Solar Energy Multiple Choice Questions on “Solar Collectors – 2”.
1. Which of the following is used to make a glass-glass evacuated tubes?
a) Borosilicate glass
b) Carbon
c) Wood
d) Plastic coating
Answer: a
Clarification: As the name suggests, glass-glass evacuated tubes is a type of evacuated-tube solar collector. It is made up of two borosilicate glass tubes fused together at one or both ends.
2. Which of the following is a problem with evacuated tubes?
a) Underheating
b) Overheating
c) Poor absorption of sunlight
d) Poor reception of sunlight
Answer: b
Clarification: Overheating is a common problem with evacuated-tube solar collector. This is because of the high temperatures of the circulating fluid caused by collection of large amount of sunlight.
3. Why does flat plate collector perceived to have higher efficiency than evacuated tube solar collector in terms of area?
a) Because flat plate collector has a large installation area
b) Because evacuated tube collector is compact
c) Because of the vacuum gap in evacuated tube collectors
d) Because of the vacuum gap in flat plate collectors
Answer: c
Clarification: In terms of area, flat plate solar collectors are generally perceived to have a higher efficiency than evacuated-tube solar collectors. This is because of the vacuum gap in evacuated tube collectors which increases their net occupied area.
4. _______ lose more heat to the environment than evacuated-tube solar collectors.
a) Photovoltaics
b) Solar stills
c) Solar air conditioners
d) Flat-plate collectors
Answer: d
Clarification: Flat-plate collectors lose more heat to the environment than evacuated-tube solar collectors. Photovoltaics, solar stills and solar air conditioners are not solar collectors.
5. Which of the following are combined to form an evacuated flat plate solar collector?
a) Flat plate solar collectors and evacuated-tube solar collectors
b) Flat plate solar collectors and bowl collectors
c) Bowl collectors and evacuated-tube solar collectors
d) Polymer collectors and bowl collectors
Answer: a
Clarification: Evacuated flat plate collectors combine the technologies of both, flat plate solar collectors and evacuated-tube solar collectors. There are not a combination of bowl and polymer type collectors.
6. Which of the following provides highest energy conversion efficiency in non-concentrating solar collectors?
a) Flat plate collectors
b) Evacuated flat plate collectors
c) Evacuated-tube collectors
d) Parabolic collectors
Answer: b
Clarification: Evacuated flat plate collectors provide the highest energy conversion efficiency in non-concentrating solar collectors. Parabolic collector is not a non-concentrating collector.
7. What is the metal sheet absorber surrounded with in an evacuated flat plate collector?
a) Low volume inside flat envelope
b) Low vacuum inside curved envelope
c) High vacuum inside flat envelope
d) Low vacuum inside thick curved envelope
Answer: c
Clarification: In an evacuated flat-plate solar collector, the metal sheet absorber is surrounded with a high vacuum. This is then placed inside a flat envelope made of glass and metal.
8. Which of the following organisations developed first high vacuum insulation?
a) NASA
b) IIT
c) Stanford
d) CERN
Answer: d
Clarification: CERN developed the first collector making use of high vacuum insulation. However, the first company to commercialise the technology was TVP SOLAR SA of Switzerland.
9. Why does an evacuated flat plate collector require a glass-metal seal?
a) To join the glass plate to the rest of metal envelope
b) To join the glass plate to a part of metal envelope
c) To disconnect the glass plate to the rest of plastic envelope
d) To disconnect the glass plate to the rest of metal envelope
Answer: a
Clarification: An evacuated flat plate collector requires a glass-metal seal. This is to join the glass plate to the rest of metal envelope. It also requires an internal structure to support such a plate against atmospheric pressure.
10. Which of the following pumps is used in an evacuated-tube solar collector?
a) Non-evaporable getter
b) Flash getter pump
c) Heat pump
d) Water pump
Answer: b
Clarification: Evacuated flat-plate solar collectors use a barium flash getter pump. This pump is used to keep the internal pressure stable throughout the operation. They do not use non-evaporable getter pumps.
11. Evacuated flat-plate solar collectors use _______ pumps.
a) Heat pump
b) Flash getter pump
c) Non-evaporable getter
d) Internal combustion
Answer: c
Clarification: Evacuated flat-plate solar collectors use non-evaporable getter (NEG) pumps to keep the internal pressure stable throughout the operation. This pump enables some regeneration in-situ by exposure to sunlight.
12. What advantage does polymer collector have over metal collector?
a) Better sales as they are produced in Europe
b) Poor sales as they are produced in Europe
c) They cannot be used in cold climate
d) They can be used in cold climate
Answer: d
Clarification: The primary advantage of a polymer collector over a metal collector is that they can be used in cold regions with low temperatures. This is because they are freeze-tolerant. Whether they are manufactured in Europe or not does is neither an advantage nor a disadvantage.
13. Bowl collectors operate similarly to _______
a) parabolic dish
b) flat plate collector
c) evacuated-tube collector
d) evacuated flat tube collector
Answer: a
Clarification: Bowl collectors operate similarly to a parabolic dish. However, they have a fixed receiver unlike a parabolic dish. This reduces efficiency but is much cheaper to build and operate.
14. Polymer flat plate collectors can use plain water.
a) True
b) False
Answer: a
Clarification: Polymer flat plate collectors can use plain water. This is because they are freeze-tolerant and do not require antifreeze agents to prevent water from solidifying.
15. Bowl collectors use a fixed curved receiver.
a) True
b) False
Answer: a
Clarification: Bowl collectors use a fixed curved receiver. They have a fixed spherical mirror with a tracking receiver.