Week 1 Stove Development

This week, the stove group spent 4 days in the AISE workshop with Bernard further refining the stove design. It was exciting finally getting to see and test the hard work of the spring travelers after only reading about it and seeing pictures of it last term. After an initial test, we started to make modifications to alleviate concerns brought up while our group was in Hanover or by the Spring travelers.

(Note: The tests we have been performing have been using sawdust. As of this moment, we have not yet been able to acquire coffee husk in addition to the fact that sawdust is readily and cheaply available. Future design plans hope to be able to burn fuels regardless of their density e.g. both coffee husk and sawdust)

In development of the stove during this trip, we are focusing more on how to make this stove viable in the marketplace. Concerns that were apparent to us was the overall cost of the stove (at ~45,000 TSH while our target is 20,000-30,000 TSH), the need to replace the inner wire mesh insert (due to the lack of durability of wire mesh), and the length of burn (which at ~1 hour is not sufficient to prepare traditional food). We have been inspired by the Kisangani Sawdust Stove produced by the Kisangani Smith Group (KSG). This stove has been very successful as a cost effective stove, lacking our wire mesh design, and producing an incredible burn duration of 6 hours. Initial distribution has also been incredibly successful. We have reached out to KSG and they have an extended an invitation to meet in person and speak about their project. If time permits on this trip, we would be very interested in traveling to Kisangani and meeting KSG.

From the initial burn, we noted that the stove burned hot and steady for about an hour but was not a particularly clean burn. When analyzing the new design of the Spring travelers, we guessed that the additional outer holes in the bottom of the stove that vent air into the fuel bed were inhibiting proper pyrolysis and causing some of the improper combustion. Using one of plates from an old stove, we covered (and have continued to cover) these outer holes. Burns showed that this did not make a marked difference in the burn temperature or time but slightly improved the cleanness of the burn.

Keeping the Kisangani design in mind the next day, we tried to pack our fuel much like how it is packed in the Kisangani stove. We removed the wire mesh insert and placed a small wood log in the middle of the stove before loading the fuel. As we loaded the fuel into the fuel canister, we compressed the fuel. After completely filling the canister, the log was carefully twisted and pulled out leaving an intact chimney. Initial tests were tremendously exciting. We achieved burns of over 1.5 hours (time was limited due to the working hours of the workshop on the day of that test, but much fuel was left unburned) that were very hot with almost no smoke produced. The burn continued steadily without tending which was a major concern in previous models. We were tremendously excited about the possibility of removing the wire mesh from our design as well as the longer burn time initially exhibited before the test was stopped.

However, the initial success proved not to be repeatable. For the same afternoon, we only made one modification, hammering out the flanges on the plate we attached to the bottom of the stove to allow more primary air to reach the stove. The subsequent test that afternoon started with the same intensity, but stopped only 10 minutes into the test. Due to the high wind that afternoon and the fact that the flanges probably played some role in mitigating the effect of wind in the previous test, we concluded that the wind of the day limited the success of that test.

Unfortunately since then, the 3 tests we have run have not produced the same strong burn of the first day. Modifications we have made have been to cut the center of the bottom of the stove out to allow increased primary air and to hammer the flanges on the plate back down to imitate that initial successful test. From these tests, we have noted 2 major issues currently. First, with the pot on the stove, it seems as there is insufficient updraft to provide the necessary oxygen for combustion. Each time we place the pot on the stove, the burn will stop within 3 minutes. Without the pot on, the stove will continue burning for longer. Second, it seems as though the white ash building on the center of the chimney insulates the unburned fuel from air and heat.

During this last week, we were tantalized by the single very successful test that produced most of the characteristics we want our final product to have. In the coming week, we will continue trying to reproduce that successful test. Furthermore, we are planning on attempting to recreate the Kisangani stove to better understand their successes and how to improve upon them. We are hoping this next week will prove fruitful towards development of our final product.