fueled Jiko and a Jatropha-Oil fueled Lamp
by Erwin Protzen, November 1997
Development work took off in mid-May 1997. The guiding idea throughout has been that any designs for Jatropha jikos and lamps should, to simplify the exercise, at least start from existing standard designs for spent engine oil and kerosene.
A functioning prototype jiko and two functioning prototype lamps have been developed. The work has not been as easy as was originally anticipated. The lamps can be sent to the field for testing, but some development work in connection with wicks and air supply still needs to be conducted in the case of the jiko.
Unfortunately Jatropha oil has not been as available for development activities as would have been hoped. All that was available, were four litres of Jatropha oil and most trials were done with substitutes that perform similarly.
Vegetable Oils as Fuels for Jikos and Lamps
Some simple basic research has been conducted on burning vegetable oils using standard textile wicks. This research has been done on one hand, to find a substitute for Jatropha oil that would allow work to continue despite its scarcity, and on the other to get an understanding of vegetable oils as fuel. The cheap standard jikos and lamps, available in Tanzanian shops, all have wicks.
Experiments were done with oils from the following plants in addition to Jatropha:
The findings can be summarized as follows:
Experiments have been conducted primarily with a very simple lamp. A Æ ¼" copper tube is cut to the length of a small glass and a Æ ¼" wick is fed into it.
The tube with the wick in it is placed into the glass which is filled with oil. Incidentally this lamp is simpler than the kerosene "kibatari". Since vegetable oil does not readily ignite, the reservoir (glass) does not need a cover. The tube with the wick simply stands in an open container with oil.
Originally it was thought that all findings made with the lamp can be transferred automatically to the jiko. This is not absolutely the case, so oils have had to be tried again in the "Butterfly" jiko once it had been modified for use with vegetable oil rather than kerosene.
| Oil | Performance in Jiko | Performance in Lamp |
| (Modified Butterfly) | (Æ ¼"copper tube with Æ ¼" wick dipped in oil) | |
| Jatropha | Burns 2 hrs, smokeless | Burns 4 hrs |
| Wild Borage | Burns 2 hrs, smokeless | Burns 4 hrs |
| Mexican Poppy | ? | Burns 2 hrs |
| Sunflower | Burns ¾hrs, smoke | Burns 2 hrs |
| Safflower | Burns 2 hrs, smoke | Burns 4 hrs |
| Sesame | Burns 2 hrs, smoke | Burns 4 hrs |
| Macademia | ? | Burns 6 hrs |
The Development of a Prototype Vegetable Oil Fueled Jiko
There are a number of directions that might be taken in the development of a simple and cheap Jatropha-fueled jiko. As far as the conditions of the current assignment have permitted, two such directions have been looked at in some detail:
The principle made use of here, is that if water is added to oil with a temperature higher than that of the boiling temperature of the water, the water will evaporate instantly and disperse oil in the form of fine droplets which will burn easily if ignited.
In a jiko that makes use of this principle, oil and water are dribbled onto a cascade of hot steel plates in its combustion chamber. The water evaporates instantly and in so doing disperses a mist of oil that readily burns in air that is drawn into the chamber by a chimney.
An informal artisan in Arusha manufactures quite large jikos of this type for cooking and baking with spent engine oil. A smaller prototype copy as seen on next pages has been made for use with vegetable oils.
How to Fire the Prototype Oil-and-Water Jiko forVegetable Oils
When the jiko is fired for the first time, the two tanks at each side are filled with water and oil respectively. The door at the front of the combustion chamber is opened, the bench forming a simple cascade is withdrawn, and some ashes are strewn onto the bottom of the chamber. A little kerosene is poured onto the ashes, the bench is replaced, and fire is set to the kerosene. When after about thirty seconds to a minute the bench is hot, the oil and water valves are set to allow a very fine stream of oil and about thirty to sixty drops of water to enter the chamber through the funnel onto the upper plate of the bench. The oil will start to burn with a sizzling noise and after a while the door can be partially closed. Cooking takes place on the hot plate covering the opening on top of the jiko.
To extinguish the the fire, water and oil are simply turned off.
For any subsequent firings, the level of oil and water in the tanks is checked and kerosene is poured onto the ashes which are already in place at the bottom of the combustion chamber.
Modification of a Chinese Adjustable Wick Wheel Brand Stove Model 641
The Wheel Brand Stove Model 641 is very easily available in all places in Tanzania in which kerosene is available. The modification of this stove has consisted of lowering the wick adjustment mechanism into the oil reservoir so that the combustion zone is just above the oil level when the tank is full.
After the modification, the chimney which sits on the wick mechanism, obviously also comes down. The bottom edge of the chimney actually fits into the tank and is just above the oil. For any sensible results the outer mantle of the chimney has to be removed from the inner perforated core and raised to allow air to circulate freely. In actual fact the outer mantle was raised by 35mm with wooden blocks, sowith bringing it back to its original position under the cooking ring.
Modification of a Chinese Adjustable Fuel Butterfly Brand Stove Model 2413
The Butterfly Brand stoves are difficult to get in Tanzania but they are popular in Kenya. The modification has been very simple.
The flat wick of this stove, which is made from some metallic material interwoven with asbestos, lies in a groove that contains fuel, the level of which is maintained by an inverted bottle. This level has been raised by 8mm with leather spacers placed between the bottle and its holder.
To adapt the air supply to the requirement of Jatropha, openings have on one hand been cut into the bottom of the chimney core, and on the other, the whole chimney has been lifted by 3.5mm from its seat with metal strips.
