COMPARING CHARCOAL AND WOOD-BURNING
COOKSTOVES
IN THE CARIBBEAN
by
Jeffrey L. Wartluft
MONTSERRAT FUELWOOD/CHARCOAL/COOKSTOVE PROJECT
A cooperative effort by the
GOVERNMENT OF MONTSERRAT, MINISTRY OF AGRICULTURE (GOM)
CARIBBEAN DEVELOPMENT BANK (CDB)
VOLUNTEERS IN TECHNICAL ASSISTANCE (VITA)
and
UNITED STATES AGENCY FOR INTERNATIONAL DEVELOPMENT (USAID)
Published by
VITA
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 * Fax: 703/243-1865
Internet: pr-info@vita.org
TABLE OF CONTENTS
Acknowledgements
1. Introduction
2. The Project
Stove selection
Trial charcoal cookstoves
Trial wood-burning cookstoves
Efficiency tests
Economics
Acceptability
3. Results and discussion
Efficiency
Economics
Acceptability
4. Conclusions and recommendations
Appendixes
I. Cookstove designs
II. Water boiling test procedures
III. Water boiling test data sheet
IV. Kitchen performance test data sheet
V. Cookstove location sheet
VI. Conversion factors
Bibliography
ACKNOWLEDGEMENTS
This paper summarizes the efforts of many individuals, particularly
our Montserrat project team, which consisted of: Joseph
Daniel, energy officer; Stedford White, project assistant; James
Silcott, stove tester; and Meredith White, secretary.
Many other Montserratians helped with cookstove fabrication, information
gathering and dissemination, and field testing of cookstoves.
Support for the team's efforts was provided by Dan Chalmers, Dr.
Jeffrey Dellimore, Carolyn Cozier, and David Moore of the Caribbean
Development Bank (CDB); and Richard J. Fera, John M. Downey,
Jane Kenny, Paula Gubbins, Margaret Crouch, and Julie Berman of
Volunteers In Technical Assistance.
--Jeffrey L. Wartluft
Project Manager
1. INTRODUCTION
In English-speaking countries of the Caribbean, liquid petroleum
gases (lpg) are the most common cooking fuels. With the exception
of Trinidad, lpg is imported and so is expensive for families
as well as a drain on a country's treasury. Lpg supply to
these countries is uncertain too. It depends on seasonal demand
and shipping and refinery schedules. The occasional long lines
at the lpg dealers bear witness to this problem. Families who
can afford to, have purchased two lpg cylinders to get around
delivery uncertainties. Someday in the future there will be no
affordable lpg--it is not renewable.
For most islands there is an alternative cooking fuel which is
local, renewable, and viable right now. In fact, families have
cooked with it for centuries, and still do. This fuel is wood
from forests. However, this valuable resource is renewable only
if used wisely. Such use involves many activities--measuring
supplies and demands of different products, and satisfying these
demands over the long term by efficient utilization of the forest
and, if necessary, prudent plantations of suitable tree species.
The Government of Montserrat had the foresight to initiate a
project that would guide the country in managing its forest
resource, particularly for fuel. In this effort they enlisted
help from the Caribbean Development Bank (CDB), Volunteers In
Technical Assistance (VITA), and the United States Agency for
International Development (USAID). The Montserrat Fuelwood/Charcoal/Cookstove
Project, begun in 1982, is studying 20 fast-growing
tree species in experimental plantations, assessing the
fuel supply from natural forests, finding efficient ways to
convert wood to charcoal, and finding efficient ways to cook with
both charcoal and wood. This paper reports on the results of the
cookstove portion of the Montserrat project. Because cooking
methods and cookstoves are similar enough throughout most of the
Caribbean, the results of the Montserrat work are likely applicable
across the region.
The 1980 Commonwealth Caribbean Population Census stated that 40
percent of the people in Montserrat cooked with traditional wood
and charcoal fuels (GOM, 1980). This surprisingly high estimate
prompted the initiation of the project out of concern for the
future of Montserrat's forest resource. Our own estimates of
traditional fuel use were:
Use Fuel Percent of Population
full time charcoal 20
occasional charcoal 60
full time wood 5
occasional wood 40
Meals cooked with charcoal customarily used cookstoves called
coal pots (Appendix I). There were several models using various
materials, but with very similar designs and sizes (Figure 2).
48p02b.gif (393x393)
In fact, the Caribbean coal pot design was similar to many charcoal
cookstove designs in Asia and Africa. Cookstoves like these
have been shown in laboratory tests to have efficiencies (amount
of heat absorbed by the water/amount of heat available in the
fuel x 100) around 30 percent (de Silva, 1981; Singer, 1961; and
Tata, 1980). Little is known about the efficiency of these
stoves in actual use.
When wood is used as a cooking fuel, it is usually burned in a
three-stone fireplace (Figure 1 and Appendix I). The literature
48p02a.gif (393x393)
has been harsh in its evaluation of three-stone fireplace efficiency,
leading one to believe it is in the order of five to 10
percent. Recent laboratory and field testing, however, has shown
a higher percentage of efficiency, around 17 (Yameogo et al.,
1983).
For certain cookstove models to "catch on" we felt they should be
efficient, economical, and acceptable. So we tested cooking
techniques to measure these three criteria. Twenty-six cookstove
models including the current standards were compared. Interpretation
of the data suggested that the smaller cookstoves were
more efficient and economical, but at a cost in time to bring
food to cooking temperatures. Positive air control was important
for efficiency but difficult to achieve in inexpensive stoves.
Kitchen performance field testing was valuable in determining
efficiency, economics, and fuel demand, but definitive data would
require a large input of time and effort.
2. THE PROJECT
The objectives of the Montserrat Fuelwood/Charcoal/Cookstove
Project were to:
1. Substitute local renewable cooking fuel from the forest
for imported liquid fuels,
2. Use the forest resource wisely, and
3. Create local industry and employment.
Specifically for the cookstove portion of the project, all three
objectives would be enhanced by identifying and testing
techniques for efficiently using charcoal and wood fuel for
cooking.
STOVE SELECTION
In order to know if any improvements were made, we had to know
the performance of the stoves currently in use. So we selected
four models of coal pots--cast iron, cast aluminum, clay, and the
converted steel auto wheel--and the only cookstove used with wood
fuel, the three-stone fireplace (Figures 1 and 2). In Montserrat,
wood fuel is also used in massive stone ovens for baking, but
ovens were not tested.
Trial cookstove designs expected to be improvements over the
standard cookstoves were chosen according to strict criteria.
They had to be:
1. simple to build and use,
2. made locally with local materials,
3. inexpensive,
4. appealing in looks, and
5. formerly tried and reported in the literature.
The only locally available materials in quantity were sand,
stone, and clay. From the start, "mud" stoves were not considered
due to the strong local feeling that their use would be a
step backward in progress. Even though clay coal pots were not
in much favor because they broke so easily, attractive double-walled
models were made for both charcoal and for wood fuel.
A limited number of metal recyclable components were also available
locally. Our trial designs incorporated used oil drums,
five-gallon buckets, steel pipe, paint cans, and tin cans. All
other materials, galvanized sheet metal, wire mesh, one quarter
inch rod, and cement used in trial stoves were imported.
The large variety in design and size of pots used for cooking in
Montserrat made decisions on stove dimensions difficult. Improved
stove features called for shielding and insulating around the
pots. So a stove designed for a 10-inch diameter pot would be
too small for a 12-inch pot, and allow unnecessary heat loss when
cooking with an eight-inch pot. Most trial designs were dimensioned
for 10-12-inch pots. Coal pots and three-stone fireplaces
were very flexible in accommodating various pot sizes, even
frying pans.
Chimneys were not considered very important in our trial designs.
Other stove programs have found chimneys to be a mixed blessing
(Foley and Moss, 1983). And Montserratians were not fond of the
idea of holes in their roofs. Cooking with wood was generally
done outside. Even though much charcoal was used inside, Montserratian
homes were always well ventilated to get the cooling
effects of constant breezes. Smoke and carbon monoxide have not
caused problems. Only the two-hole cement wood-burning trial
cookstoves had chimneys.
Even though there was interest in ovens and grills based on
traditional fuels, the project did not have sufficient time to
design and test these. There were several types of charcoal
"Charlie Man" ovens in use. One design employed a used oil drum,
inside of which was placed a coal pot for heat. It had a hinged
door for access, and two steel mesh shelves for baking. For
added heat, charcoal was burned on the top. These drums were not
insulated. A better design was the wooden box with hinged door,
tin lining inside, and shelves. This oven was heated by placing
a coal pot with burning charcoal inside. Both ovens were easy to
build and required no welding tools or special skills.
Trial Charcoal Cookstoves
The simplest design selected for testing was a coal pot modification,
a sheet metal pot ring. The ring fit over the top of a
standard coal pot and had a hole cut in it to match the pot
diameter (Appendix I). This was an attempt at keeping the heat
closer to the pot to enhance heat transfer into the pot.
The double skin (DS) fired clay charcoal stove mentioned earlier
provided a wind screen, preheated secondary air, an insulated
firebox, and draft control (Figure 3; Appendix I; and Joseph and
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Trussell, 1981). This sophisticated design originated in Africa.
For use in Montserrat, the design was slightly modified and was
beautifully executed by potter Joseph Howson.
Another design of African origin, the Umeme, was selected. The
Umeme was made with galvanized sheet metal and several types of
insulation--air, soil, and cement. It featured a wind screen,
tapered firebox, ash drawer, and draft control (Figure 4; Appendix
48p05b.gif (393x393)
I; and Hassrick, 1982). Craftsmen fabricating trial cookstoves
for the project were encouraged to add their own creativity
to their work. Three tinsmiths, James Sweeney, Cecil Roach,
and John Harris, were enlisted to build the Umeme. Using the
same drawings, each came up with quite different looking versions.
Only one stove selected was manufactured outside Montserrat. The
Z Ztove, mass produced in California, USA, was a sophisticated
design made with sheet metal and ceramic fiber insulation. It
was tested because of the possibility of mass producing them in
Montserrat for the Caribbean market. Features of the Z Ztove
included preheated secondary air, firebox insulation, and positive
separate controls for primary and secondary air (Figure 5
48p06a.gif (437x437)
and Appendix I).
As stove testing progressed, modifications and new trial designs
were born as a result of user feedback and our own efforts to
improve stove performance or acceptance. For instance, the Z Z
Corporation made several two-burner and larger burner Z Ztoves at
our request.
Two models that would be inexpensive and easy to construct in the
home were tried. The Advanced Charcoal (AC) Stove used a juice
tin inside of a paint can, with cement insulation between the
cans (Figure 6 and Appendix I). It was conceived by Joseph
48p06b.gif (437x437)
Daniel, the Energy Officer in Montserrat. The AC stove was
tested in three sizes, and with and without a combustion air
preheater and draft control.
The idea for the two-can stove design was sparked by a simplified
copy of the Z Ztove built by Montserratian stove tester James
Bradshaw. In this simple design a motor oil can was placed
inside a paint can (Figure 7 and Appendix I). The design allowed
48p06c.gif (437x437)
both primary and secondary air to reach the burning charcoal.
In an effort to overcome the lack of durability of the Z Ztove
and two-can stove, the project team designed an attractive Satellite
stove (Figure 8 and Appendix I). Materials used included
48p06d.gif (437x437)
six-inch diameter steel pipe, steel plate, and steel reinforcing
rod. The Satellite stove had an ash drawer and draft control.
Tests were run with clay and cement liners.
Trial Wood-burning Cookstoves
The African double-skinned fired clay stove was selected for
testing. It had provision for primary and secondary combustion
air (Figure 9 and Appendix I).
48p07a.gif (437x437)
A simple stove was made from a used five-gallon resin bucket and
some 1/4-inch rod. The bucket served as the firebox and pot wind
screen. The large fuel opening in both the clay and bucket
stoves allowed sticks of any length to be used with the stove,
but did not allow for combustion air control.
Two reinforced cement cookstoves were built for trial with wood
fuel. Each was built by different masons, incorporating some
individual creativity. One built by Tony Carty and Charles White
had thicker walls, a grate, and a removable firebox door. The
other, built by Joseph Sweeney and David Lake, had thinner walls,
a hinged firebox door, and a weight-saving hollow under the
sloping firebox floor (Figure 10). Each had two holes for pots
48p07b.gif (486x486)
and a short four-inch diameter chimney. They were built to be
portable for demonstration purposes (Appendix I).
EFFICIENCY TESTS
Two different tests for efficiency were performed with trial
cookstoves: the water boiling test (WBT), and the kitchen performance
test (KPT). Provisional international standards for
these tests were developed during a meeting of experts at VITA
headquarters (VITA, 1982). We followed these standard procedures
with a few modifications.
The WBT measured the amount of heat used in raising water
temperature and evaporating water in a ratio over the amount of
heat used from the fuel. Results were reported as percent heat
utilized (PHU). We also reported the time required for a
standard quantity of water to boil, and the amount of fuel that
would fit in the firebox.
