5 ms·

Making a Three-Stone Hearth as Efficient as an Improved Cookstove

84 points by nkurz 11y ago

emohamad 11y ago
Hey does anyone have experience in designing such stoves (or stoves in general)?
- digikata 11y ago
  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 11y ago
    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.
- rwmj 11y ago
  I found these were quite good overview articles: http://www.lowtechmagazine.com/2014/06/thermal-efficiency-cooking-stoves.html http://www.lowtechmagazine.com/2014/06/thermal-efficiency-co... http://www.lowtechmagazine.com/2014/07/cooking-pot-insulation-key-to-sustainable-cooking.html http://www.lowtechmagazine.com/2014/07/cooking-pot-insulatio...
- sliverstorm 11y ago
  Stoves can be fun. Spend much time talking to backpackers and you'll find a few who are constantly experimenting with how to cook faster, more efficiently, and with simpler lighter rigs. It's their hobby.
deleted 11y ago
[deleted]
rbobby 11y ago
Are there any better pictures?
- phasetransition 11y ago
  +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.
ChuckMcM 11y ago
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.
- CydeWeys 11y ago
  Burning hotter is fine; simply use less fuel to compensate (which is the whole point of this invention).
- regularfry 11y ago
  It's also a matter of preventing the burnt ash from clogging the airflow as it collapses downwards.
  - ChuckMcM 11y ago
    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.
dalke 11y ago
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 11y ago
  From TFA: "The operator and the conditions of use largely determine the effectiveness of operation."
  - dalke 11y ago
    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?
    - semi-extrinsic 11y ago
      Ah, sorry, tab mixup on my end, the quote is from another article linked in the comments below; http://www.lowtechmagazine.com/2014/06/thermal-efficiency-cooking-stoves.html http://www.lowtechmagazine.com/2014/06/thermal-efficiency-co... Anyway, the question you pose is a good one.
oneJob 11y ago
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 11y ago
  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 11y ago
    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 11y ago
      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 11y ago
        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.
SwellJoe 11y ago
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 11y ago
  It'd be interesting to test whether fuel savings (immediate) or health benefits (long-term) drive adoption better.
  - SwellJoe 11y ago
    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.

84 points by nkurz 11y ago

emohamad 11y ago

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

digikata 11y ago
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 11y ago
  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.
rwmj 11y ago
I found these were quite good overview articles: http://www.lowtechmagazine.com/2014/06/thermal-efficiency-cooking-stoves.html http://www.lowtechmagazine.com/2014/06/thermal-efficiency-co... http://www.lowtechmagazine.com/2014/07/cooking-pot-insulation-key-to-sustainable-cooking.html http://www.lowtechmagazine.com/2014/07/cooking-pot-insulatio...
sliverstorm 11y ago
Stoves can be fun. Spend much time talking to backpackers and you'll find a few who are constantly experimenting with how to cook faster, more efficiently, and with simpler lighter rigs. It's their hobby.

deleted 11y ago

[deleted]

rbobby 11y ago

Are there any better pictures?

phasetransition 11y ago
+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.

ChuckMcM 11y ago

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.

CydeWeys 11y ago
Burning hotter is fine; simply use less fuel to compensate (which is the whole point of this invention).
regularfry 11y ago
It's also a matter of preventing the burnt ash from clogging the airflow as it collapses downwards.
- ChuckMcM 11y ago
  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.

dalke 11y ago

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 11y ago
From TFA: "The operator and the conditions of use largely determine the effectiveness of operation."
- dalke 11y ago
  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?
  - semi-extrinsic 11y ago
    Ah, sorry, tab mixup on my end, the quote is from another article linked in the comments below; http://www.lowtechmagazine.com/2014/06/thermal-efficiency-cooking-stoves.html http://www.lowtechmagazine.com/2014/06/thermal-efficiency-co... Anyway, the question you pose is a good one.

oneJob 11y ago

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 11y ago
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 11y ago
  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 11y ago
    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 11y ago
      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.

SwellJoe 11y ago

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 11y ago
It'd be interesting to test whether fuel savings (immediate) or health benefits (long-term) drive adoption better.
- SwellJoe 11y ago
  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.