The Water Boiling Test
(WBT)
with
ISO/IWA Metrics
and
ARC Equipment
July 30, 2012
Stove Camp
Updated by Abraham Mooney
The Water Boiling Test (WBT)
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Standardized, reproducible lab test
Boil and simmer water
Measure the boil time, fuel use, efficiency, emissions
Trained tester carefully tends the fire (COV)
High and low power test phases
Cold stove and hot stove test phases
Allows for multiple pots on one stove
Stove Testing Continuum
Increasing control of variables
Increasing isolation of stove performance
Increasing quantification of emissions
Increasing intervention of testers
WBT
Lab
CCT
Field
Increasing cost
Increasing sample size and variability
Increasing measurement of in-home use
Increasing relation to WHO air quality guidelines
KPT
Purpose of WBT


Effective design tool to evaluate
design changes of a stove
Stove Improvement through comparison
(High Accuracy equip.)
Advantages of the WBT

Reproducible, standardized

Stoves from around the world can be compared

Stove design changes observed clearly and
quickly

Benchmark evaluation and comparison
Disadvantages of the WBT
 Not
always reproducible
Fuel irregularities, and “to error is human.”
 Not
representative of field use
Only one simulated cooking task
 Hard
to do for some stoves
Batch-loading stoves: TLUD’s, charcoal
WBT Procedure
Phase
Task
Record
COLD
START
Bring to
Boil 5L in
first pot
Time
Fuel
Water
Charcoal
HOT
START
Bring to
Boil fresh
5L in first
pot
Time
Fuel
Water
*Assume Same
Charcoal as Cold Start*
SIMMER
Simmer
remaining
5L for 45
minutes
Time
Fuel
Water
Charcoal
WBT Procedure
 45 min. SIMMER 
COLD START
HOT START
Tboil
Tboil-6degC
Water
Temperature
Fresh Water
Troom
Time
WBT – Preparing for the Test
First do a practice test to:
• Get familiar with the stove
• Determine if the stove should be tested
with 2.5 or 5 liters
• How much fuel is required?
• Boiling temperature of water (local)?
WBT – Preparing for the Test
Gather Supplies
1. Scale - 6000g range, 1g
resolution
2. Temperature sensor –
waterproof
3. Fixture for suspending
temperature sensor
4. Wood moisture meter or
oven for fuel MC
WBT – Preparing for the Test
Gather Supplies
5.
6.
7.
8.
9.
10.
11.
Timer or watch
Pot – standard or dedicated, no lid
Heat resistant pad for scale
Charcoal scooper/tongs
Char tray
Heat resistant gloves
Water – room temp,
- at least 10 liters
12. Fuel – air dried, uniform
- 2 bundles ~ 2kg each
WBT – Conducting the Test
Phase 1: High Power Cold Start
• Set the pots on the stove with 5000g of water with the temp sensor suspended in
the water of Pot 1.
• Record:
-Starting weight of pots with water
-Starting water temperatures
-Initial mass of the bundle of fuel
• Light the fire - record start time
• Tend fire and bring water to a boil
WBT – Conducting the Test
Phase 1: High Power Cold Start
• When Pot 1 boils record:
 time
 temperature of all pots
 pot plus water weights
 fuel remaining
• break char off tips of
burned sticks
• Put char on tray and
record weight of char
plus tray
WBT – Conducting the Test
Phase 2: High Power Hot Start
• Refill the pots with cool water and repeat the boil procedure starting with a hot stove
• Use a new bundle of wood
• This time, when Pot 1 boils
keep the char in the
combustion chamber. DO
NOT WEIGH THE CHAR
• Weigh the pots and place
them back on the stove
• Weigh the wood, place it back
in the combustion chamber,
then re-light it.
WBT – Conducting the Test
Phase 3: Low Power Simmer
• Record the start time once the fire is lit
• Transfer over the fuel weight, pot and water weights, and water temp from the results
column at the end of the hot start
• Tend the fire to keep the
water temp of the pot at 36 degrees C below boiling
for 45 min
• After 45 min of simmer record:
 Final water temperature
 Weight of Pot 1 plus water
 Final weight of fuel and
char remaining
WBT Results
Three test phases,
real-time
measurement
(CO2, CO, PM)
THE NEW DEAL
WBT Results
Thermal Efficiency (%)
=
𝐸𝑛𝑒𝑟𝑔𝑦ℎ𝑒𝑎𝑡 𝑤𝑎𝑡𝑒𝑟 +𝐸𝑛𝑒𝑟𝑔𝑦𝑒𝑣𝑎𝑝 𝑤𝑎𝑡𝑒𝑟
x100
𝐸𝑛𝑒𝑟𝑔𝑦 𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑏𝑦 𝑓𝑢𝑒𝑙
High efficiency ≠ low fuel consumption
because high power stoves evaporate
lots of water and also use lots of fuel
*IWA
Metric
WBT Results
Low Power Specific Consumption (MJ/min/L)
𝐸𝑛𝑒𝑟𝑔𝑦𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑓𝑟𝑜𝑚 𝑤𝑜𝑜𝑑
=
𝑇𝑖𝑚𝑒𝑠𝑖𝑚𝑚𝑒𝑟 𝑥(𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔)
*IWA
Metric
WBT Results
High Power CO (g/MJd)
Low Power CO (g/min/L)
=
𝐶𝑂
𝐸𝑛𝑒𝑟𝑔𝑦𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 𝑡𝑜 𝑝𝑜𝑡
𝐶𝑂
=
𝑇𝑖𝑚𝑒 𝑥(𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔)
*IWA
Metrics
WBT Results
High Power PM (mg/MJd)
=
𝑃𝑀
𝐸𝑛𝑒𝑟𝑔𝑦𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 𝑡𝑜 𝑝𝑜𝑡
𝑃𝑀
Low Power PM (mg/min/L) =
𝑇𝑖𝑚𝑒 𝑥(𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔)
*IWA
Metrics
WBT Results
Indoor Emissions CO
(g/min)
Indoor Emissions PM
(mg/min)
𝐶𝑂
=
𝑇𝑖𝑚𝑒
𝑃𝑀
=
𝑇𝑖𝑚𝑒
*IWA
Metrics
WBT Results
Temperature Corrected Specific Fuel Consumption (g/L)
75
𝑒𝑞𝑣𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑑𝑟𝑦 𝑤𝑜𝑜𝑑 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 (𝑔)
=
∗
𝑇𝑏𝑜𝑖𝑙 − 𝑇𝑖𝑛𝑖𝑡
𝑙𝑖𝑡𝑒𝑟𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔 (𝐿)
Eq. dry wood
consumed
=
dry wood mass
–
wood mass that
was consumed to
evaporate the
moisture in the
wood
--
equivalent mass of
wood stored as char
Best indicator of fuel consumption
WBT Results
Average Firepower (W)
𝑡𝑜𝑡𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑏𝑦 𝑓𝑢𝑒𝑙 𝑑𝑢𝑟𝑖𝑛𝑔 𝑡ℎ𝑒 𝑡𝑒𝑠𝑡 𝑝𝑒𝑟𝑖𝑜𝑑 (𝐽𝑜𝑢𝑙𝑒𝑠)
=
𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡𝑒𝑠𝑡 𝑝𝑒𝑟𝑖𝑜𝑑 (𝑠𝑒𝑐𝑜𝑛𝑑𝑠)
How big is your stove
WBT Results
Turndown Ratio
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑏𝑜𝑖𝑙 𝑓𝑖𝑟𝑒𝑝𝑜𝑤𝑒𝑟(𝑊)
=
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑖𝑚𝑚𝑒𝑟 𝑓𝑖𝑟𝑒𝑝𝑜𝑤𝑒𝑟 (𝑊)
WBT Sample Size
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At least three full tests per stove design are recommended
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Then do more tests if necessary to achieve the desired statistical
significance measured by the COV (Coefficient of Variation)
𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛
𝐶𝑂𝑉 =
∗ 100
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑣𝑎𝑙𝑢𝑒

