<div class="gmail_quote"><div>Dear Charlie Sellers, Crispin and All,</div><div><br></div><div>Testing the stoves is one of the ways of understanding stoves. I am thankful to this group especially Crispin, for sharing so much regarding the stoves. I started writing a small reply, but it ended up so length. </div>
<div><br></div><div>Although there are various methods of
testing the stoves, the most important testers are the users. The multiple factors
for a successfully adopted stove in time and space also vary. In the last two months, I have done about 100
tests for some of my stoves, followed WBT 4.1.2 methodology. Since last 7
years, had been designing stoves, testing them, training on stoves, getting the
community (user) feedback etc., some of my experiences, observations and
insights into the stoves are as such.</div><div>
<p class="MsoNormal"><span class="apple-style-span">Testing the stoves involves not only
following the standard procedures but also the tester having the experience.
Apart from the values, the testers experience would help a lot in designing good
stoves. </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238498"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Fuel wood</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span">Size of
fuel wood: It was observed that for fuel many testers chose thin sticks. In our
region people chose wood of 1.5 inches to 2.5 inches diameter. The wood is never
split perfectly into square cross sections, as usually one uses during the testing
of stoves. Splitting the wood into thin size say 2 cms x 2 cms is very
difficult and consumes energy and time. The length of the wood is usually about
1.5 feet to 4 feet. Bundling and transportation of the cut wood is not
convenient if the wood length is too short. Sometimes the wood carried by head loads is
very long say about 5 to 8 feet in length. The women / men balance the wood on their
heads, to carry it. In a tribal area, people use trunks of wood without cutting
as fuel wood, they are often 6 to 12 feet in length and nearly 4 inches to 12 inches in diameter. The trunks of
wood as fuel is a common practice for many institutional stoves. Such usages are
commonly found in the habitations located in the forest areas / in forest
fringe areas. </span></p>
<p class="MsoNormal"><span class="apple-style-span">Type of wood:
Different types of wood are available such as Neem, Accacia Nilotica, Prosopis
Juliflora, etc.</span></p>
<p class="MsoNormal"><span class="apple-style-span">Wood
moisture: In many tropical and semi-arid environments on a dry day the wood moisture
varies between 12 to 18%.</span></p>
<p class="MsoNormal"><span class="apple-style-span">Very thin
wood <1 cm is used for kindling. Sometimes kerosene is used (about 5 to 10
ml). Thin wood is not preferred by communities for cooking (except for kindling).
Thin wood burns conveniently with very less smoke, but sometimes they yield soot.
The stove users does not like soot deposit on the utensils and on their walls. The
bark of the wood although good for fire but sometimes leads to excess sooth
emissions. The kerosene added for starting the fire, leads to conspicuous soot
emission. </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238499"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; font-weight: normal; ">Size
of the stove:</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; font-weight: normal; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span">In our region, 8 inches height of the stove
is ideal. Any stove too high about 12 inches or more is inconvenient. Women prefer
sitting comfortably on the floor and cook. Many of the activities done by women
in the rural areas are by sitting. Especially while making rotis, they prefer
the low height of the stove. Scientifically the chimney effect would help the
smoke to burn in tall stoves. But, as per the ergonomics and local practices,
it is not convenient to the user. Sometimes a scientist is successful in the lab,
but fails at the community level. Often the pan for making rotis is about 10 to
12 inches in diameter. In a 4 inch diameter stove, the stove should be operated
in high power for the flames to spread underneath the pan for complete burning
of a roti. The diameter of the stoves about 7 inches is ideal for different
types of the utensils used in the region. </span></p>
<p class="MsoNormal"><span class="apple-style-span">Two of my stove designs were a failure
due to small diameter of the stove and also being tall. As a designer there is
a need to balance between the science and user requirements (including ergonomics
and many other factors).</span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238500"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Stove
life and efficiency</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"> </p>
<p class="MsoNormal">The thermal
efficiency is also dependent on the mass of the stove. The light weight metal
stoves are thermally more efficient, especially during the cold start phase. During
the hot start phase they show slight improvements in thermal efficiency. Heavy
stoves are thermally less efficient during the cold start phase. During the hot
start phase of testing, heavy stoves having the retained heat, show better
efficiencies. A compact stove is more adoptable then, the stove with more movable
or removable parts. It costs more to make stoves with two or more materials. </p>
<p class="MsoNormal">Insulation
and refractory are two important factors in a stove design. Getting a material
which has both the properties is of great value. The refractory material
available in the markets (aluminum and iron based bricks) are heavy and bad
insulators. But the life of the stove is guaranteed for even 10 years. The
thermal efficiency goes down. The cost of the stove goes up because of the cost
of refractory bricks and excess weight of the stove. Heavy stoves are difficult
to facilitate. The volume of the stove and the surface area of the stove increases
relatively for more durable stoves. There ought to be loss of heat due to
radiation for durable stoves.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Air is the
best insulation material. Even by using the thin metal sheets for combustion
chamber (with air holes - side air / secondary air hole features), the life of
the combustion chamber can be increased. For safety another thin sheet can be
used as external wall. The surface area of contact between the hot parts and
