Promotion of stoves has formed an important part of Liana (NGO) development projects in Northern Tanzania from 2009 to 2011.

As we wanted to offer some choice of stoves to families with very differing means and needs, nine of the better documented models or locally known models were introduced to the farmers in Mwanga and Moshi in the initial theory training sessions. Following an exercise in which each farmer selected a stove type s/he would like to have and could afford to have in her/his home, the number of potentially suitable stoves was reduced. As women became more aware of the dangerous effects of indoor smoke, having a chimney became more and more important and many models without chimney dropped out.

Thus we remained with four main stove models. These are Vita metal stove, Upesi burned clay stove, Lorena mud stove (or built with bricks inside) and a rocket Brick and cement stove. During the process two of the stove models, Vita and Upesi were considerably modified. Vita obtained a short chimney (90cm measured from the middle of the hole to the top, 8x8cm) and Upesi was developed into two slightly different new models, both with a fire grate allowing air intake to the fire chamber through holes in the grate.

As part of our project Save firewood by improved stoves we assessed the stoves. The report of this assessment has the results of the boiling point tests, controlled cooking tests and an interview study on user experiences in Mwanga and Moshi.

You can access the report from the following link:

La Estufa Lorena - INCAP
Instituto de Nutricion de Centro America y Panama, Organizacion Panamericana de la Salud (OPS/OMS)
centro de Aprendizaje e Intercambio del Saber en Seguridad Alimentaria y Nutricional del INCAP (CAIS/INCAP)Manual 11 2006

Insights Into Fuel Efficiency and the Dissemination of Mud and Ceramic Stoves in Southern Africa
Peter Scott, Biomass Energy Consultant, December 23, 2007
Lorena 2 Pot 2003Lorena 2 Pot 2003

Shielded One Pot 2003Shielded One Pot 2003
Dear all

I wanted to offer a couple of brief insights into the recent dialogue regarding fuel efficiency and the dissemination of mud and ceramic stoves in southern Africa

First, A little back ground:

I worked with GTZ-EAP in Uganda for 3 weeks in August of 2003 . During that time I built a number of metal and brick stoves - both household and institutional - as well as bread ovens and a number of insulated ceramic combustion chambers . I didn't design the 2 pot Lorena stove but I did offer some suggestions on its design .

When I arrived GTZ had already begun developing prototypes for the two pot 'rocket ' Lorena mud stove as well as a single pot shielded mud stove. I made a number of recommendations: that they insulate the combustion chamber of the 2 pot stove and follow some simple rocket stove principles (shelf under fire, internal rocket elbow geometry, insulation, and proper gaps for optimal heat transfer).

2 pot Rocket Lorenas in Kampala
A number of tests of these stoves were performed by GTZ using the original WBT/PHU testing protocol (GTZ-EAP has the test data and the specific results so Im hoping that Leonard Magerwa might post the test data - Leonard are you out there?) during 2003

From my recollection the results looked something like this:

2 pot 'insulated' Rocket Lorena. Three versions were constructed and tested:
a.. -with pumice combustion chamber
b.. with 50/50 vermiculite c combustion chamber
c.. -with sawdust clay (unfired/non ceramic)

All of these stoves had very similar test results , something like slightly
above 30% PHU

2 pot mud rocket Lorena
a.. This stove performed slightly worse , something like 28% PHU

Single pot shielded fire mud stove
a.. This single pot stove had similar performance to the 'insulated' 2 pot stove. Around 30%. (sorry that's the best picture I have. Leonard , do you have a better one?)

Note: These 'lab' results are from the stove testing site that was set up in Kampala. They were built to exact specifications (stove built around 2 standardized pots and a 1 cm gap around both pots). As Dean and Tom pointed out, the stoves that were tested by USAID were most likely not constructed as per the original specifications nor were they used in the manner they were intended ( i.e. pots not submerged)

a.. The 'Insulated' versions all produced similar results in overall
efficiency even though they offer a spectrum of insulation quality : from
relatively high quality insulative materials such as pumice to a lower
quality insulative material such as unfired clay ceramic model .

a.. There was only a few percentage points of efficiency gained by
insulating the 2 pot stove

a.. Given the similarity of the results of the insulated stoves we could
conclude that in terms of fuel efficiency , the insulation of the
combustion chamber does not have a great impact on overall efficiency ie
reduction in fuel consumption. ( One would imagine that they had an improved
combustion efficiency, Unfortunately emission testing equipment was not
available during these tests but it did appear that the insulated stoves
were producing less visible smoke than the non insulated version)

a.. The un-insulated single pot chimneyless shielded fire proved to have
a similar efficiency as an insulated 2 pot chimney stove

