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A PRELIMINARY COMPARISON BETWEEN THE HETEROGENEOUS PROTOCOLS AND
THE WATER BOILING TEST
Tafadzwa Makonese1,2, James Robinson1,2, Crispin Pemberton-Pigott1, Harold
Annegarn2,1
1. GTZ SeTAR Centre, University of Johannesburg2. Department of Geography, Environmental Management and Energy Studies, University of
Johannesburg
DUE Conference 2011 11-14 April 2010
Background
•Improved cookstoves have an extended history in relation to a comprehensive set of issues
•Range from local health and environmental implications to global impacts.
•Impetus through launch of Global alliance for cookstoves in 2010
•Stove performance tests are important as a basis for global climate prediction models and IPCC inventories
•Significant contribution to regional estimates of carbon aerosols and inventories of greenhouse gases
Fuel/Stove Assessments
•No agreed set of stove testing protocols devised under the guidance of a professional standards setting agency
•Majority of protocols not validated and certified•ad hoc protocols for specific stove programmes and
communities•Non uniformity in testing regimen e.g. Variants in WBT
•Certification of such protocols could be useful– in the support of legislation on air quality and– for claims under the clean development mechanism (CDM) or
Gold Standard.
•Need for robust stove testing protocols, validated and certified
DUE 2011
Evaluation of Fuel/Stove combinations
DUE 2011
The UCB Water Boiling Test (WBT) Version 3.0
Evaluation of Fuel/Stove combinations cont……
•Inter-governmental Panel on Climate Change (IPCC) stove emission factors and
•emissions inventories for climate modelling are ultimately derived from the WBT
•Estimates of emissions using the standard WBT are flawed
•Discrepancy between modelled emissions estimates and measured atmospheric concentrations
DUE 2011
Methodology-Stove tested
•An ethanol gel stove was used
•Small fuel chamber, maximum of 200 g of the ethanol gel •Lever for determination of power setting•Operated according to manufacturer’s instructions
Experimental Setup
0000
Thermocouple
Gas sampling probe
Computer
Analyser
Weighing platform
Stove
Pot with lid
Extraction hood
Steam outlet pipe
Criteria for Comparison
DUE 2011
•Criteria for evaluating stove testing protocols for CDM certification:
•GHG emissions over an entire cycle representative of real-world uses of stoves
•Identification of stove design weaknesses and advantages
•Expression of results in a normalised manner
Test Results and DiscussionsExperimental results from WBT
DUE 2011
Time to boil (mins)
WBT (High Power Test)
WBT (Simmering Test)
27.2 ± 2.6 n/a
Burn rate (g min-1) 2.8 ± 0.3 1.9 ± 0.1
Thermal efficiency (%) 75.0 ± 2.0 75.0 ± 1.0
Fire power (watts) 906 ± 92 616 ± 41
Specific fuel consumption# (g L-1)
42.6 ± 0.7
Specific fuel consumption$ (g L-1)
70.3 ± 6.4
Turn down ratio* n/a 1.47 ± 0.20
# Boiling task: To heat water from 25°C to boil $ Simmering task: To maintain water at simmer for 45 minutes * See text for revised definition
Experimental Results from the HTP
DUE 2011
Power Setting
Small Pot Large Pot
High Medium Low High Medium Low
Time to boil (mins) 24.6 ± 1.0 n/a n/a 56.0 ± 1.4 n/a n/a
Burn rate (g min-1) 2.21 ± 0.06 1.01 ± 0.25 0.92 ± 0.16 2.35 ± 0.06 1.15 ± 0.13 0.98 ± 0.08
Thermal efficiency (%) 68.9 ± 4.0 69.6 ± 8.1 73.5 ± 5.4
71.6 ± 2.9 78.1 ± 5.4 80.3 ± 7.2
Fire power (watts) 710 ± 20 330 ± 80 270 ± 40 760 ± 20 370 ± 40 320 ± 30
Specific fuel consumption (g L-1)
27.9 ± 1.7 27.3 ± 0.9
Turn down ratio 3.1 2.7
Efficiency Curves-HTP result
DUE 2011
Relationship between firepower and thermal efficiency
60%
65%
70%
75%
80%
85%
90%
200 300 400 500 600 700 800
Power [W]
Th
erm
al E
ffic
ien
cy
[%
]
Small Pot Big Pot High Medium Low
Conceptual analysis between HTP and WBT
Criteria Used WBT HTP
Representative emissions over an entire burn cycle
-cannot measure emissions over a range of conditions-emissions are an average of a burn cycle (same as efficiency)-trade off between efficiency and emissions cannot be investigated
-measures emissions over a range of conditions-important to point out polluting phases of the burn cycle-trade off between efficiency and emissions investigated
Identification of design weaknesses and strength
-method does not use continuous assessment of emissions and thermal efficiency-sums performance metrics to give a single integrated number
-method use continuous assessment of emissions and thermal efficiency-performance metrics determined at different phases of the fire
Expression of results for comparison between different stoves
-emission factors are not normalised-difficult to compare between different stoves performing different tasks
-emission factors are normalised to O% excess oxygen-possible to compare between different stoves performing different tasks
Conclusion
•Similar results in thermal efficiency, and time to boil•Subtle differences in intent of the methods.•Differences in fire-power, specific fuel consumption, burn rate and turn down ratio.
•Use of pot lid has potential to reduce fuel consumption; represents good cooking practice.
•HTP provide a set of performance curves; make informed decisions about which stove to promote.
•Task based performance, repeated 10 times and known exactly, is not a substitute for a set of performance curves.
•Need for the HTP protocols to be evaluated against in-field assessments.
Acknowledgements
• CEF and GTZ BECCAP for commissioning the work.
• NRF Focus Area bursary to TM
• Vincent Molapo, and David Kimemia for the lab-work.
• Maxwell Vhareta, School of Physics, Wits University
• GTZ BECCAP/ProBEC for funding of SeTAR centre at
University of Johannesburg.
• University of Johannesburg Quick Wins Grant for the
EnerKey Sustainable Megacities programme
• SANERI