Equipment used in the WBT included:
* two 11-inch diameter aluminum pots with flat bottoms
and lids,
* two eight-inch diameter aluminum pots with flat bottoms
and lids,
* balance accurate to 1/10 gram with a capacity of 6,250
grams,
* four rubber stoppers with single holes,
* four mercury thermometers reading to 250 [degrees] F (two spares),
* electric oven with accurate temperature control to 220 [degrees] F,
* small tongs,
* heavy leather gloves,
* clock reading to the nearest minute,
* Zip fire fuel pellets (for standardized kindling), and
* magic markers.
The detailed procedure is presented in Appendixes II and III.
The second test measured the relative efficiency of the stove and
operator together. The KPT was performed by many different
Montserratian families. Participating families were selected to
represent different economic levels and geographic areas. In
order to have reliable results, we needed many families to participate
due to the added variability of different stove operators,
cooking styles, food prepared, and eating habits. Since our time
was limited, we field tested stoves with as many families as we
could accommodate in our schedule. Only charcoal stoves were
tested in the KPT.
We loaned a trial stove to each family and gave them a 10-pound
bag of charcoal with instructions to keep track of the number of
meals cooked on that stove with that bag of charcoal--no more or
less. We also asked them to keep track of the number of people
who ate those meals, their ages and sex. Each family was given a
KPT data sheet to help them record data (Appendix IV). When we
returned in two to four weeks we reviewed the data sheet with
them. We asked for their likes and dislikes about the stove, if
they used it for heat needs other than daily meals, and checked
to make sure they did not use the fuel in different stoves, they
used all the fuel, and no fuel in addition to what was in the
bag. At that point we offered to let them repeat the KPT with a
different model stove. Once a family had tested two or more
trial stoves, we asked them to repeat the KPT with their standard
coal pot. When we returned for the last results, we gave them a
bag of charcoal in appreciation for their cooperation. The charcoal
was from our kiln trials in the other segment of our Montserrat
project.
Results of the KPT were expressed as the number of standard adult
equivalent meals (SAEM) prepared per 10 pounds of charcoal. SAEM
were figured according to a widely used League of Nations formula
which uses the following values.
Sex and Age Standard Adult Equivalent Meal
Child, 0-14 years 0.5
Female, over 14 years 0.8
Male, 15-59 years 1.0
Male, over 59 years 0.8
Since there were a number of stoves with different Montserratian
families under test simultaneously, and the stoves were switched
around among families, we used a stove location sheet for each
stove (Appendix V). By keeping these up to date, we knew where
each stove was and when it was time to visit each family.
ECONOMICS
Economic comparisons of stoves were figured on the cost to use
each type of stove per SAEM. We maintained records on the:
1. material and labor costs of building the stoves,
2. maintenance costs, and
3. fuel costs.
To arrive at the investment or depreciation cost, we estimated
stove life and divided the original cost of the stove by the expected
SAEM over its life. Maintenance costs included any replacement
of parts over the life of the stove. Again these costs
were divided by the expected SAEM over its life. Fuel costs were
based on EC$5 per 10 pounds of charcoal divided by the average
SAEM per 10 pounds of charcoal from all families testing a particular
stove. To get the total cost to use each stove model,
the three costs per SAEM were added. Each trial stove model's
cost of operation was compared to the average cost of operating
all standard coal pots over one year. This showed the savings or
losses of trial stove operation compared to the conventional
cooking methods. Since we only ran KPT on charcoal stoves, no
economic comparisons were made for wood-burning stoves.
ACCEPTABILITY
It was very difficult to quantify the acceptability of any given
stove model, so all comparisons made about stove acceptability
were subjective. Notes were kept on the comments that people
made about each stove model. Most information was collected from
families participating in the KPT. During each visit with a family,
they were specifically asked what they liked and disliked
about the stove (Appendix IV). When participants were reluctant
to answer the general questions, more specific questions were
asked about stove size, materials, looks, and operating features.
Feedback from families testing stoves was valuable in guiding our
attempts to modify stove features for greater acceptance.
3. RESULTS AND DISCUSSION
The limited duration of this project did not allow definitive
answers to the question of which cooking technique among those
tested was the best in terms of efficiency, economics, and acceptability.
However, the tests did allow us to establish some
baseline data on traditional cooking practices and to pick out
some general indications for improving them.
EFFICIENCY
There were several differences between the two tests for efficiency.
With WBT we intended to screen stove models and features
in order to select two or three of the best for the important KPT
field testing. WBT results were not indicative of expected fuel
savings of cookstoves in actual use because they did not measure:
the operator variable. So to get a measure of the efficiency of
stoves and operators together, we ran the KPT.
We found the KPT results particularly useful. Besides (1) comparing
the efficiency of different stove models in actual use, we
(2) applied the results in our economic comparison of stoves, (3)
used feedback for gauging acceptance of different stove models,
and were able to (4) estimate the demand for fuel from the forest,
which could then be matched with forest inventory data to
see if tree plantations were-necessary to satisfy demand without
depleting the resource.
WBTs were easier to conduct than KPTs. WBTs only involved our
project team, while KPTs involved many people and required travel
and visit time. In two months time, 160 WBTs were performed, an
average of four per day. In approximately six months time, 55
families participated in the KPT, with 37 usable responses collected.
Many families did not fully understand our purpose--or
pretended not to understand in order to keep the trial stoves for
longer periods of time. We made up to four visits to the same
family to get a single response. In order to speed up data
collection, we enlisted the help of teachers and agriculture
extension agents. This effort, too, brought variable results.
Due to the greater variability of KPT results, more tests were
needed than in WBT for the same degree of predictability. Unfortunately,
the more useful information required a much greater
effort.
Interestingly, the cheapest and simplest cookstove, the two-can,
had the highest average WBT efficiency, 34 PHU (Table 1). Other
cookstoves that rated above 30 PHU in this comparison were the
small AC with preheater and air control and the cast aluminum
coal pot, each with 32 PHU, and the five-gallon bucket woodburning
stove at 31 PHU. The poorest performers were the cement
wood-burning stoves, the Satellites, and the Umemes, all with
less than 20 PHU.
Among the traditional coal pots, the cast aluminum averaged 10
percentage points better than the clay, cast iron, or steel. All
tested coal pots had similar shapes and sizes. Since clay was
the best insulator of the materials tested, we expected it to
perform better than the metals, which were all good conductors of
heat. One possible explanation for aluminum's superiority was
that its relatively high emissivity or ability to reflect heat
back into the fire overcame its ability to conduct heat away from
the fire. Indeed, some cookstove researchers have lined fireboxes
with shiny metals to improve stove efficiency. Perhaps if
the firebox walls of the cast aluminum coal pot were polished, it
would be an even better stove.
We got conflicting results testing firebox insulation. The Umeme
stove worked best with cement, next best with soil, and poorest
with air insulation. The Satellite did best with clay, next best
with cement, and poorest with no insulation. On the other hand,
the two-can stove was more efficient without a clay liner, and
Table 1. Cookstove Efficiency Test Results
Water Boiling Test [a] Kitchen Performance
Time No. Meals
Fuel to PHU of per SAEM
charge boil coef. re- lb coef.
(lbs) (min) PHU of spon- coal of
Cookstove & features [b] [c] (%) var. ses (SAEM) var.
Charcoal Cookstoves
Clay coal pot 1.27 22 21 .57 - - -
Cast iron coal pot 1.29 21 22 .27 2 2.5 .04
Cast alum. coal pot 1.16 22 32 .40 2 3.7 .11
Wheel coal pot 1.46 24 22 .24 1 1.0 -
" /pot ring 1.32 25 22 .14 2 5.4 .28
Umeme/cement insul. 1.40 22 20 .28 6 2.8 .30
" /soil insul. 1.11 22 16 .24 6 4.0 .37
" /air insul. 1.27 29 14 .09 - - -
Small AC .57 34 21 .22 4 5.7 .57
" /preheater .32 38 25 .11 1 6.2 -
Medium AC .57 27 25 .26 - - -
Large AC .79 24 24 .15 - - -
" /preheater .66 22 25 .16 - - -
Z Ztove .42 24 27 .45 5 4.7 .80
" /double burner .48 26 25 .14 6 5.6 .66
" /large burner 1.26 20 22 .10 - - -
Two can .28 27 34 .28 1 3.3 -
" /clay liner .34 29 26 .27 - - -
Satellite 1.36 29 11 .43 - - -
" /cement liner .91 29 16 .27 1 2.0 -
Table 1 - Continued
Water Boiling Test [a] Kitchen Performance
Time No. Meals
Fuel to PHU of per SAEM
charge boil coef. re- lb coef.
(lbs) (min) PHU of spon- coal of
Cookstove & features [b] [c] (%) var. ses (SAEM) var.
" /clay/preheat. .72 23 24 .14 - - -
Short satellite/cement .63 26 22 .25 - - -
Wood-burning Cookstoves
3-stone fireplace 27 .43 - - -
5-gallon bucket 31 .45 - - -
Cement/grate [d] 10 14 .94 - - -
" /sloping floor [e] 10 12 .59 - - -
[a] Averages based on at least five tests.
[b] To convert to kilograms, multiply by .454.
[c] Amount boiled was 2 kg. Does not include first five
minutes from the time of lighting.
[d] Based on four tests, PHU total of two pots.
[e] Based on three tests, PHU total of two pots.
the non-insulated five-gallon bucket wood-burning stove was more
efficient than the cement walled wood-burning stoves. In the
case of the two-can stove, the air that was insulating the firebox
was heated, then moved beneficially into the fire as preheated
secondary combustion air. The insulating air in the Umeme
was dead air. Once heated, it then transferred the heat to the
outer shell of the stove from where it escaped into the air.
In the five-gallon bucket stove, increased efficiency was probably
due more to the fact that in the simmer stage the fuel was
retracted from the firebox for heat control. In the Umeme,
Satellite, and cement wood-burning stoves, heat was not as effectively
lowered by closing the not-so-positive air controls, loose
fitting ash drawers and doors. Therefore, more heat than needed
was used up. So if positive air control or ability to manipulate
fuel are features of a cookstove, insulation is not as important.
For instance, the three-stone fireplace did not have insulation
or even a wind shield; but with manipulation of the fuel, its PHU
was a respectable 27.
Recent African stove testing programs pointed out that thin-walled
metal cookstoves were more efficient than massive cookstoves
for cooking durations less than 100 minutes. Only when
cooking times were longer, say for restaurants or institutions,
or at high altitudes, would massive stoves lose less heat through
conduction (Baldwin, 1984).
Combustion air preheaters seemed to improve efficiency. In both
the small and large AC stoves and the Z Ztove (the double burner
Z Ztove did not have preheated secondary air) where this feature
was tested, the preheaters added one to four PHU to the stove's
efficiency.
Even though grates were not tested for charcoal cookstoves, it
was obvious in the smaller models that the maximum air possible
was necessary. In small stoves without secondary combustion air,
ash build-up tended to close off the holes in grates. For this
reason all of the smaller charcoal cookstoves were provided with
grates of 1/4-inch wire mesh. One of the two cement wood-burning
models had an iron bar grate. Its efficiency was two PHU greater
than the model without a grate.
Control of combustion air was important to stove efficiency.
With good air control fuel consumption was lowered to the amount
needed for simmering, once the pot was boiling. In the AC stove,
a slide control over the draft opening increased the stove's
performance by seven PHU. The Z Ztoves all had positive air
controls and good PHUs.
The variability of test results seemed high considering the tests
were controlled to minimize variation. PHU coefficients of variation
ranged from 10 to 94 percent. Wood-burning cookstoves had
much more variation than charcoal cookstoves. Wood was a more
variable fuel than charcoal in size, shape, and moisture content.
Wood fires were trickier to control. Charcoal cookstove results
with high variation included the clay coal pot, Z Ztove, Satellite,
and cast aluminum coal pot. There was no obvious common
trait to explain their higher variability. A certain amount of
variation was certainly due to the stove testers. Three of us
from the project team did the testing. I suspect from observation
that some of the variation in performance not specific to
any one stove model but more likely to affect smaller stoves, was
due to the random arrangement of fuel and how it affected air
flow through the fuel. The same stove operated in exactly the
same manner would sometimes fire up quickly and lively and other
times barely perk along.
It took anywhere from 20 to 38 minutes to boil two kilograms of
water with charcoal. This did not include the first five minutes
after lighting the fire and allowing it to catch. Among charcoal
cookstoves the ability to boil faster belonged to those with
larger fireboxes (Table 1). The small AC stove with the next to
smallest amount of fuel charge required the longest times to
boil. The five-minute waiting period before putting on the pot
to boil was arbitrary. Some additional testing determined that a
charcoal fire needed about 10 minutes to be fully lit, after
which boiling times averaged around 15 minutes. The fastest
individual boiling time with charcoal was on the Z Ztove with 12
minutes to fully light, and nine minutes to boil. By contrast,
the same amount of water was boiled in the same pot on an lpg
cookstove in six to 14 minutes, depending on burner size.
The manufacturer of the Z Ztove also made a multi-fuel backpacking
stove that was supercharged with a C cell battery and small
fan. Charcoal was fully lit in it after just one minute. In
about two minutes some of the charcoal was white hot, indicating
temperatures near 2800 [degrees] F. And flames from the stove made it look
like a gas stove. The project team built a bellows to supercharge
trial stoves. It worked well, but required a cook's
attention. Besides, a traditional piece of cardboard for fanning,
although not as effective, was much cheaper.
In actual use the AC stoves were the most efficient according to
KPT (Table 1). They cooked an average 5.8 SAEM per pound of charcoal.
Next were the Z Ztoves with 5.2 SAEM per pound of charcoal,
and then the coal pots with 3.5 SAEM per pound of charcoal.
The Umeme stoves averaged 3.4 SAEM per pound of charcoal, no
better than the standard coal pots. Since there were few test
responses, we grouped these stove types for comparison. These
tests suggested that the smaller the stove, the more efficiently
it worked under actual conditions.
Since the two-can and Satellite charcoal cookstoves were models
developed late in the project, only one KPT response was available
for each. Dissemination of these results is to take place
during the second year of the project. The KPTs will be ongoing
in conjunction with dissemination.
No tests were made of the clay DS stoves as they broke after a
few uses.
A comparison of the results of the WBT and KPT showed that WBT
results could not be used to predict fuel savings of cookstoves
under actual use. For example, the WBT results for coal pots as
a group were in the mid range, but under KPT were clearly inferior.
Though the KPT results indicated that a 49 to 66 percent fuel
savings would be possible by using AC stoves or Z Ztoves rather
than coal pots, these estimates were based on few data. And
"improved" stove use would also hinge on their economics and
their acceptance.
ECONOMICS
A comparison of the economics of using cookstoves showed that the
AC stoves were cheapest, followed by the Z Ztoves (Table 2). The
Umeme stoves were more costly to use than the coal pots. Since
the economic calculations were based on KPT results, insufficient
data were available to compare the two-can, Satellite, and all
wood-burning cookstoves. In fact, we grouped the data by stove
type for this comparison because there were few KPT responses.
Fuel cost emerged as a more influential cost than investment or
maintenance costs. The stoves with smaller fireboxes and less
fuel consumption per meal, the AC and Z Ztoves, would save about
EC$100 and EC$25 respectively per year compared with the use of
traditional coal pots. The use of Umeme stoves would actually
cost about EC$65 more than using coal pots.
Theoretically, with improvements in cooking practices brought
about by public education campaigns, cooking could become more
efficient and economical than our estimates of present day practices.
With this in mind, the Energy Officer in Montserrat
issued a kitchen calendar with tips on fuel conservation such as
using lids on cooking pots, using smaller amounts of water when
cooking vegetables, using pressure cookers, etc.
It is important to realize that our economic comparisons ignored
the capacity of a particular stove to cook for different sized
families. A small cookstove could not adequately cook a large
pot of food. Of course a large family could use several small
cookstoves and experience the same savings, as long as large pots
were not used for cooking. However, cooking in large pots is
common in the Caribbean. The fact that smaller cookstoves were
shown to be more efficient and economical does not guarantee that
they would be acceptable to users.
Table 2. Economic Comparison of Charcoal Cookstove Use
Coal Z
Item pots Umeme Ztove AC
Purchase cost (EC$) 44 180 83[a] 30
Estimated stove life (years) 7 3 2 4
Maintenance cost over life
of stove (EC$) 15 9 30 8
Stove/operator efficiency
(SAEM/pound charcoal) 3.5 3.4 5.2 5.8
KPT responses (no.) 7 12 11 5
Fuel cost (EC$/SAEM) [b] 0.143 0.147 0.096 0.086
Investment cost (EC$/SAEM) [c] 0.003 0.032 0.022 0.004
Maintenance cost (EC$/SAEM) [c] 0.001 0.002 0.016 0.001
Total cost (EC$/SAEM) 0.147 0.181 0.134 0.091
Savings [loss] compared to
coal pots (EC$/year) [c] - [64.53] 24.67 106.29
[a] Purchase cost as imported.
[b] Fuel cost, EC$.50 per pound.
[c] Average family of three cooks 5.2 SAEM per day or
1898 SAEM per year.
ACCEPTABILITY
Inasmuch as people's opinions on any single subject vary tremendously,
there was no one trial cookstove model that was universally
acceptable. A range of cookstove models would have to be
available to satisfy all people's desires and cooking needs.
To begin with, there was no perceived need among the users of
coal pots and three-stone fireplaces for improving upon traditional
cooking systems. The government felt the need to protect
its valuable forest resource by introducing more efficient cooking
methods.
So there was a need to develop a consciousness in the people
about cooking fuel efficiency. Therefore, very few comments were
made about a cookstove's efficiency, the major reason for the
project's existence. Most concerns were expressed about cookstove
appearance, how well they worked, how they fit the cooking
needs, how durable they were, what the working features were,
their cost, and their efficiency, in roughly that order of importance
to potential users.
The most excited feedback we received was based on a trial
stove's looks. Older users seemed to prefer the Umeme, perhaps
because they were more like coal pots than other trial cookstoves.
Younger folks seemed to like the smaller, more modern
looking stoves. The most coveted design was the Z Ztove, with
its manufactured look.
People liked the way the smaller stoves worked, but the stoves
did not always fit their needs. Cooking capacity generally was
lacking. Comments such as these led us to enlarge several cookstove
models. At our request, the Z Ztove manufacturer sent us
modifications of the Z Ztove that were double burners and single
but larger burners. We had local tinsmiths make two larger sizes
of AC stoves. The larger models were well received.
Cookstove durability was a concern. Clay coal pots were not
favored due to their fragility. We found that expensive sheet
metal lining around fireboxes lasted only one to three months.
The Umeme, Z Ztoves, AC stoves, and two-can stoves had these
liners. It was of little concern in the Umeme and AC stoves with
their cement insulation. Once the tin burned out the cement
became the firebox wall. The tin merely acted as a form for the
cement. But the firebox lining had to be replaced periodically
in the other stoves. The Z Ztove had easily replaceable liners,
and the two-can stove used easily replaced motor oil cans. But
the Umeme with soil insulation required shaping sheet metal into
a cone for relining. Concern was registered for the durability
of wire mesh grates, but these were inexpensive and easily replaced.
Of the working features of cookstoves, the most appreciated was
the ash drawer for ease in emptying the ashes. The ash drawers
also doubled as air control, but there seemed to be little esteem
for its value in conserving fuel.
The fact that much food was cooked in frying pans led to our
modified wind shield with slot for frying pan handle on the Umeme
stoves. That made them more acceptable.
The large Umemes with cement or soil insulation were very heavy.
Montserratians moved their coal pots around--to light them outside,
bring them inside for cooking, and back outside for emptying
ashes. We tried reducing the weight of cement insulated
models by incorporating charcoal fines into the cement mix. We
never really overcame that objection to the Umeme.
Another objection to the Umeme stoves was the lack of air getting
to the fire. The only combustion air in Umemes was that which
was pulled up to replace the hot air rising out of the stove.
Coal pots were designed such that when the "arch" (draft opening)
was faced into the breeze, the air going into the arch was all
forced up into the fire. Breezes simply passed under the Umeme.
For many families the cost of a cookstove was not important.
Nevertheless a segment of the stove testers complained about not
being able to afford a new cookstove. For these people we developed
the AC and two-can charcoal stoves, and introduced the five-gallon
bucket wood-burning stove. Each of these models was
inexpensive and easy enough for most families to make in their
own home. However, the two charcoal stoves were small and had a
homemade look, which detracted from their acceptance. And because
wood fuel use was associated with families in the lowest
economic group, any wood-burning cookstove had to overcome that
debasement to be acceptable.
If we had to rank cookstoves according to their overall acceptability,
they would roughly follow in order of descending acceptance:
1. coal pots for their familiarity,
2. Satellite stove for its good looks and durability,
3. Z Ztove for its good looks and working ability,
4. Umeme stove for its similarity to coal pots and ash
drawer,
5. AC stove for its simplicity and low cost,
6. two-can stove for its simplicity and low cost,
7. five-gallon bucket stove for its simplicity and low
cost,
8. the cement wood-burning stoves, and
9. the clay cookstoves.
As time goes by this ranking could change. People will become
more aware of the value of improved stove efficiency as lpg
becomes more expensive and competition for wood and charcoal
becomes more keen.
Cooking with wood and charcoal was dirtier and slower than cooking
with lpg. In an effort to help clean up the handling of
charcoal, the project introduced the use of inexpensive ice tongs
and scoops cut from discarded plastic bleach bottles. For faster
starting of charcoal fires, a tin juice can with top and bottom
removed, and side air holes punched around the bottom was promoted.
With one sheet of crumpled newspaper in the bottom and
charcoal in the top of the upright cylinder, a fast fire was
assured for even the novice fire builder (providing the charcoal
was dry).
It was hoped that all of these efforts at improving cookstoves
and cooking systems would help elevate the status of using wood
and charcoal fuels, and assure a perpetual supply of these local
renewable resources.
4. CONCLUSIONS AND RECOMMENDATIONS
Test results and user comments led us to the following conclusions:
1. Smaller charcoal cookstoves were more efficient and
economical than traditional coal pots, but required
more cooking time and often were not suitable to the
cooking needs of Montserratian families.
2. Positive air control was difficult to achieve in cookstoves,
but improved their efficiency.
3. Insulating the firebox was most useful in cookstoves
without air control or the ability to retract the fuel.
4. Grates in smaller charcoal cookstoves needed maximum
air holes.
5. The cast aluminum coal pot was superior to other coal
pots in efficiency.
6. Kitchen performance testing (KPT) of cookstoves yielded
information for many important uses, but required a
large input of time and effort.
7. The operator variable in cooking system efficiency is
so great that more impact on fuel conservation might be
possible through public education (people improvement)
than through stove improvement.
And finally, we concluded that a number of suggestions for
further work are in order:
1. Continue kitchen performance testing of stove models to
obtain solid baseline data on the number of standardized
meals prepared by each oven dry pound of fuel.
2. Participate in public education efforts to conserve
cooking fuels.
3. To overcome problems in production and quality control,
develop systems to mass produce inexpensive cookstoves.
4. Develop a small battery-powered fan unit with variable
speeds to hook to small cookstoves for supercharging
combustion air.
5. Develop a more durable firebox and top for the Z Ztove.
6. Polish the firebox walls of the aluminum coal pot and
retest for efficiency.
APPENDIX I
COOKSTOVE DESIGNS
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove TRADITIONAL COAL POT-CARRIBEAN
Name of stove builder(s) VARIOUS
Construction date 1982 Materials used CAST ALUMINUM,
CAST IRON, CLAY, OR CEMENT WITH WIRE ROD AND DRUM STEEL.
<FIGURE A>
48ap01.gif (600x600)
Details of stove construction GRATE IS CAST SEPARATELY. CLAY
COAL POTS CLAY GRATES, WHILE CEMENT COAL POTS USE OIL DRUM
STEEL WITH PUNCHED HOLES.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CLAY DOUBLE-SKINNED - AFRICA (MODIFIED)
Name of stove builder(s) Joseph Howson
Construction date 2/83 Materials used CLAY MIXTURE WITH
WHITE VOLCANIC POWDER AND ONE NAIL.
<FIGURE B>
48ap02.gif (600x600)
Details of stove construction INSIDE AND OUTSIDE CYLINDERS WERE
TURNED SEPARATELY, JOINED, CURED, AND FIRED AT 900-1100 [degrees] C. SECONDARY
AIR HOLES WERE 12-IN. DIAM. AND SLANTED UPWARD TOWARD THE INSIDE. WALLS
OF FIREBOX WERE ROUGH TO PROMOTE MIXING OF GASES AND AIR. DRAFT
DOOR ADJUSTABLE WITH NAIL.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove UMEME - AFRICA (MODIFIED)
Name of stove builder(s) John Harris, James Sweeney, Cecil Roach
Construction date 2/83 Materials used SHEET METAL WITH
CEMENT, AIR, OR SOIL INSULATION, NAILS, 1/4-INCH ROD, AND DRUM STEEL
<FIGURE C>
48ap03.gif (600x600)
Details of stove construction NAIL RIVETS FASTENED THE ASH DRAWER,
DRAFT SLIDE AND DRAWER RAIL TO THE BOTTOM, AND THREE LEGS
TO THE BOTTOM. CHARCOAL FINES WERE MIXED WITH CEMENT TO LESSEN
THE WEIGHT. POT SUPPORT RODS EXTENDED INTO THE CEMENT. NOTCH IN
WIND SCREEN WAS FOR FRYING PAN HANDLE.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove ADVANCED CHARCOAL (AC) - MONTSERRAT
Name of stove builder(s) JOHN HARRIS, JAMES DYER
Construction date 4/83 Materials used VARIOUS CANS, NAILS,
DRUM STEEL, 1/4-INCH AND 1-INCH WIRE MESH, 1/4-INCH ROD, AND CEMENT
<FIGURE D>
48ap04.gif (600x600)
Details of stove construction CEMENT INSULATION WAS REINFORCED
BY 1-INCH MESH WIRE. POT REST/WIND SHIELD AND HANDLES MADE WITH
DRUM STEEL, FASTENED WITH NAIL RIVETS. DRAFT DOOR AND AIR PREHEATER
MADE WITH TIN. 1/4-INCH ROD SUPPORTS AIR PREHEATER WHICH
SUPPORTS 1/4-INCH MESH GRATE.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove Z ZTOVE - U.S.A.
