WBT_w_IWAandARC_equi..

foulgirlsUrban and Civil

Nov 15, 2013 (3 years and 6 months ago)

70 views

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)


Standardized, reproducible lab test


Boil and simmer water


M
easure the boil time, fuel use, efficiency, emissions


Trained tester carefully tends the fire (COV)


H
igh and low power test phases


Cold stove and hot stove test phases


Allows for multiple pots on one stove


Stove Testing Continuum

WBT

CCT

KPT

Increasing cost

Increasing sample size and variability

Increasing measurement of in
-
home use

Increasing relation to WHO air quality guidelines

Increasing control of variables

Increasing isolation of stove performance

Increasing quantification of emissions

Increasing intervention of testers

Lab

Field

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

COLD
START

HOT
START

SIMMER

Task

Bring to
Boil 5L in
first pot

Bring to
Boil fresh
5L in first
pot

Simmer
remaining
5L for 45
minutes

Record

Time

Fuel

Water
Charcoal

Time

Fuel

Water

*Assume Same
Charcoal as Cold Start*

Time

Fuel

Water

Charcoal

WBT Procedure

Time

Water

Temperature

T
boil

T
room

T
boil
-
6degC

Fresh Water

COLD START

HOT START



45 min. SIMMER


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


H
ow much fuel is required?


Boiling temperature of water (local)?

WBT


Preparing for the Test

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

Gather Supplies

WBT


Preparing for the Test

5.
Timer or watch

6.
Pot


standard or dedicated,
no lid

7.
Heat resistant pad for scale

8.
Charcoal scooper/tongs

9.
Char tray

10.
Heat resistant gloves

11.
Water


room temp,


-

at least 10 liters

12.
Fuel


air dried, uniform


-

2 bundles ~ 2kg each


Gather Supplies

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:



t
ime



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
3
-
6
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

Three test phases,
real
-
time
measurement

(CO
2
, CO, PM)

WBT Results

THE NEW DEAL

WBT Results

Thermal Efficiency (%)

=
𝐸  𝑦
ℎ 

 
+
𝐸  𝑦


 
𝐸  𝑦

𝑙 

𝑦

𝑙
x
100

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)

*IWA
Metric

=
𝐸
  




𝑇𝑖
𝑖

(
 

𝑅 𝑖𝑖
)

WBT Results

High Power CO (g/
MJ
d
)

*IWA
Metrics

=
𝐶
𝐸
 𝑖






Low Power CO (g/min/L)

=
𝐶
𝑇𝑖

(
 

𝑅 𝑖𝑖
)

WBT Results

High Power PM (mg/
MJ
d
)

=

𝐸
 𝑖






Low Power PM (mg/min/L)

=

𝑇𝑖

(
 

𝑅 𝑖𝑖
)

*IWA
Metrics

WBT Results

*IWA
Metrics

Indoor Emissions CO
(g/min)

=
𝐶
𝑇𝑖

Indoor Emissions PM
(mg/min)

=

𝑇𝑖

WBT Results

Temperature Corrected Specific Fuel Consumption (g/L)

=
75
𝑇
𝑖𝑙

𝑇
𝑖 𝑖


𝑖






 

(

)
𝑖





 𝑖𝑖

(

)

=
dry wood mass


--


equivalent mass of
wood stored as
char


wood mass that
was consumed to
evaporate the
moisture in the
wood

Eq. dry wood
consumed

Best indicator of fuel consumption

WBT Results

Average Firepower (W)

=




  



 

 𝑖

ℎ



𝑖

(
𝐽 
)
ℎ





𝑖

(

)

How
big

is your stove

WBT Results

Turndown Ratio

=


 

𝑖

𝑖 
(

)

 

𝑖

𝑖 

(

)

WBT Sample Size


At least three full tests per stove design are recommended



Then do more tests if necessary to achieve the desired statistical
significance measured by the
COV (Coefficient of Variation)



𝐶
=
  


𝑖 𝑖

 




100





(
%
)



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%


is very good

COV = 10% or 25%

is also acceptable


Aprovecho

Emissions Equipment

PEMS & LEMS

P
ortable (or
L
ab)

E
missions
M
easuring
S
ystem

IAP Meter

I
ndoor
A
ir
P
ollution
M
eter

PEMS


Collection hood collects stove emissions


Sensor box measures:

1.
CO

2.
CO2

3.
PM (laser)

4.
Flow rate in duct

5.
Temp in duct

6.
Pot temp




Uses:

1.
Measure stove emissions (WBT, CCT)

2.
Stove design tool

PM Sensor: Scattering Photometer

PEMS

CO Sensor: Electrochemical Cell


Diagram Courtesy
Monox


PEMS

CO2 Sensor: NDIR

PEMS

PEMS Data Processing
Software


Outputs include:


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


PEMS

LEMS and Gravimetric

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)
.

LEMS

With gravimetric we move
to…

Categorization

studies

(e.g. Tier 4)

Laser vs. gravimetric


Photometer


Output = scattering coefficient (1/m)


Physical meaning: fraction of light scattered away for every meter a light beam travels

PEMS

Mass concentration estimated by:


Indoor Air Pollution Meter


Measures concentrations of:



CO (Carbon Monoxide)



PM (Particulate Matter)


Uses:



Measure room concentration



Measure personal exposure


wear meter in backpack with sample tube



CCT, KPT, other comparative tests


Stores data on SD Memory Card


Why use gravimetric?


Gravimetric



Particles are collected on a filter and
weighed.





PEMS

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


LED indicates meter is on


Serial port for live graphing

Indoor Air Pollution Meter

Data Processing Software


Outputs include:


Graph of emissions vs time


Average concentrations


Maximum and minimum concentrations


15 minute average concentrations

IAP Meter

Summary

PEMS


Measures
emissions:
CO, PM, and CO2


Stove
total
emissions



Measures
pot temp for
WBT



Cost:

$
10,000 USD

IAP Meter


Measures
emissions:
CO and PM


R
oom
concentrations
and personal exposure





Cost
: $
2,400 USD

More Information

www.aprovecho.org



Spec sheets


Brochures


Manuals


Data processing spreadsheets

Documentation


www.aprovecho.org/lab/pubs/testing



Download testing protocols