[Stoves] Fuel and Forestry etc.

Thu Jan 23 00:07:17 CST 2014

Dear Samer Again

>In particular I will be keen to explore more deeply the ramifications for
testing, actual fuel use, and the memes that relate these to problems of
deforestation and health.

In order to complete the description and not leave the circle incomplete, I
will cover also the major facets of the development of the new direction in
testing.

I refer of course to the technical aspects of the method. There was a large
number of people who had input to this because it is an accumulation of
small 'lines of code' that resolved lots of questions and where possible a
clear definition obtained.

The main ingredient to the successful performance test is to measure what
the customer asked for and to report it in a manner they expected. It is
communication of knowledge through the medium of numbers. This is the
distilled version:

The question most commonly asked is, "What is the fuel saving ability of
this stove?" The answer expected, as so often discussed here, is the amount
of fuel taken from the available supply (a forest in this case) each time
the stove completes a set of daily cooking tasks. The second question is the
level of smoke to which the user is exposed, which is defined as the PM2.5
and CO emitted. (Sometimes the heating efficiency is wanted, but another
time.)  These three simple requirements are, however, not sufficient to
satisfy the questions posed by the social scientists who constantly reminded
us that a stove assessment is a lot more than some narrowly defined
technical metrics. I will leave the details out, but basically a technical
evaluation will be followed by an assessment by focus groups, i.e. a two
stage process. This protects the project in two ways: first it answers the
technical requirements that are popular in the donor community. Quite why
technical requirements dominate the popular notion of stove performance is
worthy your investigating powers, but that is how it is at the moment.
Second, it tests the social acceptability of one or more stoves before money
is spent promoting them.

The issues that arise for social acceptance are centered on the ability of a
stove to cook the local meals properly, and that is a very wide ranging
demand if you look across the world's cultures. So the first thing to do is
to limit the test-cooking requirements to those in the area where the stove
will be sold (obviously). We cannot be worried in the slightest how that
compares with any arbitrary cooking cycle from somewhere else.

Cooking is the application to food of heat that is already in the pot. The
cooking power, the rate at which heat is gained the pot can be expressed in
Watts. It is not the heat delivered to the pot, only the heat retained and
gained (a pot has losses).  It is possible to determine the cooking power (I
like the term pot-Watts!) by reproducing the firepower and heating pots of
water and monitoring the temperature change. Any cooking cycle can be
reproduced in two forms, actually cooking using the firepower people use,
and the same fuels of course, or using that same firepower cycle to heat
water and determine the rate that heat gets into the pot at every stage of
the burn. Knowing this, the emissions per MJ in the pot can be calculated
directly.

Cooking tasks are selected and observed and the technical performance
measured while reproducing the meal in the lab. Sometimes that takes
practice, sometimes not.  The cooking power is separately determined and the
total heat gained during cooking calculated from that assessment.

The result is the same metrics one gets from any popular water boiling test
but instead of the complex manner of calculation so often applied, this is a
direct measure of the heat gained by a pot that is put through an actual
cooking cycle people use in the area. Combining two or more cooking cycles
measured in this manner creates a lab test that can be reproduced quite
accurately, and which is representative of the average cooking in the
community.

The cooking tasks selected (by the social science team) are chosen to be as
different as possible while still remaining 'typical'. They can be
'frequency weighted'.  If a new stove can cook properly, meaning reproduce
the cooking power cycle in the pot, and on condition that the baseline
cooking experience was acceptable in the community, so too the new stove
will be acceptable to the cooks.

One of the surprising findings has been that the rate at which heat enters a
pot per square centimeter of heated surface is surprisingly constant over a
range of pot sizes for a stove running at a constant power. People can try
it to see. What this means is that it is possible to use watts per sq cm as
a common metric to compare stoves cooking with different pots. It is
surprisingly useful and I expect it will become a popular metric. If a stove
can heat the maximum practical size of pot for that stove at the same rate
as the traditional stove, it will have the same cooking power.

By reproducing the lowest cooking power level experienced when cooking, the
heat gain rate at low power is determined, and therefore a minimum turn down
ratio required by the community is established. The ratio is typically 4 or
so.

