Rookie Wood Stove Makers Get Highest Score in Design Workshop

Taylor Myers and Ryan
Fisher with the Mulciber,
the highest ranking stove.

A stove designed and built by graduate engineering students received the 

highest score in an international Stove Design Workshop focused on automated wood stove technology.  The goal of the event was to assess innovative technologies that can help stoves reduce real-world emissions that result from poor operation by the consumer and use of unseasoned wood, both of which are widespread problems. 

Ten judges scored the stoves based on emissions, efficiency, innovation, market appeal and safety.  The highest scoring stove, the Mulciber, adapted emission control techniques that are in automobiles, such as an oxygen sensor that controls the fuel-to-air ratio, a continuously engaged catalyst and an exhaust gas fan.  The Mulciber was also tested with unseasoned, 50% moisture content wood and performed quite well.   The team, who had never built a stove before the 2013 Wood Stove Decathlon, overhauled their first prototype and have now formed the company MF Fire to bring the stove to market.  

The Workshop was held at the DOE’s Brookhaven National Laboratory in New York and brought together a diverse range of stakeholders - students, professors, industry, regulators, air quality experts - who spent a week together analyzing the problems and solutions to residential cord wood emissions.

Five stoves competed in the event, which is part of the ongoing Wood Stove Design Challenge run by the non-profit group, Alliance for Green Heat. In 2013, the Design Challenge hosted the Wood Stove Decathlon on the National Mall in Washington DC, a high profile event modeled after the Solar Decathlon.  This year, the event was at a lab so that stoves could be tested more rigorously and test data could be shared with the participants.

The core problem is that most consumers do not operate wood stoves well and many use unseasoned wood.  In addition, EPA certification testing for wood stoves do not simulate how wood is burned in people’s homes.  For decades, manufacturers have been building stoves to pass that test, but not necessarily to burn cleanly in homes.  This workshop addressed that by testing with cordwood that was not fully seasoned, capturing some start-up emissions in the test and assessing how automation can reduce operator error.  At Brookhaven, stoves were tested at four parts of their burn cycle: warm start, steady state 1, hot reload and steady state 2. The current EPA stove certification test uses seasoned 2x4s and 4x4s and only tests for emissions after the start-up period, once the stove is hot.

Automated stoves, where computers, not consumers, adjust the air-to-fuel ratio, cannot be tested by EPA test methods so they are not able to enter the US marketplace.   A major goal of the Workshop was to start designing an alternative test method to the EPA’s method, so that automated stoves can be tested and become certified in the US, as they already are in Europe. Tom Butcher, a senior scientist at Brookhaven Lab, hosted one of the public webinars during the week on that topic.

Rankings: The judges gave double weight to emissions and efficiency, as they did in the 2013 Wood Stove Decathlon, because of the importance of those values.  This year, the judges decided not to judge affordability since most of the stoves were prototypes or technologies designed to be integrated into other stoves and ultimate costs and pricing was too speculative. Each of the 10 judges scored each stove on innovation and market appeal.  The other three criteria were based on lab tests.

“We want to congratulate the MF Fire team - and all the teams - for participating in a process of sharing innovation, ideas and test results,” said John Ackerly, coordinator of the event and President of the Alliance for Green Heat.  “These stoves have many of the solutions to excessive smoke from modern-day wood stoves and are challenging the EPA and the stove industry, to catch up with new technologies and new opportunities,” Ackerly said.

The Wittus team with the Twinfire.

While MF Fire stove, the Mulciber, had the highest combined score, several of the other stoves stood out in key areas.  The German Twinfire, designed by the Wittus team, had the second highest overall efficiency, at 74%, and one of the lowest emission rates on a test run.  Its automated air regulation enabled the stove to perform consistently well at different part of the burn cycle and it received the highest score for consumer appeal, for its downdraft flame into a lower chamber.  

The VcV, wired to monitor
temperature in key spots

The VcV, a New Zealand mechanical device that operates without any electricity, achieved the highest average efficiency, at 82% based in part on the lowest average stack temperature at 167 degrees (F), and the lowest emission rate on one of its tests.  It also received the second highest marks for innovation.  This was the only stove that did not require electricity and will be very affordable. Three out of four tests were very, very good, but on one the hot reloads, something happened and that reduced its overall numbers, and took it out of contention for first or second place.  This device has undergone extensive R&D and is one of the entries that is closest to being ready for the market.

The Catalus Ventus by ClearStak, received the highest score of all for CO reduction, and the second

The ClearStak team with the
Catalus Ventus

highest for emissions.   It was a highly innovative entry, employing dual cyclones, a pre-heated, continuously engaged catalyst and a fabric filter.  Its sensors and controller kept the oxygen rates incredibly steady, within half a percentage point. The technology could be integrated into a new stove, or added on to an existing stove. The designers did not try to optimize efficiency, which impacted their overall score.   

