[Stoves] Wonderwerk stove, more information (Crispin Pemberton-Pigott)

Traveller miata98 at gmail.com
Sun Jul 31 13:36:14 CDT 2016


List Moderator:  Apologies for unintended offense. Crispin's post took me
back 33 years. The topic hasn't changed, and nor have conclusions.
-----
Crispin:

"Happy testing everyone. Check the fine print."?? Yeah, right. What's new?
Biomass stovers keep testing and checking the fine print, and ignore the
big picture - Up in Smoke, as that Caravan piece says.

Pardon me, I got a chuckle out of your "long haul efforts trying to get
these things corrected".  Academics prefer the long haul, while old cooks
waste away and die.

Back in 1984, Fernando Manibog noted the obvious truth that "efficiency
varies significantly as a function of power output during various phases of
the cooking period" and that "Stove technologists have not adequately
addressed this question of power-output range."

My view then was that they cannot, since there is no fixed "power-output
profile" for cooks of this world.

Manibog also said, "To sort out this welter of confusion, a meeting of
international stove experts (ref.) has introduced provisional international
standards for testing the fuel performance of wood-burning cook stoves and
for preparing results in terms of *specific consumption and time required *for
cooking measures that can be more easily explained to users than can
efficiency. *Three types of tests are recommended: water boiling,
controlled cooking, and kitchen performance*. For each, detailed
instructions on required equipment, testing procedure, and data calculation
and reduction are provided along with reporting forms for the test series.
This development is urgently needed, given the inconsistency so far
encountered in stove testing and reporting of results. However, for several
reasons, it may take some time before these procedures are applied widely
in the field."

Seems to me the "welter of confusion" continues. No surprise; we keep
generating more lab results and revised estimates for saved trees and lost
lifeyears.

The question of power-output range is not just about efficiency and
emissions but also about control and convenience. From what I can
tell, "time required for cooking" or convenience is no longer a performance
metric; wasn't a part of the Lima groupthink back when. It would seem
experts have all the time to keep on cooking publications (or now YouTube
<https://www.youtube.com/channel/UCVWC67A7VcBK8rSFh0h_xKg> videos). The
poor can die leisurely.

Manibog concluded then, "The currently prevalent question is the following
: can ICS programs ever bring about widespread dissemination up to the
millions? Based on important advances in the evaluation of field experience
and in the knowledge of technical principles governing ICS design, it
appears that a few of the elements required for success are nearly in
place."

Global dalliances notwithstanding, I don't think that conclusion needs to
be changed yet. Wake me up in the other world.

I will spare you dire predictions unless you really want to hear them.

N
---------

Message: 1
Date: Mon, 25 Jul 2016 00:35:45 -0400
From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
To: "'Discussion of biomass cooking stoves'"
        <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Wonderwerk stove, more information
Message-ID: <COL401-EAS1581513BD7BF5AB2B518E3FB10D0 at phx.gbl>
Content-Type: text/plain; charset="utf-8"

Dear Kirk

I have been looking into the math of the results you obtained. They were
prepared by LBNL using a set of calculations coded in Python that mimic the
calculations described in the WBT 4.2.3 but do not exactly follow the
calculations in the accompanying spreadsheet, where the sheet differs from
the protocol. In other words, they are preparing the numbers according to
normal engineering standards and then re-expressing them according to the
WBT theory.

In fact they do not normally present WBT calculations and metrics unless
you ask for them because, as most labs are aware, they answers are not all
that useful for real work ? and I am serious about that. They prepare
formal performance numbers but if someone insists on a ?WBT result?, they
are provided according to the WBT method.

Not only are they correcting the numbers, LBNL also does not use the
standard EPA test apparatus having found they get better answers using
other approaches. They have a SeTAR type diluter ? I knew about that
because I provided the drawings though I don?t know when it is used. They
are also using dry CO2-free air for dilution as per the SeTAR/SEET/BST
labs. I was most interested to hear they are already recording the humidity
in the stack (in the diluter and via dilution number). This is important
because the real time determination of the fuel analysis (what just burned)
can be calculated if the humidity is known. Watch this space, testers.