Name of stove builder(s) ZZ CORPORATION
Construction date 2/83 Materials used SHEET METAL,
POP RIVETS, 1/4-INCH WIRE MESH, AND CERAMIC FIBER.
<FIGURE E>
48ap05.gif (600x600)
Details of stove construction THE Z ZTOVE IS MASS PRODUCED
FROM PRE-CUT SHEET METAL PARTS. THEY ARE BENT IN PRESSES, GANG
DRILLED, AND POP RIVETED. THE INNER BURNER BOWL IS REPLACEABLE
AFTER IT BURNS OUT.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove TWO CAN STOVE - MONTSERRAT
Name of stove builder(s) ANYONE
Construction date 7/83 Materials used PAINT CAN, MOTOR
OIL CAN, DRUM STEEL, AND NAILS.
<FIGURE F>
48ap06.gif (600x600)
Details of stove construction FIRST PUNCH MOTOR OIL CAN FULL OF HOLES,
THEN REMOVE ITS TOP, CUT PAINT CAN LID RADIALLY LEAVING SHORT TABS UNTIL
THE MOTOR OIL CAN FITS DOWN IN IT AND IS SUPPORTED BY ITS FLARED TOP
EDGE. PLACE LID WITH MOTOR OIL CAN ON PAINT CAN. THEN CUT OPENING
FOR DRAFT AND MAKE POT REST WITH DRUM STEEL AND NAIL RIVETS.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove SATELLITE STOVE - MONTSERRAT
Name of stove builder(s) SYLVESTER MEADE
Construction date 9/83 Materials used SIX-INCH STEEL PIPE
1/8-INCH STEEL PLATE, 1/2-INCH REBAR, 1/4 INCH ROD, SHEET METAL, 1/4-INCH WIRE MESH
<FIGURE G>
48ap07.gif (600x600)
Details of stove construction PIECES WERE WELDED TOGETHER,
ASH DRAWER WAS FASHIONED FROM SHEET METAL. A CLAY CYLINDER
AND CEMENT WERE TRIED AS INSULATION.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove THREE-STONE FIREPLACE - UNIVERSAL
Name of stove builder(s) ANYONE
Construction date 9/83 Materials used THREE STONES
<FIGURE H>
48ap08.gif (600x600)
Details of stove construction PLACE THREE STONES SO THEY
SUPPORT THE POT ABOVE THE GROUND AND LEVEL.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CLAY DOUBLE-SKINNED WOOD-BURNING STOVE-AFRICA (MONFIED)
Name of stove builder(s) Joseph Howson
Construction date 2/83 Materials used
<FIGURE I>
48ap09.gif (600x600)
Details of stove construction INSIDE AND OUTSIDE CYLINDERS WERE
TURNED SEPARATELY, JOINED, CURED, AND FIRED AT 900-1100 [degrees]. SECONDARY
AIR HOLES WERE 1/2-INCH DIAM. AND SLANTED UPWARD TOWARD THE
INSIDE. WALLS OF FIREBOX WERE ROUGH TO PROMOTE MIXING OF GASES
AND AIR.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove FIVE-GALLON BUCKET WOOD-BURNING STOVE-AFRICA
Name of stove builder(s) ANYONE
Construction date 8/83 Materials used FIVE-GALLON BUCKET
AND 1/4-INCH ROD.
<FIGURE J>
48ap10.gif (600x600)
Details of stove construction SIMPLY PUNCH THREE EQUIDISTANT
HOLES AROUND THE CIRCUMFERENCE, INSERT 11-INCH LONG RODS AND
BEND ROD ENDS. THEN CUT OUT THE DRAFT OPENING.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CEMENT WOOD-BURNING STOVE-MONTSERRAT
Name of stove builder(s) TONY CARTY AND CHARLES WHITE
Construction date 4/83 Materials used CEMENT, 1/2-INCH
REBAR, REINFORCING MESH, WOOD, SHEET METAL, AND NAILS.
<FIGURE K>
48p11.gif (600x600)
Details of stove construction THE TOP SLAB IS POURED AROUND THE
ACTUAL POTS. POTS ARE REMOVED AND POT HOLES SMOOTHED WHEN CEMENT
IS PARTIALLY CURED. DOOR IS WOOD-LINED WITH TIN INSIDE. GRATE IS
MADE OF REGARS. AND REBAR HANDLES ALLOW FOR PORTABILITY. REINFORCING
MESH IS INSIDE CEMENT.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CEMENT WOOD-BURNING STOVE-MONTSERRAT
Name of stove builder(s) Joseph Sweeney and David Lake
Construction date 9/83 Materials used CEMENT, CHICKEN
WIRE, WOOD, SHEET METAL, HINGES, AND NAILS.
<FIGURE L>
48ap12.gif (600x600)
Details of stove construction THE TOP SLAB IS POURED AROUND THE
ACTUAL POTS. POTS ARE REMOVED AND POT HOLES SMOOTHED WHEN CEMENT
IS PARTIALLY CURED. THE HINGED DOOR IS WOOD LINED WITH TIN ON
THE INSIDE. THE CHIMNEY IS SHEET METAL. CHICKEN WIRE IS USED
TO REINFORCE THE CEMENT.
APPENDIX II
WATER BOILING TEST PROCEDURES
In order to compare different designs of stoves, all variables
other than stove design that might affect efficiency such as
fuelwood species, moisture content, size, and amount; operator
and operating sequence and schedule; weather (mainly wind); and
pot design, size, material, and contents were held as consistent
as possible.
The testing was conducted according to the following procedures:
1. We sampled the fuel to determine moisture content (MC). For
charcoal we disregarded MC unless it had been wetted. The
MC samples were at least 100 grams and were chosen to be
representative of the fuel being used. They were cut just
before the WBT. We weighed the samples immediately to the
nearest 1/10 gram and recorded the weight. We identified
each sample by marking a number directly on it with a magic
marker. The samples were put in an oven at 215 [degrees] F for at
least 24 hours (until they lost no more weight) and reweighed.
The oven dry weights were recorded. Then MC was
calculated on the green weight basis by the formula:
percent MC = (green weight - oven dry weight/green
weight) x 100.
2. We weighed the fuel put in the stove and recorded the weight
in pounds.
3. We weighed an 11-inch diameter flat bottomed aluminum pot
without the lid. The weight was recorded. Then we added
two kilograms (four pounds, six ounces) of water at ambient
temperature and recorded the weight. The lid was fitted
with a stopper through which a mercury thermometer was
placed. The lid was put on the pot and the thermometer
adjusted to be about one inch from the bottom of the pot.
For two-pot stoves we used an 11-inch and an eight-inch
diameter pot of the same design.
4. We used two Zip fire fuel pellets for kindling, lit them and
recorded the time. We added the fuel.
5. After allowing five minutes for the fire to get started, we
put the pot(s) on. The fire was maintained for maximum heat
until the water was boiling.
6. At each five-minute interval, the time and temperature of
each pot were recorded. When the thermometer reached 212 [degrees] F
the time was recorded. For two-pot stoves only the first
pot directly over the fire was used for this determination.
7. After the water boiled, the stove was adjusted to simulate
simmering, to provide just enough heat to keep the water
lightly boiling for 30 minutes. In charcoal stoves this was
done by closing draft controls or loosely blocking draft
openings on stoves without draft controls. In the cement
wood-burning cookstoves the doors were closed. And in the
three-stone fireplace and five-gallon bucket, we pulled the
wood pieces outward to slow down the fire.
8. During the test we recorded miscellaneous observations such
as the amount of flame or smoke, how hot the stove was to
touch, etc.
9. At the end of the 30 minutes of simmering we did the following
in rapid sequence:
- recorded the water temperature,
- weighed and recorded in pounds the amount of water
remaining, and
- weighed and recorded in pounds the amount of unburned
fuel. When wood was the fuel, we separated the wood and
charcoal before weighing.
10. Calculations were made on the following:
WE - Amount of water evaporated (pounds) = initial weight of pot
and water minus the final weight of pot and water.
CT - Change in water temperature ([degrees] F) = highest water temperature
minus the beginning water temperature.
CB - Weight of charcoal burned (pounds) = initial fuel weight
minus the weight of the unburned remainder.
DW - Weight of oven-dry wood burned (pounds) = [initial weight of
wood put in stove times 1 - MC in decimal form] minus the
weight of wood and charcoal unburned.
FM - Weight of moisture in fuel (pounds) = initial weight of fuel
put in stove times MC in decimal form.
EF - Stove efficiency (PHU) = [CT x original weight of water in
pounds] + [WE x 1,050]/[DW x 8,500 - FM X 1,2001 - [pounds
of charcoal remaining x 12,500] x 100.
where:
- 1,050 was the latent heat of water in Btu per pound at
room temperature,
- 8,500 was the heat value of oven dry wood in Btu per
pound,
- 1,200 was the heat needed to drive moisture out of wood
fuel in Btu per pound of water,
- 12,500 was the heat value of oven dry charcoal in Btu
per pound,
- for charcoal stoves the denominator was simply CB x
12,500, and
- DW and FM were considered accurate for our use since
there was little unburned fuel.
SSC - Standard Specific Consumption = DW/WE.
APPENDIX III
WATER BOILING TEST DATA SHEET
DATE: ______________________________ STOVE TYPE: ______________
OPERATOR(S): _______________________ MODIFICATIONS: ___________
TEST NUMBER: _______________________ FUEL: ____________________
MOISTURE CONTENT SAMPLES:
Identification Fresh weight Oven-dry weight MC (Green basis)
FUEL WEIGHT AT START: __________________ POT WEIGHT: _____________
INITIAL WEIGHT OF POT & WATER: _________ INITIAL WATER TEMP: _____
ELAPSED WATER FUEL WEIGHT
TIME TIME TEMPERATURE ADDED COMMENTS
______ 0_______ _________________ _______________ __________
______ 5_______ _________________ _______________ __________
______ 10______ _________________ _______________ __________
______ 15______ _________________ _______________ __________
______ 20______ _________________ _______________ __________
______ 25______ _________________ _______________ __________
______ 30______ _________________ _______________ __________
______ 35______ _________________ _______________ __________
______ 60______ _________________ _______________ __________
FINAL WEIGHT OF POT AND WATER: _____________
WEIGHT OF WOOD REMAINING: __________________
WEIGHT OF CHARCOAL REMAINING: ______________
APPENDIX IV
KITCHEN PERFORMANCE TEST DATA SHEET
STOVE TYPE: ________________________ FAMILY NAME: ___________________
LOCATION: _____________________________________________________________
NUMBER OF PEOPLE FED: ______________ STANDARD ADULT EQUIVALENTS:
children 0 - 14 years _________ x 0.5 =
women over 14 years _________ x 0.8 =
men aged 15 - 59 years ________ x 1.0 =
men over 59 years _____________ x 0.8 =
NUMBER OF MEALS COOKED: OTHER USES:
breakfast __________ ironing ____________
lunch __________ baking ____________
dinner __________ others ____________
other cooking__________ ____________
WAS THERE ANY LEFTOVER CHARCOAL IN THE STOVE? ________________
WHAT DID YOU DO WITH IT?
WOULD YOU USE MORE _____ OR LESS _____ FUEL FOR SIMILAR
MEALS IN THE CONVENTIONAL COAL POT?
GENERAL COMMENTS:
APPENDIX V
COOKSTOVE LOCATION SHEET
STOVE MODEL: _____________________ FEATURES: _________________________
DATE DATE
START FINISH ADDRESS USER COMMENTS
APPENDIX VI
CONVERSION FACTORS
1 pound = 0.454 kilograms
1 kilogram = 2.2 pounds
1 Btu = 0.252 kilocalories
1 kilocalorie = 3.968 Btus
1 Btu/pound = 2.32 Joules/gram
[degree] C = [degree] F - 32/1.8
[degree] F = (1.8 x [degree] C) + 32
BIBLIOGRAPHY
Baldwin, Sam. "New Directions In Woodstove Development." VITA
News, January 1984, pp. 3-13, 19-23.
de Silva, Dhammika. "A Charcoal Stove From Sri Lanka." Appropriate
Technology Vol. 7, No. 4, 1981, pp. 22-24.
Foley, Gerald and Moss, Patricia. "Improved Cooking Stoves In Developing
Countries." Earthscan Technical Report No. 2, 1983,
175 pp. Illus.
Government of Montserrat. Preliminary Data of the 1980 Commonwealth
Caribbean Population Census, Part I: Household and
Housing Information, 1980, 26 pp.
Hassrick, Phillip. "Umeme: A Charcoal Stove from Kenya." Appropriate
Technology Vol. 9, No. 1, 1982, pp. 6-7.
Joseph, Stephen and Trussell, Jenny. Report on Advisory Visit to
the VITA Wood Stove Project in Upper Volta. Intermediate
Technology Consultants Ltd. report to VITA, 1981, 52 pp.
Illus.
Singer, H. "Improvement of Fuelwood Cooking Stoves and Economy in
Fuelwood Consumption." Report to the Government of Indonesia
No. 1315. Rome, Italy: Food and Agriculture Organization
of the United Nations, 1961, 58 pp.
