Sunken pot, 50% thermal efficiency cook stove with chimney
When (oh, when!) will PM2.5 be included in carbon offset methodologies?
Who can blame stove manufacturers for selling high thermal efficiency/low combustion efficiency stoves when protecting health is not financially rewarded?
Factories can only sell what the market demands even when they manufacture better stoves. Manufacturers, like SSM, already have slightly more expensive, much cleaner burning stoves ready to go.
Including PM2.5 in carbon revenue might go a long way to help projects pay for higher combustion efficiency stoves.
PM 2.5 needs to be reduced by ~ 90% to protect health in kitchens with 15 air exchanges per hour. The needed % reduction is halved when air exchange rates are doubled. This may be the most cost effective way to protect health? Cooking outdoors with an estimated 60 air exchange rates per hour is very effective in reducing exposure.When cooking inside, perhaps a durable stove with improved combustion efficiency and a chimney would help the large percentage of cooks who, for many reasons, continue to cook with biomass?
https://aprovecho.org/wp-content/uploads/2024/09/sunken-pot-cad.jpg630438Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-09-06 15:46:042024-09-06 16:04:40Increased Air Exchange Rate Protects Health
Wow, heat transfer efficiency is easy to understand!
Read on…
Raising the Temperature of gases flowing next to the heat exchanger (the pot in a cook stove) is probably the most effective technique in a Rocket stove to increase heat transfer efficiency (use less wood for cooking).
Doubling the Temperature of gases doubles heat transfer efficiency.
Doubling the Area exposes to the gases doubles heat transfer efficiency.
Doubling the Velocity of gases ~doubles heat transfer efficiency.
Doubling Radiation increases heat transfer efficiency to the 4th power.
Increasing the view factor helps, too! That’s the proportion of the radiation strikes the bottom surface of the pot.
A 6mm to 7mm channel gap pot skirt increases heat transfer efficiency by ~ 25%.
Simmering at the needed low firepower can save a lot of fuel, too.
https://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.png00Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-08-30 14:27:352024-08-30 14:27:36Heat Transfer Efficiency!
New SSM Health/Climate Biomass Heating Stove Buildings
Here is a video I made last week, introducing some of the the new things I saw on my visit to Shengzhou Stove Manufacturer (SSM). I keep on saying in the video (Sorry!) how much I admire Mr. and Mrs. Shen. Mr. Shen is a great engineer who has built the new buildings, installed the machines, and taken the ideas that Dr. Winiarski brought to him and manufactured over five million durable, affordable Rocket stoves. Mrs. Shen runs the business, does HR, sells the stoves, etc.
An amazing combination! Daughter, Kristina and nephew Chenkai, are being trained to assist the business. You’ll meet the younger generation in the video. Kristina went to the University of Oregon and is now a Vice President at SSM. Chenkai leads a team selling stoves out of his offices in Shenzen.
I walked around new buildings, tested clean burning stoves (including the Jet-Flame and forced draft TLUD) and saw a new wing being built (above) with huge machines to make health/climate biomass heating stoves, a new venture. Since 1976, Aprovecho has helped approximately one hundred stove projects, with SSM becoming the most commercially successful, rolling profits into expanding capacity.
I just returned to the Oregon lab from a two-week visit to Shengzhou Stove Manufacturer. The next few newsletters will be about SSM and progress made. There’s a lot to talk about! SSM has sold over 5 million stoves and the factory is a wonderful place to visit.
SSM started testing stoves for durability twenty-four hours a day (three eight hour shifts at a nearby farming community) three years ago. The farmers keep fires going in eight SSM stoves and the tests continue for one year of each stove. That’s 8, 860 hours.
It’s great that SSM has been doing long term, real life testing of their stoves. Previously, tests in a kiln with wet, salted pieces of metal resulted in confusing estimates of durability. In 2017, M.P. Brady and T.J. Theiss shocked the stove world by showing that in a wet, salty, hot kiln even very expensive metals were not long lasting. (Energy for Sustainable Development 37 (2017) 20–32, “Alloy Corrosion Considerations in Low-Cost, Clean Biomass Cookstoves for the Developing World”, Michael P. Brady, et al.).
The SSM testing is being written up. It seems to show much longer durability of various combustion chamber metals when real fires are used. Full details to follow.
https://aprovecho.org/wp-content/uploads/2024/08/PHOTO-2024-08-11-00-06-57.jpg8101080Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-08-16 15:29:022024-08-16 15:29:42Durability Testing at SSM
Using the ISO testing protocols, Champion (2021)* reported energy emission factors (g/MJ) from the Three Stone Fire, a forced draft Pellet Stove, a forced draft Wood Fan stove, a natural draft Rocket stove and a charcoal stove. ARC added results from a Jet-Flame stove. Using the estimates of global warming potential from the Gold Standard 2017 Methodology** we started to develop a feeling for how various stoves might address climate change.
The calculations suggest that the Three Stone Fire could be a lot worse for climate when Black Carbon and short-term climate forcers are included in offset calculations. At the same time, forced draft stoves appear to have the potential to generate increased emissions reductions (and higher carbon revenues).
*Champion, Wyatt M., et al. “Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols.” Environmental Science & Technology, 2021, 55, (22), 15333-15342. DOI: 10.1021/acs.est.1c03390
Community organizers often say that to be successful the solution has to come from the folks with the problem. Another important factor is to appreciate the culture and long evolved expertise in their technical and social solutions. The women at Rancho San Nicolas, where I lived for eight years, were incredibly skillful at cooking on an open fire and were understandably proud of their abilities when cooking perfect tortillas, fish, beans, soup, etc. At a fish camp, guys who were not cooking every day, had a lot of trouble making anything close to a succulent home cooked meal.
Along with the hundreds of technical skills that made ranching fun, culture made life easier and more beautiful. Ranch culture was at least half of competency and expertise. Laughing at life’s problems made overcoming them much more likely. Religion, nature, the beauty of living outdoors and liking the slow pace were strengths in my friends that I grew to envy and attempted to emulate.
Bringing innovations started with lots of failure. The first Rocket stoves became flowerpots. The first solar cookers became toilet seats and windows. Eventually, ARC appropriate technologists made prototypes that were simply put on public display. Of our many attempts to introduce ‘helpful’ technology, cement rat proof boxes were the biggest success.
We learned a lot more than we taught, starting with listening to our expert hosts. The shorter and higher firepower Rocket stove that has gone viral was created by women in 18 villages in Southern India. Dr. Winiarski had the idea and the cooks made it practical.
https://aprovecho.org/wp-content/uploads/2022/07/7.11.22-Batil-Camp-SuperPot.jpg591725Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-07-26 16:14:342024-07-26 16:34:21Appreciating Local Expertise
Catching up to changing stove expectations reminds me of human maturation. Babies may only need to laugh to keep parents happy, but as kids grow up the stages of development result in further complications. Happily, meeting the expanding goals of protecting deforestation, health and climate can make stoves increase their abilities without changing an essential character that continues to please the cook.
Designed to protect forests, the initial stove featured increased thermal efficiency.
The health-protecting stove added burning up carbon monoxide (CO) and particulate matter (smoke, especially PM2.5).
Protecting climate matures the same stove as harmful climate forcers are combusted as well (NOx, Black Carbon, VOCs, Methane, etc.). Importantly, attempting to burn 100% renewable biomass can zero out the warming effect of Carbon dioxide (CO2).
In simple terms, a stove loved by cooks can be changed to cook using as little wood as possible, then CO and PM2.5 are combusted and then the previously uncounted gasses and black component in smoke are burned up, too. The biomass fuel should be as renewable as possible to decrease adding CO2 to climate.
The same stove does better and better making stakeholders proud.
Wood burning cookstoves make smoke and many different gases that change climate. Carbon dioxide (CO2) is absorbed when the plant grows and the same amount of carbon dioxide can be released when that biomass is burned. So emissions of CO2 can be zero with no effect on global warming (carbon neutral) if the burned biomass is used at the same rate as it grows.
But other emissions from combustion are also bad for climate change. Generally, wood burning cookstoves do not make a lot of methane and carbon monoxide so these gases do not add a lot to their effect on climate change.
On the other hand, biomass cookstoves without engineered forced draft can make a lot Black Carbon (the soot in smoke) and BC is very bad for climate change. For this reason, when protecting climate, cookstoves should make as little black smoke as possible.
White smoke can have a cooling effect on climate. ARC has been learning how to make combustion chambers that emit as little smoke as possible and make 95% white smoke and 5% black smoke. We are working with manufacturers to make stoves with health/climate combustion chambers.
https://aprovecho.org/wp-content/uploads/2024/07/7.12.24-biomass.jpeg400700Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-07-12 08:12:242024-07-12 08:12:25Black and White Smoke
It is not difficult to estimate the emissions of Black Carbon from cook stoves.
The emissions that change climate include various gases and the colors of smoke. If the wood used for cooking is 100% renewably harvested, the emissions of CO2 can be carbon neutral. Why? CO2 is absorbed when the plant grows and the same amount of CO2 can be released when biomass is burned.
100% renewability can help CO2 to become climate neutral. However, the fraction of non-renewability (fNRB) does not change the amounts of other climate forcing emissions. Smoke is smoke. Etc.
What are the most powerful cook stove emissions affecting climate?
In general, adding methane and carbon monoxide to Carbon dioxide (CO2) adds a bit to the total warming influences (CO2e).
However, adding short-lived climate forcers such as NOx, SOx and Black Carbon to the above has been estimated to more than double the warming potential.
For this reason, it seems to be important to add the short-lived climate forcers when calculating how to address climate change with cook stoves.
https://aprovecho.org/wp-content/uploads/2024/06/6.28.24-black-carbon.jpeg400700Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-06-28 15:50:012024-06-28 16:12:43Short-lived Climate Forcers and Climate Change
Unfortunately, although introductions to lab tests warn that results do not predict actual performance, the recent use of lab data to earn carbon credits has made an unfortunate error more commonplace. For decades, introductions to lab tests have warned that only field-testing can determine actual efficiency, emissions, effectiveness, market validity, etc. The World Health Organization based their stove standards aimed at protecting health on field-testing for this reason.
Lab tests are helpful when comparing performance to understand how fire might be more useful.Starting with the 1985 International Standards, test users were advised not to use lab data to predict actual performance. While improving other carbon methodologies, using field-testing to estimate reductions would dramatically improve the accuracy of offsets.
Carefully performed lab tests tend to overestimate fuel efficiency and underestimate emissions. This has landed cook stoves and heating stoves in serious controversy. A lab tested Tier 4 cookstove can be Tier 2 in real life – or mistaken for a flowerpot. My first Rocket stoves were often used for this important function in Mexico.
A lab tested 2 g/hr PM heating stove often emits a lot more smoke when the harmful pollutant is measured from chimneys in houses. In an effort to reduce confounding variables, lab tests show closer to optimal performance. Real life human beings tend to operate stoves with less care, wood is wet, life deserves attention, too.
Maybe the test warnings should have been highlighted in green?
International Standards, 1985
“This is a laboratory test…while it does not necessarily correlate to actual stove performance, when cooking food, it facilitates the comparison of stoves under controlled conditions with relatively few cultural variations.” (Testing the Efficiency of Wood Burning Cookstoves, International Standards 1985).
(ISO 19867-1)
“This document provides a standard test sequence that can be used to compare the performance of various cookstove types, cookstove fuels, and cooking practices under controlled laboratory test conditions, as specified in this document. For evaluation of the performance and predicted outcomes of a cooking system in the field [comprising cookstove(s), fuel(s), cooking vessel(s), kitchen, ventilation, and user(s)], ISO 198691 applies.”