(%)
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COV is a measure of how much your results vary
COV indicates how good you are at getting repeatable results

For stove testing
COV = 5%
COV = 10% or 25%
is very good
is also acceptable
Aprovecho Emissions Equipment
PEMS & LEMS
Portable (or Lab)
Emissions Measuring System
IAP Meter
Indoor Air Pollution Meter
PEMS
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Collection hood collects stove emissions
Sensor box measures:
1.
2.
3.
4.
5.
6.
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CO
CO2
PM (laser)
Flow rate in duct
Temp in duct
Pot temp
Uses:
1.
2.
Measure stove emissions (WBT, CCT)
Stove design tool
PEMS
PM Sensor: Scattering Photometer
PEMS
CO Sensor: Electrochemical Cell
Diagram
Courtesy Monox
PEMS
CO2 Sensor: NDIR
PEMS
PEMS Data Processing
Software
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Outputs include:
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Graph of emissions vs. time
Standard performance measures
Specific fuel consumption (grams/liter)
Total emissions (grams)
Specific Emissions (grams/liter)
Emissions Factors (grams/kg fuel)
Efficiency and Firepower
LEMS and Gravimetric
LEMS
Why use gravimetric?
 Photometer:
Estimates the REAL TIME
mass concentration of particulate matter
from optical measurements
 Gravimetric:
Measures total mass
concentration of particulate matter, at end
of test (scale c10^-5 g).
With gravimetric we move to…
Categorization studies
(e.g. Tier 4)
PEMS
Laser vs. gravimetric

Photometer

Output = scattering coefficient (1/m)
Physical meaning: fraction of light scattered away for every meter a light beam travels

Mass concentration estimated by:
Indoor Air Pollution Meter
•
Measures concentrations of:
CO (Carbon Monoxide)
PM (Particulate Matter)
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Uses:
Measure room concentration
Measure personal exposure
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wear meter in backpack with sample tube
CCT, KPT, other comparative tests
Stores data on SD Memory Card
PEMS
Why use gravimetric?
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Gravimetric
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Particles are collected on a filter and weighed.

Indoor Air Pollution Meter
PM Sensor: Scattering Photometer
(same as PEMS)
Indoor Air Pollution Meter
CO Sensor: Electrochemical Cell
(Also used in PEMS)
Diagram
Courtesy Monox
Indoor Air Pollution Meter
Features

Sample speed selection
Fast:
Every 10 seconds
Battery life: 3 days
Medium: Every 1 minute
Battery life: 2 weeks
Slow: Every 10 minutes
Battery life: 1 month
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LED indicates meter is on
Serial port for live graphing
IAP Meter
Data Processing Software
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Outputs include:
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Graph of emissions vs time
Average concentrations
Maximum and minimum concentrations
15 minute average concentrations
Summary
PEMS
 Measures emissions:
CO, PM, and CO2
 Stove total emissions
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IAP Meter
 Measures emissions:
CO and PM
 Room concentrations
and personal exposure
Measures pot temp for
WBT
Cost: $10,000 USD

Cost: $2,400 USD
More Information
www.aprovecho.org
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Spec sheets
Brochures
Manuals
Data processing spreadsheets
Documentation
 www.aprovecho.org/lab/pubs/testing
Download testing protocols