Solar Cooker

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Phyics project
Solar Cooker
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Introduction

• People use solar cookers primarily to cook food
  and pasteurize water, although additional uses
  are continually being developed. Numerous factors
  including access to materials, availability of
  traditional cooking fuels, climate, food
  preferences, cultural factors, and technical
  capabilities affect people's approaches to solar
  cooking.

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Materials and tools

• We use materials available in daily life. These
  include corrugated cardboard boxes, black paper,
  aluminum foil, plastic sheets, plastic canister
  etc.We also use the following toolswhite glue,
  double-sided adhesive tape, transparent adhesive
  tape, scissors, cutter, ruler, magic marker etc

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Design and construction skills
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Design and construction skills

• The more directly the glass faces the sun, the
  greater the solar heat gained. Although the glass
  is the same size for box 1 and box 2, more
  sunlight shines through the glass on box 2
  because it faces the sun more directly. Note
  that box 2 also has more area for heat loss.

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Design and construction skills

• Single or multiple reflectors bounce additional
  sunlight through the glass and onto the solar
  box. This additional input of solar energy
  results in higher cooker temperature.

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Design and construction skills

• Solar cooker facing the sun at noon should be
  longer in the east/west dimension to make better
  use of the reflector over a cooking period of
  several hours. As the sun travels across the sky,
  this configuration results in a more consistent
  cooking temperature. With square cookers or ones
  having the longest dimension to the north/south,
  
• a greater percentage of the
• early morning and late
• Afternoon sunlight is reflected
  from the reflector
  to the ground,
  missing the box collection
  area.

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Application of physics principles
in the design

• Greenhouse effect results in the heating of
  enclosed spaces into which the sun shines through
  a transparent material such as glass or plastic.
• The light energy that is absorbed by dark pot
  underneath the pot is converted into longer
  wavelength heat energy and re-radiates from the
  interior materials. Most of this radiant energy,
  because it is of a longer
  wavelength,
  cannot pass through the
  
• glass and is therefore trapped
  
  within the enclosed space.

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Application of physics principles in the design

• Conduction

Conduction is the process of heat flow from
regions of higher temperatures to regions of
lower temperatures through a medium. But
conduction is not efficient in insulator, so we
can use the insulating material such as plastic
and glass to trap heat inside the solar cooker
and heat energy cannot lose by conduction to the
air easily.
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Application of physics principles in the design

• Convection

Heat can be transferred in a fluid by convection
in which the heated fluid expands, rises and is
replaced by the surrounding fluid. So we should
use something covering it up,
having the hot air trapped inside the solar
cooker to keep the
temperature steady.
Thus we use glass to cover it up.
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Application of physics principles in the design

• Radiation

Energy is gained on absorbing infra-red
radiation. Dull black surfaces are good absorbers
and good radiators of radiation. Silvery surfaces
are poor absorbers and poor radiators of heat. So
we cover the outside with black paper and use
silvery paper inside.
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Test of solar cooker-First Time
Time/min. 0 5 10 15 25 30 35 40 45 50 55 60
Temp/oC 25 27 28 29 34 35 37 37 39 40 43 45
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Test of solar cooker-Second Time
Time/min. 0 5 10 15 20 25 30 35
Temp./oC 20 21 21 21.5 22 22 23 24
Time/min. 40 45 50 55 60 65 70 75
Temp./oC 25 25.5 26 26 27.5 28.5 29 29.5
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Test of the solar cooker Third Time
Time/min. 0 5 10 15 20 25 30 35
Temp./oC 19 21 22 22 23 23.5 24 24
Time/min. 40 45 50 55 60 65 70
Temp./oC 25 26 28 29 31 31.5 32
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Discussion

• We have read a lot of books and search for
  information in the internet. Each of us brings up
  different opinion. Actually there are lots of
  ways to make the solar cooker.We look for all
  sample we think that is good. But Our solar
  cooker have a big defect. The collector we used
  is difficult to absorb sunlight in the evening.
  It is only suitable for use when the light shines
  on top of our solar cooker.

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Conclusion

• We thought that this project is very interesting
  but our solar cooker is not so good, If we can do
  it again we think we must do it better.We think
  we have learned a lot of things about the solar
  energy through this project. We also used amount
  less than 30 to do this project. This project
  is good for students!

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• Group leaderLau Chun Kin 4D (29)
• Group memberCheung Wai Pan 4D(21)
• Choi Chi Hoi 4D (23)
• Chu Wa Hung 4D (25)
• Wong Kam Hong 4D (39)

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The End

• Thank you very much!

Bye -bye