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Solar Energy Multiple Choice Questions on “Solar Collectors – 1”.
1. What is a solar collector?
a) A system to collect heat by absorbing sunlight
b) A system to collect rainwater using sunlight
c) A system to collect electricity by using sunlight
d) A device to reflect sunlight back
Answer: a
Clarification: A solar collector is a system to collect heat by absorbing sunlight and use it for various applications. It is neither a system to collect rainwater nor electricity. However, it could be used to perform such processes.
2. What is aperture area in a solar collector?
a) Area of the system
b) Area in the receiver that receives the solar radiation
c) Area occupied by the system after installation
d) Cross-sectional area of the receiver
Answer: b
Clarification: Aperture area of a receiver is that area which receives the solar radiation. It need not be same as the entire size of the receiver. It is not same as the area occupied by the system after installation.
3. Aperture area of a solar collector is roughly equal to _______
a) Coolant area
b) Generator area
c) Absorber area
d) System area
Answer: c
Clarification: In a solar collector, the aperture area is approximately equal to absorber area. This enables absorption of (almost) all the sunlight that is incident on the aperture area.
4. What are the components of a flat plate collector?
a) Flat box, a plate with reflective coating and fluid circulation passageways, an opaque cover, a circulating fluid
b) Flat box, a dark coloured plate with fluid circulation passageways, an opaque, a circulating fluid
c) Flat box, a dark coloured plate with fluid circulation passageways, a transparent cover
d) Flat box, a dark coloured plate fluid circulation passageways, a transparent cover, a circulating fluid
Answer: d
Clarification: A flat plate solar collector consists of various components. Firstly, it consists of a flat box or an enclosure to hold the entire setup. A dark coloured plate is fitted with fluid circulation passageways and transparent cover. Finally, a circulating fluid which flows through the entire setup.
5. Why is a transparent cover used in a flat plate collector?
a) To maximize transmission of the incident sunlight into the box
b) To minimize transmission of the incident sunlight into the box
c) To entirely reflect the incident sunlight back
d) To ensure partial transmission of the incident sunlight into the box
Answer: a
Clarification: A transparent cover is used in a flat plate collector. This is because it maximizes the transmission of the incident sunlight into the box thereby collecting maximum sunlight for thermal energy.
6. Which of the following is generally used as circulating fluid in tropical and sub-tropical climates?
a) A mixture of ethylene glycol and water
b) Water
c) A mixture of propylene glycol and water
d) Glycerol
Answer: b
Clarification: Water is used as circulating fluid in tropical and sub-tropical climates. This is because it has good properties as a coolant. A mixture of water with ethylene glycol or glycerol or propylene glycol is not used as coolant in tropical and sub-tropical climates.
7. Which of the following is generally used as circulating fluid in freezing climates?
a) Liquid carbon dioxide
b) Water
c) A mixture of propylene glycol and water
d) Liquid nitrogen
Answer: c
Clarification: In freezing climates, antifreeze solution like a mixture of water with propylene glycol or ethylene glycol or glycerol is used as coolants. Liquid carbon dioxide, water and liquid nitrogen are not used as coolants in freezing climates.
8. Why are antifreeze solutions (antifreeze agents with water) used as coolants in freezing climates?
a) To increase boiling point of water
b) To decrease boiling point of water
c) To increase freezing point of water
d) To decrease freezing point water
Answer: d
Clarification: Antifreeze solution is used as coolants in freezing climates. This is because they decrease the freezing point of water thereby preventing it from solidifying into ice.
9. Adding antifreeze agents to water _________
a) increases its durability as coolant
b) decreases its durability as coolant
c) turns water into a coolant
d) prevents water from acting as a coolant
Answer: a
Clarification: Adding antifreeze agents to water increases its durability as coolant. This is because it depresses the freezing point of water and prevents it from becoming ice.
10. Which of the following is a circulating fluid in evacuated flat-plate solar collectors?
a) Water
b) Steam
c) Nitrogen
d) Hydrogen
Answer: b
Clarification: Evacuated flat-plate solar collectors are a more recent technology. It uses steam as its circulating fluid. Nitrogen and hydrogen are not used as circulating fluid. Water is mainly used in flat-plat collectors.
11. Evacuated flat-plate solar collectors are a type of _______
a) concentrating collectors
b) photovoltaic technology
c) non-concentrating collectors
d) solar stills
Answer: c
Clarification: Evacuated flat-plate solar collectors are a type of non-concentrating collectors. Solar stills and photovoltaic technology are not solar collectors.
12. Which of the following are used as absorbers in evacuated-tube solar collectors?
a) Carbon tubes
b) Wooden or metallic tubes
c) Plastic or glass tubes
d) Metallic or glass tubes
Answer: d
Clarification: Metallic or glass tubes are used as absorbers in evacuated-tube solar collectors. Wood and plastic are thermal insulators and hence, cannot be used to create passageways for the heat carrying circulating fluid.
13. What is a heat pipe?
a) A heat-transfer device
b) A pipe made of heat
c) A pipe that consists of heat
d) A heat pumping device
Answer: a
Clarification: A heat pipe is a heat-transfer device. It combines the principles of thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.
14. For better efficiency, solar collectors do not coat their transparent cover with an anti-reflective coating.
a) True
b) False
Answer: b
Clarification: For better efficiency, solar collectors coat their transparent cover with an anti-reflective coating. The anti-reflective coating reduces the amount of reflection dramatically. Thus, the amount of sunlight collected is increased.
15. Evacuated tube solar collectors use a glass tube to surround absorber with high vacuum.
a) True
b) False
Answer: a
Clarification: Evacuated tube solar collectors use a glass tube to surround absorber with high vacuum. This is used to effectively resist atmospheric pressure and reduce conductive and convective losses.
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