A Summary of My Experience
Project Conducted Under the Guidance of Dr. Soboyejo
The purpose of the
project was to introduce engineering solutions to two villages in
Two schools were chosen. At one school, the Mpala school, standard one and standard two students were taught; at the other school standard seven and standard eight students were taught. Julianne Davis was the primary teacher for the younger class and Ishani Sud was the primary teacher for the older class. Both classes had slightly more than twenty-five students. Teaching took place two days a week at each school, focusing on issues like conservation, solar energy, and renewable vs. nonrenewable resources. The older student’s were able to explore more complex topics including the relationship between the earth and the sun.
The older students also spent one additional day each week physically building the solar ovens. Small experiments were conducted throughout the building process to help students understand specifically how the ovens functioned. The final step involved a “parent-day” during which the students shared with the parents what they learned. The older students also showed their parents how the solar ovens work. Care was taken to explain the oven’s usage in a culturally sensitive manner, explaining how local recipes can be adapted for cooking in the solar oven.
Several other projects were also started, including solar charged lanterns for lighting in an ecotourism lodge and solar panels for charging batteries for a mobile clinic. Designs were also developed for a solar/manual pool pump and a solar hot water heater.
The objectives of the
project were to introduce engineering solutions to two villages in
Two different classes
were selected for instruction. The
classes were at two different schools.
One class consisted of standard 1 and standard 2 students. The other consisted of standard 7 and
standard 8 students. The goal was for
the students to understand how the solar ovens worked and also understand why
they are a better option than burning wood.
Curriculum was developed using standard templates for teaching. Nancy Rubenstein, a registered teacher in the
For the older students, a series of demonstrations were developed to qualitatively introduce the concept of material selection for the solar ovens to the students. These included: black metal vs. white metal in the sun, metal vs. wood in the sun, and glass allowing light through.
FIGURE 1. Solar Cooker Basic Design
Figure 1 shows the basic solar
cooker design. For this project, the
cooker design was built and tested at
The purpose of component A in
Figure 1 is to optimize reflection of sunlight into the solar cooker. For component A the most reflective locally
available material within cost restraints should be selected. Component B should be a highly transmissive
sheet that allows light through, but also has insulative properties. This could be a number of materials (glass,
plexiglass, polymer sheet, etc.)
Component C should be a highly absorbent layer or material. This material converts solar radiation into
heat. Care should be taken to select
materials that can withstand high temperatures without burning or releasing
toxic gases. While boiling water within
the cooker, the water vapor within the cooking chamber will increase, making
black cloth a better choice to common household paint. D denotes the convective heat transfer from
the component C to the air within the cooking chamber. The equation governing this property is
TW is the surface temperature of Component C (K), T0 is the air temperature (K), and h is the heat transfer coefficient (W/m2K). Component E is an insulative material. There are two criteria for the component E. First, the heat diffusion through the material has to be small enough to allow the cooking chamber to reach a sufficient temperature. Second, the diffusion rate should be low enough to allow sufficient cooking time before the exterior of the cooker reaches unsafe temperatures. The equation governing this property is:
Where t is time, λ is the thermal conductivity, Cp is the specific heat, and ρ is the density. Heat diffusion is minimized by minimizing (λCpρ)1/2 (Ashby, 1993). Given a certain choice of materials for insulation, based on cost and availability, the material with the lowest (λCpρ)1/2 is therefore the best choice.
were developed at
Unique Approach to Teaching
Lessons were kept as simple and active as possible. An effort was made to include a variety of material and teaching techniques. Also, crafts and active demonstrations were included to help students understand concepts despite a language barrier. For example, on the first day of class, the older students learned about the solar system. They painted and put together solar system models. The active demonstration was physically modeling how planets farther from the sun require the longest to make a full revolution. One student was selected as the sun. Nine students then formed a line and were assigned a planet corresponding to their position in line. The students then “orbited” the sun, counting the number of steps required for them to complete the revolution. The students then reported the number of steps they took, and the students could see that Pluto has a longer orbit than Mercury.
It quickly became apparent that the typical method of teaching was dictation and memorization. Emphasis was not placed on understanding. When students were asked if they understood, they always replied “yes,” whether or not they had absorbed the material. Therefore, an attempt was made to ask questions to determine whether or not students had understood material. For example, a student might be asked if Jupiter’s orbit takes more than or less than 365 days.
The last day each week, for the older students, was devoted to physically building the solar ovens. Students were divided into four groups of six students. Each group had one adult supervisor. The students took pride in their work and were able to understand directions.
The solar cooker can be optimized by optimizing each of the component pieces. Therefore, testing can either be done on each piece individually, or in a controlled environment a single component can be varied at a time and the difference in overall temperature noted. When working in undeveloped areas, the second method of testing might be the easiest.
One test that can be done is measuring the temperature within the cooking chamber as a function of the angle of component A relative to the box. This should be done under controlled conditions, where only the angle is being altered, with the luminosity and exterior temperature being held constant.
GRAPH 1. Time vs. Temperature for Varying Angles of Component A
Graph 1 summarizes results
A parent day was held at each of the two schools. The parent days were held on Saturdays. The entire village communities were invited. In addition to sharing material with the parents, students at the schools that could not be a part of the classes due to size constraints, had a chance to participate. The parent days included a variety of activities including crafts, games, and demonstrations. The demonstrations included the students creating a sundial using a metal rod and rocks to mark the hours, placing black and white metal in the sun, and inflating a balloon using baking soda and vinegar. The children were particularly intrigued with the crafts stations where they had popsicle sticks, Styrofoam, paints, paper, pipe cleaners, and a variety of other standard craft materials. Many of the parents, the mothers in particular, were quite young and enjoyed games like jump roping.
There were a number of unique issues that future students should be aware of. The first is probably the most obvious, there is a language barrier. Even with a translator, all issues cannot be resolves. First, it takes considerably longer to teach through a translator. Second, complicated explanations are completely lost in translation. Lessons and explanations need to be communicated in small pieces with plenty of visual aids.
Also, there is not a
Better Business Bureau, or any means of formal complaint if you are unhappy
with customer service. For example, a
local wood company claimed to be providing
Logistics can also create some problems. Road conditions and transportation can be difficult. Things do not always happen on time and shipments can take a very long time to arrive. One should be careful and allow plenty of margin time in schedules. Also, goals should be reasonable and not incredibly ambitious.
In some sense, it seems like I learned more from the Mpala community
than I was able to teach them. The
experience was truly wonderful. The
locals have a very rich culture, and it was amazing to see how the children
entertained themselves without any toys.
It was also the first time I had a chance to see a number of species of
animals outside of the zoo. The locals
knew to be afraid of elephants, I did not.
They were amazed when I told them that we can pet elephants at the
circus, or that I had ridden elephants in
This experience was truly unique. For the first time I could see the potential for engineering solutions in the third world. Simple ideas and designs are greatly appreciated by the locals and have incredible potential.
Mrs. Rubenstein and Dr. Rubenstein
Dr. Miguel Centeno and PIIRS
Dr. Bruno Bosacchi
Mpala Research Centre Administration and Staff
Global Science Club
All students and friends who helped Julie and I prepare and plan for the trip
Ashby, M. F. Materials Selection in Mechanical Design.