https://tse4.mm.bing.net/th?id=OIP.tR-juYhOLOvthnEU_gOqKgAAAA&pid=Api&P=0
Dr. Mouhsine Serrar and the Rocket institutional stove designed by Dr. Larry Winiarski

There are at least three ways to make institutional stoves with chimneys, all of which work well and save fuel and decrease emissions. Here they are:

  1. Shell Foundation supported the making of an eight-part video, a step by step guide to making a 50 to 100 liter institutional Rocket stove, with a heat resistant metal Rocket combustion chamber. It is a great stove with lots of successful field testing but it costs the most to construct because heat resistant metals like 410 stainless or FeCrAl are increasingly expensive. The super insulated combustion chamber requires these types of metal. 304 stainless will not last. https://youtu.be/VdhLWMW7IXA
  2. Cooking With Less Fuel: Breathing Less Smoke shows how to make the same institutional stove using bricks for the Rocket combustion chamber. Construction details can be found at aprovecho.org in the publications section. The book was written with the World Food Program in Rome. This is a less expensive stove that is slightly less fuel efficient at cold start but lasts longer and is easier to make in places where 410 stainless and FeCrAl are not available.
  3. Making a VITA style institutional stove without a Rocket combustion chamber is the least expensive way to create an institutional stove. The open fire under the pot is supported on a grate and the hot gases flow up the inside of the skirt, down the outside of the skirt and exit out the chimney placed below the bottom of the pot as in the Rocket stoves shown above. You can find a video we made about constructing the VITA stove at: http://aprovecho.org/video-gallery/

Lots of manufacturers do not use the chimney but we think that protecting health is very important. We try to follow Don O’Neals advice (HELPS International) to always include chimneys whenever possible, imagining our mothers cooking and getting ill from exposure to the harmful emissions without the protection of the chimney.

In 2009, The New Yorker published an article about the Rocket stove entitled Hearth Surgery: The quest for a stove that can save the world. One year later, USAID funded field tests in Africa showed that the insulated Rocket stove was not cleaner burning than the open fire. The Rocket with skirt saved 40% of the fuel to cook and emissions were only reduced by that amount.

Not a Planet Saver, yet!

The insulated Rocket combustion chamber raised temperatures but as Dr. Winiarski realized at the time, flame, air, and gases were not adequately mixed to achieve sufficient combustion efficiency. Larry knew that the Rocket was smoky but it was simple to make and with a pot skirt saved fuel. He wanted to provide folks with a stove that was helpful and he realized that it wasn’t perfect.

Larry’s idea went viral worldwide and continues to be a favorite on the internet and in many low- and middle-income countries. Millions of Rocket stoves are manufactured and sold yearly by factories large and small.

Going viral is great but can have a downside especially when the initial products are not technically mature. It’s normal for first generation products to be improved as time goes by. The process of development continues in 2022.

A major accomplishment of the past few years has been the creation of thirty Regional Testing and Knowledge Centers (RTKCs). Many of these facilities rely on emissions equipment and training from Aprovecho Research Center. They are usually created as an addition to a university in a developing country, and were initially funded by large development organizations such as the Global Alliance for Clean Cookstoves.

Once a month we’re turning our newsletter over to Sam Bentson, to tell you more about their activities:

Hello to everyone at the Regional Knowledge and Testing Centers (RTKCs), and to our newsletter readers, from Sam Bentson, General Manager at Aprovecho!

Sam was recently in Ghana and Senegal and then visited the Instituto de Investigación y Desarrollo de Procesos Químicos (CPC) in La Paz, Bolivia helping with stove testing and their LEMS emission hood. La Paz has the highest elevation of any government city in the world at an altitude of 3,650m!

The atmospheric pressure at CPC in La Paz is 20Hg. Our lab in Oregon is 241 meters above sea level where the atmospheric pressure is 30Hg. Sam and the CPC staff determined that at their high elevation, and with the voltage applied to the Jet-Flame motor increased to 8V, the mass flow in the Jet-Flame was 82% of the mass flow measured at the ARC lab.

Altitude had a big effect on boiling water and on the Jet-Flame!

