Wednesday, June 30, 2021

Myren Consulting and AGH apply for Department of Energy R&D Grant

Down drafting stove would be open-source

Myren Consulting and the Alliance for Great Heat, along with Stonybrook University and German experts from DBFZ (Deutsches Biomasseforschungszentrum) are seeking to build an open-source wood stove that can help any manufacturer adopt the innovative approaches used by this stove. The goal is to make an ultra-clean wood stove that will consistently burn around 1 gram an hour without a catalyst and 0.5 grams with a catalyst, regardless of who loads and starts the stove.

The stove will use a downdraft airflow that brings the flames through the coal bed, and it will have a fan that induces the draft until the flue gases are hot enough to shut it off. The team will employ Computational Fluid Dynamics (CFD) to optimize the design and the air flow. The stove will also have a robust, multi-purpose data logger that can engage the operator via lights on the stove or through a sophisticated smart phone app. The app will feature content from our partner groups and walk consumers through all stages of the purchase, installation, operation, troubleshooting and maintenance. The consumer can choose if they will be the only one with access to the data, or whether they are willing to share it with the manufacturer, the retailer and/or a chimney sweep, for example.

Throughout the entire project, if funded, the team will share R&D decisions, designs, and data with the stove industry, regulators, and the public. The team will also seek to “crowd-source” solutions to problems and issues that may emerge by regularly seeking input from a range of stakeholders, from industry players to public health and low-income advocates. The stove will undergo a series of rigorous tests in Ben Myren’s lab over a 3-year period because a novel, top-notch stove needs that amount of time to get the design, airflow and other features just right. The stove will be tested to the traditional EPA reference Method 28, and the more recently approved ASTM 303-5 and IDC protocols. The stove will also undergo in situ real world testing, round-robin lab testing and be tested to the rigorous Blue Angel standard in Germany (not with DOE funds) to understand how it can handle a variety of loading and testing methods. 

Current certified stove design configurations have been developed since the mid 1980’s and are all based upon the draft generated by an EPA freely communicated lab chimney that is 15 ±1 ft. These designs have been developed somewhat over the years using a vast number of prototypes that have had many design changes made to them during this multi-year, multi-prototype R&D process. However, R&D in the stove community has not been robust and most manufacturers simply follow a well-known design pattern that has proved to be successful enough. We are attempting to disrupt that design pattern by maximizing secondary combustion in the upper part of the firebox but then drawing the gases down through the coal bed for an even more efficient secondary (or tertiary) emission reduction process.

With the change in draft proposed in this proposal, that entire body of knowledge becomes questionable.  And the project’s timeframe doesn’t provide for the typical long, slow development of a stove that will meet the current emissions standards. Thus, we propose to build upon a technique that we have been successfully using where some stove components are bolted together, rather than being welded together. This technique will allow us to rapidly make design changes which will hasten the entire R&D process. It will also enable us to fine-tune the combustion system in the stove by changing known critical components, e.g., the internal cross-sectional area of secondary air side manifolds, to facilitate the reduction of particulate matter (PM) emissions. The following table contains a (partial) list of critical components known to affect emissions.  Almost all of these features will still be relevant for a downdraft stove, but their size, shape and placement may change based on the downdraft design and the results of computational fluid dynamics (CFD) analysis.


  • LPAO: Lower primary air orifice
  • Horizontal throat gap: shortest distance between the front edge of the baffle and the backside of the air wash
  • Vertical throat gap: shortest distance between the top of the baffle and the bottom of the top

All equipment used in the revised dilution tunnel system will be maintained and calibrated using current EPA criteria. Our stove will first assess how consistently we can operate under 1 gram an hour without a catalyst, but we plan on designing a model with a catalyst as well. Wood stoves are often not sufficiently optimized in terms of low-emission combustion, so that the catalyst is subjected to excessive overloading.

The initial group of expert advisors who wrote letters of commitment include the Tribal Healthy Home Network, the German Biomass Research Centre, the Danish Technological Institute, the Hearth, Patio & Barbecue Association (HPBA), the National Fireplace Institute, Industrial Chimney Company-Renewable Solid Fuel (ICC-RSF), Masonry Heater Association, Sunstein Intellectual Property Law Firm, and 509 Fabrications.

The $2 million price tag would include $1.3 million expenses at Myren lab, $300,000 at AGH, $215,00 at Stony Brook University, $125,000 by the German team working at Myren labs (no DOE funds will be spent abroad) and about $70,000 for other vendors and subcontractors.  We are requesting $1.6 from the DOE’s Bioenergy Technology Office.

