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Solar Cooking

Quinton Stowell

Product Development Manager

Nordson UV Ltd

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Overview of sessions

  • 1. Theory of Solar Energy/Cooking
  • 2. Solar –v– Wood/gas
  • 3. Design features of Solar Cookers
  • 4. Case Study in Peru
  • 5. Successful initiatives
  • 6. Practical session

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Who am I? – Nordson UV?

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Links with Peru

  • Peru Children’s Trust

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  • Shantytown in Peru

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Why is Solar Cooking Important?

  • 2,000 million cook with wood (TFL)
  • 20-25,000km2 of forest lost/year (UNEP)
  • Contaminated water = 80% illnesses
  • ARI (Acute Respiratory Infections)
  • Solar Cooking = no wood & no smoke

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Energy from the Sun?

  • Solar Constant = 1367 W/m2
  • Clear sunny day = 83% = 1134 W/m2
  • Engineers= 1kW/m2

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Energy from the Sun?

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Theory behind Solar Energy

  • Low grade energy
  • Collect/retain…..
  • Box type cooker
  • Magnification…..
  • Parabolic cooker

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Parabolic and Box Cookers

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Wood/Gas – V – Solar

Smoke free cooking

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Smoke filled rooms = ARI (Acute Respiratory Infections)

Solar energy is free

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Takes time to collect wood, and is using up natural resources.

Advantages

Disadvantages

Solar Cookers

Wood Burners or Gas

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Wood/Gas – V – Solar

Need to store cooker in rainy season.

Cook summer and winter.

Box cookers take time to heat up. Parabolic cookers need frequent adjustment.

Gas is instantaneous and controllable.

Only cook when it is sunny.

Cook any time. Day/night/cloudy.

Disadvantages

Advantages

Solar Cookers

Wood Burners or Gas

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Parabolic – Design Features

  • Size of reflector
  • Reflectivity of reflector
  • Accuracy of reflector
  • Emmisivity of cooking vessel

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Energy Calculations

  • Area = 1 m2
  • Power = 700 Watts
  • 1 litre of water = 7 to 8 minutes
  • Temperature at focus =

420 deg C. (small black thermocouple)

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Box Cooker – Design Features

  • Greenhouse principle
  • Area of collection
  • Transmission of glass/plastic
  • Emissivity of cooking �vessel
  • Insulation of box
  • WAPI (Water Pasteurisation Indicator)

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SUNSTOVE ® Design

  • Low cost enclosure
  • Sloped side walls, scrap Aluminium
  • Fibreglass insulation
  • Clear glass/plastic cover
  • 80 – 100 deg C
  • 10,000 in SA & India

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Parabolic – v – Box Cooker

Advantages

Disadvantages

Adjust once an hour.

Needs frequent adjustment

Very stable

Unstable

Much less reflected light.

More likely to be dazzled by reflected light.

Box Cooker

Parabolic Cooker

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Parabolic – v – Box Cooker

Not too sure it is working! (WAPI – 65 deg C)

Easy to see it cooking quickly.

Cooking takes much longer.

More like a BBQ or Grill

Only 80 – 100 deg C.

Very high temperatures.

Disadvantages

Advantages

Box Cooker

Parabolic Cooker

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Trip to Peru

  • 10 teenagers
  • £30 of materials
  • Woodwork
  • Cardboard
  • Metalwork
  • Fun time

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How did it go?

  • Workshops
  • Language!
  • New skills
  • Too small!
  • Too big!
  • Rainy season
  • Years later….

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What makes an Initiative Successful?

  • Choosing the right design for the right location.
  • Not this one for £750 in Australia!

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What makes it successful?

  • Over 4kWhr per m2 per day.
  • e.g. India, China, South Africa.
  • Robust, easy to use.
  • Perform well/efficient.
  • Local materials.
  • Very low cost.

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Scheffler Design

Community Kitchen - India

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Refugee Camp - CooKit

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What makes an Initiative Successful?

  • Marketing & contacts with organisations
  • Existing charities
  • NGO’s – sustainable development
  • Government initiatives
  • Demonstrators – evangelists
  • Local entrepreneurs
  • Empowering the right people

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Useful information

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Making your Solar Cooker

  • Split into groups
  • 2 hours
  • Safety

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Inner and outer sheets

  • Mark out according to the drawing
  • Cut with a pair of sharp scissors
  • Fold with a block of wood.

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Make wooden frame and fit outer

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Fit insulation then inner panel

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Paint base plate and fit acrylic cover