CPC in La Paz, Bolivia from left to right: Libertad Mariana Casanova Velasquez, Dalia A. Borja, Sam Bentson, Jazmin Gidari Ruiz Mayta, and Karen Fabiana Paz Quispe

When Sam returned home, he started thinking about keeping in touch with all of his friends at the RTKCs and to share reports of activities. We are starting with CPC and highly recommend that anyone interested in doing research or a stove project make use of this wonderful resource in Bolivia!

Contact:

Marcelo Gorritty
Email: mgorritty@gmail.com
Calle Campos, Esq. Pasaje Villegas.
Edificio Artemis 367. PB Of. 7
La Paz, Boliviawww.cpc-bolivia.org

Dr. Kirk Smith, a hero

ARC worked closely with Dr. Kirk Smith (1947-2020) when we helped to include emissions in the Water Boiling Test, used to evaluate biomass cookstove performance, for the Shell Foundation. We included the first “Tiers of Performance” with a simple approach that divided stoves into two categories: improved and unimproved. It was great to know Kirk and I admired him tremendously.

Kirk was a professor at the University of California at Berkeley and was, in my opinion, the most effective advocate for the billions of people afflicted by breathing smoke. Kirk and ARC continued to work together during the Breathing Space project in India. Here is a video that ARC helped to produce in 2009, which describes the project. 

The goal of Breathing Space was to introduce the Rocket stove into India. We hoped that the Rocket stove, after being re-designed by women in 18 villages, would “go viral” and protect health. Eventually, Envirofit become the distributor and project manager. Envirofit and the Shell Foundation worked together to bring Rocket stoves into markets worldwide.

In 2011, Kirk Smith announced that switching to LPG seemed more likely to protect health. By 2017, Envirofit was including LPG and gas stoves in their catalog of options. Trying to create and disseminate truly clean burning biomass stoves had proven to be difficult and a more successful, wide scale intervention was needed. Although people liked it, the combustion efficiency of the Rocket stove just was not good enough. The Justa stove with chimney (with Rocket combustion chamber) that Kirk tested in Guatemala leaked, and when many stoves were in use the outside air became smoky. Maybe gas stoves, even though the fuel is not renewable, had a better chance to succeed?  

What would Kirk Smith recommend in 2022?

Can market driven biomass stoves (with hay boxes, solar stoves, pot skirts, SuperPots, Jet-Flames, etc?) successfully address health and climate change? Maybe we should keep working and find out?

I think that Kirk would not object.

Fred & Lise Colgan, founders of InStove
Fred & Lise Colgan, from InStove

Fred and Lise Colgan created InStove, manufacturing and distributing institutional stoves initially designed by Dr. Larry Winiarski. They developed and sold large Rocket stoves that cooked food, sterilized medical equipment, and pasteurized water.

The autoclave, sold by Wisconsin Aluminum Foundry, works like a big pressure cooker and sterilizes quickly using steam and pressure. The unit fits into a Rocket stove that delivers the heat using less wood compared to traditional stoves. A chimney removes smoke from the room. The system can sterilize about 7 gallons of surgical instruments, dressings, and other medical supplies at a time, making them safe for either reuse or hygienic disposal.

These larger Rocket stoves combine the same strategies that are used in smaller versions. A pot skirt cylinder surrounds the sterilizer creating a narrow channel gap that is especially effective in transferring heat, in part because the pot is larger. Big pots have more surface area so increased percentages of heat pass into the water. When a chimney is attached to the stove, the hot gases are forced to flow down another channel on the outside of the pot skirt. In this way, adding a chimney to the stove does not diminish the fuel efficiency. A lot of the heat has already scraped against the pot and been absorbed before it exits out of the chimney. The light weight bricks used in a larger Rocket stove combustion chamber can be thicker and larger than bricks used in a smaller stove. The Institutional Stove described in the Institutional Rocket Stove pdf on the Publications page can handle pots from 50 to 300 liters. The downloadable Excel worksheet Institutional Stove Gap Calculator can help you determine the measurements of an institutional stove designed to fit the large pot you have available for use.

Would any manufactured stove that you know of work well for this woman? Maybe not?

Working with local women to design cooking solutions is not hard when the team is located in the project area. It’s only natural to include the user in developing the product. But when wood stoves are created by foreigners, that invaluable input easily goes missing and the stove, although technically fine, usually misses other necessary attributes. That’s why ARC tries to develop stoves in the field, while learning how fire works in the lab.