other parts of the stove should be least. By using pointed or thin screws,
ceramic watchers, the heat transfer to the outer body can be reduced. Often between
the inner and outer walls insulation material is filled. The contact between
the grate and the stove body should be least. This can be achieved through pointed
supports for the grate.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">For
facilitation to wider geographies, the convenient weight of the stove is around
2 to 4 kgs. The stoves weighing more than 10 kgs, are the most difficult stoves
to sustain as an enterprise. It is even more difficult to sustain the
facilitating team, if the stoves weigh more. The stoves facilitated through subsidies
/ stoves facilitated through the schemes are often heavy. Majority of the
stoves available in the market and sold on a large scale (although inefficient)
are always light. These stoves being light also cost less and are also less
durable.</p>
<p class="MsoNormal">In heavy
stoves, it is convenient to sustain the simmering test as compared to light
weight stoves.</p>
<p class="MsoNormal"> </p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
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<h2><a name="_Toc311238501"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Removable grate:</span></a><span style="font-size: 11pt; font-family: Calibri, sans-serif; "> </span></h2>
</div>
<p class="MsoNormal">The holes in
the grate should be small and at the same time should not affect the life of the
grate. Too much primary air / too little air underneath the grate affects the
stoves performance.</p>
<p class="MsoNormal"> </p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238502"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Capacity
of the domestic stove:</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span">A domestic stove often serves on an
average about 5 members in a family. The same stove should also support if
there are more number of guests on occasions say 10 members. It is very
difficult for many families if they can’t have this flexibility of cooking. The
range of cooking pots used are of 1 to 5 liters capacity.</span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238503"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Charcoal in the stoves</span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">Many stoves achieve higher efficiencies
because of continuing to consumption of charcoal in the stoves (including the TLUD
stoves). However during the testing of stoves, one of the most difficult tasks
is weighing the charcoal as the water reaches boiling point. Dousing the flames
is convenient when the wood is pushed into the sand. Scrapping all the charcoal
from the wood is a difficult task. Some time is lost in the process of weighing
the charcoal, weighing the wood and the water in the pot after boiling.</span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238504"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Charcoal yield</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span"> The charcoal yield from Magh 3G stove is
around 15% by weight. For TLUDs the yield is about 25%.</span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238505"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Cooking conditions</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">In the semi-arid region, cooking is
often done is semi-ventilated conditions. The cooking pots are closed with the
lid while cooking. Sometimes for stirring / during simmering of rice, etc. the
lid is opened or semi-closed. While making Rotis the pan is completely exposed.
Utensils used for cooking vary: i.e., pots are cylindrical, taper from mid way
of the pot, semi-spherical, or bowl shape, etc. For the WBT test, cylindrical utensil
of about 3 to 3.5 liters capacity is used. </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238506"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Time of testing</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">If the tests are conducted at the transition
phase of sun rise / sun set, the air temperature changes are very fast. Sometimes
chill effect will be there on the stove and the pot. The places selected for
testing are not completely closed, so there could be influence of the local
weather and other environmental conditions. The ideal time for testing the
stove could be other than those two timings. </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
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<h1><a name="_Toc311238507"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Flame</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span">The observation of the flame is very
important, for which the photographs would be more useful then the videos. In a
dark room the observations about the stove performance can be more convenient. Blue
flame is best visible in the dark conditions. </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
mso-border-bottom-themecolor:accent1;padding:0in 0in 1.0pt 0in">
<h2><a name="_Toc311238508"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Rushing and dancing flame</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h2>
</div>
<p class="MsoNormal"><span class="apple-style-span">There are two types of flames, rushing
flame (as in rocket stoves) and dancing flame (say as in Magh 3G stove). Rushing
flames are common where there is chimney effect and also due to chimneys. In
the rushing flame stoves, although the flames appear dynamic and impressive,
but the conduction of the heat to the pot is low. Where as in dancing flame
stove, there is through mix of air with the combustible gases, and the flame
takes its time without rushing to combust the gases underneath the pot. Therefore
the heat conduction to the pot is high. </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
mso-border-bottom-themecolor:accent1;padding:0in 0in 1.0pt 0in">
<h2><a name="_Toc311238509"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Color of flame</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h2>
</div>
<p class="MsoNormal"><span class="apple-style-span">The reddish color flame yields more
soot. The yellowish-red color flame is common. The bluish-yellowish-reddish
flame is good. (Observing the flames is the best experience, one could spend hours
just watching the flames, because the color is energetic and flames are dynamic
change their form continuously),</span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
