# Solar Energy Questions and Answers – Solar Furnaces

This set of Solar Energy Multiple Choice Questions & Answers (MCQs) focuses on “Solar Furnaces”.

1. What is solar furnace?
a) Uses concentrated solar power to produce high temperatures for industry
b) Uses solar energy to evaporate water and collect it within the same closed system
c) Uses solar energy to dry substances
d) Uses solar energy to dry liquids

Explanation: Structures that use concentrated solar power to produce extremely high temperatures for industry and other applications are called solar furnaces. Solar dryers are devices that use solar energy to dry substances. Devices that use solar energy to evaporate water and collect its condensate within the same closed system are called solar stills.

2. Which of the following concentrates sunlight onto a focal point?
a) Plane mirrors
b) Parabolic mirrors
c) Silver coated surface
d) Black surface

Explanation: Parabolic mirrors concentrate light onto a focal point. Plane mirrors and silver coated surfaces reflect sunlight but not onto a focal point. Black surface absorbs sunlight.

3. What is the typical range of temperature at the focal point of a parabolic mirror in solar furnaces? Note that C stands for Celsius
a) Between 100 and 150 degree C
b) Upto 20 degree C
c) Between 1000 and 2000 degree C
d) Between 50 and 100 degree C

Explanation: The typical range of temperature at the focal point of a parabolic mirror in solar furnaces is between 1000 and 2000 degree C. The temperatures may rise upto 3500 degree C and can be used to generate electricity, melt steel, etc.

4. What are concentrated solar powered systems?
a) Systems that use only a small concentrated portion of sunlight
b) Systems that generate solar power by using photovoltaics
c) Systems that generate solar power by using mirrors and lenses to absorb concentrate a large area of sunlight onto an absorber
d) Systems that generate solar power by using mirrors and lenses to concentrate a large area of sunlight onto a receiver

Explanation: Large area of sunlight is concentrated onto a receiver. This is performed by concentrated solar power systems which then. The receiver then converts the light into heat and transports it to other constituents of the concentrated solar power system that further convert it into usable forms of energy.

5. Which of the following uses concentrated solar power systems?
a) Solar thermo-mechanical power systems
b) Solar stills
c) Solar dryers
d) Solar photovoltaics

Explanation: Solar thermo-mechanical power systems use mirrors and lenses to focus the light onto a receiver which is then converted into thermal energy. The thermal energy is then used to drive a heat engine connected to an electrical power generator.
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6. Which of the following does a heliostat consist of?
a) Plane mirror
b) Plane mirror and parabolic mirror
c) Fresnel reflector
d) A metal absorber

Explanation: A heliostat is a device that includes a plane mirror. The mirror is turned to keep the reflecting sunlight towards a predetermined target. This compensates for the sun’s motion throughout the day.

7. What are the types of concentrating technologies?
a) Parabolic trough and solar stills
b) Parabolic dish and solar furnace
c) Solar power tower and parabolic trough/dish
d) Solar furnace and solar stills

Explanation: Concentrating technologies exists in four types, namely, parabolic trough, dish solar power tower and concentrating linear Fresnel reflector. Solar furnace use concentrating solar power technologies. Solar stills are not a type of concentrating technology.

8. What are the types of solar furnaces?
a) Indirect and concentrating solar power technology
b) Active and direct
c) Passive and heliostat
d) Direct and heliostat

Explanation: Direct solar furnace and heliostat solar furnace are the two types of solar furnaces. Active and passive are types of solar stills. Indirect solar dryer is a type of solar dryer.

9. Which of the following is an application of solar furnace?
a) Producing hydrogen fuel
b) Drying food
c) Distilling water
d) Generating concentrating solar power technologies

Explanation: Apart from generating electricity and melting steel, producing hydrogen fuel is another major application of solar furnaces. Solar stills are used to distill water. Solar dryers are used to dry food.

10. Archimedes is said to have repelled attacking Roman ships with the help of “burning glass”.
a) False
b) True

Explanation: Archimedes is said to have repelled attacking Roman ships with the help of “burning glass”. The ships were set on fire using this so called “burning glass” which may very well have been an array of mirrors.

11. Solar furnaces are used to generate temperatures around ______ to produce hydrogen. Note that C indicates Celsius.
a) 1000 degree C
b) 500 degree C
c) 1400 degree C
d) 3500 degree C

Explanation: Solar furnaces are used to generate temperatures around 1400 degree C to produce hydrogen. Hydrogen is produced by cracking methane molecules.

12. What is the typical temperature generated by solar furnaces to test materials for extreme environments? Note that C indicates Celsius.
a) 100 degree C
b) 500 degree C
c) 1400 degree C
d) 2500 degree C

Explanation: The typical temperature generated by solar furnaces to test materials for extreme environments is around 2500 degree C. Materials are tested for applications like nuclear reactors or space vehicle.

13. What is a major drawback of solar furnaces to be used as a renewable source of energy on earth?
a) Heavily reliant on sun
b) Not reliant on sun
c) Finances
d) Cannot be used as a source of energy

Explanation: One of the major drawbacks of solar furnaces particularly if it has to be used a renewable source of energy on earth it is heavily reliant on sun. Another problem is the availability of land to install huge systems to convert energy.

14. Solar furnaces can be used as solar cookers for domestic purposes.
a) False
b) True

Explanation: Solar furnaces are not directly used as solar cookers particularly for domestic purposes. However, their principle is being used to make inexpensive solar cookers.

15. The largest solar furnace is in France.
a) True
b) False

Explanation: The largest solar furnace opened in 1970. It is located at Odeillo in the Pyrenees-Orientales in France. Sunlight is gathered and used for applications with the help of an array of plane mirrors.

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