Tata Energy Research Institute. Solid Fuel Cooking Stoves. Bombay,
India, 1980. 118 pp. Illus.
Volunteers in Technical Assistance (VITA). Testing the Efficiency
of Wood-Burning Cookstoves: Provisional International
Standards. Arlington, Virginia: Volunteers in Technical
Assistance (VITA), 1982, 76 pp. Illus.
Yameogo, Georges; Bussman, Paul; Simonis, Philippe; and Baldwin,
Sam. Comparison of Improved Stoves: Lab, Controlled Cooking,
and Family Compound Tests. I.V.E/T.H.E. Eindhoven/GTZ/
CILSS/VITA, 1983, 67 pp. Illus.
========================================
========================================
IN THE CARIBBEAN
by
Jeffrey L. Wartluft
MONTSERRAT FUELWOOD/CHARCOAL/COOKSTOVE PROJECT
A cooperative effort by the
GOVERNMENT OF MONTSERRAT, MINISTRY OF AGRICULTURE (GOM)
CARIBBEAN DEVELOPMENT BANK (CDB)
VOLUNTEERS IN TECHNICAL ASSISTANCE (VITA)
and
UNITED STATES AGENCY FOR INTERNATIONAL DEVELOPMENT (USAID)
Published by
VITA
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 * Fax: 703/243-1865
Internet: pr-info@vita.org
TABLE OF CONTENTS
Acknowledgements
1. Introduction
2. The Project
Stove selection
Trial charcoal cookstoves
Trial wood-burning cookstoves
Efficiency tests
Economics
Acceptability
3. Results and discussion
Efficiency
Economics
Acceptability
4. Conclusions and recommendations
Appendixes
I. Cookstove designs
II. Water boiling test procedures
III. Water boiling test data sheet
IV. Kitchen performance test data sheet
V. Cookstove location sheet
VI. Conversion factors
Bibliography
ACKNOWLEDGEMENTS
This paper summarizes the efforts of many individuals, particularly
our Montserrat project team, which consisted of: Joseph
Daniel, energy officer; Stedford White, project assistant; James
Silcott, stove tester; and Meredith White, secretary.
Many other Montserratians helped with cookstove fabrication, information
gathering and dissemination, and field testing of cookstoves.
Support for the team's efforts was provided by Dan Chalmers, Dr.
Jeffrey Dellimore, Carolyn Cozier, and David Moore of the Caribbean
Development Bank (CDB); and Richard J. Fera, John M. Downey,
Jane Kenny, Paula Gubbins, Margaret Crouch, and Julie Berman of
Volunteers In Technical Assistance.
--Jeffrey L. Wartluft
Project Manager
1. INTRODUCTION
In English-speaking countries of the Caribbean, liquid petroleum
gases (lpg) are the most common cooking fuels. With the exception
of Trinidad, lpg is imported and so is expensive for families
as well as a drain on a country's treasury. Lpg supply to
these countries is uncertain too. It depends on seasonal demand
and shipping and refinery schedules. The occasional long lines
at the lpg dealers bear witness to this problem. Families who
can afford to, have purchased two lpg cylinders to get around
delivery uncertainties. Someday in the future there will be no
affordable lpg--it is not renewable.
For most islands there is an alternative cooking fuel which is
local, renewable, and viable right now. In fact, families have
cooked with it for centuries, and still do. This fuel is wood
from forests. However, this valuable resource is renewable only
if used wisely. Such use involves many activities--measuring
supplies and demands of different products, and satisfying these
demands over the long term by efficient utilization of the forest
and, if necessary, prudent plantations of suitable tree species.
The Government of Montserrat had the foresight to initiate a
project that would guide the country in managing its forest
resource, particularly for fuel. In this effort they enlisted
help from the Caribbean Development Bank (CDB), Volunteers In
Technical Assistance (VITA), and the United States Agency for
International Development (USAID). The Montserrat Fuelwood/Charcoal/Cookstove
Project, begun in 1982, is studying 20 fast-growing
tree species in experimental plantations, assessing the
fuel supply from natural forests, finding efficient ways to
convert wood to charcoal, and finding efficient ways to cook with
both charcoal and wood. This paper reports on the results of the
cookstove portion of the Montserrat project. Because cooking
methods and cookstoves are similar enough throughout most of the
Caribbean, the results of the Montserrat work are likely applicable
across the region.
The 1980 Commonwealth Caribbean Population Census stated that 40
percent of the people in Montserrat cooked with traditional wood
and charcoal fuels (GOM, 1980). This surprisingly high estimate
prompted the initiation of the project out of concern for the
future of Montserrat's forest resource. Our own estimates of
traditional fuel use were:
Use Fuel Percent of Population
full time charcoal 20
occasional charcoal 60
full time wood 5
occasional wood 40
Meals cooked with charcoal customarily used cookstoves called
coal pots (Appendix I). There were several models using various
materials, but with very similar designs and sizes (Figure 2).
48p02b.gif (393x393)
In fact, the Caribbean coal pot design was similar to many charcoal
cookstove designs in Asia and Africa. Cookstoves like these
have been shown in laboratory tests to have efficiencies (amount
of heat absorbed by the water/amount of heat available in the
fuel x 100) around 30 percent (de Silva, 1981; Singer, 1961; and
Tata, 1980). Little is known about the efficiency of these
stoves in actual use.
When wood is used as a cooking fuel, it is usually burned in a
three-stone fireplace (Figure 1 and Appendix I). The literature
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has been harsh in its evaluation of three-stone fireplace efficiency,
leading one to believe it is in the order of five to 10
percent. Recent laboratory and field testing, however, has shown
a higher percentage of efficiency, around 17 (Yameogo et al.,
1983).
For certain cookstove models to "catch on" we felt they should be
efficient, economical, and acceptable. So we tested cooking
techniques to measure these three criteria. Twenty-six cookstove
models including the current standards were compared. Interpretation
of the data suggested that the smaller cookstoves were
more efficient and economical, but at a cost in time to bring
food to cooking temperatures. Positive air control was important
for efficiency but difficult to achieve in inexpensive stoves.
Kitchen performance field testing was valuable in determining
efficiency, economics, and fuel demand, but definitive data would
require a large input of time and effort.
2. THE PROJECT
The objectives of the Montserrat Fuelwood/Charcoal/Cookstove
Project were to:
1. Substitute local renewable cooking fuel from the forest
for imported liquid fuels,
2. Use the forest resource wisely, and
3. Create local industry and employment.
Specifically for the cookstove portion of the project, all three
objectives would be enhanced by identifying and testing
techniques for efficiently using charcoal and wood fuel for
cooking.
STOVE SELECTION
In order to know if any improvements were made, we had to know
the performance of the stoves currently in use. So we selected
four models of coal pots--cast iron, cast aluminum, clay, and the
converted steel auto wheel--and the only cookstove used with wood
fuel, the three-stone fireplace (Figures 1 and 2). In Montserrat,
wood fuel is also used in massive stone ovens for baking, but
ovens were not tested.
Trial cookstove designs expected to be improvements over the
standard cookstoves were chosen according to strict criteria.
They had to be:
1. simple to build and use,
2. made locally with local materials,
3. inexpensive,
4. appealing in looks, and
5. formerly tried and reported in the literature.
The only locally available materials in quantity were sand,
stone, and clay. From the start, "mud" stoves were not considered
due to the strong local feeling that their use would be a
step backward in progress. Even though clay coal pots were not
in much favor because they broke so easily, attractive double-walled
models were made for both charcoal and for wood fuel.
A limited number of metal recyclable components were also available
locally. Our trial designs incorporated used oil drums,
five-gallon buckets, steel pipe, paint cans, and tin cans. All
other materials, galvanized sheet metal, wire mesh, one quarter
inch rod, and cement used in trial stoves were imported.
The large variety in design and size of pots used for cooking in
Montserrat made decisions on stove dimensions difficult. Improved
stove features called for shielding and insulating around the
pots. So a stove designed for a 10-inch diameter pot would be
too small for a 12-inch pot, and allow unnecessary heat loss when
cooking with an eight-inch pot. Most trial designs were dimensioned
for 10-12-inch pots. Coal pots and three-stone fireplaces
were very flexible in accommodating various pot sizes, even
frying pans.
Chimneys were not considered very important in our trial designs.
Other stove programs have found chimneys to be a mixed blessing
(Foley and Moss, 1983). And Montserratians were not fond of the
idea of holes in their roofs. Cooking with wood was generally
done outside. Even though much charcoal was used inside, Montserratian
homes were always well ventilated to get the cooling
effects of constant breezes. Smoke and carbon monoxide have not
caused problems. Only the two-hole cement wood-burning trial
cookstoves had chimneys.
Even though there was interest in ovens and grills based on
traditional fuels, the project did not have sufficient time to
design and test these. There were several types of charcoal
"Charlie Man" ovens in use. One design employed a used oil drum,
inside of which was placed a coal pot for heat. It had a hinged
door for access, and two steel mesh shelves for baking. For
added heat, charcoal was burned on the top. These drums were not
insulated. A better design was the wooden box with hinged door,
tin lining inside, and shelves. This oven was heated by placing
a coal pot with burning charcoal inside. Both ovens were easy to
build and required no welding tools or special skills.
Trial Charcoal Cookstoves
The simplest design selected for testing was a coal pot modification,
a sheet metal pot ring. The ring fit over the top of a
standard coal pot and had a hole cut in it to match the pot
diameter (Appendix I). This was an attempt at keeping the heat
closer to the pot to enhance heat transfer into the pot.
The double skin (DS) fired clay charcoal stove mentioned earlier
provided a wind screen, preheated secondary air, an insulated
firebox, and draft control (Figure 3; Appendix I; and Joseph and
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Trussell, 1981). This sophisticated design originated in Africa.
For use in Montserrat, the design was slightly modified and was
beautifully executed by potter Joseph Howson.
Another design of African origin, the Umeme, was selected. The
Umeme was made with galvanized sheet metal and several types of
insulation--air, soil, and cement. It featured a wind screen,
tapered firebox, ash drawer, and draft control (Figure 4; Appendix
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I; and Hassrick, 1982). Craftsmen fabricating trial cookstoves
for the project were encouraged to add their own creativity
to their work. Three tinsmiths, James Sweeney, Cecil Roach,
and John Harris, were enlisted to build the Umeme. Using the
same drawings, each came up with quite different looking versions.
Only one stove selected was manufactured outside Montserrat. The
Z Ztove, mass produced in California, USA, was a sophisticated
design made with sheet metal and ceramic fiber insulation. It
was tested because of the possibility of mass producing them in
Montserrat for the Caribbean market. Features of the Z Ztove
included preheated secondary air, firebox insulation, and positive
separate controls for primary and secondary air (Figure 5
48p06a.gif (437x437)
and Appendix I).
As stove testing progressed, modifications and new trial designs
were born as a result of user feedback and our own efforts to
improve stove performance or acceptance. For instance, the Z Z
Corporation made several two-burner and larger burner Z Ztoves at
our request.
Two models that would be inexpensive and easy to construct in the
home were tried. The Advanced Charcoal (AC) Stove used a juice
tin inside of a paint can, with cement insulation between the
cans (Figure 6 and Appendix I). It was conceived by Joseph
48p06b.gif (437x437)
Daniel, the Energy Officer in Montserrat. The AC stove was
tested in three sizes, and with and without a combustion air
preheater and draft control.
The idea for the two-can stove design was sparked by a simplified
copy of the Z Ztove built by Montserratian stove tester James
Bradshaw. In this simple design a motor oil can was placed
inside a paint can (Figure 7 and Appendix I). The design allowed
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both primary and secondary air to reach the burning charcoal.
In an effort to overcome the lack of durability of the Z Ztove
and two-can stove, the project team designed an attractive Satellite
stove (Figure 8 and Appendix I). Materials used included
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six-inch diameter steel pipe, steel plate, and steel reinforcing
rod. The Satellite stove had an ash drawer and draft control.
Tests were run with clay and cement liners.
Trial Wood-burning Cookstoves
The African double-skinned fired clay stove was selected for
testing. It had provision for primary and secondary combustion
air (Figure 9 and Appendix I).
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A simple stove was made from a used five-gallon resin bucket and
some 1/4-inch rod. The bucket served as the firebox and pot wind
screen. The large fuel opening in both the clay and bucket
stoves allowed sticks of any length to be used with the stove,
but did not allow for combustion air control.
Two reinforced cement cookstoves were built for trial with wood
fuel. Each was built by different masons, incorporating some
individual creativity. One built by Tony Carty and Charles White
had thicker walls, a grate, and a removable firebox door. The
other, built by Joseph Sweeney and David Lake, had thinner walls,
a hinged firebox door, and a weight-saving hollow under the
sloping firebox floor (Figure 10). Each had two holes for pots
48p07b.gif (486x486)
and a short four-inch diameter chimney. They were built to be
portable for demonstration purposes (Appendix I).
EFFICIENCY TESTS
Two different tests for efficiency were performed with trial
cookstoves: the water boiling test (WBT), and the kitchen performance
test (KPT). Provisional international standards for
these tests were developed during a meeting of experts at VITA
headquarters (VITA, 1982). We followed these standard procedures
with a few modifications.