So, if you were to ask them for the performance numbers based on regular
criteria such as the fuel efficiency based on fuel consumed per replication
and work performed (no ?credit? for char) you get the energy efficiency.
That number can be used to directly compare stoves and their fuel
consumption. Obviously you would have to have it for the other stoves as
well to make a fuel consumption comparison. Some number are available from
the CSI Indonesia approved stoves list as that is one of the metrics if you
want to check.

The emissions per net MJ delivered to the pot is a common one, and the
emissions per minute. No emissions number ?per litre? are valid so don?t
accept/claim those unless you are sure it was for high power and it was
based on the initial water volume.

The unfortunate news is that as they do not provide a ?WBT spreadsheet?
filled in so it is not possible to work backwards and recover low power
metrics that are valid (because you would have to multiply by the number of
litres remaining to get them, and you don?t know how much there was).

For those following this thread, have a look through the stove test result
posted on the GACC website and you will notice that some stoves are
providing a ?spreadsheet? of outputs and others provide just the numbers on
a form. One that I noticed has a very long list of outputs that is copied
from the Results page of a PEMS/LEMS. Please note that the results
calculated by that sheet (assuming you have used the updated version) does
not give the same answers as the WBT spreadsheet 4.2.3 or 4.2.4 because
Nordica corrected some of the calculations on the LEMS ?Test? sheet.
Compare with caution.

> When and if the test you support is available the Wonderwerk will do well
when tested by it, as will the other four stoves Aprovecho has developed,
and other good stoves everywhere.  The CO and the PM are measured directly
with precise instruments.  There are no questions here and good stoves will
show their quality.

That is what we always expect. The issue is not that these stoves are ?not
good? it is that in order to accept a stove into a program it has to be
tested and reported using valid metrics. I have tried very hard to find
your raw data so that I can produce for you valid reporting metrics. The
WBT low power metrics are not, so we can?t use your results. Anyone
interested can read the literature and find out what the problem is. The
EPA reproduced the experiments concerned, validating the claims in Zhang et
al, 2014 that there is no validity in a low power metric where the
measurements have been divided by the number of litres remaining in the
pot, so that pretty much settles it.

If, during the coming stoves camps, stove producers ask for the actual test
results on the original spreadsheet, there are some calculations that we
can make to extract valid performance numbers that are good enough to make
recommendations for further investigation. It would be helpful if the whole
community of stovers insisted on this because in spite of long haul efforts
trying to get these things corrected, we are still faced with results
presented using invalid or incorrectly calculated metrics. Dean Still has
confirmed to the US-DOE that I have been trying to get these corrected for
10 years. Imagine!

>?Where is your test?

While I am flattered that you once again call it ?my? test. It is a team
effort. You can get a copy from the list of protocols at the GACC website
http://cleancookstoves.org/technology-and-fuels/testing/protocols.html

At the same location there is a slightly old version of the SeTAR HTP
v1.05. When it comes to calculating the thermal performance it is very
similar in some ways to the Indian CIS 13152 (just underneath). That has
been updated to become the CSI-Indonesia test.  It is a water heating test,
and uses a monitored heat exchanger in the pot so the water never boils. It
can report the heat flux into the pot in real time as well as emissions at
different power levels, as well as overall numbers. This will be combined
with the ?decombustion? formulas sometime this year to provide the most
accurate real time reporting theoretically possible. It will be of great
interest to stovers producing char while cooking.

The space heating version of the HTP v1.05 was validated by SGS in the
Netherlands in 2011 for use in the Mongolian Clean Air Project. It is now
their National Standard and includes additional (perhaps, obscure) metrics
recognizable to power station and combustor design engineers. One, for
example, reports power per unit volume. Kind of interesting.

The CSI Technical Test document is below that.

A test that I did create alone is the UCT 2011 from the University of
Johannesburg, further down the page. That was validated by DGIS in 2008, if
I recall correctly, for their Access to Modern Energy programme implemented
by (then) GTZ. It is similar in many ways to the method used by Omar Masera
in Mexico City although they were developed quite independently.

Happy testing everyone. Check the fine print.

Crispin
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