A report of laboratory test results of the Protostar

2015
A report of laboratory test
results of the Protostar™ stove
Kimemia, David
Tested at the Sustainable energy Technology and Research
(SeTAR) Centre, University of Johannesburg, a facility
supported by the Global Alliance for Clean Cookstoves
(GACC)
SeTAR Centre,
University of Johannesburg
www.setarstoves.org
16 March 2015
STOVE MANUFACTURER
STOVE MODEL
PROTOCOL
FUEL USED
POT USED
TEST DATES
REPORT NO.
Proto-Energy
Protostar Bhubezi
Heterogeneous Testing Protocols
Methanol
5L
17 – 19 February 2015
S/2015/001
TEAM: H. Annegarn, D. Kimemia, T. Makonese, T. Sithole
1. Introduction
The Protostar is a one-plate methanol-fuelled stove that is designed for cooking and heating purposes.
All high temperature components of the stove is made of stainless steel, all low temperature
components of stove (e.g. the legs) are made from a high quality galvanised mild steel (PRE-GAL
Z275) with anti-slip rubber pads at bottom of the three legs (Figure 1). The Protostar comes with a
detachable heater and a barbecue kit, plus a tool for removing the movable parts. Primary airflow for
combustion purposes is supplied to the device via 6 mm diameter air inlets situated on the burner
head. Power is adjusted by moving a small lever to open or restrict these air inlets.
Figure 1: Image of the Protostar stove – BHUBEZI model
A pre-production model of the Protostar stove was submitted for thermal, emissions, and safety
evaluation to the SeTAR Centre laboratory by the developer in February 2015. Methanol fuel in
sealed 500 ml plastic cartridges was part of the consignment. Three stage testing was done on the
device: screening tests (Appendix A) were done for firepower output and safety, followed by
cooking observation tests (done to map the burn cycle) (Appendix B), and technical tests for
emissions and thermal performance (HTP protocol, downloadable from www.setarstoves.org).
The technical tests were based on the observed cooking cycles and form the main thrust of this report.
The stove was tested at two power levels (i.e. high power – primary air inlets fully open; and medium
power – primary air inlets half-open). Safety tests were carried out based as specified by the IWA
Stove Safety Protocol (available at http://www.cleancookstoves.org/our-work/standards-andtesting/learn-about-testing-protocols/). The safety tests included: checks on the surface temperature of
the body of the stove, stability during operation, sharp edges and containment of fuel. Other safety
checks were done as per the SABS requirements for non-pressurised paraffin stoves (SANS 1243) and
included specifically an upper limit on the ration of CO to CO2, and the ability of the stove to
extinguish within three seconds after switch-off.
 SeTAR Centre, University of Johannesburg
1
Version: Final
2. Test Procedures
Screening Tests
The purpose of the screening tests is to assess the firepower and safety features of the candidate stove.
This is done outside the technical test rig using simple equipment, such as weighing scale,
thermometers, and stopwatch.
The Protostar stove was weighed, then fuelled with 500 ml of methanol and ignited. The stove was
operated on high power for 30 minutes, first without a pot of water, and then repeated with 2 L pots of
water. After each burn cycle, the mass of remaining fuel was taken. The fuel burn rate and the
firepower of the stove were then computed. The surface temperature during operation was measured
using a contact thermometer placed at different points on the body of the stove.
Cooking Observation Tests
Two standard meals were cooked on the Protostar stove. The first meal consisted of samp (dry maize
and beans) and tripe, while the second meal was made up of pap (thick cornmeal porridge) and
cabbage. These meals are chosen from common menus of the targeted stove market in Gauteng. The
foods were cooked at high power (~1.0 kW) and medium power settings (~0.7 kW). The medium
power was found convenient for test purposes as the lowest possible power setting on the device was
below the firepower required for reduced-power cooking – simmering. Adjustments to the power
level settings were done at the discretion of the cook. Five-litre aluminium pots were used, with the
amount of food cooked sufficient for a meal for seven adults.
The cooking observation test involved recording the time taken to cook each meal from start to finish,
noting the time of changes between the two power level settings as required by the recipes. The
observed cooking cycle was dictated by the cook, type of food being prepared, recipe and the design
capacity of the stove, rather than by the technician. The technician’s job was to observe and record the
happenings, specifically the time of operation at each power level and to assist in changing the power
levels.
The observed cooking cycles (duration of operation at each power level from ignition to completion
of the cooking) for the two meals were combined into a technical burn cycle, intended to represent
typical use of the stove by the target user communities.
Technical Tests
The technical burn cycle is replicated on the testing rig (under an emissions collection hood) with a
pot of water to be heated as a surrogate for a pot of food. The test under the emissions collection hood