The WBT measured the amount of heat used in raising water
temperature and evaporating water in a ratio over the amount of
heat used from the fuel. Results were reported as percent heat
utilized (PHU). We also reported the time required for a
standard quantity of water to boil, and the amount of fuel that
would fit in the firebox.
Equipment used in the WBT included:
* two 11-inch diameter aluminum pots with flat bottoms
and lids,
* two eight-inch diameter aluminum pots with flat bottoms
and lids,
* balance accurate to 1/10 gram with a capacity of 6,250
grams,
* four rubber stoppers with single holes,
* four mercury thermometers reading to 250 [degrees] F (two spares),
* electric oven with accurate temperature control to 220 [degrees] F,
* small tongs,
* heavy leather gloves,
* clock reading to the nearest minute,
* Zip fire fuel pellets (for standardized kindling), and
* magic markers.
The detailed procedure is presented in Appendixes II and III.
The second test measured the relative efficiency of the stove and
operator together. The KPT was performed by many different
Montserratian families. Participating families were selected to
represent different economic levels and geographic areas. In
order to have reliable results, we needed many families to participate
due to the added variability of different stove operators,
cooking styles, food prepared, and eating habits. Since our time
was limited, we field tested stoves with as many families as we
could accommodate in our schedule. Only charcoal stoves were
tested in the KPT.
We loaned a trial stove to each family and gave them a 10-pound
bag of charcoal with instructions to keep track of the number of
meals cooked on that stove with that bag of charcoal--no more or
less. We also asked them to keep track of the number of people
who ate those meals, their ages and sex. Each family was given a
KPT data sheet to help them record data (Appendix IV). When we
returned in two to four weeks we reviewed the data sheet with
them. We asked for their likes and dislikes about the stove, if
they used it for heat needs other than daily meals, and checked
to make sure they did not use the fuel in different stoves, they
used all the fuel, and no fuel in addition to what was in the
bag. At that point we offered to let them repeat the KPT with a
different model stove. Once a family had tested two or more
trial stoves, we asked them to repeat the KPT with their standard
coal pot. When we returned for the last results, we gave them a
bag of charcoal in appreciation for their cooperation. The charcoal
was from our kiln trials in the other segment of our Montserrat
project.
Results of the KPT were expressed as the number of standard adult
equivalent meals (SAEM) prepared per 10 pounds of charcoal. SAEM
were figured according to a widely used League of Nations formula
which uses the following values.
Sex and Age Standard Adult Equivalent Meal
Child, 0-14 years 0.5
Female, over 14 years 0.8
Male, 15-59 years 1.0
Male, over 59 years 0.8
Since there were a number of stoves with different Montserratian
families under test simultaneously, and the stoves were switched
around among families, we used a stove location sheet for each
stove (Appendix V). By keeping these up to date, we knew where
each stove was and when it was time to visit each family.
ECONOMICS
Economic comparisons of stoves were figured on the cost to use
each type of stove per SAEM. We maintained records on the:
1. material and labor costs of building the stoves,
2. maintenance costs, and
3. fuel costs.
To arrive at the investment or depreciation cost, we estimated
stove life and divided the original cost of the stove by the expected
SAEM over its life. Maintenance costs included any replacement
of parts over the life of the stove. Again these costs
were divided by the expected SAEM over its life. Fuel costs were
based on EC$5 per 10 pounds of charcoal divided by the average
SAEM per 10 pounds of charcoal from all families testing a particular
stove. To get the total cost to use each stove model,
the three costs per SAEM were added. Each trial stove model's
cost of operation was compared to the average cost of operating
all standard coal pots over one year. This showed the savings or
losses of trial stove operation compared to the conventional
cooking methods. Since we only ran KPT on charcoal stoves, no
economic comparisons were made for wood-burning stoves.
ACCEPTABILITY
It was very difficult to quantify the acceptability of any given
stove model, so all comparisons made about stove acceptability
were subjective. Notes were kept on the comments that people
made about each stove model. Most information was collected from
families participating in the KPT. During each visit with a family,
they were specifically asked what they liked and disliked
about the stove (Appendix IV). When participants were reluctant
to answer the general questions, more specific questions were
asked about stove size, materials, looks, and operating features.
Feedback from families testing stoves was valuable in guiding our
attempts to modify stove features for greater acceptance.
3. RESULTS AND DISCUSSION
The limited duration of this project did not allow definitive
answers to the question of which cooking technique among those
tested was the best in terms of efficiency, economics, and acceptability.
However, the tests did allow us to establish some
baseline data on traditional cooking practices and to pick out
some general indications for improving them.
EFFICIENCY
There were several differences between the two tests for efficiency.
With WBT we intended to screen stove models and features
in order to select two or three of the best for the important KPT
field testing. WBT results were not indicative of expected fuel
savings of cookstoves in actual use because they did not measure:
the operator variable. So to get a measure of the efficiency of
stoves and operators together, we ran the KPT.
We found the KPT results particularly useful. Besides (1) comparing
the efficiency of different stove models in actual use, we
(2) applied the results in our economic comparison of stoves, (3)
used feedback for gauging acceptance of different stove models,
and were able to (4) estimate the demand for fuel from the forest,
which could then be matched with forest inventory data to
see if tree plantations were-necessary to satisfy demand without
depleting the resource.
WBTs were easier to conduct than KPTs. WBTs only involved our
project team, while KPTs involved many people and required travel
and visit time. In two months time, 160 WBTs were performed, an
average of four per day. In approximately six months time, 55
families participated in the KPT, with 37 usable responses collected.
Many families did not fully understand our purpose--or
pretended not to understand in order to keep the trial stoves for
longer periods of time. We made up to four visits to the same
family to get a single response. In order to speed up data
collection, we enlisted the help of teachers and agriculture
extension agents. This effort, too, brought variable results.
Due to the greater variability of KPT results, more tests were
needed than in WBT for the same degree of predictability. Unfortunately,
the more useful information required a much greater
effort.
Interestingly, the cheapest and simplest cookstove, the two-can,
had the highest average WBT efficiency, 34 PHU (Table 1). Other
cookstoves that rated above 30 PHU in this comparison were the
small AC with preheater and air control and the cast aluminum
coal pot, each with 32 PHU, and the five-gallon bucket woodburning
stove at 31 PHU. The poorest performers were the cement
wood-burning stoves, the Satellites, and the Umemes, all with
less than 20 PHU.
Among the traditional coal pots, the cast aluminum averaged 10
percentage points better than the clay, cast iron, or steel. All
tested coal pots had similar shapes and sizes. Since clay was
the best insulator of the materials tested, we expected it to
perform better than the metals, which were all good conductors of
heat. One possible explanation for aluminum's superiority was
that its relatively high emissivity or ability to reflect heat
back into the fire overcame its ability to conduct heat away from
the fire. Indeed, some cookstove researchers have lined fireboxes
with shiny metals to improve stove efficiency. Perhaps if
the firebox walls of the cast aluminum coal pot were polished, it
would be an even better stove.
We got conflicting results testing firebox insulation. The Umeme
stove worked best with cement, next best with soil, and poorest
with air insulation. The Satellite did best with clay, next best
with cement, and poorest with no insulation. On the other hand,
the two-can stove was more efficient without a clay liner, and
Table 1. Cookstove Efficiency Test Results
Water Boiling Test [a] Kitchen Performance
Time No. Meals
Fuel to PHU of per SAEM
charge boil coef. re- lb coef.
(lbs) (min) PHU of spon- coal of
Cookstove & features [b] [c] (%) var. ses (SAEM) var.
Charcoal Cookstoves
Clay coal pot 1.27 22 21 .57 - - -
Cast iron coal pot 1.29 21 22 .27 2 2.5 .04
Cast alum. coal pot 1.16 22 32 .40 2 3.7 .11
Wheel coal pot 1.46 24 22 .24 1 1.0 -
" /pot ring 1.32 25 22 .14 2 5.4 .28
Umeme/cement insul. 1.40 22 20 .28 6 2.8 .30
" /soil insul. 1.11 22 16 .24 6 4.0 .37
" /air insul. 1.27 29 14 .09 - - -
Small AC .57 34 21 .22 4 5.7 .57
" /preheater .32 38 25 .11 1 6.2 -
Medium AC .57 27 25 .26 - - -
Large AC .79 24 24 .15 - - -
" /preheater .66 22 25 .16 - - -
Z Ztove .42 24 27 .45 5 4.7 .80
" /double burner .48 26 25 .14 6 5.6 .66
" /large burner 1.26 20 22 .10 - - -
Two can .28 27 34 .28 1 3.3 -
" /clay liner .34 29 26 .27 - - -
Satellite 1.36 29 11 .43 - - -
" /cement liner .91 29 16 .27 1 2.0 -
Table 1 - Continued
Water Boiling Test [a] Kitchen Performance
Time No. Meals
Fuel to PHU of per SAEM
charge boil coef. re- lb coef.
(lbs) (min) PHU of spon- coal of
Cookstove & features [b] [c] (%) var. ses (SAEM) var.
" /clay/preheat. .72 23 24 .14 - - -
Short satellite/cement .63 26 22 .25 - - -
Wood-burning Cookstoves
3-stone fireplace 27 .43 - - -
5-gallon bucket 31 .45 - - -
Cement/grate [d] 10 14 .94 - - -
" /sloping floor [e] 10 12 .59 - - -
[a] Averages based on at least five tests.
[b] To convert to kilograms, multiply by .454.
[c] Amount boiled was 2 kg. Does not include first five
minutes from the time of lighting.
[d] Based on four tests, PHU total of two pots.
[e] Based on three tests, PHU total of two pots.
the non-insulated five-gallon bucket wood-burning stove was more
efficient than the cement walled wood-burning stoves. In the
case of the two-can stove, the air that was insulating the firebox
was heated, then moved beneficially into the fire as preheated
secondary combustion air. The insulating air in the Umeme
was dead air. Once heated, it then transferred the heat to the
outer shell of the stove from where it escaped into the air.
In the five-gallon bucket stove, increased efficiency was probably
due more to the fact that in the simmer stage the fuel was
retracted from the firebox for heat control. In the Umeme,
Satellite, and cement wood-burning stoves, heat was not as effectively
lowered by closing the not-so-positive air controls, loose
fitting ash drawers and doors. Therefore, more heat than needed
was used up. So if positive air control or ability to manipulate
fuel are features of a cookstove, insulation is not as important.
For instance, the three-stone fireplace did not have insulation
or even a wind shield; but with manipulation of the fuel, its PHU
was a respectable 27.
Recent African stove testing programs pointed out that thin-walled
metal cookstoves were more efficient than massive cookstoves
for cooking durations less than 100 minutes. Only when
cooking times were longer, say for restaurants or institutions,
or at high altitudes, would massive stoves lose less heat through
conduction (Baldwin, 1984).
Combustion air preheaters seemed to improve efficiency. In both
the small and large AC stoves and the Z Ztove (the double burner
Z Ztove did not have preheated secondary air) where this feature
was tested, the preheaters added one to four PHU to the stove's
efficiency.
Even though grates were not tested for charcoal cookstoves, it
was obvious in the smaller models that the maximum air possible
was necessary. In small stoves without secondary combustion air,
ash build-up tended to close off the holes in grates. For this
reason all of the smaller charcoal cookstoves were provided with
grates of 1/4-inch wire mesh. One of the two cement wood-burning
models had an iron bar grate. Its efficiency was two PHU greater
than the model without a grate.
Control of combustion air was important to stove efficiency.
With good air control fuel consumption was lowered to the amount
needed for simmering, once the pot was boiling. In the AC stove,
a slide control over the draft opening increased the stove's
performance by seven PHU. The Z Ztoves all had positive air
controls and good PHUs.
The variability of test results seemed high considering the tests
were controlled to minimize variation. PHU coefficients of variation
ranged from 10 to 94 percent. Wood-burning cookstoves had
much more variation than charcoal cookstoves. Wood was a more
variable fuel than charcoal in size, shape, and moisture content.
Wood fires were trickier to control. Charcoal cookstove results
with high variation included the clay coal pot, Z Ztove, Satellite,
and cast aluminum coal pot. There was no obvious common
trait to explain their higher variability. A certain amount of
variation was certainly due to the stove testers. Three of us
from the project team did the testing. I suspect from observation
that some of the variation in performance not specific to
any one stove model but more likely to affect smaller stoves, was
due to the random arrangement of fuel and how it affected air
flow through the fuel. The same stove operated in exactly the
same manner would sometimes fire up quickly and lively and other
times barely perk along.
It took anywhere from 20 to 38 minutes to boil two kilograms of
water with charcoal. This did not include the first five minutes
after lighting the fire and allowing it to catch. Among charcoal
cookstoves the ability to boil faster belonged to those with
larger fireboxes (Table 1). The small AC stove with the next to
smallest amount of fuel charge required the longest times to
boil. The five-minute waiting period before putting on the pot
to boil was arbitrary. Some additional testing determined that a
charcoal fire needed about 10 minutes to be fully lit, after
which boiling times averaged around 15 minutes. The fastest
individual boiling time with charcoal was on the Z Ztove with 12
minutes to fully light, and nine minutes to boil. By contrast,
the same amount of water was boiled in the same pot on an lpg
cookstove in six to 14 minutes, depending on burner size.
