Summary of this project
by Lorin Symington (dec. 2008)

What type of concentrator was built?
A Helios bread oven.

Where and when did the construction occur?
Bamako, Mali between the 26th of December 2007 and the 13th of January 2008.

How much time did the construction take?
18 days from start to finish so around 15 days of work. I must warn that these numbers are not particularly accurate in their representation of the amount of work that goes into a Helios because the tools we were using were uncooperative, we needed to re-build a couple of components and I was very often away from the workshop, searching for more tools and materials. Based on the experience I would say that two people working for two weeks in a well equipped shop could build a Helios.

How many people participated meaningfully in the construction?
5 people participated from start to finish and another dozen or so watched or chipped in here and there.

Where is the machine now? Has the machine traveled and if yes, how?
The machine is now on the Hill of Badalabougou at the National Center for Solar and Renewable Energies. The machine traveled in a pickup truck around Bamako to be demonstrated at a number of events. To move it, we took the mirrors off the rakes and packed them in a wooden crate, which we placed in the truck bed along with the oven. The rakes and the rest of the structure were tied to the overhead rack. I think it is possible to pack two Helios’ in a pickup such as the one we were using, which was midsized. We found that it would take two knowledgeable people around 2.5 hours to unpack, mount and focus the machine and around 30 minutes to pack it back into the truck.

What materials were recycled or borrowed and what was bought?
All the materials were bought.

Why?
Firstly, because we were in a hurry. We didn’t spend much time looking, though, because it quickly became evident that there was not a great deal to recycle. We tried a little bit, but everything of value is recovered very quickly by people who make their living staking out the junkyard and sorting through trash as it comes in. After the construction was finished, I visited the markets where recycled goods are made and sold, but the materials are of low quality, often rusted or hammered back into shape (and thus weakened). Broken mirrors are not easily found, as even small pieces of broken mirrors are used in households. With more experience and knowledge of the area I believe it is possible to reduce the cost of the machine slightly by recycling and reusing bits and pieces, but nevertheless, the majority of the materials will need to be bought new.

How much did you spend?
210 000 F CFA or 320€.

Did something cost more than predicted? Why? As a consequence, were any alternatives considered or developed?
Mirrors were slightly more expensive that predicted at 7000 CFA/m2. Closer to an industrial center or in bulk, they should cost about half that. We visited many glass and mirror vendors and this price was the cheapest by 2000 CFA/m2. We experimented with white wood glue as opposed to Bulldog Industrial Adhesive, which cannot be had locally. It worked well enough for the time being, but I have some doubts about the long term durability. High temperature ceramic glass for the oven is another component that cannot be had locally (and is expensive), but thanks to the engineers who developed the Scheffler Reflectors, we discovered that it is possible to use normal glass so long as it is cut into strips no more than 5cm wide (thus our normal 30cm x 30cm oven window is cut into 6 strips 5cm x 30cm)

Is the machine still being used today? If yes, for what?
I believe the machine is still at CNESOLER and is used for demonstrations from time to time.

How is the machine aging (detail the climatic conditions)?
After 4 months in semi arid conditions (hot and dusty) and more mounting/dismounting than any domestic array will have to endure, there was no sign of wear and tear.

What were you able to cook with the machine?
Bread, cakes, chickens, rice, soups & stews, potatoes, eggs, roasts, pizzas… anything you can make in an oven.

What technical data do you have on the machine?
Few, unfortunately. Our first oven had some obvious shortcomings and so I delayed comprehensive testing until such a time as we were happy with the final design. Regardless, I can describe the oven we were working with and some rough performance figures. The oven: length 90cm, width 45cm, height 80cm. The walls were in 7/10th black tin and were 5cm thick, filled with fiberglass insulation. The useable interior cooking space was 80cm by 35cm by 40cm. At noon the temperature rose to 300 degrees C in 30 minutes. The Helios has 54 mirrors measuring 30cm by 30cm, giving a total surface area of 4.86m2, mounted on a frame 25 degrees from vertical.

Was there any economic activity developed around the concentrator?
At an event concerning women entrepreneurs, we baked and sold cakes, but no regular or long term business was conducted.

What could be improved on this machine and how?
The oven is still not optimized for size and heat distribution. The system of cables to control the mirrors has a few slight problems which would be solved by proper spacing of the arms on the back of the rakes. The design of the structure must be adjusted so that the oven end of the main beam is higher, so that the window of the oven is between the second and third row of mirrors.

How did people react when shown the machine?
Above all, surprised. When the stick of wood bursts into flame the thing we heard most often was an exclamation of "It’s not possible!" Upon learning how the machine works and how it is made, people said that solar is necessarily the future of Mali since sunlight is one of the few things Mali has in abundance (another is sand). Many people thought that the machine was too big and I was often asked to make one smaller, but without diminishing the power (!). Many people thought it was expensive and that to really popularize and diffuse the technology, cooperatives and institutional micro-lending would be key. On a handful of occasions I was told that it would never catch on because the Malian woman wants either her traditional wood fire or the gas stove of the European woman.

Did you organize demonstrations or educational events?
We organized the Exhibition of the prototype Helios at the ’City of Children’ in Niamakoro, where we demonstrated the capacities of the Helios to members of government, civil society and the public. The Helios was also demonstrated at a number of other events, including the Forum National pour l’Environnement organized by the NGO Mali-Folkecenter Nyetaa, The National living-space Salon of Bamako 2008, The Week for Entrepreneurial Women of Mali, and the international journalistic conference « L’Afrique face aux enjeux majeurs de l’environnement ».

After this construction, how many people do you think know how to make this concentrator?
3 people