[Stoves] The WBT allows for comparison between tests and stoves, says Winrock

Derby, Elisa ederby at winrock.org
Mon Nov 20 21:13:28 CST 2017


Dear Xavier,

Thanks for your message and for reading the toolkit, I'm glad you were able to find it. I can't imagine that anyone who has ever worked with Winrock or even read just the consumer preferences section of the toolkit could get the impression that Winrock would recommend making stove selection decisions based only on *any* laboratory test.

It seems you may have missed the "best practices" intro to that same section you quote that emphasizes the importance of local testing of stoves to ensure that they perform well with local foods and fuels.  And where we say that cookstoves that perform well in the lab won't necessarily perform well in homes cooking specific local foods, or with nonstandard fuels. And where we highlight the importance of updating and reviewing testing protocols to ensure methods for lab and field testing provide the best possible depiction of how each stove performs.

If you read the whole toolkit and still have that impression, please give me a call, as that would be a truly problematic take-away, and I'd like to better understand your perspective.  My direct line is 1-617-524-0466 or we can talk on skype.  Even better-come to ETHOS at the end of January and we can discuss further; you'd be welcome to also present to the group on your ideas and suggestions for the sector. It's a great place to have these kinds of discussions in-person.

Have you considered joining TC 285 to help inform the testing protocols our sector is developing through the consensus-based ISO process? Or the guidelines for how these voluntary standards get explained and rolled out? Having more perspectives at the table makes for a better outcome.

Kind regards,
Elisa

From: Xavier Brandao [mailto:xvr.brandao at gmail.com]
Sent: Sunday, November 19, 2017 12:38 PM
To: 'Discussion of biomass cooking stoves' <stoves at lists.bioenergylists.org>
Cc: Derby, Elisa <ederby at winrock.org>
Subject: The WBT allows for comparison between tests and stoves, says Winrock

Dear all,

Winrock has recently published, on September 2017, on its website, a toolkit:
https://www.winrock.org/wp-content/uploads/2017/09/Winrock_Cookstove_final_reduced.pdf
The toolkit < can be used by various stakeholders, but is primarily aimed at bringing USG staff and external project developers and implementers up-to-speed on significant developments in the cookstove sector in recent years. >

According to the toolkit, p 20, < Standardized laboratory testing protocols and metrics allow for replicability and comparability among tests and across stoves >, and < The laboratory-based WBT is the most standardized of the three, and allows for comparison between stoves. >

It is unbelievable that Winrock still publishes this kind of claim, today. I am baffled. This has been time and time again proven wrong, and time and time again repeated, on this list and elsewhere that the WBT did not allow to compare stoves. That it should not be used to select stoves, for programmatic or project purposes.
Even the very rare supporters of the WBT (I am not sure who they are actually) agree about that.

I am not even talking about the proofs that the WBT is not even good to develop stoves.

In February 2017, a study by Lombardi and al. summarized the issues:
< Some of WBT critical issues remain unsolved. In particular, the main weakness of the WBT concerns its real-life relevance. [...] Criticism about WBT concerns also the repeatability of the protocol, with a number of researchers claiming that it would need to be reviewed in terms of accuracy. [...] As a matter of fact, uncertainties related to temperature reading and vaporisation in the boiling region lead to high variability between test replicates.
A lot of debate has been made around formulation of metrics, primarily on thermal efficiency, which is often interpreted as the most immediate and distinctive stove performance parameter. Studies from Bailis et al. highlighted how relying on WBT thermal efficiency outputs, regardless of the relative importance of high and low power cooking tasks among the target population, can lead to misleading interpretations. Furthermore, Zhang et al. and Jetter et al. questioned the scientific meaningfulness of thermal efficiency at simmering.
Finally, some unsolved issues concerning statistical significance of data are worth mentioning. WBT 4.2.3 includes "Statistic Lessons for Performance Testing". The appendix specifies that the minimum number of test replicates for each model of stove should be three, [...] Wang et al. investigated this topic using a simplified version of the WBT 3.0 and demonstrated that more than 5 replicates are likely to be required to avoid impractically large 95% confidence intervals and that even more replicates may be required to demonstrate a statistically significant difference in performance between two or more stoves. >

Yet, Winrock, like the GACC and D-Lab and their handbook, are again proving themselves to be the gravediggers of the already struggling project developers and implementers, rather than the much needed support they should be, on matters of testing.

This is totally irresponsible from Winrock, and very concerning.

I put Elisa Derby in copy of this email.

Elisa, I am very much looking forward to hear your views on that.

Best,

Xavier


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