The manufacturer of the Z Ztove also made a multi-fuel backpacking
stove that was supercharged with a C cell battery and small
fan. Charcoal was fully lit in it after just one minute. In
about two minutes some of the charcoal was white hot, indicating
temperatures near 2800 [degrees] F. And flames from the stove made it look
like a gas stove. The project team built a bellows to supercharge
trial stoves. It worked well, but required a cook's
attention. Besides, a traditional piece of cardboard for fanning,
although not as effective, was much cheaper.
In actual use the AC stoves were the most efficient according to
KPT (Table 1). They cooked an average 5.8 SAEM per pound of charcoal.
Next were the Z Ztoves with 5.2 SAEM per pound of charcoal,
and then the coal pots with 3.5 SAEM per pound of charcoal.
The Umeme stoves averaged 3.4 SAEM per pound of charcoal, no
better than the standard coal pots. Since there were few test
responses, we grouped these stove types for comparison. These
tests suggested that the smaller the stove, the more efficiently
it worked under actual conditions.
Since the two-can and Satellite charcoal cookstoves were models
developed late in the project, only one KPT response was available
for each. Dissemination of these results is to take place
during the second year of the project. The KPTs will be ongoing
in conjunction with dissemination.
No tests were made of the clay DS stoves as they broke after a
few uses.
A comparison of the results of the WBT and KPT showed that WBT
results could not be used to predict fuel savings of cookstoves
under actual use. For example, the WBT results for coal pots as
a group were in the mid range, but under KPT were clearly inferior.
Though the KPT results indicated that a 49 to 66 percent fuel
savings would be possible by using AC stoves or Z Ztoves rather
than coal pots, these estimates were based on few data. And
"improved" stove use would also hinge on their economics and
their acceptance.
ECONOMICS
A comparison of the economics of using cookstoves showed that the
AC stoves were cheapest, followed by the Z Ztoves (Table 2). The
Umeme stoves were more costly to use than the coal pots. Since
the economic calculations were based on KPT results, insufficient
data were available to compare the two-can, Satellite, and all
wood-burning cookstoves. In fact, we grouped the data by stove
type for this comparison because there were few KPT responses.
Fuel cost emerged as a more influential cost than investment or
maintenance costs. The stoves with smaller fireboxes and less
fuel consumption per meal, the AC and Z Ztoves, would save about
EC$100 and EC$25 respectively per year compared with the use of
traditional coal pots. The use of Umeme stoves would actually
cost about EC$65 more than using coal pots.
Theoretically, with improvements in cooking practices brought
about by public education campaigns, cooking could become more
efficient and economical than our estimates of present day practices.
With this in mind, the Energy Officer in Montserrat
issued a kitchen calendar with tips on fuel conservation such as
using lids on cooking pots, using smaller amounts of water when
cooking vegetables, using pressure cookers, etc.
It is important to realize that our economic comparisons ignored
the capacity of a particular stove to cook for different sized
families. A small cookstove could not adequately cook a large
pot of food. Of course a large family could use several small
cookstoves and experience the same savings, as long as large pots
were not used for cooking. However, cooking in large pots is
common in the Caribbean. The fact that smaller cookstoves were
shown to be more efficient and economical does not guarantee that
they would be acceptable to users.
Table 2. Economic Comparison of Charcoal Cookstove Use
Coal Z
Item pots Umeme Ztove AC
Purchase cost (EC$) 44 180 83[a] 30
Estimated stove life (years) 7 3 2 4
Maintenance cost over life
of stove (EC$) 15 9 30 8
Stove/operator efficiency
(SAEM/pound charcoal) 3.5 3.4 5.2 5.8
KPT responses (no.) 7 12 11 5
Fuel cost (EC$/SAEM) [b] 0.143 0.147 0.096 0.086
Investment cost (EC$/SAEM) [c] 0.003 0.032 0.022 0.004
Maintenance cost (EC$/SAEM) [c] 0.001 0.002 0.016 0.001
Total cost (EC$/SAEM) 0.147 0.181 0.134 0.091
Savings [loss] compared to
coal pots (EC$/year) [c] - [64.53] 24.67 106.29
[a] Purchase cost as imported.
[b] Fuel cost, EC$.50 per pound.
[c] Average family of three cooks 5.2 SAEM per day or
1898 SAEM per year.
ACCEPTABILITY
Inasmuch as people's opinions on any single subject vary tremendously,
there was no one trial cookstove model that was universally
acceptable. A range of cookstove models would have to be
available to satisfy all people's desires and cooking needs.
To begin with, there was no perceived need among the users of
coal pots and three-stone fireplaces for improving upon traditional
cooking systems. The government felt the need to protect
its valuable forest resource by introducing more efficient cooking
methods.
So there was a need to develop a consciousness in the people
about cooking fuel efficiency. Therefore, very few comments were
made about a cookstove's efficiency, the major reason for the
project's existence. Most concerns were expressed about cookstove
appearance, how well they worked, how they fit the cooking
needs, how durable they were, what the working features were,
their cost, and their efficiency, in roughly that order of importance
to potential users.
The most excited feedback we received was based on a trial
stove's looks. Older users seemed to prefer the Umeme, perhaps
because they were more like coal pots than other trial cookstoves.
Younger folks seemed to like the smaller, more modern
looking stoves. The most coveted design was the Z Ztove, with
its manufactured look.
People liked the way the smaller stoves worked, but the stoves
did not always fit their needs. Cooking capacity generally was
lacking. Comments such as these led us to enlarge several cookstove
models. At our request, the Z Ztove manufacturer sent us
modifications of the Z Ztove that were double burners and single
but larger burners. We had local tinsmiths make two larger sizes
of AC stoves. The larger models were well received.
Cookstove durability was a concern. Clay coal pots were not
favored due to their fragility. We found that expensive sheet
metal lining around fireboxes lasted only one to three months.
The Umeme, Z Ztoves, AC stoves, and two-can stoves had these
liners. It was of little concern in the Umeme and AC stoves with
their cement insulation. Once the tin burned out the cement
became the firebox wall. The tin merely acted as a form for the
cement. But the firebox lining had to be replaced periodically
in the other stoves. The Z Ztove had easily replaceable liners,
and the two-can stove used easily replaced motor oil cans. But
the Umeme with soil insulation required shaping sheet metal into
a cone for relining. Concern was registered for the durability
of wire mesh grates, but these were inexpensive and easily replaced.
Of the working features of cookstoves, the most appreciated was
the ash drawer for ease in emptying the ashes. The ash drawers
also doubled as air control, but there seemed to be little esteem
for its value in conserving fuel.
The fact that much food was cooked in frying pans led to our
modified wind shield with slot for frying pan handle on the Umeme
stoves. That made them more acceptable.
The large Umemes with cement or soil insulation were very heavy.
Montserratians moved their coal pots around--to light them outside,
bring them inside for cooking, and back outside for emptying
ashes. We tried reducing the weight of cement insulated
models by incorporating charcoal fines into the cement mix. We
never really overcame that objection to the Umeme.
Another objection to the Umeme stoves was the lack of air getting
to the fire. The only combustion air in Umemes was that which
was pulled up to replace the hot air rising out of the stove.
Coal pots were designed such that when the "arch" (draft opening)
was faced into the breeze, the air going into the arch was all
forced up into the fire. Breezes simply passed under the Umeme.
For many families the cost of a cookstove was not important.
Nevertheless a segment of the stove testers complained about not
being able to afford a new cookstove. For these people we developed
the AC and two-can charcoal stoves, and introduced the five-gallon
bucket wood-burning stove. Each of these models was
inexpensive and easy enough for most families to make in their
own home. However, the two charcoal stoves were small and had a
homemade look, which detracted from their acceptance. And because
wood fuel use was associated with families in the lowest
economic group, any wood-burning cookstove had to overcome that
debasement to be acceptable.
If we had to rank cookstoves according to their overall acceptability,
they would roughly follow in order of descending acceptance:
1. coal pots for their familiarity,
2. Satellite stove for its good looks and durability,
3. Z Ztove for its good looks and working ability,
4. Umeme stove for its similarity to coal pots and ash
drawer,
5. AC stove for its simplicity and low cost,
6. two-can stove for its simplicity and low cost,
7. five-gallon bucket stove for its simplicity and low
cost,
8. the cement wood-burning stoves, and
9. the clay cookstoves.
As time goes by this ranking could change. People will become
more aware of the value of improved stove efficiency as lpg
becomes more expensive and competition for wood and charcoal
becomes more keen.
Cooking with wood and charcoal was dirtier and slower than cooking
with lpg. In an effort to help clean up the handling of
charcoal, the project introduced the use of inexpensive ice tongs
and scoops cut from discarded plastic bleach bottles. For faster
starting of charcoal fires, a tin juice can with top and bottom
removed, and side air holes punched around the bottom was promoted.
With one sheet of crumpled newspaper in the bottom and
charcoal in the top of the upright cylinder, a fast fire was
assured for even the novice fire builder (providing the charcoal
was dry).
It was hoped that all of these efforts at improving cookstoves
and cooking systems would help elevate the status of using wood
and charcoal fuels, and assure a perpetual supply of these local
renewable resources.
4. CONCLUSIONS AND RECOMMENDATIONS
Test results and user comments led us to the following conclusions:
1. Smaller charcoal cookstoves were more efficient and
economical than traditional coal pots, but required
more cooking time and often were not suitable to the
cooking needs of Montserratian families.
2. Positive air control was difficult to achieve in cookstoves,
but improved their efficiency.
3. Insulating the firebox was most useful in cookstoves
without air control or the ability to retract the fuel.
4. Grates in smaller charcoal cookstoves needed maximum
air holes.
5. The cast aluminum coal pot was superior to other coal
pots in efficiency.
6. Kitchen performance testing (KPT) of cookstoves yielded
information for many important uses, but required a
large input of time and effort.
7. The operator variable in cooking system efficiency is
so great that more impact on fuel conservation might be
possible through public education (people improvement)
than through stove improvement.
And finally, we concluded that a number of suggestions for
further work are in order:
1. Continue kitchen performance testing of stove models to
obtain solid baseline data on the number of standardized
meals prepared by each oven dry pound of fuel.
2. Participate in public education efforts to conserve
cooking fuels.
3. To overcome problems in production and quality control,
develop systems to mass produce inexpensive cookstoves.
4. Develop a small battery-powered fan unit with variable
speeds to hook to small cookstoves for supercharging
combustion air.
5. Develop a more durable firebox and top for the Z Ztove.
6. Polish the firebox walls of the aluminum coal pot and
retest for efficiency.
APPENDIX I
COOKSTOVE DESIGNS
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove TRADITIONAL COAL POT-CARRIBEAN
Name of stove builder(s) VARIOUS
Construction date 1982 Materials used CAST ALUMINUM,
CAST IRON, CLAY, OR CEMENT WITH WIRE ROD AND DRUM STEEL.
<FIGURE A>
48ap01.gif (600x600)
Details of stove construction GRATE IS CAST SEPARATELY. CLAY
COAL POTS CLAY GRATES, WHILE CEMENT COAL POTS USE OIL DRUM
STEEL WITH PUNCHED HOLES.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CLAY DOUBLE-SKINNED - AFRICA (MODIFIED)
Name of stove builder(s) Joseph Howson
Construction date 2/83 Materials used CLAY MIXTURE WITH
WHITE VOLCANIC POWDER AND ONE NAIL.
<FIGURE B>
48ap02.gif (600x600)
Details of stove construction INSIDE AND OUTSIDE CYLINDERS WERE
TURNED SEPARATELY, JOINED, CURED, AND FIRED AT 900-1100 [degrees] C. SECONDARY
AIR HOLES WERE 12-IN. DIAM. AND SLANTED UPWARD TOWARD THE INSIDE. WALLS
OF FIREBOX WERE ROUGH TO PROMOTE MIXING OF GASES AND AIR. DRAFT
DOOR ADJUSTABLE WITH NAIL.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove UMEME - AFRICA (MODIFIED)
Name of stove builder(s) John Harris, James Sweeney, Cecil Roach
Construction date 2/83 Materials used SHEET METAL WITH
CEMENT, AIR, OR SOIL INSULATION, NAILS, 1/4-INCH ROD, AND DRUM STEEL
<FIGURE C>
48ap03.gif (600x600)
Details of stove construction NAIL RIVETS FASTENED THE ASH DRAWER,
DRAFT SLIDE AND DRAWER RAIL TO THE BOTTOM, AND THREE LEGS
TO THE BOTTOM. CHARCOAL FINES WERE MIXED WITH CEMENT TO LESSEN
THE WEIGHT. POT SUPPORT RODS EXTENDED INTO THE CEMENT. NOTCH IN
WIND SCREEN WAS FOR FRYING PAN HANDLE.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove ADVANCED CHARCOAL (AC) - MONTSERRAT
Name of stove builder(s) JOHN HARRIS, JAMES DYER
Construction date 4/83 Materials used VARIOUS CANS, NAILS,
DRUM STEEL, 1/4-INCH AND 1-INCH WIRE MESH, 1/4-INCH ROD, AND CEMENT
<FIGURE D>
48ap04.gif (600x600)
Details of stove construction CEMENT INSULATION WAS REINFORCED
BY 1-INCH MESH WIRE. POT REST/WIND SHIELD AND HANDLES MADE WITH
DRUM STEEL, FASTENED WITH NAIL RIVETS. DRAFT DOOR AND AIR PREHEATER
MADE WITH TIN. 1/4-INCH ROD SUPPORTS AIR PREHEATER WHICH
SUPPORTS 1/4-INCH MESH GRATE.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove Z ZTOVE - U.S.A.