In the spirit of this open source project and collaboration with other teams, the following materials can be downloaded:

The full technical volume 

Letters of commitment

Summary slide


Diversity, Equity and Inclusion Plan

Results of AGH Newsletter Survey

This past month, we sent out a survey to everyone subscribed to our newsletter in order to get to know our readers better and evaluate our work as a non-profit. We received 290 responses, and are grateful to all the respondents who provided us thoughtful feedback about their interests, goals, and opinions on AGH’s work. Thank you! Below are some results from each question of the survey, with commentary from members of the AGH board and staff. 
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Question 1: What are your areas of interest? (Check all that apply)

We received 289 responses to this question. Federal and state government updates as well as stove R&D were the most popular, while conferences and webinars were the least popular. Among the 10 “Other” responses, DIY stove designs and pellet heating were also popular. We don’t frequently host or promote conferences and webinars, but there is likely to be another Wood Stove Design Challenge, announced later this year.

Question 2: Which of the following expresses your opinion of residential wood and pellet heating? (Check all that apply)
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We made an unfortunate mistake right before publishing the survey of deleting a fourth option that was more in support of wood and pellet heating – and once we started receiving responses, we were not able to change or add options. We noted this in the intro to the survey, and noticed that the number of responses took a big hit – a decrease of almost 100 from the previous question. Many respondents in question 12’s “any other feedback” section explained that they would have chosen a response more positive of wood and pellet heating than the other three responses gave. We apologize for this mistake but feel the responses to the other 3 options are still informative.

Question 3: What, in your opinion, are the top three ways to reduce air pollution from wood smoke? (Check all that apply)
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After the decrease in responses to question 2, we were pleased to see a high level of response to this question. Consumer education and changeout program expansion were both popular responses, while increased enforcement of existing state regulations and more state regulations in general was less popular. In other sections, including question 12’s other feedback section, consumer education was deemed very popular. The more difficult question is how a small group like ours can effectively do more consumer education.

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Question 4: What U.S. state or foreign country do you live in?

We received 260 responses to this question, most of which were U.S. states. The results are summed up on the following heat map, which shows that most AGH readers, at least in this sample size, tend to reside in more northern states, with southern states being much less represented. In terms of foreign countries, 22 respondents said they lived in Canada, and much lower numbers were also received for Chile, Kenya, Sweden, Germany, France, the U.K., Japan, New Zealand, and Poland.

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Question 5: Which of the following appliances do you own? (Check all that apply)

This question received a wide variety of answers without a strong trend besides the comparative popularity of wood stoves as primary and secondary heat sources as compared to pellet stoves, wood/pellet boilers, and the other green heat systems listed. Among the “other” responses, air source heat pumps and masonry heaters were also popular responses. This question helps us understand what kind of information is applicable and/or useful to those reading our content.

Questions 6, 7, & 8: 

These three questions regarded research AGH is doing into how wood and pellet stoves are evaluated in energy audits. In response to question 6, (“Have you had an energy audit done on your home in the last 3 years?”) 30 responded "yes." Out of those 30, only 5 responded “yes” to question 7, which asked, “If you own a wood or pellet heater, did the energy auditor inspect it?” We reached out to all respondents who provided their email address in order to contact them about their energy audit experience, and have received very helpful responses from a number of people. Once again, if you would like to share your energy audit report or experience with us, please email because we would love to hear from you!

Question 9: How would you rate AGH’s monthly e-newsletter on a scale of 1 to 5?

We are relieved that an average of 83%of respondents think the newsletter is a good length, has a good frequency, and is not too biased for or against wood heating. AGH is a pro-wood heating group, but we also think it is important to address wood smoke and a range of other issues head-on. 

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Question 10: In your opinion, on which areas should the Alliance for Green Heat focus?

Just as in question 3 and 1, education and outreach appeared to be very important to our survey respondents, while social media and engagement of other non-profits appeared to be less so. We do maintain Instagram, Facebook, and Twitter accounts, although this is not where we direct most of our effort!

Question 11: The Alliance for Green Heat promotes modern wood and pellet heating systems as low-carbon, sustainable, and affordable energy solutions. In your opinion, how effective is AGH in achieving this mission?
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It was encouraging to see that the majority of respondents rated us as somewhat or very effective, though we know we can always improve.

Question 12: Is there any other feedback you wish to share with AGH? 

We received 92 written responses to this question! Most responses provided encouragement, suggestions for content, questions, or clarification on prior survey responses. We read and appreciate every single survey response we got.

Question 13: Biolite camp stove drawing: We have a winner!!
Finally, out of the 216 respondents to this question who entered our stove drawing, Ken Hansen of Washington State was randomly selected to receive a FREE $350 Biolite electricity-generating wood grill. From Mr. Hansen: “I'm looking forward to surprising my hiking partners by recharging our phones/cameras while I grill the carne asada after a day of hiking!”

Thanks again to everyone who participated in the survey!