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: