Our friends at InStove are hosting a stove conference next weekend. We hope to see you there. Click below for the schedule, and read on to learn more.
ARC is involved with many cook stove projects around the world. Mostly we assist with technical information to improve emissions and performance and to set up stove laboratories. Once in a while we help commercial projects to manufacture stoves, get carbon credits, or write business plans. Each year we host at least one hands-on conference, “Stove Camp“, during which inventors and policy makers learn from each other to advance the state of the art of biomass cook stove technology. Could you help us to get a feeling for the ‘big picture’ of the commercial stove market so that we can better direct the creative energy during our next Stove Camp? We very much appreciate your help!
Stove camp attendees
We hope that you might take a moment to inform us about stoves sold in your country. Could you provide responses to the following questions in a reply to this email? THANK YOU!!!
1.) Where are you located?
2.) What type of stove is purchased most often?
3.) Can you estimate how many stoves are sold?
4.) Where are the stoves purchased?
5.) About how much does the stove cost?
6.) If you were going to sell a stove in your region what are the two most important features it should have?
7.) Would folks purchase a stove with a chimney?
THANKS AGAIN! All answers are private, of course.
Dean and Sam
Clean Burning Biomass Cookstoves: A Quick Summary
- The stove body and interior (including the combustion chamber) is low mass and insulative. The heat from the fire goes into the cooking process and is not diverted into the stove.
- The heat transfer efficiency is close to optimal resulting in over 40% thermal efficiency. One successful technique is to combine moderate firepower (2.5kW) with very small channel gaps (6mm) around the pot. Burning less wood results in fewer emissions.
- Emissions are reduced by increasing combustion efficiency. An appropriate amount of wood gas is made. The rate of reactions is controlled by adjusting the primary air or by metering the fuel.
- A zone of mixing of air, gases, smoke, and flame is created using jets of secondary air. The jets of secondary air can be powered by natural draft in a Top Lit Up Draft stove or by forced draft in both Rocket and TLUD stoves.
- Increasing the velocity of the jets of air can improve the effectiveness of the zone of mixing.
- The cooling effect of the secondary air jets is not allowed to decrease thermal efficiency below 40%.
- The amount of flame, air, and wood gas entering the zone of mixing is adjusted until close to optimal combustion efficiency is obtained.
- Emissions in the exhaust stream can be further reduced with a catalyst.
- Removing the emissions from the living space in a chimney is mandatory in the United States. The ARC stoves have chimneys to comply with new WHO guidelines.
- The prototype stove moves through an iterative development process by testing one change at a time under the emissions hood. The Water Boiling Test and the Controlled Cooking Test are both used to evolve a stove that is clean burning, fuel efficient, and cooks as well or better than the local model.
- The cooking function of the stove is designed by local users. The market viability of the product is determined by field testing involving stakeholders such as distributors, manufacturers, funders, consumers, etc. Market testing precedes and informs manufacturing.
- Reducing adverse health effects requires the new stove to be a successful intervention. The intervention involves many infield factors that influence the effectiveness of the whole package. Identifying these factors begins the process of creating the successful intervention.
- The stove is only one part of the successful intervention! A recent study in Malawi (commentary, article) of a clean burning stove found no decrease in PM exposure related illnesses, but less than 50% of the stoves were in use.
From “Clean Burning Biomass Cookstoves” found for free at aprovecho.org
Dr. Tom Reed: The Father of Clean Burning?
Well, Tom is certainly one of a small group including Paal Wendelbo and Ron Larson who started making “Tier 4” stoves in the 1980’s. I think of Tom when I light his wonderful forced draft TLUD camp stove which I do to demonstrate a simple ‘no smoke’ stove. Tom’s webpage says,” In 1972 Tom Reed became concerned about the energy and fuel futures of the U.S. and began working on alternate fuels on the side while working at MIT in the field of solid state research. He was the first person to use alcohol blends during this period and when he wrote “Methanol – A Clean Fuel for the 21st century”, for Science magazine, it changed his career. In this article he said that for the short term methanol would be made from natural gas, but in the long term biomass could supply our needs forever.
Looking out of the ARC office windows, the rural Oregon road that curves past the campus is lined with 100 foot tall trees and the forest, even after decades of logging, is immense. Learning how to cleanly combust wood seems important here in the US as it does in other countries. Sustainably harvested energy is only amazing if it does no harm when burned and complete combustion opens a carbon neutral alternative that may be necessary in all sorts of applications.
How close is the complete combustion of biomass? Pellet stoves, industrial burners, and forced draft in general gets pretty close. Scrubbing the remaining emissions gets closer. In the cook stove world progress has been faster than I imagined as back yard R&D coupled with university analysis, supported by the DOE and EPA, inches science closer to the zero emission goal. As I envision the steps needed to complete the understanding leading to complete combustion, I’m thinking that reaching the goal is almost inevitable, with thanks to true believers like Dr. Tom Reed who helped to start the ball rolling.
How to Install a Catalyst in an Existing Heating Stove
When starting a cold stove the catalyst is disengaged from the gas stream by pulling on a steel rod. A green light will indicate when the stove gases are above 600F. The catalyst can then be engaged by pushing in the rod.
In one experiment in the ARC lab the installed catalyst reduced the emissions of PM 2.5 in a simple steel box stove made in Mongolia to about 1g/hour which meets the 2020 EPA Heating Stove Standard.
The following is a summary of a January/February 1983 article from Mother Earth News that describes design principles for installing a catalytic converter in a wood burning stove:
- Ceramic or metal catalytic converters are coated with platinum and/or palladium and/or rhodium.
- A catalytic converter can reduce the ignition temperature of carbon monoxide and hydrocarbons from upward of 1300°F to the 500-700°F range.
- Once the smoke passing through the catalyst reaches that threshold, it will oxidize as long as the combustibles in it are well mixed with a sufficient supply of air.
- After it is “lit,” the converter will produce enough heat to maintain ignition, even though the temperature of the incoming “wood gas” may drop slightly below 500°F.
- The basic concept can be applied to just about any roughly cubic metal (steel or iron) wood burner.
- Since the converter must reach a temperature of at least 500°F before it “lights off,” a location close to the fire will insure that the unit starts working as soon as possible and continues to do so throughout the burn.
- It is strongly suggested that a baffle arrangement is incorporated, diverting flame, residues, and ash, since eliminating the baffle could result in drastically shortened catalyst life.
- There must be adequate oxygen at the catalyst, however, it was determined that specific provisions for secondary air weren’t needed. Under all burn conditions, there was always an adequate air supply remaining at the converters.
- Hotter air (both primary and secondary) means better performance. Well warmed primary air encourages efficient primary combustion, and hot secondary air is vital to maintaining ignition temperature at the catalyst.
- A well sealed, strong bypass valve is mandatory. Even though the cell structure of the catalyst is relatively open (in comparison with that of the automotive variety), the unit does restrict natural draft to some extent, particularly when the catalyst isn’t lit. For that reason, there must be a valve that allows you to shunt smoke around the catalyst while a new fire gets going and whenever the stove’s doors are opened.
- As we’ve already mentioned, the single most important precaution is to always bypass the converters when the doors are opened. Furthermore, that same valve will have to be open while you’re getting a fire going.
- And should the catalyst go out for some reason, we’ve found the thermometer to be the only easy way to tell.
- After the charge of wood burns down — but not out — you can open the bypass, add more fuel, and then close the bypass immediately.
- Materials such as coal, wood pellets, paper with colored ink, tires, plastics, and treated or painted lumber, may “poison” the catalyst and render it ineffective.
Testing was designed to occur before manufacturing. 42 years after the International Standards were published, how many stove projects are spending a year or two in their project areas to make sure that the cooks love the intervention and that it decreases pneumonia before starting to make stoves?
Testing the Efficiency of Wood Burning Cookstoves: International Standards was published in 1985 and was the result of three international conferences. The purpose was to describe three tests that would enable stove projects to create interventions that met their goals. Testing was intended to happen before manufacturing to make sure that the stove and the entire intervention (a lot more than the stove!) works to save fuel, decrease pneumonia, protect kids from burns, or whatever is important in the context.
Using stove testing after the stove is manufactured to see if project goals are met is a great idea, too. But, bringing a stove into a village without good information showing what is needed in the cultural context to accomplish goals is obviously foolish. The WBT, CCT, and KPT were designed to result in reliable data to try to make sure that project was proven, before dissemination of the stove, to be successful.
The recent pneumonia study in Malawi showed that the new stove was used less than 1/3 of the time for cooking. Prior studies using the WBT, CCT, UCT, KPT, etc. with emission equipment could have been used to create a successful intervention that then would have been followed up to analyze results. This approach uses testing to identify the interwoven factors involved in the design of a useful medical intervention. When ARC created a Rocket stove for the Shell Foundation project in India it took about a year with months spent in villages (and in the lab) to discover what made both cooks and funder satisfied. We were trying to make sure that the consumer would love and buy the product and that it was significantly improved before it was made available on the market.
The aprovecho.org domain was unavailable from about Dec. 27 to Jan 4. Our emails weren’t working during that period. We’re back! Thanks for your patience.
Aprovecho Research Center
PO Box 1175
Cottage Grove, OR 97424, USA