edit this page Getting Technologies to the market by Christa Roth, Andreas Michel and Dr. Christoph Messinger
[top] [end]Wasteful baseline technology A survey conducted in 2003 in Malawi revealed that the majority of institutional cooking was done with firewood using ineffi cient technologies, including open fires (Figures 1 & 2). The Bellerive-type, which is an excellent, but expensive stove, was only found in a few places, as its selling price in Malawi is beyond the reach of most customers.
[top] [end]New technology that works better In order to create an improved and more affordable technology, GTZProBEC asked Peter Scott in 2004,from Aprovecho Institute, to apply the rocket stove principle to stoves, in Malawi, for 50 – 300 litre pots. The first prototypes were developed in 2004 in Mulanje and designed with a square combustion chamber. Much has been written in this magazine previously about rocket stove technology, and so we present only a very brief summary here, taken from a presentation by Peter Scott (Figure 3). The rocket stove principle combines improved combustion efficiency, whilst reducing smoke output, with optimised heat transfer efficiency. More details and a video can be found at: www.aprovecho.org/web-content/media/ashden.htm
 Figure 1: Inefficient firewood cooking at Maula prison (photo: Christa Roth) |
The rocket stove principles are optimally suited for institutional stoves:
 Figure 2:Inefficient firewood cooking lauderdaletea factory in Mulanje district (photo:Christa Roth) |
Firstly, more energy is wasted from an open fi re as pot size increases, therefore the potential savings are greater for larger pot sizes. In the first tests at the kitchen of Lauderdale Tea Factory in Mulanje, it took 170 kg of wood to cook 100 litres of the staple food nsima (maize meal) on the open fire, whereas the first rocket stove built by Peter Scott required less than 17 kg of wood.
Secondly, the rocket principle relies on optimised gaps between pot and stove to deliver the best results. This is easier to achieve in institutional cooking, as normally the variety of food cooked and pot sizes are limited, unlike in households. In Malawi a stainless steel pot is cheaper than a rocket stove by a factor of two, so it is economic sense to keep the existing pot which institutions already use to prepare food. The rocket stove is then tailor-made to fit the existing pot, reducing the overall investment costs for a new stove. This not only makes the technology switch considerably cheaper but increases willingness to do so.
 Figure 3 :Diagrams showing the principles behind the fuel efficiency in rocket stoves (diagram:Peter Scott) |
[top] [end]Why is it better than what was there before? Due to better combustion and heat transfer efficiencies, rocket stoves give the following benefits:
[top] [end]Reduced health risks - Reduced smoke emissions: shorter-term benefits included less coughing and burning eyes whilst longer-term benefi ts include a reduction of respiratory and eye infections for the cooks.
- flames are contained within the combustion chamber and the hot flue gases are shielded by a skirt (enhancing heat-transfer to the pot). The exhaust gases leaving the gap between the skirt and the pot normally don’t exceed 190°C.
- Reduced danger o the cook from burning, as the cook is not exposed to an open flame.
 Figure 4: In this school in Tanzania, this sight of a Bellerive-type stove, right, being used with long uncut pieces of wood and the door left open is not uncommon. However, it is still an efficient stove compared to the 3 stone fire, even when the door is open. Its high cost has prevented further dissemination (photo: Christa Roth) |
Convenience is a factor that should not be underestimated when discussing stove design and efficiency. Cooks will always find the most convenient way to use a stove, which often does not favour efficiency, or they will not use an inconvenient stove at all (Figure 4). This means that even the most effi cient stove-design will then have zero impact! For example, the Bellerive stove is a very efficient stove (Figure 4), but the draft system is designed to work with a closed door to function efficiently. This requires firewood not only to be split, but cut into 20cm long pieces to fit into the fire chamber. Reality often shows a different picture: normally it is the cook’s duty to prepare the firewood. Unless the economic savings achieved by this extra work are shared out to the cook, there is no incentive to use the stove properly.
Cooks from the kitchen shown in Figure 4 preferred the rocket stove because: - Less time and effort needed to prepare wood: the rocket stove can take any length of firewood, therefore there is no need to cut wood.The only requirement is to split the wood lengthwise into pieces ideally around 3-6 cm thickness, which is not as strenuous as cutting. Also, less wood needs to be prepared due to the economy of the stove on fi rewood use (Figure 5).
- Less smoke even without a chimney.
- No chimney to sweep, therefore less maintenance work. Reduced cooking times compared
 Figure 5:Less wood is needed to cook theequivalent amount of food with a rocket stove (photo: Christa Roth) |
The usual feedback from rocket stove users is similar to that from Emmanuel Teacher Training College in Blantyre: the three cooks really treasure the stove and look after it, and do not wish to return to using the open fi re, when they had to take turns of less than ten minutes in the kitchen filled with biting smoke in order not to choke. They attribute health improvements to the rocket stove. Athough they mention that the rocket stove needs more frequent attention to push the firewood in at the right pace than the open fi re, but that it is outweighed by shorter overall cooking times.
