wind tower height
d) Increasing rotor speed

Answer: a
Clarification: Twisting and tapering any airfoiled blade further increases its efficiency. The other options may increase efficiency but they are not related to blade designs.

8. Why is a blade twisted along its length rather than its width?
a) Drag reduction
b) Weight reduction
c) Drag reduction and improvement in angle of attack
d) Aesthetic reasons

Answer: c
Clarification: A rotor blade is twisted along its length to improve the angle of attack and reduce drag. It is not done to reduce weight or for aesthetic reasons. Every engineering design has a logical reason.

9. Which of the following blade designs further increases the efficiency of airfoil blades?
a) Reducing wind tower height
b) Twisting and tapering the blades
c) Increasing wind tower height
d) Increasing rotor speed

Answer: b
Clarification: Twisting and tapering any airfoiled blade further increases its efficiency. The other options may increase efficiency but they are not related to blade designs.

10. Why does wind speed increase with height above ground?
a) More slip boundary conditions
b) Less obstructions and no slip boundary conditions
c) More obstructions and slip boundary conditions
d) Gas molecules have less mass

Answer: b
Clarification: Increase in wind speed with increasing height is due to both, less number of obstructions and no slip boundary conditions. While the fluid analysis at ground level assume these conditions, the mathematics for analyzing at a considerable height above ground level is suitable changed.

11. Increased wind tower height and longer blades do not result in an increase in power.
a) True
b) False

Answer: b
Clarification: Increasing the wind tower height and blade length results in increased output power. However, the benefits of increasing the form factor comes at the expense of economics and safety.

12. Why should longer turbine blades be made of stronger materials?
a) Longer turbine blades experience greater forces
b) Longer turbine blades experience lesser forces
c) Stronger materials are cheaper
d) Stronger materials are available in abundance

Answer: a
Clarification: Longer turbine blades experience greater aerodynamic forces – lift and drag forces. Hence, they need to be made of stronger materials which are not particularly cheap.

13. Which of the following is best reason for not using longer blades even though they produce greater output power?
a) Longer turbine blades experience greater forces
b) Longer turbine blades experience lesser forces
c) Safety concerns due to greater momentum of longer blades
d) Stronger materials are available in abundance

Answer: c
Clarification: Though longer turbine blades produce greater output power; they are not used commercially because they have more mass. If any of the blades falls off the tower, its net momentum could cause extensively damage the environment.

14. Which theory is used to model the wind turbine?
a) Blade element momentum theory
b) Kinetic gas theory
c) Archimedes principle
d) Einstein’s theory of photoelectric effect

Answer: a
Clarification: Blade momentum theory is used to for aerodynamic modelling due to its simplicity. Kinetic gas theory is related to gas molecules and energy of a gas molecule. Archimedes principle is related to floatation and immersion of a body in a liquid. Einstein’s theory is related to the photoelectric effect which is a quantum mechanical phenomenon.

15. What is blade element momentum theory?
a) It is same as blade element theory
b) It is same as momentum theory
c) It talks about the motion of a body in a given frame of reference
d) It is used to calculate the local forces on the propeller or blade

Answer: d
Clarification: Concepts of both, element theory and blade momentum theory are combined and used in Blade element momentum theory. It is used to aerodynamically model turbine blades and rotors and calculate the respective local forces on them.

Biomass Energy Multiple Choice Questions on “Biomass Gasification – 1”.

1. What is unique about the gasification agent entering in a fluidized gasifier?
a) Enters from bottom at a relatively fast rate as compared to a fixed bed gasifier
b) Enters from bottom at a relatively slow rate as compared to a fixed bed gasifier
c) Enters from top at a relatively fast rate as compared to a fixed bed gasifier
d) Enters from top at a relatively slow rate as compared to a fixed bed gasifier

Answer: a
Clarification: In a fluidized gasifier, the gasification agent enters the bed from the bottom at a relatively faster rate and exits from the top. This type of gasification features a uniform temperature distribution in the bed zone.

2. What ensures consistency of temperature in fluidized gasifier?
a) Gasification agent
b) Air-fluidized bed material
c) Biomass
d) Air non-permeable bed material

Answer: b
Clarification: Fluidized gasifier features a uniform temperature distribution in the bed zone. This is achieved using an air-fluidized bed material. Biomass and gasification agent do not contribute towards the temperature consistency.

3. What are the three types of fluidized gasifiers used?
a) Single fluidized bed, dual fluidized bed and bubbling fluidized bed
b) Straight fluidized bed, dual fluidized bed and bubbling fluidized bed
c) Circulating fluidized bed, dual fluidized bed and bubbling fluidized bed
d) Single fluidized bed, dual fluidized bed and straight fluidized bed

Answer: c
Clarification: Circulating fluidized bed, dual fluidized bed and bubbling fluidized bed are the three main types of fluidized gasifiers used. They are mainly used to achieve a uniform temperature distribution.

4. How is the temperature maintained in a bubbling fluidized bed?
a) Biomass
b) Gasification agent
c) A constant ratio of biomass and gasification agent
d) Manipulating the ratio of biomass and gasification agent

Answer: d
Clarification: A bubbling fluidized bed gasifier applies inlet from the bottom and moves the bed of fine-grained materials. The temperature is maintained by manipulating the ratio of biomass and gasification agent.