Researchers associated with the Regional Testing and Knowledge Center in Accra, Ghana might agree with this strategy. They recently published a paper in which 20 biomass cook stoves available in Ghana were evaluated for high-power thermal efficiency, low power specific consumption rate, turn down ratio, high power CO emissions, high power PM2.5 emissions, low power CO emissions, low power PM2.5 emissions, affordability, fuel saving potential, operations and maintenance cost, time saving, indoor CO, and indoor PM2.5 emissions.

The authors concluded that none of the cook stoves satisfied the conditions of all of the performance indicators. The forced draft stoves were generally high performing on the technical and environmental attributes, but low performing on the economic and social/public health metrics like affordability, maintenance and operation costs, and fuel saving potential. The more traditional stoves did not perform very well technically and environmentally but ranked highest economically, being more affordable than the cleaner burning alternatives like forced draft stoves.

Available natural draft stoves were a better alternative considering the economic, technical, and environmental attributes.  The high cost of forced draft stoves (most are imported), their operation and maintenance cost, and the requirement of electricity resulted in adoption rates being low. The suitability to prepare Ghanaian staples, which require rigorous stirring, were also generally underestimated. Locally made natural draft stoves did not score well in terms of emissions but were much less expensive, did not require the preparation of fuel, and were made to prepare Ghanaian staple foods. 

The study highlights the need to consider all the performance criteria simultaneously in order to choose the “best performing” stove. 
The authors conclude with the hope that locally made stoves can be technically improved while maintaining the other necessary attributes. (Gloria Boafo-Mensah, et al., Biomass and Bioenergy 150, 2021).

It just so happens that our General Manager Sam Bentson is at the Regional Testing and Knowledge Center in Accra right now, working with Ms. Boafo-Mensah and the rest of the team on some exciting projects. We look forward to sharing Sam’s report about his trip when he returns!

In our newsletter “Making It Real,” we described how feedback from the field in Rwanda suggested that the Jet-Flame’s power cord would last longer if the whole device was inserted from the side of the combustion chamber. (It was originally designed to go through the door, with the sticks placed on top.) So of course we ran some tests, and discovered more benefits.

Is the Jet-Flame, when inserted into the combustion chamber from the side of the CQC stove, as effective in reducing emissions as when it enters through the fuel door?  

Yes, performance seems to have even improved a bit. After testing the Jet-Flame with side entry, it seems that it’s better to get the hot metal out from under the parts of the fuel that you don’t want to heat up. To burn cleanly, natural draft Rockets like to burn something like 8cm of the end of the sticks. Instead of laying the entire length of the sticks on the heated metal of the Jet-Flame, the side entry only exposes a limited amount of the sticks to high temperatures.

As seen in the photo, the sticks are now supported by a white homemade high mass brick and only the tips are exposed to Jet-Flame heat well inside the stove. It’s nice how a suggested change from Jean Marie Kayonga in Rwanda ends up having some unexpected benefit, not just better protecting the cord. Thanks again, Jean Marie! www.Jet-Flame.com

The time to boil, thermal efficiency, temperature in the combustion chamber, CO, and PM were improved with side entry while firepower rose. Excess air fell from 3.38 times stoichiometric to 2.57. I liked operating the stove because the sticks seemed to burn more at their tips as Dr. Winiarski described in the Rocket Design Principles. See: http://bioenergylists.org/stovesdoc/Still/Rocket%20Stove/Principles.html

A woman sits next to two rocket stoves.
A woman sits next to two rocket stoves.
Firewood is stored between a pair of CQC’s TLC Rocket Stoves.

C-Quest Capital recently announced a collaboration with Macquarie Group Ltd., a financial services company with A$550 billion in assets under management and 16,000 employees in 35 countries. The two firms will fund and deploy efficient cook stoves with pot skirts to one million rural households across Malawi, Zambia and Tanzania. CQC’s preferred rural stoves project standard is two stoves per household to decrease user fallback on three-stone fires.

USAID in-field testing in Africa showed that Rocket stoves with pot skirts reduced smoke emissions by 40% due to the use of less wood while cooking. Addressing health by increasing the air exchange rate in the kitchen and home is a fundamental component of this project. This is done by strategic placement of windows and doors, and promoting half-wall kitchens or well-protected external cooking spaces. A minimum of one visit per year by trained staff to each household to help repair, maintain, and ensure good use of the Rocket stoves is also essential to elevating adoption rates in the targeted areas.