is referred to as a ‘technical test’ and is carried out to determine the thermal and emissions
performance of the device.
 SeTAR Centre, University of Johannesburg
2
Version: Final
Technical tests at the SeTAR Centre are done according to the Heterogeneous Testing Protocol (HTP
protocol, downloadable from www.setarstoves.org), which refers to testing a device at multiple power
levels with 5-L or 2-L pots of water. The tests are based on a technical burn cycle, derived from
culturally appropriate cooking observation tests. In the HTP, the pot of water is substituted on
reaching 70ºC with a fresh pot of water at room temperature to avoid complexities brought about by
water evaporation. The water temperature is monitored with a thermocouple placed inside the pot.
Combustion products are sampled by gas probes placed in the emissions hood and channelled to flue
gas analysers. Two Testo™ gas analysers are used – one for diluted and the other for undiluted gas
stream. A DRX Dust Tracker™ is used for in-situ monitoring of particulate emissions. The stove and
pot combination are placed on a mass balance and remain there from ignition to completion of the
test. The readings for fuel burnt, trace gases and particulate matter emissions are logged at 10 s
intervals. The technical test provides important information on gaseous emissions (e.g. CO, CO/CO2
and PM2.5) and thermal performance (e.g. fuel burn-rate, firepower, cooking power, and cooking
efficiency) of the test stove.
3. Results
Screening and Cooking Observation Tests
Ignition of the Protostar stove was easily achieved. The stove produced a blue-flame, which implies
good combustion efficiency. There was no discernible smoke during the screening and cooking
observation tests. The stove required no refuelling during the cooking of each meal, requiring the
sequential preparation of two dishes (starch and sauce). The raised edge around the pot rest ensures
that the pot remains secured during cooking thus reducing the risk of injury from food and liquid
spills as the pot is stirred or accidentally bumped.
The results of the screening tests show that the device delivered a gross firepower of 1.05 kW. The
stove achieved a heating rate of 8.5 minutes per litre of water boiled, from 25ºC to 94ºC, on high
power setting.
The two dishes for the cooking observation tests were cooked in sequence. Each sequential meal was
cooked without refuelling. The averaged burn cycle for the two cooking tests was 116 minutes. The
observed cooking cycles are depicted in Table 1.
Table 1: Protostar stove cooking cycle (5-L aluminium pot) (two dishes were prepared sequentially)
Cooking time (minutes) at different firepower levels
Meals
Samp and
High
Medium
70
15
tripe
Pap and
30
50
 SeTAR Centre, University of Johannesburg
Medium
77
0
29
0
53
None
10
cabbage
Averaged burn cycle
High
13
3
Version: Final
Safety
The temperature of the stove handles rises to about 30ºC during operation, while the reservoir housing
reaches about 33ºC. As such there is no risk of contact burns on the touchable surfaces of the stove, as
the temperature remains under 40ºC even after continuous operation. The only part that gets elevated
temperature is the burner casing (rises to ~90ºC); however, it does not constitute a touchable part.
The Protostar is squat with a low centre of gravity. The tip-off angle for the Protostar was measured at
55º which signifies a high degree of stability. This implies that the stove is not easily tipped-over,
thereby reducing the risk of injuries from fires and spilt liquids and foods. Once refuelled, the stove
can be turned over without fuel spillage, further minimising the risk of fires in case of accidents.
The stove extinguishes completely immediately it is switched off, which implies that it complies with
SABS requirements for a cookstove to extinguish the flame within three seconds after being switched
off (SANS 1243). Simulation of accidental knock-over shows that the stove successfully triggers the
switch-off mechanism 50% of the time. Although this is a major improvement over similar stoves in
the market, the device fails to comply with the SABS requirement for this particular safety aspect.
The developer is advised to resolve the design towards a 100% effectiveness of this important safety
aspect.
The Protostar cannot be refuelled during operation – as refuelling takes place through the center of the
burner, the stove needs to be extinguished before refuelling. Consequent to this design feature, there is
no filler cap that can be opened during operation, or lost. The fuel is delivered in sealed 500 ml plastic
capsules, without lid or opening, so it is not possible for the fuel containers to be opened in the normal
sense, thus minimising the chances of accidental ingestion by toddlers or children. Fuelling of the
stove is done by impaling the capsule on a spike in the center of the burner and allowing the fuel to
drain into the reservoir. The central cylinder of the reservoir intrudes into the volume of the reservoir,
such that even if the entire stove is turned upside down, it is not possible for any fuel to spill. The
methanol fuel is fully miscible with water, so in the event of a spill, the fire can readily be