5. What is the temperature range in a bubbling fluidized bed?
a) Between 700 and 900 degree Celsius
b) Less than 500 degree Celsius
c) Above 1000 degree Celsius
d) Between 100 and 200 degree Celsius

Answer: a
Clarification: The temperature range in a bubbling fluidized bed gasifier is between 700 and 900 degree Celsius. This distribution is achieved by manipulating the ratio of biomass and gasification agent.

6. What is the biomass decomposed to in a bubbly fluidized bed?
a) Producer gas
b) Char and gas products with a low tar percentage
c) Char and gas products with a high tar percentage
d) Char with a low tar percentage

Answer: b
Clarification: The biomass is decomposed to char and other gaseous products with a low percentage of tar. Since this is a gasifier, one of the products has to be a gas. So, the option without gaseous products is incorrect.

7. What are the two main units in a circulating fluidized bed?
a) Bubbling fluidized bed and dual fluidized bed
b) Bubbling fluidized bed and gasifier unit
c) Circulating unit and gasifier unit
d) Circulating unit and dual fluidized bed

Answer: c
Clarification: The two main units in a circulating fluidized bed are circulating unit and gasifier unit. Bubbling fluidized bed and dual fluidized bed are types of fluidized gasifier. They are not a part of circulating fluidized bed gasifier.

8. Where can the ash and hot gas be separated in a circulating fluidized bed gasifier?
a) Gasifier unit
b) Circulation unit
c) Tornado separator
d) Cyclone separator

Answer: d
Clarification: Ash and hot gas can be separated in the cyclone separator. The bed material and the char is circulated between the reaction chamber and the cyclone separator where the separation takes place.

9. The two separate fluidized beds in a dual fluidized bed gasifier are used for pyrolysis and combustion process.
a) True
b) False

Answer: a
Clarification: A dual fluidized bed gasifier consists of two separated fluidized beds. One of the beds is used for pyrolysis and the other is used for combustion. Generally, the first bed is used for pyrolysis.

10. Which of the following best indicates the process in a dual fluidized bed gasifier?
a) Combustion reactor → pyrolysis reactor
b) Pyrolysis reactor → combustion reactor
c) Evaporation reactor → condensation reactor
d) Combustion reactor → condensation reactor

Answer: b
Clarification: The first bed in a dual fluidized bed gasifier is used for pyrolysis. The second bed is used for combustion. The second reactor provides heat by burning char provided from the first reactor.

11. What are the two types of entrained flow gasifiers?
a) Bubbling fluidized gasifier and dual fluidized gasifier
b) Bubbling fluidized gasifier and top-fed gasifier
c) Top-fed gasifier and side-fed gasifier
d) Side-fed gasifier and dual fluidized gasifier

Answer: c
Clarification: The two main types of entrained flow gasifiers are top-fed gasifier and side-fed gasifier. Bubbling fluidized bed and dual fluidized bed gasifiers are fluidized bed gasifiers and not entrained flow gasifiers.

12. Which of the following gasifiers is suitable for integrated gasification combined cycle (IGCC)?
a) Fluidized gasifier
b) Fixed bed gasifier
c) Downdraft gasifier
d) Entrain flow gasifier

Answer: d
Clarification: Entrail flow gasifiers are suitable for IGCC. They are applied in large-scale gasification and are widely used for coal, biomass and refinery residues. Downdraft is a type of fixed bed gasifier which is not suitable for IGCC.

13. Which of the following is a problem due to tar formation in gasifiers?
a) Equipment blockages
b) High system efficiency
c) Improved quality of gas
d) Reduction in maintenance

Answer: a
Clarification: Tar formation in a gasifier leads to equipment blockage, lower system efficiency and increased maintenance. The most important problem is that it contaminates the gas and reduces its quality.

14. Which of the following is a component of tar?
a) Sodium
b) Benzene
c) Chlorine
d) Nickel

Answer: b
Clarification: Tar is generally composed of carbon compounds like benzene, naphthalene, single-ring aromatic hydrocarbons, toluene, etc. It does not contain of non-carbon materials like sodium, chlorine and nickel.

15. Tar is removed by choosing the appropriate catalyst.
a) True
b) False

Answer: a
Clarification: Tar is removed by choosing the appropriate catalyst. Other methods include setting the appropriate operation parameter and downstream removal after gasification – mechanical method and thermal cracking.

Solar Energy Multiple Choice Questions on “Sun, Earth Radiation Spectrums – 2”.

1. Which of the following is used to measure the flux of outgoing long-wave radiation?
a) Watt/square meter
b) Watt
c) Joules
d) Watt/cubic meter
Answer: a
Clarification: The flux of energy transported by outgoing long-wave radiation is measured in watt/square meter. While Watt is used to measure power, Joule is used to measure energy.

2. Which of the following process is involved in long-wave radiation?
a) Adsorption
b) Scattering
c) Evaporation
d) Condensation
Answer: b
Clarification: In earth’s climate system, the processes involved in long-wave radiation are absorption, scattering and emissions. The emissions are from atmospheric gases, aerosols, clouds and the surface. Condensation is the process of gas converting to liquid due to decrease in temperature.