Name of stove builder(s) ZZ CORPORATION
Construction date 2/83 Materials used SHEET METAL,
POP RIVETS, 1/4-INCH WIRE MESH, AND CERAMIC FIBER.
<FIGURE E>
48ap05.gif (600x600)
Details of stove construction THE Z ZTOVE IS MASS PRODUCED
FROM PRE-CUT SHEET METAL PARTS. THEY ARE BENT IN PRESSES, GANG
DRILLED, AND POP RIVETED. THE INNER BURNER BOWL IS REPLACEABLE
AFTER IT BURNS OUT.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove TWO CAN STOVE - MONTSERRAT
Name of stove builder(s) ANYONE
Construction date 7/83 Materials used PAINT CAN, MOTOR
OIL CAN, DRUM STEEL, AND NAILS.
<FIGURE F>
48ap06.gif (600x600)
Details of stove construction FIRST PUNCH MOTOR OIL CAN FULL OF HOLES,
THEN REMOVE ITS TOP, CUT PAINT CAN LID RADIALLY LEAVING SHORT TABS UNTIL
THE MOTOR OIL CAN FITS DOWN IN IT AND IS SUPPORTED BY ITS FLARED TOP
EDGE. PLACE LID WITH MOTOR OIL CAN ON PAINT CAN. THEN CUT OPENING
FOR DRAFT AND MAKE POT REST WITH DRUM STEEL AND NAIL RIVETS.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove SATELLITE STOVE - MONTSERRAT
Name of stove builder(s) SYLVESTER MEADE
Construction date 9/83 Materials used SIX-INCH STEEL PIPE
1/8-INCH STEEL PLATE, 1/2-INCH REBAR, 1/4 INCH ROD, SHEET METAL, 1/4-INCH WIRE MESH
<FIGURE G>
48ap07.gif (600x600)
Details of stove construction PIECES WERE WELDED TOGETHER,
ASH DRAWER WAS FASHIONED FROM SHEET METAL. A CLAY CYLINDER
AND CEMENT WERE TRIED AS INSULATION.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove THREE-STONE FIREPLACE - UNIVERSAL
Name of stove builder(s) ANYONE
Construction date 9/83 Materials used THREE STONES
<FIGURE H>
48ap08.gif (600x600)
Details of stove construction PLACE THREE STONES SO THEY
SUPPORT THE POT ABOVE THE GROUND AND LEVEL.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CLAY DOUBLE-SKINNED WOOD-BURNING STOVE-AFRICA (MONFIED)
Name of stove builder(s) Joseph Howson
Construction date 2/83 Materials used
<FIGURE I>
48ap09.gif (600x600)
Details of stove construction INSIDE AND OUTSIDE CYLINDERS WERE
TURNED SEPARATELY, JOINED, CURED, AND FIRED AT 900-1100 [degrees]. SECONDARY
AIR HOLES WERE 1/2-INCH DIAM. AND SLANTED UPWARD TOWARD THE
INSIDE. WALLS OF FIREBOX WERE ROUGH TO PROMOTE MIXING OF GASES
AND AIR.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove FIVE-GALLON BUCKET WOOD-BURNING STOVE-AFRICA
Name of stove builder(s) ANYONE
Construction date 8/83 Materials used FIVE-GALLON BUCKET
AND 1/4-INCH ROD.
<FIGURE J>
48ap10.gif (600x600)
Details of stove construction SIMPLY PUNCH THREE EQUIDISTANT
HOLES AROUND THE CIRCUMFERENCE, INSERT 11-INCH LONG RODS AND
BEND ROD ENDS. THEN CUT OUT THE DRAFT OPENING.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CEMENT WOOD-BURNING STOVE-MONTSERRAT
Name of stove builder(s) TONY CARTY AND CHARLES WHITE
Construction date 4/83 Materials used CEMENT, 1/2-INCH
REBAR, REINFORCING MESH, WOOD, SHEET METAL, AND NAILS.
<FIGURE K>
48p11.gif (600x600)
Details of stove construction THE TOP SLAB IS POURED AROUND THE
ACTUAL POTS. POTS ARE REMOVED AND POT HOLES SMOOTHED WHEN CEMENT
IS PARTIALLY CURED. DOOR IS WOOD-LINED WITH TIN INSIDE. GRATE IS
MADE OF REGARS. AND REBAR HANDLES ALLOW FOR PORTABILITY. REINFORCING
MESH IS INSIDE CEMENT.
FCCA
MONTSERRAT
FUELWOOD * CHARCOAL * COOKSTOVE PROJECT
Name and origin of stove CEMENT WOOD-BURNING STOVE-MONTSERRAT
Name of stove builder(s) Joseph Sweeney and David Lake
Construction date 9/83 Materials used CEMENT, CHICKEN
WIRE, WOOD, SHEET METAL, HINGES, AND NAILS.
<FIGURE L>
48ap12.gif (600x600)
Details of stove construction THE TOP SLAB IS POURED AROUND THE
ACTUAL POTS. POTS ARE REMOVED AND POT HOLES SMOOTHED WHEN CEMENT
IS PARTIALLY CURED. THE HINGED DOOR IS WOOD LINED WITH TIN ON
THE INSIDE. THE CHIMNEY IS SHEET METAL. CHICKEN WIRE IS USED
TO REINFORCE THE CEMENT.
APPENDIX II
WATER BOILING TEST PROCEDURES
In order to compare different designs of stoves, all variables
other than stove design that might affect efficiency such as
fuelwood species, moisture content, size, and amount; operator
and operating sequence and schedule; weather (mainly wind); and
pot design, size, material, and contents were held as consistent
as possible.
The testing was conducted according to the following procedures:
1. We sampled the fuel to determine moisture content (MC). For
charcoal we disregarded MC unless it had been wetted. The
MC samples were at least 100 grams and were chosen to be
representative of the fuel being used. They were cut just
before the WBT. We weighed the samples immediately to the
nearest 1/10 gram and recorded the weight. We identified
each sample by marking a number directly on it with a magic
marker. The samples were put in an oven at 215 [degrees] F for at
least 24 hours (until they lost no more weight) and reweighed.
The oven dry weights were recorded. Then MC was
calculated on the green weight basis by the formula:
percent MC = (green weight - oven dry weight/green
weight) x 100.
2. We weighed the fuel put in the stove and recorded the weight
in pounds.
3. We weighed an 11-inch diameter flat bottomed aluminum pot
without the lid. The weight was recorded. Then we added
two kilograms (four pounds, six ounces) of water at ambient
temperature and recorded the weight. The lid was fitted
with a stopper through which a mercury thermometer was
placed. The lid was put on the pot and the thermometer
adjusted to be about one inch from the bottom of the pot.
For two-pot stoves we used an 11-inch and an eight-inch
diameter pot of the same design.
4. We used two Zip fire fuel pellets for kindling, lit them and
recorded the time. We added the fuel.
5. After allowing five minutes for the fire to get started, we
put the pot(s) on. The fire was maintained for maximum heat
until the water was boiling.
6. At each five-minute interval, the time and temperature of
each pot were recorded. When the thermometer reached 212 [degrees] F
the time was recorded. For two-pot stoves only the first
pot directly over the fire was used for this determination.
7. After the water boiled, the stove was adjusted to simulate
simmering, to provide just enough heat to keep the water
lightly boiling for 30 minutes. In charcoal stoves this was
done by closing draft controls or loosely blocking draft
openings on stoves without draft controls. In the cement
wood-burning cookstoves the doors were closed. And in the
three-stone fireplace and five-gallon bucket, we pulled the
wood pieces outward to slow down the fire.
8. During the test we recorded miscellaneous observations such
as the amount of flame or smoke, how hot the stove was to
touch, etc.
9. At the end of the 30 minutes of simmering we did the following
in rapid sequence:
- recorded the water temperature,
- weighed and recorded in pounds the amount of water
remaining, and
- weighed and recorded in pounds the amount of unburned
fuel. When wood was the fuel, we separated the wood and
charcoal before weighing.
10. Calculations were made on the following:
WE - Amount of water evaporated (pounds) = initial weight of pot
and water minus the final weight of pot and water.
CT - Change in water temperature ([degrees] F) = highest water temperature
minus the beginning water temperature.
CB - Weight of charcoal burned (pounds) = initial fuel weight
minus the weight of the unburned remainder.
DW - Weight of oven-dry wood burned (pounds) = [initial weight of
wood put in stove times 1 - MC in decimal form] minus the
weight of wood and charcoal unburned.
FM - Weight of moisture in fuel (pounds) = initial weight of fuel
put in stove times MC in decimal form.
EF - Stove efficiency (PHU) = [CT x original weight of water in
pounds] + [WE x 1,050]/[DW x 8,500 - FM X 1,2001 - [pounds
of charcoal remaining x 12,500] x 100.
where:
- 1,050 was the latent heat of water in Btu per pound at
room temperature,
- 8,500 was the heat value of oven dry wood in Btu per
pound,
- 1,200 was the heat needed to drive moisture out of wood
fuel in Btu per pound of water,
- 12,500 was the heat value of oven dry charcoal in Btu
per pound,
- for charcoal stoves the denominator was simply CB x
12,500, and
- DW and FM were considered accurate for our use since
there was little unburned fuel.
SSC - Standard Specific Consumption = DW/WE.
APPENDIX III
WATER BOILING TEST DATA SHEET
DATE: ______________________________ STOVE TYPE: ______________
OPERATOR(S): _______________________ MODIFICATIONS: ___________
TEST NUMBER: _______________________ FUEL: ____________________
MOISTURE CONTENT SAMPLES:
Identification Fresh weight Oven-dry weight MC (Green basis)
FUEL WEIGHT AT START: __________________ POT WEIGHT: _____________
INITIAL WEIGHT OF POT & WATER: _________ INITIAL WATER TEMP: _____
ELAPSED WATER FUEL WEIGHT
TIME TIME TEMPERATURE ADDED COMMENTS
______ 0_______ _________________ _______________ __________
______ 5_______ _________________ _______________ __________
______ 10______ _________________ _______________ __________
______ 15______ _________________ _______________ __________
______ 20______ _________________ _______________ __________
______ 25______ _________________ _______________ __________
______ 30______ _________________ _______________ __________
______ 35______ _________________ _______________ __________
______ 60______ _________________ _______________ __________
FINAL WEIGHT OF POT AND WATER: _____________
WEIGHT OF WOOD REMAINING: __________________
WEIGHT OF CHARCOAL REMAINING: ______________
APPENDIX IV
KITCHEN PERFORMANCE TEST DATA SHEET
STOVE TYPE: ________________________ FAMILY NAME: ___________________
LOCATION: _____________________________________________________________
NUMBER OF PEOPLE FED: ______________ STANDARD ADULT EQUIVALENTS:
children 0 - 14 years _________ x 0.5 =
women over 14 years _________ x 0.8 =
men aged 15 - 59 years ________ x 1.0 =
men over 59 years _____________ x 0.8 =
NUMBER OF MEALS COOKED: OTHER USES:
breakfast __________ ironing ____________
lunch __________ baking ____________
dinner __________ others ____________
other cooking__________ ____________
WAS THERE ANY LEFTOVER CHARCOAL IN THE STOVE? ________________
WHAT DID YOU DO WITH IT?
WOULD YOU USE MORE _____ OR LESS _____ FUEL FOR SIMILAR
MEALS IN THE CONVENTIONAL COAL POT?
GENERAL COMMENTS:
APPENDIX V
COOKSTOVE LOCATION SHEET
STOVE MODEL: _____________________ FEATURES: _________________________
DATE DATE
START FINISH ADDRESS USER COMMENTS
APPENDIX VI
CONVERSION FACTORS
1 pound = 0.454 kilograms
1 kilogram = 2.2 pounds
1 Btu = 0.252 kilocalories
1 kilocalorie = 3.968 Btus
1 Btu/pound = 2.32 Joules/gram
[degree] C = [degree] F - 32/1.8
[degree] F = (1.8 x [degree] C) + 32
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Baldwin, Sam. "New Directions In Woodstove Development." VITA
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de Silva, Dhammika. "A Charcoal Stove From Sri Lanka." Appropriate
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175 pp. Illus.
Government of Montserrat. Preliminary Data of the 1980 Commonwealth
Caribbean Population Census, Part I: Household and
Housing Information, 1980, 26 pp.
Hassrick, Phillip. "Umeme: A Charcoal Stove from Kenya." Appropriate
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Joseph, Stephen and Trussell, Jenny. Report on Advisory Visit to
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Tata Energy Research Institute. Solid Fuel Cooking Stoves. Bombay,
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Assistance (VITA), 1982, 76 pp. Illus.
Yameogo, Georges; Bussman, Paul; Simonis, Philippe; and Baldwin,
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