Over the next decade, this investment will deliver over 40 million high quality carbon credits with verified Sustainable Development Contributions to the Voluntary Carbon Market. It is the first leg of a three-pronged program to transform the lives of low-income communities across Sub-Saharan Africa at scale. Ken Newcombe, CEO of CQC, comments, “Our hope is to include something like 100,000 Jet-Flames, assembled by Ener-G-Africa in Lilongwe, Malawi, in the project. Field tests have indicated that the Jet-Flame dramatically reduces PM2.5 emissions and exposure to cooks and their families, further protecting health. If the deployment doesn’t get to 100,000 sold by end of next year it’s not because of the demand – it’s because we couldn’t get the working capital and distribution channels to get the product to the market. Of course, we are exploring all possibilities.”

Manufacturing pot skirts

In 2013, C-Quest Capital (CQC) began distributing and installing the TLC Rocket Stove (TLCRS), a high-efficiency, long-life metal and brick improved cookstove, to the rural poor of Malawi. Early learning has resulting in many upgrades to the stove to improve sustained use and a long life. Over the past two years, CQC has installed the TLCRS in 450,000 Malawian households. Beginning in January 2020, Ener-G-Africa (EGA), a Malawian entity formed by CQC and Malawian entrepreneurs, began manufacturing all the metal stove parts for CQC’s sub-Saharan Africa TLCRS program and has since produced more than 300,000 sets of parts.

Interior view of EGA Stove factory in Lilongwe, Malawi
Stove Kits ready to ship at Ener-G-Africa’s factory in Lilongwe, Malawi

More recently, in February 2021, CQC placed irrevocable orders for the first 10,000 Jet-Flames from Shengzhou Stove Manufacturer in China, marking the first large scale commercial commitment to Jet-Flame distribution in the world. With CQC’s funding, EGA’s factory in Lilongwe is currently building the second solar panel assembly plant in sub-Saharan Africa and will begin manufacturing the solar panels, and eventually the batteries, needed for the Jet-Flame Kit.  CQC is hoping the superior cost and cooking amenity provided by the Jet-Flame will make serious inroads to the charcoal user market.

Through the growing partnership between CQC and EGA, the TLCRS will be installed on a two stove per household basis in three million households across eight sub-Saharan African countries in the next four years. Together, CQC and EGA are setting a new standard for cookstove projects in rural Africa. 

Manufacturing pot skirts
Welded pot supports
Parts ready for packing
Manufacturing area at Ener-G-Africa’s factory in Malawi
CQC stove set up for testing under the LEMS hood

ARC is investigating how to optimize the performance of the SSM Jet-Flame in the CQC earthen brick stove. Forty six thirty-minute ISO 19867 Water Heating Tests were completed under the LEMS hood at seven fan speeds. Two 4 cm x 4 cm douglas fir sticks were burned side by side. Five liters of water in a seven liter pot were heated, and the CQC pot skirt was used in all tests.

Results

Tier 4 ISO Voluntary Performance Targets:

  • Thermal Efficiency           40% to 49%
  • CO                                     <4.4g/MJd
  • PM2.5                               <62mg/MJd

Time to boil: The time to boil decreased with an increase in fan speed.

Thermal efficiency: The thermal efficiency stayed close to 35% in most cases and was higher at 3 and 8 volts (around 40%).

Firepower: The firepower rose to 6.8kW at 8 volts, starting at 2.6 kW at 2 volts.

Emissions of Carbon monoxide: Generally emissions decreased with increasing fan speed.

Emissions of PM2.5: 7 and 8 volts scored the best, at half of the result of 5 volts.

Combustion chamber temperatures: The mid combustion chamber temperatures rose with increases in fan speed from 382C to 730C.

Excess air:  Lambda fell as voltage increased from 4.1 to 1.9.

We recommend that the project do enough field testing to determine what settings are preferable to local cooks, remembering that higher voltages consume more power. In this way, the Jet-Flame/CQC stove can be tailored to regional cooking, keeping in mind the power output and use patterns of the CQC photovoltaic solar system.

Here’s what the flame looks like when varying the voltage: