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Various tests are available to compare solar cookers (see below). Not everyone in the solar cooking community agrees on how to best test solar cooker variations, and how to report the results of these tests. Some argue for a standardized test with standard measurements calibrated to report absolute results. Others argue for a more low-tech, approach that measures only the relative difference between cookers or cooker variations when tested side-by-side.

There is also a discussion about what to test and how to rate cookers. Is a cooker that cooks very fast, but has to be turned frequently to follow the sun better than a cooker that cooks slowly but never needs to be turned?

Relative tests

A possible testing scenario:

  • Heat a liter of water simultaneously in two cookers, one with the modification to be tested and one without. The two cookers to be tested could also be two completely different models.
  • After a time (before the water boils in either cooker), measure the temperature of the water in both cookers.
  • Use these measurements to determine how many degrees each cooker raised the temperature of the water.
  • Calculate the percentage difference between these two temperature changes and report this along with a description of the modification that you tested.

Absolute tests

Partnership for Clean Indoor Air: Stove Performance Testing Protocols

  • "Stove performance varies greatly, and the performance of a specific stove is often different in the lab and in the field. Testing allows implementers to learn how well stoves perform and to quantify improvements in fuel efficiency and emissions. Test results can be used to guide implementation decisions and to improve stove design and performance. Below is a collection of stove testing resources that may be of interest to PCIA Partners." - PICA

Water Boiling Test (WBT)

  • The Water Boiling Test is a laboratory test that evaluates stove performance while completing a standard task (boiling and simmering water) in a controlled environment to investigate the heat transfer and combustion efficiency of the stove. They are the easiest, quickest, and cheapest to conduct, but reveal the technical performance of a stove, not necessarily what it can achieve in real households.
  • WBT testing protocol

Controlled Cooking Test (CCT)

  • The Controlled Cooking Test is a field test that measures stove performance in comparison to traditional cooking methods when a cook prepares a local meal. The CCT is designed to assess stove performance in a controlled setting using local fuels, pots, and practice. It reveals what is possible in households under ideal conditions but not necessarily what is actually achieved by households during daily use.
  • CCT testing protocol

Kitchen Performance Test (KPT)

  • The Kitchen Performance Test is a field test used to evaluate stove performance in real-world settings. It is designed to assess actual impacts on household fuel consumption. KPTs are typically conducted in the course of an actual dissemination effort with real populations cooking normally, and give the best indication of real world changes. The KPT is benchmark testing that solar cookers will also need to be evaluated with. It will help in finding the appropriate solar cooking technology to partner with other clean-fuel cooking options. The primary goal is to find integrated cooking solutions to stem the environmental damage currently being caused by deforestation, and eliminating respiratory disease from cooking with smokey, inefficient fuels over open fires.
  • KPT testing protocol

Recent news and developments

  • November 2012: ASABE (the society for engineering applicable to agricultural, food, and biological systems) is revising the international standard, S580, "Testing and Reporting Solar Cooker Performance." The intent of this standard is to make it possible to test solar cookers with a minimum investment in technology, in any location, while arriving at a value that is repeatable independent of climate, and easily understood. It uses Watts of cooking power to rate box-type, panel-type and concentrating (or parabolic dish-type) solar cookers. The document may be viewed here: http://solarcooking.org/asae_test_std.pdf and comments may be sent to: pfunk@nmsu.edu.
  • February 2012: Ajay Chandak, a respected and experienced innovator with solar cooking technologies, has provided the following insights to stove testing. It appears one of his greatest concerns is that all stoves, solar and bio-fuel types, be tested with the same procedures and using the same criteria. This will provide relevant information to be able to compare all the various cooking technologies. His comments are below:
I think we need all three tests. During recent training program at our end we included WBT and CCT for solar cookers. My view is that all three tests are required for any cook stove for following reasons.
1. WBT: This test is useful for rating cookstoves in one category: For e.g. if we talk of solar dish cookers then this test compare different dish cookers on their performance, efficiency etc. Same is valid for other cookstoves. We can compare all woodstoves on one to one basis. I think the test needs to be simplified from the current form.
2. CCT: This test provides fuel saving potential of the cookstove with presumption that both the existing cooking option and proposed new cookstoves are operated in the best possible manner. All cookstoves, irrespective of fuel type, renewable or fossil, solar, biogas, biomass, LPG, kerosene will be compared with what so ever the cookstoves we want to replace. So this test provides comparison amongst different technologies while WBT provides comparison amongst same technology. CCT is utmost important to get solar also introduced as one of the possible options, and it can only be accepted by different committees and bodies if we provide them comparative scale of solar with other technologies. CCT will also form the benchmark for any carbon funding activity for renewable energy project to know what is the carbon emission saving potential of a particular technology.
3. KPT: This is practical version of CCT. In CCT we presume that the existing cooking technology and new proposed technology are used in best possible manner. However in practice it is not so. Moreover in CCT fuel/emission saving potential will depend on time of usage by the end user, which we take by estimate. In KPT we are replicating real life situation to find out actual saving potential considering all uncertainities in usage timing, variation in food habits, variation in cooking quantities, variation in cooking practices etc.
For this reason we need to consider same set of tests for all technologies. There may be additional tests for few technologies, but at least WBT, CCT and KPT should be common to all. Any way WBT and CCT also hardly require any costly equipments, normally a thermometer and weighing machine is adequate for these tests. I feel that all tests should be as simple as possible and sample sizes to be reduced to less than 3% in case of KPT. As CCT establishes the benchmark on how much can be saved, it makes sense to reduce the sample size in KPT.

What to test

A focus only on speed and highest temperatures eliminates one important preferred feature for some. The intuitive "fastest, hottest is always best" overlooks the benefits of slow, unattended cooking where food never burns and sun angle adjustments are seldom needed. This is often mentioned as a favorite feature by consumer feedback from women around the world. A bias against slow, gentle solar cookers that cook like crock pots - ideal for many favored dishes - reduces market access for large populations of women whose daily needs and finances don't match "hottest, fastest" devices. Commercial avenues for spreading solar cookers have failed more often than not, and cooker designers' reliance on what they THINK is best for women is too seldom confirmed by consumer feedback, which varies widely with region-specific foods, women's daily demands, climate, etc. for this reason, it has been proposed that parabolic cookers be separated from all other solar cookers and that the remaining cookers be rated separately for each of six or seven features other than cooking temperature or speed. This can accelerate finer target market adjustments through marketing studies.

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