3. How does earth lose its excess solar radiation?
a) By storing the radiation in its core
b) By using the radiation to generate more magma
c) By radiative cooling
d) By conductive cooling
Answer: c
Clarification: Earth loses its excess solar radiation by radiative cooling. The outgoing long-wave radiation takes the excess energy from earth back into the space.

4. How do all the living organisms on receive energy?
a) From wind
b) From fossil fuels
c) From earth’s heat
d) From sun
Answer: d
Clarification: Sun is the source of energy for all living organisms on earth. It provides energy for photosynthesis which triggers the biological food cycle and food web. Thus, the energy is transferred between organisms as described in the biological energy pyramid.

5. What is earth’s energy budget?
a) Balance between received energy and emitted energy after the distribution of energy throughout the five components of earth’s climate system
b) Balance between received energy and emitted energy before the distribution of energy throughout the five components of earth’s climate system
c) Balance between received energy and emitted energy
d) Balance between received energy and emitted energy without the distribution of energy throughout the five components of earth’s climate system
Answer: a
Clarification: Earth’s energy budget is the balance between received energy and emitted energy after the distribution of energy throughout the five components of earth’s climate system. It is important to note the outgoing energy is the energy after distribution.

6. What happens to earth when incoming energy is greater than the outgoing energy?
a) Earth’s temperature decreases
b) Earth’s temperature increases
c) Earth’s temperature is not affected
d) Water level rises
Answer: b
Clarification: When the incoming energy is greater than the outgoing energy, the earth’s temperature rises. This results in global heating and the entire planet feels the “heat”.

7. What happens to earth when incoming energy is less than the outgoing energy?
a) Earth’s temperature is not affected
b) Earth’s temperature increases
c) Earth’s temperature decreases
d) Entire planet freezes
Answer: c
Clarification: When the incoming energy is lesser than the outgoing energy, the earth’s temperature decreases. This results in global cooling. If the difference is large and average global temperature decreases even by 1 degree Celsius, the entire planet may be covered with snow.

8. What is solar irradiance?
a) Solar radiation received by earth
b) Solar radiation directly received by earth’s surface
c) Solar radiation received by earth’s surface after scattering
d) Intensity with which the solar radiation enters the earth’s atmosphere
Answer: d
Clarification: Solar irradiance is the intensity with which the solar radiation enters the earth’s atmosphere. Solar radiation directly received by earth’s surface is called direct solar radiation. Solar radiation received by earth’s surface after scattering is called indirect solar radiation.

9. During night, the net-all-wave radiation is dominated by _____
a) long-wave radiation
b) short-wave radiation
c) visible range
d) gamma rays
Answer: a
Clarification: During night, the net-all-wave radiation is dominated by long-wave radiation. The long-wave radiation dominates the net all-wave radiation in polar regions as well. It is important to note that net-all-wave radiation is for a surface.

10. Why is the earth’s temperature nearly stable?
a) Because the outgoing radiation dominates the incoming solar radiation
b) Because the incoming short-wave solar radiation nearly equals the outgoing long-wave radiation
c) Because the incoming long-wave solar radiation dominates the outgoing short-wave radiation
d) Because the incoming long-wave solar radiation dominates the outgoing long-wave radiation
Answer: b
Clarification: Earth’s temperature is nearly stable. This is because the incoming short-wave solar radiation nearly equals the outgoing long-wave radiation. Any variation in the global average temperature is detrimental to the planet.

11. Which of the following best describes intensity?
a) Energy supplied to a bulb
b) Power supplied to a bulb
c) Brightness of glowing bulb
d) Energy the bulb radiates as heat
Answer: c
Clarification: Intensity is best described by the brightness of a glowing bulb. Energy the bulb radiates as heat is the power that is wasted by the bulb during its operation.

12. Solar irradiance is measured in ______
a) watts
b) meters/sec
c) newtons
d) watts/square meter
Answer: d
Clarification: Solar irradiance is measured in watts/square meter. It is the amount of radiant flux on an area and hence those units. Speed and velocity are measured in meters/s.

13. Which of the following influences solar irradiance?
a) Scattering elements like clouds
b) Shape of the location receiving the radiation
c) Type of the radiation
d) Type of the receiving surface
Answer: a
Clarification: Solar irradiance received by a location or water body depends on the elevation above sea level, angle of sun and scattering elements like clouds. It does not depend on the type of radiation and type of receiving surface.

14. Ozone absorbs UV light and hence affects solar irradiance.
a) True
b) False
Answer: a
Clarification: Ozone absorbs UV light and hence affects solar irradiance. The lower the angle of the sun, the larger the amount of ozone the light has to pass through.

15. The distance that the solar radiation has to travel will be lowest when the sun is directly overhead.
a) True
b) False
Answer: a
Clarification: The distance that the solar radiation has to travel will be lowest when the sun is directly overhead. The angle of sun is dependent on latitude, time of year and the time of day.

Solar Energy,
social networks below and stay