Although these tests obviously aren't definitive they do point in a
certain direction which seem to support what Aprovecho has been saying for some time:

a.. Optimizing Heat transfer is important for reducing fuel consumption.
This means : using a skirt and/or tapering the slope underneath the pot so
that it reduces cross sectional area by .75 X

a.. Insulating the combustion chamber will have a greater impact on
improving combustion efficiency than it will on heat transfer and fuel

a.. With out standardization we can expect high performance or consistent

GTZ-EAP for a number of reasons - that they could elaborate upon - decided to promote the 2 pot Rocket Lorena ( my understanding is that the insulated version is promoted where possible, but due to poor access to materials,
it is the un-insulated version that is often produced in the field

When the stoves were designed it was recognized that they would face some significant dissemination challenges:

a.. Design drift. without proper tools and training the local producers
would not be able to produce the stove to the exact specifications of the

a.. Material substitution. Many owners would not be able to afford the
metal chimney that was needed for optimal use of the stove. Instead local
producers often made shorter chimneys out of mud that were difficult or
impossible to clean and very slow to generate draft due to their higher
mass .

a.. User 'error' Users using different size pots and not submerging the
pot into the stove. This would obviously decrease heat transfer , increase
fuel consumption and lead to increased smoke in the kitchen ie not produce
similar tests results as those produced at the Kampala test site.

The 2 pot sunken pot Rocket stove has been a meaningful experiment ( I would like to acknowledge The staff at GTZ_EAP (Phillipe Simonis, John Kutesakwe and Leonard Magerwa ) have worked very hard to produce a large quantity of stoves in a relatively short time period ( 50,000+ in 3 years)

Way forward?

Any household stove project is going to be faced with many challenges. How do we bring fuel efficient stoves to the people who can least afford them but need them the most?. How do we bring standardized stoves , which require technical ability , accurate tools and perhaps even advanced materials to these users. Who is going to pay for them if the users cant? It seems that that CDM mechanisms and factory production are one option for delivering
stoves to the poorest.

Of course, one avenue that has not been fully explore din Africa is dissemination of the single sunken pot shielded fire mud stove. Given the results of the testing done in Kampala in 2003 , it seems that there is potential for this stove to save fuel . Of course there is still plenty of opportunity for that stove to be poorly built and used.. Although given that it doesn't require two pots for it to work , nor an expensive chimney there is the chance that it could fill a certain niche in the stove world.

I can envision multiple shielded fire stoves being constructed in and outside of the house . Each stove sized to a specific pot. Since the stoves would be very low cost , the users could build many stoves as needed.

Its is an exciting time in the household stove world. We still have not come up with a fuel efficient stove and dissemination strategy to bring stoves to poor households in Africa. Its going to take a lot of trial and error , and
fumbling around in the dark to work out how to do this.

New Lorena Stove Design in Mexico
Dean Still and Jeremy Foster, Aprovecho Research, ETHOS March 2003

Dean Still and Jeremy Foster, ETHOS March 2003

Jeremy Foster is working on a new Lorena type stove in Mexico. Here are a few details:

Jeremy Foster:

I am located in and around Lake Patzcuaro, about a 4 hr. drive west of Mexico City. The closest airport, 1 hr. away, is Morelia, which has many flights from Mexico City. However, coming from the western US it is better and cheaper to fly to Guadalajara, 3 1/2 hr. drive in the other direction.

Total population in the region is some 600,000 of which about a quarter are pure Tarascan. The main features of the most popular Lorena model are: A 50 cm. dia. clay comal in front over a single firebox. Two smaller holes (18-25 cm.) are side by side behind, with separate tunnels leading from the comal hornilla. These holes are sized to a particular family's need and due to shape of ollas are sunk in no more than 5 cm. below the surface. All ollas and cazuelas are ceramic and round-bottomed. Clay comals are used pretty exclusively. Metal comals have been very unpopular.

I had thought at first I would build a plancha stove with cutouts for comal, etc. On reflection, it seems to me it might be better to modify one of these Lorena stoves using rocket stove principles in order to more directly compare the two. I have been experimenting with the local baldosas which appear very suitable. The most useful size is 30cm. which actually
measures a little under 11" square X 1 1/8". I have gotten an elbow as hot as I could then doused it with cold water with no ill effect. The drawback is that the interior size is only 4" square. They also make one measuring 14"square. By also using this one to make a 7" wide back, I have made one with interior size 4 3/4" X 4 3/4" which seems about right but involves a lot of cutting and wastage.

Am amazed and grateful for all the great advice pouring in. Certainly a lot to think about.

The baldosa cutting sequence is just great and my hacksaw just can't through a 14" baldosa anyway, although I wonder if a 14" chimney with 6" square opening might not be good power for a nixtamal stove.

Uganda, How to Build the Improved Household Stoves: A construction guide for the Rocket - Lorena and Shielded Fire Stoves, Energy Advisory Project, GTZ, Uganda Ministry of Energy and Mineral Development, Peter Scott, July 2005

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