- Decrease amount of harmful smoke and toxins in homes.
- Decrease CO2 emissions
- Decrease amount of fuel needed, thus lessening the amount of violent crimes and rapes that occur during gathering
- Keep food warmer for longer
- Cultural boundaries
- Unlike traditional African cooking methods
- Integration into daily cooking methods – We tried to stick with materials that are readily-available in African villages, making the product as appropriate for the culture as possible.
- Wood: $35
- Rice Hulls: $9
- Fabric: $10
- Chicken wire mesh: Free
- Total: ~ $50
Women who do the majority of the cooking in small villages in Uganda, Africa. Uganda has a population of 39.03 million. Uganda has a young population that is growing rapidly. Uganda has one of the highest fertility rates in the world, with 5.8 children per woman. The infant mortality rate is 57.6 in 1,000 live births. The life expectancy in Uganda is 55.4 years. The inflation within the country is at 5.6%. GDP per capita is $2,000. 78.4% of those 15 and over are literate, 16.2% of males and 18.7% of women have attended secondary school. The families of the area tend to be male-headed and follow Christian faith. Children and mothers tend to do the cooking and house work. The community as a whole is very keen on sharing food and other resources. The country exports coffee, fish and fish product, tea, cotton, flowers,horticultural products, and gold. Uganda mostly imports capital equipment, vehicles, petroleum, medical supplies, and cereal.
- Blanket / Basket
- Vacuum insulation
- Wonderbag ($35-40)
- Can reduce a family’s fuel usage by up to 30%
- Food won’t burn – 20% of food in Africa is burned using current cooking methods.
- Material: recycled chip foam which is a byproduct of mattress and furniture manufacturing in South Africa, that would otherwise go to landfill or be dumped in the ocean -you might consider a heavy fabric bag immersed in rice hulls? This might be easier to use and cheaper than the wire mesh interior that you have.
- 1 million Wonderbag users accounts for 500,000 tons of carbon saved
- As of 2015, the Wonderbag has:
- prevented 2 million trees from being cut down
- dramatically reduced the number of rapes that occurred during fuel collection; firewood collection now happens only once per week
- Saved $36 million in poor homes
- Reduced indoor air pollution and smoke inhalation by 80%
|Cost ($)||Size||Ease of use||Compatibility||Portability||Insulative?||Total|
|Rice Hull Box||9||10||7||8||3||7||7.8|
Fuel Consumption in Uganda:
6 trips of firewood each month – each trip costs $84
$1,512 spent on fuel collection each school term
Each school term lasts 3 months
$2.02 per person per school term
avg number of family size in Uganda = 4.7
2.02 x 4.7 = 9.49
Multiply by 4 to account for BOH’s savings by buying in bulk
It costs $37.98 per family per school term
37.98 x 4 school terms = 151.91
An average family in Uganda will spend $151.91 on fuel collection per year
(Calculated from numbers from Beacon of Hope)
Model of our cooker as a cylinder of length L and outer radius r2 with a cylindrical cavity inside with length l and radius r1. The k is the coefficient of thermal conductivity.
(The following equations for our model came from Pete Schwartz’s ISEC paper “Insulated Solar Electric Cooking – Tomorrow’s healthy affordable stoves?”
The temperature of the interior at time t is given by
Tt -Tt-1= E/mC
Where Tt and Tt-1 correspond to temperatures (in kelvin) at the current time t and the temperature at the previous timestep t-1. E corresponds to the change in energy inside the cavity.
The energy E inside the cylinder is being lost to the outside environment at a rate E=P(T)*dt
Where P(T) is the amount of power entering the system (we expect this value to be negative since heat is leaving the system). The T in P(T) indicates that this power will change as the internal temperature changes.
P(T) is given by P(T)=(Tt-Tout)/R where Tout is the temperature outside of the r2 cylinder and R is the thermal resistance calculated from our model.
R comes in three portions, an open-ended cylindrical shell given by Rc=ln(r2/r1)/2lc
And two shorter, solid cylinders given by R1,2=l1,2/r22. The total thermal resistance of our system is calculated using the inverse relationship of parallel resistors, 1/Rtot=1/Rc+1/R1 +1/R2.
Now we can solve the theoretical curve Tin (t) numerically using our recursion relation and compare to the data we’ve taken.
Ideally, the data will match our theoretical model so that we can alter the system based on needs like how long the food needs to cook, how much space is available, how much water will be put in the cavity, and what the Tout is. All of these parameters will affect the time to reach the danger zone Tin(t)=60 C.
The theoretical curve does not quite fit the data. Instead, the theory predicts that the Magic Basket is more insulative than it actually is (no surprise there). The theoretical curve didn’t take into account two things, convective currents carrying heat from the system, and the capacity for heat to be stored in the rice hulls themselves.
In future implementations of the magic basket, it may be cheaper to construct it from a bag rather than a wooden box. Another alternative would be to utilize the ground and dig a hole that is insulated with rice hulls. While this would be the cheapest option, it may be affected by rain or vulnerable to other damages. In terms of the impact that our Magic Basket would potentially have on African homes, we believe it would have similar outcomes as the Wonderbag by reducing carbon emissions, improving safety during fuel collection, and minimizing indoor smoke pollution.
This team really followed the motto “Weeks in the lab save hours in the Library” future groups should take this into consideration and save themselves time and money by doing their research first, doing some testing, and then building a model. Instead of following our method of building a model, testing, and then doing research.
John Robertson: Senior, Liberal Arts and Engineering Studies major
Cole van Brunt:
Maya Fernandez: Junior, Psychology major, Political Sciences minor. Wants to work in Restorative Justice in the future, enjoys long walks on the beach in the present.
Max Yarbrough: Senior physics major. I will be working toward my single-subject teaching credential starting Fall, 2017. After spending the past 9 years studying science and the technology it produces, I wish to focus on the community aspect of technology. I hope to learn about the misconceptions communities form regarding technology and its implementation such that I can help develop and implement safer and sustainable technologies.