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The Water Boiling Test for Solar Cookers WBT SC


The Water Boiling Test for Solar Cookers WBT SC Is designed to measure water boiling performances of all ... See ppt-stove-testing-wbt.ppt of Nordica ... – PowerPoint PPT presentation

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Title: The Water Boiling Test for Solar Cookers WBT SC

The Water Boiling Test for Solar Cookers WBT SC
  • Version 1.0.3
  • Prepared April 2014 by
  • Bernhard S. Müller, Historian on Solar Cooking,
    former owner of the solar cookers manufacturer
    Mueller Solartechnik, Eschborn, Germany
  • Faustine L. Odaba, Founder and CEO of the NGO
    NAREWAMA Natural Resources and Waste Management
    Alliance, Nairobi, Kenya

  • The Water Boiling Test for Solar Cookers WBT SC
  • Is designed to measure water boiling performances
    of all solar cookers.
  • Is based on standard amounts of water 1 or 2.5
  • Is easy to understand.
  • Is easy to conduct.
  • Does not need sophisticated test equipment.
  • Is in close proximity to the WBT 4.2.x of
    Aprovecho Research Center (ARC).
  • Compares solar cooker boiling performances.
  • Depends on data contributions from various
    latitudes, altitudes and temperatures.
  • Gives users world wide a fair chance to buy what
    they need and not what they are told by

  • The Water Boiling Test for Solar Cookers WBT SC
  • Is not intended to run tests with other
    objectives than water boiling, e.g. drying or

  • Not included in the protocol, to maintain its
  • The consumed solar energy, neither for time
    segments nor in total.
  • Specifically consumed energy for losses due to
    reflector material quality, glass refractions or
    absorber material properties.
  • Losses due to convection, vaporization and
    insufficcient insulation.
  • However, specialists can extract further data by
  • of the aperture area, the estimation of the
    insolation and the
  • specific heat capacity. Contributions for an
    extension of the
  • WBT SC regarding the energy consumption are

  • Advantages to the WBT SC
  • It is easy to understand and to conduct.
  • No need of sophisticated test equipment.
  • Solar cookers from around the world can be
    compared even with other water boiling devices,
    such as rocket stoves, micro gasifiers, open
    fires, etc.
  • Wrong or incomplete thus misleading
    statements of solar cooker producers can be
  • The WBT SC is widely adjusted to the WBT 4.2.x of
    Aprovecho Research Center ) with the exception
    of the documentation of simmering time and fuel
  • ) See ppt-stove-testing-wbt.ppt of Nordica
    MacCarthy, Laboratory
  • Manager at Aprovecho Research Center

  • Disadvantages to the WBT SC
  • The test protocol depends on as many
    contributions as possible from around the world.
    It has less value, if users fail to report their

  • Supplies
  • Pot with lid, both with dull black surface.
  • Thermometer or thermocouple.
  • Scale to weigh water and pot.
  • A form to note the data. An ExcelTM spreadsheet
    can be downloaded free athttp//www.mueller-solar
  • The lid shall have a hole to support the
  • measuring device.
  • Excel is a trade mark of Microsoft Corp.

To conduct the WBT SC properly, please note
  • Amount of water ( 1 or 2.5 liters).
  • Initial water temperature.
  • Ambient temperature.
  • Type of cooker (box, parabolic, panel, etc.).
  • Sun angle at beginning and end of test.
  • Name and country of test location.
  • Altitude of test location.
  • Coordinates of test location.
  • Date and time.
  • Reflector material (if any).
  • Insulation material (box cookers only) if any.
  • Heat trapping material (oven bag, glass, etc.).
  • Aperture area.
  • Water temperature every 10 minutes.

For reasons of convenience it is recommended to
use the downloaded WBT SC Excel file
  • All necessary data shall be entered in the green
    fields only.
  • The local boiling point is displayed
    automatically once the altitude of the test site
    is entered.
  • Explanation tags pop up on hovering over the
  • Like the entire test protocol, the Excel
    spreadsheet is easy to understand.

Presently, the Excel spreadsheet is available in
English, German and Spanish language
  • Lower part of the form
  • The time intervals are displayed automatically.
    Just enter the start time.
  • The initial water temperature is entered also
    automatically from the upper part of the form.
  • Contact the authors for assistance.

  • Optional, to allow further elaborations
  • The elapsed time to reach 65C water temperature
    shall be noted. This information is helpful to
    determine the water pasteurization abilities of
    the solar cooker.
  • It is helpful to note weight and material of pot
    and lid for future energy consumption
    calculations an intended extension of the WBT

  • The test is done. What to do now?
  • Send the completed form as eMail attachment to Do not forget to
    enter WBTSC in the reference line of your message
    to avoid that it will be categorized as spam.
  • The site with all required downloads, including
    this presentation, is located in the Internet at
  • http//

  • Annex
  • What is the knowledge of the local boiling point
    good for?
  • The local boiling point specifies the
    temperature, at which
  • water comes to a rolling boil. The higher the
    altitude, the
  • lower the boiling point. This can be important
    for heat storage
  • devices, such as insulation baskets (fireless
    cookers) because
  • the temperature decay time is the shorter, the
    lower the local
  • boiling point is.
  • To mention the local boiling point is also an act
    of fairness.
  • The user gets clear information that the same
    cooker performs
  • differently, even on the same latitude and at the
    same ambient
  • temperature.