- Types: Box, parabolic, forty fivers, trough, panel, integrated convective
- Examples: www.solarcooking.org
- Pros and cons: wind, burning, portability, need for accuracy, etc.
- Energy Balance and temperature
- Effect of steam: latent heat of water = 970 Btu/lb
- Water pasteurization - only 150 degrees fahrenheit is required.
- Timing/Aspect ratio
- Effect of outside air temperature
- Cultural advantages: avoid travel for firewood, avoid deforestation.
- Cultural barriers: round vs. square, inhibitions about using the sun's
- Books: Heavan's Flame (See www.homepower.com), etc.
- Barbara Kerr, P.O. Box 576, Taylor, Arizona 85939 USA.
- History: The first solar cooker we know of was invented by
Horace de Saussure, a Swiss naturalist experimenting as early as 1767. Later
developments by Herschel, etc.
- Solar Cookers International: Sponsors the solar cooking
- Projects in many countries, early projects mostly
failed, some later successes.
- 100,000 cookers in use in both India and China.
- The solar box cooker project in the Indian Himalaya, sponsored by the
Indo-German Dhauladhar Project: earth and brick ovens double glazed with
glass. An inner tin oven is fabricated from used ghee or oil containers.
Husk from a rice sheller provides insulation around the tin oven.
- Recent major breakthrough by Solar Cookers International using the
Bernard panel sun cooker.
- Making your own:
- Glazing; tempered glass, low iron, avoid plexiglas. Double glass/low-e
glass increases temperature
- insulation: cardboard, aluminum foil (radiant reflector), feathers
(down feathers are best), spun fiberglass, rockwool, cellulose, rice
hulls, wool, straw, and crumpled newspaper.
- angles and reflector strategies
- inner surface: foil, Aluminum flashing. Reflective sides, black
bottom. Black paint should be thoroughly cured, and never in contact
with food (especially metallic paints).
- Using it:
- Wear sunglasses - retinal damage cannot be felt
- Cure an oven first before using it
- Some people report difficulty with odors from brocolli and similar
- Watch out for burns with parabolic ovens.
Review of previous class:
- Algebra and units of ten: simple examples
- Basic Names and units
- Nominal Solar intensity ("irradiance") outside Earth's
atmosphere: "Solar Constant" ~ 1367 w/m2
- Nominal Solar intensity ("irradiance") at Earth's Surface:
"One Sun" = 1000 w/m2
|electricity for houses
||watt = Joule/second
kilowatt-hour (kwh) = 3.6 million Joules = 3,413 Btu
1 Ton = 12,000 Btu/hr
||British Thermal Unit (Btu) = 1055 Joules = raise 1 lb of water 1
Therm = 100,000 Btus
1MMBtu = 1 million Btus (10 therms)
1 gallon propane = 91,200 Btu
1 cubic foot natural gas = 1020 Btu
||gallon of gasoline ~ 34 kwh
||1 horsepower = 746 watts
|Output of utility scale wind turbines
|Output of power plants
||1 kg coal = 30 MegaJoules
|Powering the human body
||calorie = 4.184 Joules; heats one gram of water one degree celsius;
dietary calorie is 1000 calories
||dietary calories per day
- Simple calculations
- Calculate area needed to power US
- Calculate area needed to power a house: several hundred square feet
- Calculate area needed to power a car
- Scale of human body usage