How to Fire the Modified Adjustable Fuel Butterfly Brand Stove
The standard special wick for this type of stove is designed for longevity with kerosene as a fuel. Evidently it cokes up and becomes useless very quickly with vegetable oils. For the purpose of experimentation, cheap disposable 5/8" flat textile wicks have been used. They were cut to pieces of 30mm length for placing upright into the fuel groove.
When the jiko is fired up for the first time, the fuel bottle is filled and placed up-side-down into its retainer and onto the leather spacers. The three metal strips for lifting the chimney are pressed onto the outer lip of the chimney holder, the fuel valve is opened fully, twelve wicks are stood upright in the fuel groove (four to a partition between strips), and when they have properly absorbed fuel they are lit. After about a minute, the wicks are burning properly and the chimney can be placed over them. After a further few minutes, a blueish yellow flame emerges at the top of the chimney.
Producing very little smoke, the flame will burn for about two hours. It is possible to bring a litre of water to the boil in 15 minutes. After that, it will start to diminish, the wicks have coked up. At this point the fuel valve is turned off.
Prior to a subsequent firing, the jiko needs to be cleaned up. The chimney is removed and its bottom edges are cleaned up by scraping. The burnt out wicks are removed and thrown away. Coke and tar are removed from spacer strips and the fuel groove.
Comments on the Performance of the Various Prototype Jikos for Vegetable Oils
As a prototype each one of the jikos made or modified has its advantages and disadvantages. Lessons have been learnt with each one.
Experiments were conducted with a number of oils, whereby Jatropha and Wild Borage have proved to be superior to others.
The oil-and-water jiko is very simple, but it produces quite a lot of smoke that needs to be drawn off by a stack. It might be difficult to miniturize this type of jiko and therefore, if considered for further development it would be developed for larger kitchens as is already the case with the jikos fueled by spent engine oil.
The modified adjustable wick jiko can be adjusted to burn free of smoke, but wicks coke up the same as they do with the adjustable fuel jiko. It does not develop enough heat for any sensible cooking.
For the time being, the modified adjustable fuel jiko is the most exciting to demonstrate that it is possible to use vegetable oils such as Jatropha oil as a cooking fuel, despite the coking up of wicks after about two hours and some little smoke production.
The Development of Vegetable Oil Fueled Lamps
Development work has led to two lamps, both of which work quite satisfactorily.
A simple tool has been made for wrapping sheet metal from old tins to form tubes that will accommodate standard ½" flat textile wicks. After wrapping, these tubes are kept from springing open with some wire which also serves as a hanger for the tube in the oil container.
A lamp made in this fashion can be used as is or with a standard lamp glass placed over it to protect the flame from wind.
The Modification of a Chinese "Moon Light" Brand Kerosene Lamp
Important for any modifications are the findings on vegetable oils as fuel presented at the beginning of this report. For for a lamp, this means specifically:
1. The oil must be brought as close to the burning zone of the wick as possible, and the wick needs to be contained in a tube.
The wick advance mechanism is taken apart.
The inner actual advance is turned round
Remove 10mm from the bottom of the outer shell and likewise from the perforated (new) bottom of the advance mechanism, leaving three stays.
Bend the stays outward and reassemble the mechanism. Solder the stays to the outer shell.
One is left with a shorter advance mechanism that has a tube sticking out of the bottom.
2. The oil level in the fuel tank must vary as little as possible over time, so the fuel tank should be as broad as possible and as shallow as possible.
Mark the original level of the base of the wick advance mechanism on the uprights of the lamp. Go up 10mm and cut the tank away.
Make a new tank from old tin cans about 1½" high and 6" in diameter, with openings for the wick and the screw cap from the original tank.
The modification of the advance mechanism creates a circular groove at the bottom. Bend a ring from Æ 2mm wire to fit into this groove and solder it onto the new tank at the opening for the wick. On one hand the ring centres the advance mechanism and on the other it prevents oil from spilling out of the tank when the lamp is being moved around. Also solder the screw cap into the new tank
3. The air requirements for vegetable oils and kerosene are different. Cut away the air quide from the bottom glass holder.
4. Drill an air hole into the screw cap.
Some General Comments on the Performance of Developed Lamps
A wick is drawn into the tube of the "kibatari" type lamp and then it is hung into a contianer of oil and lit up. Especially with a glass over it, the performance of this lamp is very rewarding. Because of the overlapping edges of the sheet metal the lamp burns for about six hours before coking up.
Once all modifications have been undertaken on the "Moon Light" lamp it is assembled quite normally, filled with oil and lit up. This lamp burns for about three hours before coking up. Once this happens the flame gets smaller and the light gets dimmer. In this case, the glass is tilted away, the coke is knocked off with a match stick, the flame is reset and the glass is replaced.
As can be imagined from elaborations at the beginning of this report, both lamps perform satisfactorily with a number of vegetable oils, especially Jatropha, Wild Borage, Safflower, Sesame and Macademia.
Some Concluding Remarks and Recommendations
The work reported on has shown how vegetable oils can be utilised for lighting and cooking purposes.
Whereas the developed lamps can be put to test in the field immediately, some more development needs to take place with the jikos.
The results obtained with the modified adjustable fuel stove are very promising, but the need for a thorough clean-up and to replace wicks after each firing is disturbing. Following topics must be investigated further:
a) Air supply
b) Wicks
As far as the lamps are concerned a poor man’s version and a wealthy man’s version have been developed.
The Chinese stoves are relatively cheap at Tsh 14’000 for the adjustable wick version and Tsh 25’000 for the adjustable fuel version. Nevertheless they are unaffordable for the poor man.Therefore some more investigation needs to take place in the direction of different principles.
c) Different principles
This list of topics that need to be looked at further is by all means not exhaustive. If the started work were to be continued, some more thought would need to be put into it.
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Attachment 3, Technical Sketches for Oil-and-Water Jiko
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