[top] [end]To the owner (buyer, head of the institution):  Figure 6: Caked food from traditional fire,left, and from rocket stove, right, with same maize flour used (photo: Christa Roth) |
- Cheaper to buy than other available improved technologies, such as the Bellerive-type stove.
- Considerable savings in firewood, ranging between 50 to 95 %, depending on the inefficiency of baseline technology.
- Reduced transport costs for firewood (e.g. Maula prison: 4 truckloads of firewood per week without Rocket Stove, 1 truck load fi re wood per week with Rocket Stove).
- Less burning and waste of food.
- Better quality of food prepared in the rocket stove as compared to the open fire, as more equal heat distribution and faster cooking (Figure 6).
- No chimney to be passed through the wall or the roof (no leakages).
- Reduced deforestation as result of reduced wood consumption.
- Less wood transport on the roads, therefore a reduction in CO2 emissions from trucks.
[top] [end]How does the technology become a ‘product’ and find its way to the user? We need to look at two aspects:
- Who is involved in turning the raw materials into a sellable product?
- Who is involved in causing the product to reach the user?
[top] [end]Input supply of raw materials Metal for the structure, insulative bricks and high temperature mortar for the lining of the firechamber, are the major materials needed for a rocket stove. All metal ingredients are available from regular steel suppliers in the larger centres of the country. Manufacturing the insulation material was a challenge, as no natural material like pumice or processed vermiculite was available. Together with the clay expert Chris Stevens from Dedza pottery, insulation material was developed out of white refractory clay and sawdust, fired at 1250°C. The bricks in a 100 litre stove cost about $15, which is less than 8 % of the total cost of the stove. Dedza pottery now tailor-makes sets of insulating bricks for the three most common fi re chamber sizes. For other sizes the bricks are cut with a hacksaw blade.
ProBEC negotiated for minimum stocks to be kept, as manufacturing times for insulative bricks can exceed 6 weeks, due to the slow drying of the moisture-absorbing sawdust. The density of the fi red bricks is about 0.8 g/ cbcm. This makes them physically vulnerable, especially at sites where the fi rewood is ‘rammed’ in. Our hardest challenge was in a prison in the capital Lilongwe: cooking is done by the inmates, who are capable of destroying a stove in less than 6 months. Under normal circumstances the lifespan should exceed 3 years. This prison has become a valuable testing ground: anything sur-viving the ‘stove abuse’ there is fit for normal use. Dedza pottery developed hard, high-density tiles about 1 cm thick, made out of the same white clay mentioned previously, resistant against physical shock and abrasion. They are interlocking and fi tted on the lower part of the fi re chamber to protect the area in direct contact with the fi rewood. It is always a challenge to balance the durability versus the insulative properties of a stove. So far the tiles used since October 2006 have not reduced the efficiency of the institutional stoves as the heat loss through the tiles is compensated by the longer cooking times in the institutions. The tiles have enticed some producers to increase the warranty for the stoves from 6 to 12 months. ProBEC constantly monitors the performance of the stove components and adjusts materials and designs as the need arises.
[top] [end]Who turns the raw materials into stoves?  Figure 7: WFP type of stove: lower skirt,less L-shape at the entrance to cut costs, designed for half-220l gallon oil drum (photo:Christa Roth) |
 Figure 8: Stoves waiting to be loaded at KenSteel Engineering in Mulanje (photo: Christa Roth) |
Ken Chilewe from Ken Steel Engineering in Mulanje was the first producer to be trained in 2004 (Figure 7 & 8). Since then, he has successfully sold over 1,500 institutional rocket stoves (see as well Ashden Awards video). In 2005, a further four entrepreneurs were selected for training according to the criteria that they were already in business, had an equipped workshop and at least one successful product on the market. Even though there were promising orders available, only 3 took up stove production. A fourth was later trained and now 4 producers cover the 3 major regions of Malawi.
[top] [end]Who is involved to make the product reach the user? This will be further elaborated in a next issue of Boiling Point.
[top] [end]Download the original article  Getting Technologies to the market by Christa Roth, Andreas Michel and Dr. Christoph Messinger (233 KB)
[top] [end]Contents: Boiling Point 53 - Technologies that really work  . |
Theme Editorial - Taking Science to Hearth - Good technologies - but do they really work - Rocket mud stoves in Kenya - Green Power -Lighting up rural India - The Biogas Programme in Vietnam - Pico hydro for cost-effective lighting - Biomass gasifier systems for thermal applications - GTZ News BP53 - Energy News From Practical Action BP53- What's Cooking On The Solar Cooker Front? - Getting Technologies To The Market - SODIS - Solar Water Disinfection - A story of improving cooking stoves in a Dogon village - Micro-gasification what it is and why it works - What's happening in household energy BP53?
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