mso-border-bottom-themecolor:accent1;mso-border-bottom-themeshade:191;
padding:0in 0in 1.0pt 0in">
<h1><a name="_Toc311238510"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Air for combustion</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span">There are three sources of air possible
for a stove : - Primary air, Side air and Secondary air. </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
mso-border-bottom-themecolor:accent1;padding:0in 0in 1.0pt 0in">
<h2><a name="_Toc311238511"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Primary air</span></a><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></h2>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">This air is mainly from the bottom of
the grate / underneath the wood. Excess of air flow will, lead to excess /
uncontrolled combustion. Primary air is always required in less quantities. If
this air is preheated before reaching the wood it will make the stove perform
better. The embers at the bottom of the grate, sometime after preliminary
combustion are very much useful for preheating the primary air.</span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
mso-border-bottom-themecolor:accent1;padding:0in 0in 1.0pt 0in">
<h2><a name="_Toc311238512"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Side air:</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h2>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">In majority of the traditional stoves
this is the only source of air. From the fuel feed opening this air gushes. In
three stone stoves from all the three sides this air gushes. Too much of this
air in open air conditions has dampening effect on the flames. Controlling
gushing side air is also important. If the mouth of the fuel feed is completely
closed due to over feeding of the stoves by wood in traditional stoves, sometimes
leads to extinguishing of the flame and release of excess smoke. Using side air
shutters is a good idea. Using simple small holes on the sides, as given in
Magh 3G, would also help. In efficient stoves the fuel feed opening should be
reduced, as already primary air facility is given. </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #4F81BD 1.0pt;
mso-border-bottom-themecolor:accent1;padding:0in 0in 1.0pt 0in">
<h2><a name="_Toc311238513"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Secondary air</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h2>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">For all TLUDs this is an important
feature. This feature can also be given to the domestic stoves (as compared to TLUDs,
few holes can be given), which helps in complete combustion of any smoke
otherwise left. In the efficient stoves without chimney effect, this is a very
useful feature.</span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">Note: It is convenient to use a stove in
open air conditions with all the three air features (primary, side air and secondary
air), as compared to other stoves.</span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
mso-border-bottom-themecolor:accent1;mso-border-bottom-themeshade:191;
padding:0in 0in 1.0pt 0in">
<h1><a name="_Toc311238514"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Gap between the grate and bottom of the stove</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">In the domestic stoves, the gap between
the grate and the bottom of the stove could be around 1.5 to 2 inches. Seldom
people remove ash while cooking, and ash being a good insulator, it protects
the bottom of the stoves. The embers falling beneath the grate helps in preheating
the primary air. In any case the movement of the primary air should not be
blocked. </span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid #365F91 1.5pt;
mso-border-bottom-themecolor:accent1;mso-border-bottom-themeshade:191;
padding:0in 0in 1.0pt 0in">
<h1><a name="_Toc311238515"><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Who can test the stoves?</span></span></a><span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; "></span></span></h1>
</div>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span"> </span></p>
<p class="MsoNormal"><span class="apple-style-span">Anyone can test the stoves. One need to
have some experience of preparing the kindling wood, lighting the stove, tending
the fire, taming the flames, choosing the wood, feeding the wood, observing the
fire, all that is needed apart from cooking which means nearly 10 ways of
preparing the food. (Roasting, frying, boiling, steaming, mashing, simmering, etc.).
For WBT tests one should know only Boiling and simmering. Biomass stoves are
different as compared to other stoves. The most difficult stoves to learn and
operate are biomass stoves. Sometimes cooking on biomass stoves is like caring babies.</span></p>
<p class="MsoNormal"><span class="apple-style-span">Best way to learn cooking is to start
with the three stone stoves. Anyone who can reach thermal efficiencies of around
30% with a three stone stove (in closed conditions) is an expert. Everyone need
not be an expert for testing stoves. Patience and interest are the two most
important factors in stove testing. Best way to learn cooking is by observing and
learning from the experienced people. Operating a stove professionally for the
first time using a manual is difficult. </span></p>
<span class="apple-style-span"><span style="font-size: 11pt; font-family: Calibri, sans-serif; ">Highest thermal
efficiencies are achieved in lab conditions and only by the experts. Most often
highest thermal efficiencies achieved are reported by the stove facilitators. But
thermal efficiencies achieved by operators with different experiences and
conditions are not reported. Sometimes, stoves reported by a producer are so
high, but they fail to pass through a countries specific test. Rating the stoves
by “stars” is important, because people buy different types of stoves for
various reasons.</span></span></div><div><br></div><div>-- </div></div>Dr. N. Sai Bhaskar Reddy<br>CEO <a href="http://www.e-geo.org" target="_blank">GEO</a> | <a href="http://goodstove.com" target="_blank">GOOD STOVES</a> | <a href="http://biocharindia.com" target="_blank">BIOCHAR INDIA</a> | <a href="https://sites.google.com/site/geoweblinks/" target="_blank">GEO Resources</a><br>
Mobile No. (+91) 9246352018 or 9505760669<div><a href="mailto:saibhaskar@facebook.com" target="_blank">saibhaskar@facebook.com</a> | skype: saibhaskarnakka</div><br>