extinguished with water (in contrast to paraffin, which floats on top of water and is thus not
immediately extinguished by being splashed with water).
Technical Test
Thermal performance
The maximum firepower for the stove when cooking on high power setting was 1.03 ± 0.06 kW
(Table 2). These results are averages for three tests and are based on a fuel CV (heating value as
received) of 22.7 MJ/kg (N.B. The methanol fuel data were provided by the manufacturers, Sasol
Ltd).
The power adjustment facility shows a broad range of controllability, which is achieved without
taking the pot off the stove. The fuel burn rate and the firepower indicate a reduction of 22% and 29%
from high to medium power respectively. At the lowest operational setting, the flame still burns well,
 SeTAR Centre, University of Johannesburg
4
Version: Final
without stuttering or self-extinguishing, but is below the level required to maintain a simmer in a 5-L
pot. This is an advantage as it would allow the cook to achieve a good degree of controllability of
keeping the pot contents hot, without risk of burning the food.
The CO/CO2 ratio, and emissions of CO g/MJ and PM2.5 mg/MJ are lower at the medium power
setting. This is to be expected as the fuel evaporation surface is constrained thus providing a better
air-to-fuel mixing ratio and consequently better combustion efficiency. The cooking efficiency
reduces from high to medium power setting.
Table 2: Average performance parameters of Protostar stove at different power level settings
Power level
setting
Fuel burn
rate
(kg/h)
Firepower
(kW)
CO/CO2
(%)
Cooking
efficiency
(%)
CO
(g/MJ)
PM2.5
(mg/MJ)
High
0.18 ± 0.01
1.03 ± 0.06
1.77 ± 0.12
70.4 ± 0.9
0.72 ± 0.06
0.03 ± 0.06
Medium
0.14 ± 0.01
0.73 ± 0.06
1.23 ± 0.21
62.2 ± 4.9
0.49 ± 0.07
0.00 ± 0.00
22
29
31
12
32
100
% decrease from
high to medium
power
The average firepower for the stove over the cooking cycles (entire technical burn cycle) is
0.93 ± 0.06 kW, with an average fuel burn rate of 0.17 ± 0.01 kg/h and a cooking efficiency of
71.9 ± 1.1% (Table 3). The stove had a stable flame and stayed alight even at the lowest power setting
(primary air holes fully closed).
Table 3: Average thermal performance results for Protostar stove during the technical test (with 5 L
pot of water)
Test No.
Fuel burn rate
(kg/h)
Firepower (kW)
Cooking power
(kW)
Cooking
efficiency (%)
Space heating
(kW)
900
0.16
0.9
0.64
72.1
1.0
901
0.17
1.0
0.71
72.9
1.2
902
0.17
0.9
0.67
70.7
1.1
Mean ± SD
0.17 ± 0.01
0.9 ± 0.06
0.67 ± 0.04
71.9 ± 1.1
1.1 ± 0.1
Emissions performance
The stove depicted a modified combustion efficiency of 99.07 ± 0.06% (with average CO/CO2 ratio of
1.63 ± 0.06%) (Table 4) over the technical test burn cycle. The average CO emissions per energy
consumed was 0.65 ± 0.02 g/MJ. No emissions of PM2.5 mg/MJ were detected over the technical burn
cycle of 116 min. The emissions results depict consistency between the tests, with less than ±1
standard deviation.
 SeTAR Centre, University of Johannesburg
5
Version: Final
Table 4: Emissions performance results for Protostar stove
(HTP technical test full burn-cycle with 5-L pot)
Test No.
CO rate
(g/h)
PM2.5 rate
(mg/h)
CO/CO2
(%)
CO
(g/MJ)
PM2.5
(mg/MJ)
Modified comb
efficiency (%)
900
2.15
<0.1
1.7
0.67
<0.1
99.0
901
2.21
<0.1
1.6
0.63
<0.1
99.1
901
2.17
0.1
1.6
0.64
0.1
99.1
Avg. ± SD
2.18 ± 0.03
<0.1
1.63 ± 0.06
0.65 ± 0.02
0.00 ± 0.00
99.1 ± 0.1
The stove depicted uniform combustion properties from ignition to extinction. The CO emissions
tended to reduce (i.e. more efficient combustion) whenever the pot of water was taken off the stove on
reaching 70ºC, then increased again when a fresh pot of water was put back on the stove. The lowest
CO emissions were observed at medium power phase, that is, from the 50th to 63rd minute (Figure 2).
Ignition
Med-High
High
Low
High
End
CO(EF)
15,000
10,000
7,500
5,000
2,500
130
120
110
100
Time [Minutes]
90
80
70
60
50
40
30
20
10
0
0
CO Emission Factor, ppm(v) * λ
12,500
Figure 2: CO emission profile for the Protostar stove
Protostar Ranking on the IWA Tiers of Performance
The IWA tiers rates cookstoves on four indicators (thermal efficiency, indoor emissions, total
emissions, safety), each along five tiers (0 – least performing to 4 – highest performing) (GACC,
2015). A ranking of the Protostar test results against the IWA tiers of performance indicates that the
device is situated in tier 4 in terms of thermal efficiency, total emissions of CO and PM2.5 per MJ and
indoor emissions, and in tier 3 in terms of safety aspects (Table 5). This level of performance implies
that the Protostar is an aspirational product that possesses the highest rating to meet targets for human
health and environmental protection.
 SeTAR Centre, University of Johannesburg
6
Version: Final
Table 5: Ranking of Protostar stove performance results against the IWA tiers
Metric
Unit
Protostar value
Tier
%
70.37
4
g/MJ
0.72
4
High power PM2.5
mg/MJ
0.03
4
High power indoor emissions CO
g/min
0.04
4
High power indoor emissions PM2.5
mg/min
0.00
4
10 weighted safety parameters
Points
94
3
High power thermal efficiency
High power CO
4. Discussion and Conclusions
The general requirements for a domestic cooking appliance in South Africa are based on published
paraffin stove standards (SANS 1243):

