
Making a Three-Stone Hearth as Efficient as an Improved Cookstove - nkurz
http://www.thesolutionsjournal.com/node/237379
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dalke
I am unfortunately distracted by the large number of significant digits. House
1 burned 2.785kg @ 0.038150685 kg/min, which implies a precision of micrograms
per minute,

Using decimal math, that works out to exactly 72.99999986894075427479218263
minutes. Realistically, it's 73 minutes. There are only 2 significant digits
so the reported rate should be 0.038 kg/minutes.

Also, there's is a factor of 3 variation in wood/meal unit, compared to 25%
improvement in switching stoves. Why aren't all of the houses using the
efficient cooking technique of house 3? For that matter, how reproducible are
the numbers for each house?

Finally, I see that house 2 had no gains, using about the same wood/meal unit
with all three stoves. Does this mean that about 1/3rd of the users of the
stove will see no gain to switching? Or does it mean that there isn't enough
data to draw a good statistical conclusion? What are the odds of seeing these
results purely from random chance?

~~~
semi-extrinsic
From TFA:

"The operator and the conditions of use largely determine the effectiveness of
operation."

~~~
dalke
I am unable to find that text in the article. I am even unable to find the
word 'operator'.

In any case, I pointed out that there's a 3x difference between two houses, so
I am in complete agreement with that statement. My post asks a different
question, which is, what is the error range on the observed results? What are
the odds that the stove doesn't actually have an effect on wood use, but that
some other factor ('operator and the conditions of use') resulted in the
observed differences?

~~~
rasz_pl
Might be simple placebo effect, here have this super efficient stove.

~~~
dalke
I think you mean Hawthorne effect?

~~~
rasz_pl
I dont think so? They observed three families, but most likely told one of
them all about the new amazingly efficient stove.

~~~
dalke
"The Hawthorne effect (also referred to as the observer effect) is a type of
reactivity in which individuals modify or improve an aspect of their behavior
in response to their awareness of being observed."

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SwellJoe
So, folks are talking about efficiency, but seemingly missing the emissions
impact of this. The health consequences of cooking with wood and burned waste
are a major factor in why something like this is so valuable. The issue is
mentioned a number of times in the article, in terms of mentioning visible
soot, etc. but even it doesn't really cover how unhealthy it is to cook on a
stove like this in an enclosed or semi-enclosed space for decades. Recent
studies of stuff like fireplaces and the like indicate wood burning fires and
stoves can be (much) worse than smoking cigarettes for your respiratory
health. If a $1 upgrade to stoves (plus other innovations like cheap DIY
charcoal production which other groups have worked on) can make the air
quality vastly better for folks in the poorest regions, it can change outcomes
dramatically over decades, and can save money in the long run. Health care,
even the abysmal level of health care offered in rural villages in developing
nations, costs a lot more than $1 per family to provide.

~~~
unchocked
It'd be interesting to test whether fuel savings (immediate) or health
benefits (long-term) drive adoption better.

~~~
SwellJoe
Probably the former, for many, since even we in the west still cling to our
fireplaces, even though most of us don't need them to stay warm. I have a
friend who installed an ancient iron wood stove in her converted bus
motorhome, against my recommendation. She loves the damned thing. She cooks on
it, too, so she runs it regularly.

Part of the appeal for her is the perceived environmental benefits (though
I've tried to explain the carbon and ecological footprint of a wood stove is
much worse than propane, even though the propane had to be pumped out of the
ground and transported). People are weird and stubborn and have odd beliefs
about traditional ways being superior and safer than modern ways. The other
part of the appeal is she gets the fuel for free just by roaming around in the
woods. Propane costs $15/month, or much more during winter months, if you're
needing heat.

Anyway, the point of that rambling is that immediate benefits probably trump
long-term in this case for many people. Folks struggling from day-to-day don't
have the privilege of thinking long-term. But, folks making decisions about
how to help raise the people of developing nations out of poverty have to
think of both.

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ChuckMcM
Looks like increasing the efficiency by providing a better airflow path. This
will also make them burn hotter but presumably the cooks can compensate for
that.

Nice result from what is essentially steel scrap.

~~~
regularfry
It's also a matter of preventing the burnt ash from clogging the airflow as it
collapses downwards.

~~~
ChuckMcM
True, I saw it more like the typical stove "floor" which has holes in it so
that ash can fall past the airflow intake into a collection area below. The
effect being exactly as you describe, airflow remains constant even while
burning.

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emohamad
Hey does anyone have experience in designing such stoves (or stoves in
general)?

~~~
digikata
There's an irregular community around the 'Rocket stove' concept who seem to
love playing around with different stove designs. It's briefly mentioned in
the article, but it's a good starter term to search if you're interested in
more information.

~~~
escape_goat
An experiment I've always been interested in trying, but lack the tools to
carry out, is to take a nice dry unsplit log and drill/file the core out of it
in a somewhat conical vent shape. It would be interesting to see what it would
look like if you could get the log burning on the inside with the axis
vertical and good space for airflow underneath.

This is only related insofar as the term 'rocket stove' reminded me of the
plan, but I thought it was worth sharing in case anyone with a woodworking
router in their garage wanted to give it a try.

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rbobby
Are there any better pictures?

~~~
phasetransition
+1 A cursory look at the prototype they assembled would appear to indicate
several easy DFM wins, but it would be nice to have a clearer picture.

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oneJob
Induction cooktop.

More efficient. Solar powered (renewable) so no need for going out for fuel
which can be very dangerous and time intensive. Much, much safer than an open
flame. No fumes. Small footprint and extremely portable. Robust. Cool.

~~~
sneak
Solar panels, wiring, energy storage, and the cooktop itself are very
expensive by the standards of these communities. They also rely on rare earths
and other hard-to-source materials.

This insert costs $1 and can be locally manufactured, locally maintained.

~~~
mikekchar
I believe the parent is referring to reflective solar stoves. There is a
picture of one in the article. It's basically just a parabolic mirror and you
put the food at the focal point.

The article said that the village had such stoves, but the weren't adopted for
some reason. I may have missed it (I was skimming), but it would be
interesting to see why they weren't adopted. My guess: having to orient your
cooking around the position of the sun. Possibly the women do not have
flexible enough time schedules to do it.

~~~
unchocked
Parent is pretty clearly referring to using solar photovoltaic panels to
generate electricity to operate an induction cooktop. Pretty sure parent
grossly lacks an understanding of what global poverty is.

I knew a guy who worked in the Peace Corps in Lesotho, trying to get people to
use reflective stoves. His experience is that people didn't want to use them
because (a) they liked traditional cooking [who doesn't?] and (b) insofar as
they had aspirations, it was to buy a propane bottle and a burner, like the
middle class people in their area.

~~~
gozur88
A friend of mine was in Burkina Faso for some NGO (might have been Peace
Corps). Originally they tried a PV setup for some of the more rural villages.
Every time they'd come back to ask how things were working the panels had been
stolen and sold off. Eventually they gave up on PV altogether.

