The Water Boiling Test (WBT) Prepared by Jackson Bio-energy Lab technician CREEC

The Water Boiling Test (WBT) The WBT is intended to measure stove performance under standardized laboratory conditions: High (boiling) and Low (simmering) power Stove body starting Cold and Hot Standard amount of water in standard testing pot: 5 litres or 2.5 liters Quantities of time, fuel use, and water evaporated are measured Every stove is carefully tended to ensure it is operating at its best – all stoves given equal chance to do well. Each stove is tested at least 3 times The goal is to compare stoves performing a standard task, to see which can most effectively combust the fuel and transfer the heat into the cooking vessel.

Purpose of WBT WBT is not intended to predict field performance. It is a measure of the capability of the stove design to complete a standard task. Field performance will always depend on the local cooking practice, which cannot be standardized. The WBT does help make sure that the physical design of the stove is the best it can be.

Advantages to the WBT Stoves from around the world can be compared A target performance level (benchmark) can be set based on comparisons Effects of changes to a stove’s design can be observed quite clearly

Disadvantages to the WBT Fuel of differing composition/moisture content may behave differently User operation has a large effect Difficult to calculate for multi-task stoves griddle stove for frying, heating stoves New stoves may perform differently than stoves in use for some time chimney cleaned or not, parts burning out, etc.

WBT Supplies Supplies Needed Standard Testing Pot holding 5L of water 2.5 L can be used for low-powered stoves Electronic Scale (10-15 kg capacity, 1-2 gram resolution) with Heat-Resistant Pad Thermometer/Thermocouple (with fast response) At least 3 kilos of testing wood per test 10L or more of room-temperature water Metal Tray for Weighing Charcoal Tools for removing charcoal (tongs, spatula) Heat resistant gloves

WBT Procedure Bring 5L to boil with stove body starting cold Bring 5L to boil with stove body starting hot Continue into simmer for 45 minutes at about 3 degrees below boiling Between each phase, we measure and record: Time Mass of fuel Mass of water in pot Mass of charcoal remaining

WBT Procedure  45 min. SIMMER  COLD START HOT START Tboil Tboil-6degC Water Temperature Fresh Water Troom Time

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 Water *Assume Same Charcoal as Cold Start* Charcoal

WBT Procedure Need to determine Local boiling point Temperature as measured when a rolling boil with bubbles breaking the surface is observed Temperature stops rising Wood Species and their Calorific value:. Moisture content of wood

WBT Data Analysis Upon completion of the test, simply enter the data into the WBT Data-Calculation Spreadsheet (available online):

WBT Data Analysis Automatic Data Calculation Sheet Provides: Results are corrected for starting temperature of water moisture content of fuel Energy remaining in charcoal not provided to the pot Time to boil, firepower, and thermal efficiency are calculated. Results can best be presented in the form of temperature-corrected specific fuel consumption and specific emissions, g/L, representing the fuel and emissions per task completed. This is preferable to Thermal Efficiency

WBT Data Analysis Mass of Water Boiled Specific Fuel Consumption = X [ Starting Temperature Correction Moisture Content Correction Charcoal Correction 75 (Tboil-Tstart) X [ MassWood-MassMoisture-Mass -1.5*Char] Wood Used to Evaporate Moisture Mass of Water Boiled Specific (per Liter) Correction

WBT Data Analysis The overall number we most look investigate is: FUEL USE TO COMPLETE the 5L WBT = Average of Cold and Hot start Specific Consumption Specific Consumption to Simmer 5 x +

WBT Data Analysis In case you want to compare the Fuel use of stoves burning different energy content fuels, you can calculate energy consumption by: Energy Use (kJ) = Fuel Use (kg) * Calorific Value (kJ/kg)

WBT Sample Size At least three full tests per stove design are recommended Then variation can be analyzed and used to determine if more tests are needed

WBT Emissions “Collection Hood” -- The best way to measure emissions during the WBT is to collect them and analyze the total mass emitted during each test phase. This is done by knowing both the concentration and flow rate exiting the collection hood. “Test Kitchen” -- If all WBTs are conducted in one room with stable ventilation, then levels of IAP can be measured and compared. This is a reasonable option if a hood is not available, but will not give as precise information. It also subjects the tester to breathing smoke, and additional smoke is created between test phases.

WBT - PEMS The Portable Emissions Monitoring System (PEMS) collects all of the emissions and measures: CO Concentration CO2 Concentration PM Concentration Flow through the hood Temperature of flow Then mass of each pollutant is calculated in an automatic spreadsheet when data from the WBT is provided, giving: Total Emissions Pollutant/CO2 ratios Emissions to complete the WBT used for benchmarking