Produce a heat output of at least 1 kW

Heat a 1 L of water from 25ºC to 90ºC in less than 20 minutes, boil within 30 minutes

Have a CO/CO2 ratio of less than 2%

Have a rigid construction

Have flame regulation

Have stability on cooking surface

Touchable surfaces shall not exceed 42ºC

A smooth neat finish devoid of sharp edges

Provision of special tool for handling removable parts.
The test results reported herein indicate that the Protostar satisfies these requirements. The stove
delivers a gross firepower of 1.03 kW and an average firepower of 0.93 kW attained over high and
medium power settings over the technical test cycle. The range of adjustment from high to medium
power 100% to 71% was selected for performing the specified cooking task – further adjustment to
lower power is within the range of variation of the control lever.
The stove has low emissions of CO and PM2.5, thus placing this stove among the highest rank, Tier 4
of the IWA ratings, in terms of clean burning stoves. With a CO/CO2 of 1.63 ± 0.06%, the Protostar is
satisfies the South African Bureau of Standards specification (less than 2%) for open flame devices
allowable for indoor cooking and heating.
With a gross firepower of 1 kW, a heating rate of 8.5 minutes per litre of water from 25ºC to 94ºC,
and marginal CO and PM2.5 emissions, the Protostar is a viable option for replacement of illegal
design paraffin stoves (still widely used) and poor efficiency cookstoves used in low income
households. Risks of injuries from hot surfaces and liquid burns are diminished due to low surface
temperatures, a secure pot rest and spill proof fuel reservoir. One fuel load of 500 ml delivers a decent
firepower over a 2 h cooking cycle, which is sufficient to cook two sequential dishes of typical meals
eaten in the targeted stove market, without refuelling. The test results reported here place the Protostar
stove on Tier 4 of GACC IWA rankings (in terms of emissions and thermal performance) and Tier
 SeTAR Centre, University of Johannesburg
7
Version: Final
3 (in terms of safety aspects). This implies that the device performs at the highest level of improved
stoves and its adoption would lead to attainment of human health and environmental improvement
targets.
5. Reference
Global Alliance for Clean Cookstoves (GACC), 2015. IWA tiers of performance. Available from
http://cleancookstoves.org/technology-and-fuels/standards/iwa-tiers-of-performance.html, 16 March
2015.
“Standard for Pressurised Paraffin-Fuelled Appliances”, SANS 1243, Pretoria: South African Bureau
of Standards, 2007.
Signature
16 March 2015
Name and designation
Harold Annegarn, Prof and Director of the SeTAR Centre
Notes:
Copies of the written test protocols are available from the SeTAR Centre website: www.setarstoves.org
 SeTAR Centre, University of Johannesburg
8
Version: Final
Appendices
Appendix A: Screening Test
Gross power (without pot)
1.
Take the mass of the empty stove
2.
Fuel the stove up to the recommended capacity
3.
Note mass of stove and fuel (M1)
4.
Note the time (T1) and light the stove.
5.
Operate the stove on high power for thirty minutes.
6.
Note the final mass of stove and fuel (M2)
7.
Compute the fuel loss (M1- M2)
8.
Repeat the procedures for the other power levels.
9.
Compute the power output as per the following equation: Power (W) = CV (𝑇1−𝑇2)60
𝑀1−𝑀2
i.
Where CV = fuel calorific value in KJ/g
ii.
M1 – M2 = fuel used in grams
iii. T1 – T2 = time duration in minutes (i.e. 30 minutes in this case)