The heat flow rate per sq cm, or 'Heat Flux' provides a technical metric (a
hard number) that is a reasonable proxy for the acceptability of cooking
power levels, both high and low.  If the local community is satisfied with
their present cooking power, they should be satisfied with a stove that
meets the same performance measured in this manner, even if the pot size is
different (very important). If traditional performance is not good enough
according to the people, that fact is determined during interviews and the
required performance level adjusted accordingly. People become happier with
the new stove.

There are other practical observations made which depend on the type of
stove - perhaps how easy it was to light, if it smoked a lot in the
beginning and so on. 

Because there are dozens of definitions and metrics I won't mention them
here, but each has been examined to be sure it is produced by the fewest
number of steps possible and is derived from first principles. The validity
of the metric is also checked.  The other measurements required from the
test are the total mass of CO emitted and the same for the mass of
particulate matter.

Because people (usually) save wood from one fire to use the next, the fuel
consumption is determined by monitoring the raw fuel drawn each time the
burn cycle is replicated. This 'recycling' of fuel means that it is far
easier to determine the consumption and avoids many of the issues related to
the energy content in fuel remaining. Because fires are run with old fuel,
and 'new old fuel' is created each time, the heat content is not material.
All that matters is what new fuel is needed. Sets of three tests are
analysed as if it was one long test and a valid averaging process gives
averaged performance numbers.

The list of people involved in developing this technical aspect of the
overall system is quite long if I think of all the inputs received.
Inspirational and technical conversations were held with the members of this
discussion list, the ETHOS v4 test development team back in '08, Jim Jetter
at the EPA, Tami Bond of course, the National Biomass Stove Standards
Committees of both Indonesia and China, in particular the staff (Prof Dong)
and grad students at the China Agricultural University, Profs Philip Lloyd,
Harold Annegarn, Lodoysamba, Peter Verhaart, the SeTAR Centre plus Rowena
Sace, David Beritault, and as before, others too numerous to mention.

There was one step left however. There was a process by which the
institutional needs of all the major players were integrated, meshed, melded
so as to produce a final product acceptable to donors, governments, testers,
regulators, businesses, manufacturers and the public. There were two
significant integrators and they are Laurent Durix from the World Bank whose
strategic and conceptual skills are amazing (and quick learner) and Cecil
Cook, one of the founders of the USA's National Center for Appropriate
Technology and too many other institutions to name. He is one of those rare
people who are highly qualified in a social science but have as well decades
of technology experience. These guys helped create the detailed plot for
accessing the needed inputs and the producing final integration. Bringing
the financial side, the business development programme, the social
assessment and the technical evaluation 'plots' together into a single test
protocol requires meeting everyone's basic needs simultaneously. The number
of reviews and changes was huge.  You can understand intuitively it took
about a year just for that.

The team leader (who was mentioned before) is Dr Yabei Zhang from the World
Bank who assembled the central team, produced the overall project concept
and allowed us to find our way from some pretty dark places into the light.
There were some really long dinners. Yabei is the brains behind the finance
model which you will hear about in a few days, I hope. Connecting that
model's programme need for commercial success shaped entirely the testing
requirements. It is a 'results based finance' model meaning that the stoves
have to work as advertised, have to be purchased in the community and have
to be accepted by the purchasers (meaning used a lot) to receive support. In
order to have a simple enough lab test that makes meaningfully accurate
predictions of future use, the social and technical investigations have to
be pretty well matched to the local community.

So what is the result? It is a trial effort. Don't get too excited. It is an
experiment and expectations are we will change a number of things to refine
how well and in what ways a lab test in controlled conditions can predict
field performance in a particular community. So far indications from the
budding YDD lab are good.

The degree to which this methodology as a whole addresses the many questions
and objections raised inside and outside the stove community should be
studied in detail. We did not have time to make those comparisons. If a list
of serious objections was made, each solution could be compared with the
CSI-WBT and CSI-WHT (water heating test) to see if that issue is either
eliminated, avoided or address reasonably.

I hope, Samer, you and others will find the time to tackle this subject as
comprehensively as you have the memes from Darfur. I feel it would be a
great service to the stove and donor community. It would help create a
discussion space in which alternative methodologies can be flighted and
tried around the world.

Regards

Crispin

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