Mpala, Kenya: A Summer of Teaching, Research, and Learning




A Summary of My Experience

Ishani Sud




Project Conducted Under the Guidance of Dr. Soboyejo



            The purpose of the project was to introduce engineering solutions to two villages in Kenya.  This involved extensive planning and research at Princeton University prior to the trip, followed by six weeks of implementation within the Kenyan community.  One of the main purposes was to introduce the communities to solar solutions, specifically the use of a solar oven instead of wood fueled stoves.  The solar oven was developed at Princeton University by Ishani Sud and Lauren Wang under the supervision of Dr. Soboyejo.  To facilitate the technology transfer, the local schools were chosen as the vehicle of delivery. 

            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 Kenya and educate local school children about solar energy and conservation. The main solar solution provided was that of the solar oven.  The solar oven project began within the framework of the food group which was part of the Global Science Club at Princeton University.  It was designed and developed by Ishani Sud and Lauren Wang under the guidance of Dr. Soboyejo.  The design objective was to create a solar powered cooking/drying apparatus for rural areas at minimum cost.  Therefore, the focus was on using locally available materials.  In addition to designing the ovens, a main objective was delivering the technology in a culturally sensitive manner that the locals could accept and incorporate into their own lives. 





            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 United States assisted with curriculum development.  Ishani Sud prepared the curriculum for the older students, and Julliane Davis developed the curriculum for the younger students. The conceptual topics to be covered included conservation, food webs, the solar system, and renewable vs. nonrenewable resources. 

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.


Solar Ovens

            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 Princeton, NJ.  However, building with the dimensions and materials used in Princeton was not practical in Kenya, so modifications were made.  The general idea was to find the best material available for each of the solar cooker components while taking into account cost and availability. 

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 Newton’s law of convection:




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.

            Several prototypes were developed at Princeton based on the design in Figure 1.  Based, on the success of these models, it  was determined that optimizing the model for Kenya would require selecting the appropriate metal, black material, wood, and glass based on their respective purposes.  The equations and process included here provide an ideal method of selection.  In Kenya, much of the selection was governed by availability.


The Experience


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. 


Solar Ovens    

            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 obtained from Kenya over the summer of 2005.  The materials used were Cyprus wood, black cloth, aluminum metal, and glass.  Certain items should be noted.  First, due to logistical problems, only one thermometer was available.  It is impossible to know its degree of accuracy.  Second, the exterior temperature was not constant, and the position of the light source (the sun) was not constant.  Therefore at one point 50 degrees might result in direct sun reflection into the cooking chamber, while at a later time point this may no longer be true.  In practice the position of component A can be adjusted by the user based on the sun’s position.  Also, the box used for these experiments was carefully assembled using all necessary tools.  Results may vary in villages where quality may vary due to lack of needed tools.  However, the above graph demonstrated the potential range of the solar ovens.


Parent Days

            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. 


Unique Issues

            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 Cyprus, but actually sold pine.  They placed a layer of Cyprus on the top.  It is important to make sure you carefully inspect any material that is purchased.

            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.


My Experience

            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 India.  Also, being at a biological research centre, I had a chance to learn from other researchers about their projects.

            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.




Dr. Soboyejo

Laurel Harvey

Mrs. Rubenstein and Dr. Rubenstein

Dr. Miguel Centeno and PIIRS

Jody Whitehead

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. New York: Pergamon Press. 1992.