Gross power (pot on)
10. Fill the stove with fuel and weigh (M1)
11. Weigh 5 L water (5 000 g)
12. Take initial water temperature (Temp1) with thermocouple placed in the pot. NB the
thermocouple remains in the pot throughout the test.
13. Note time (T1), light the stove, put on the water pot
14. Operate till the water reaches a rolling boil, and note the boiling temperature (Temp2)
15. Switch-off the stove and weigh final mass of fuel and stove (M2)
16. Compute fuel loss (M1 – M2) grams;
17. Compute the time to boil 5 litres (i.e. T2 – T1) and the specific time to boil a litre of water in
minutes.
18. Compute the temperature change (Temp2 – Temp1) °C
𝑀1−𝑀2
19. Calculate the power output: Power (kW) = CV (𝑇1−𝑇2)60
20. where CV = fuel calorific value in KJ/g
1. Repeat above steps with a 2-L pot of water and note the power
 SeTAR Centre, University of Johannesburg
9
Version: Final
Appendix B: Cooking Observation Test
Derivation of the Protostar® stove burn cycle
Introduction
The cooking observation tests are conducted to establish the burn cycle, upon which technical tests
(for emissions and thermal performance) can be done on the testing rig. At SeTAR Centre we have
come up with four standard meals that are eaten in communities that are likely to buy the stoves.
These meals are:

Samp (maize and beans) and beef tripe;

Samp and lamb or beef stew;

Pap (thickened cornmeal gruel) and chicken feet;

Rice and chicken stew; and

Pap and cabbage.
Two or three meals from the above list are cooked on a candidate stove and the individual cooking
cycles averaged to form the burn cycle for technical test.
Outlined below are the procedures that were followed in derivation of the Protostar® stove cooking
cycle. The stove was tested at SeTAR Centre stove testing laboratory on 17th – 19th Feb 2015.
Cooking with the Protostar stove
Two meals were cooked on this device. The first meal composed of samp and beef tripe, while the
second meal was made up of pap and cabbage. The meals were cooked in 5 L pots and were enough
to feed seven people.

Samp and beef stew: Dry maize and beans (~850 g) were boiled together till fully cooked (the
cook decided when they were ready – sometimes asked a team member to taste for
concurrence). The cooking was accomplished on high and medium power level settings, the
former taking the longest duration.
Beef tripe relish - About 1500 g of beef was cleaned, cut to size and steamed till tender, then
garnishes were added (i.e. onions, tomatoes, pepper, garlic and salt). Cooking was done on
high power setting only. The time taken to cook part 1 and 2 of the meal and the respective
power level was noted.

Pap and cabbage: Pap - about 2.5 litres of water was brought to boil in a 5 L aluminium pot,
then cornmeal (890 g) was added and boiled till gelatinized. Enough flour was added and
stirred continuously to ensure a smooth consistency. The cooking was accomplished on high
and medium power settings.
Cabbage relish – Onions and green pepper were fried, then about 800 g of freshly chopped
cabbage was added and cooked on high power setting till done.
The average of cooking durations at each power level form the burn cycle for technical tests. The
Protostar had a burn cycle of 116 minutes, distributed as follows: 50 minutes for first high power
phase; 13 minutes medium power phase; and 53 minutes for the second high power phase. Details on
derivation of the burn cycle are depicted in Table 1.
 SeTAR Centre, University of Johannesburg
10
Version: Final