The Kleiss, ready for testing.

The Kleiss arrived at the competition with the hallmarks of an innovative, automated stove that could handle wet wood and nearly eliminate operator error.  The stoves sensors and algorithms were designed to maintain very hot combustion temperatures and to allow the operator to call for more of less heat, while prioritizing cleanliness.  However, the stove did not perform as expected, with secondary air contributing to primary burning with a large fuel load.   

Test results for all the stoves are available here.  (References to grams per hour are not comparable to EPA gram per hour tests since the Workshop used tougher test protocols.) A series of presentations by the stove designers about their stoves and other stove and combustion experts are also available.

The Wood Stove Design Challenge is a technology competition that also strives to bring key stakeholders together to assess and learn about new stove technology.  Primary funding came from the New York State Energy Research and Development Authority (NYSERDA), the Osprey Foundation and the US Forest Service.  Testing support was provided by Myren Labs, Masonry Heaters Association and Testo and Wohler, two German companies who are pushing the envelope of accurate real time lab and field testing of particulate matter.  The Chimney Safety Institute of America and Olympia Chimney donated the chimney installations, and Blaze King and Woodstock Soapstone also provided support.

The 12 member Organizing Committee oversaw developing protocols, testing and scoring and included representatives from Alliance for Green Heat, Aprovecho Research Lab, Brookhaven National Lab, Clarkson University, Hearth.com, Masonry Heater Association, Massachusetts Department of Energy Resources, Myren Labs, NYSERDA, US Forest Service and Washington Department of Ecology. The Committee is now considering options for a 2015 Stove Design Challenge.

Dec. 4 Webinar: Best Practices in Wood and Pellet Stove Programs

The University of Maryland Extension Woodland Stewardship Education program will host a one-hour webinar on Thursday, December 4th from 12:00 p.m. to 1:00 p.m. to provide an overview of the “best practices” in wood and pellet stove incentive programs across the United States. 

Sign up here.

As renewable energy programs grow around the country, more and more states are including incentives for wood or pellet boilers and stoves. Unlike other household appliances, such as refrigerators, furnaces or washing machines, wood heating equipment have no “Energy Star” labels for consumers to consult to make energy efficiency comparisons. Consequently, several states have devised a range of methods to determine the eligibility of cleaner and more efficient stoves and boilers.

This webinar will explore the features of these programs, and will use Maryland’s stove incentive program as an example of how one state met its goals for ensuring consumers purchase the most efficient appliances available. The speakers will identify what they see as emerging best practices in stove and boiler incentive programs as these initiatives become more mainstream.

This webinar features presentations from Jonathan Kays, University of Maryland Extension Natural Resource Extension Specialist; John Ackerly, President of the Alliance for Green Heat; and Emilee Van Norden, Clean Energy Program Manager of the Maryland Energy Administration.

The webinar is free and open to the public.  Sign up now to reserve a spot.

For related content: 

Pellet Stoves a Hot Commodity in Maryland Incentive Program

Federal Stove Tax Credit Not Likely to be Extended in 2014

Analysis of Maryland Stove Rebate Program (2013)

Test Results, Presentations and Photos from the 2014 Collaborative Stove Design Workshop

Test Results

Updated on Nov. 24

Part of the Workshop rules was a requirement that teams had to publicly share their test results, which is a key part of the collaborative and educational process. During the Workshop, each team presented their test data to the 50 attendees who had the opportunity to discuss the results and give feedback to the  team.  Unlike EPA test, which starts when the stove is already hot, we used a warm start, capturing some start-up emissions, we used cordwood instead of crib wood and we used higher moisture content wood. Note: any gram per hour (g/h) references in the below test results are not comparable to g/h values from EPA test labs because we did not follow the Method 28 test protocol. 

1. MF Fire, the Mulciber. Powerpoint link.
2. The Kleiss stove. Powerpoint link.
3. Wittus Twinfire, Powerpoint link.
4. The VcV, PDF link.
5. Catalus Ventus, PDF link.

Team Presentations about their Stoves
Each team presented the concepts and technologies in the stoves. For a brief technical overview of all the stoves with contact info for the Teams, click here.

1. The Mulciber (powerpoint)
2. The Wittus Twinfire (pdf)
3. The VcV (pdf)
4. The Catalus Ventus (pdf)
5. Kliess (powerpoint)

Expert Presentations
During the Workshop, there were a series of expert presentations and webinars about automation, traditional stove technology, public health implications, air quality, regulatory issues and other relevant topics.

1. Dr. Tom Butcher, Brookhaven National Lab, Review of the Automated Stove Test Protocol (powerpoint)
2. Webinar with the five teams, hosted by BTEC.
3. Glenn Miller, Fairbanks Air District,  Technology Improvements vs. Behavior Modification (powerpoint)
4. Ellen Burkhard, NYSERDA, Renewable Heat New York (powerpoint)
5. Norbert Senf, MHA, Emission Testing of Masonry Heaters (powerpoint)
6. Gael Ulrich, Smoke Particle Formation Fundamental, (pdf)
7. Peter Cullen, Wohler SM 5000 (powerpoint)
8. Phil Swartzendruber, Puget Sound Wood Stove Retrofit Open Challenge (pdf)

Feedback Survey: Results of a 10 question feedback survey about the Workshop by teams, participants and organizers.

Photos: Day 1

Ivana Sirovica, Jessica Peterson and Jeff Hallowell, from ClearStak Brookhaven National Laboratory.

Rebecca raking coal bed to prepare for the next load of fuel. 

Thanks to John Pilger and Chimney Safety Institute of America and Olympia Chimney for donating pipe and installation!

Indigo Hotel in Riverhead NY - our base for the week

The Testo shows real time emissions, with top line showing particulate matter (PM)

Rebecca Trojanowski removes filters. The dark circle in foreground are the particulates on a filter from the test burn that will be weighed to determine grams per hour.

Even the kindling is carefully weighed so that each stove gets the same warm up rick.

Jessica Peterson from ClearStak working late into the night to prepare for testing tomorrow.

Photos: Day 2

Taylor Myers showing a thermal image of the Mulciber stove. 

Ben Myren, Tom Butcher and Eric Schaeffer firing up the New Zealand VcV stove. 

Lab in Bldg 815 with the VcV and Kleiss stoves.  (They brought 2 of exact same stove in case they needed it.)

Taylor Myers showing a real time digital display, using bluetooth, of temperatures in his stove.

Developed by ClearStak, this real time digital display shows 154 degree stack temperature, 529 in the firebox and 451 in the catalyst. Estimated efficiencies were in the mid-80s. 

Glenn Miller from the Fairbanks Air District on the left, Rob Rizzo from Mass. Dept. of Energy, and Gaetan Piedalue and Marc Suave from Polytest Labs, a EPA accredited test lab. Ellen Burkhard from NYSERDA is peering into the stove. 

Ben Myren, Tom Butcher and Eric Schaeffer firing up the New Zealand VcV stove.

The Wittus Twinfire's downdraft mechanism, where the fire gets sucked into lower chamber and then passes through catalyts before going back up the stack.

Day 3

Corey Van, one of the young ClearStak staff that helped build the Catalus Ventus. 

Rebecca Trojanowski loads the Catalus Ventus.

The new Testo moisture meter that reads moisture without "pinning" the wood.

Norbert inspects the Condar, placed right below the triple walled pipe.

The tube on the right of black pipe is a Condar, which operates very similarly to a dilution tunnel. Norbert Senf is using it concurrently with the Testo PM analyzer.

A warm up test load made by Ben Myren. This top down burn, with smallest kindling on top, and larger kindling on the bottom is a very efficient way to start fires.

Amanda Aldridge of the EPA talks with Norbert Senf (behind flue pipe) about the Condar analyzer. Rob Rizzo from Mass. Dept. of Energy in upper right.

Electronic controllers that can be put in wood heating systems that were part of Jeff Hallowell's presentation. Harold Garobedian in red jacket on right, and Rafael Sanchez from the EPA behind him.

A new Testo moisture meter that works without pins. It can measure moisture at the center of the wood, not on the edge.

George Wei hangs almost upside down to put a temperature sensor in the top of the flue pipe to measure stack temperature. This is a key data point for determining efficiency.

Day 4                                          

John Ackerly on opening day, welcoming everyone and talking about how automated stoves can solve many problematic issues issues that come with widespread wood burning.

From the left to right - Ellen Burkhard from NYSERDA, Lisa Rector from NESCAUM, Amanda Aldridge from EPA and Mark Knaebe from US Forest Service.

We spent hours in this room, having different presentations every hour, with lots of discussion and debate. Here, Ben Myren is presenting the testing results of the VcV stove.

Brian Gauld of New Zealand, John Pilger of CSIA and Jeff Hallowell of ClearStak.

Team Wittus Twinfire

Gregory Elliiot and Peter Cullen from Wohler, and John Pilger from Chimney Safety Institute of America.

Ingo Hartman, measuring glass temperature on his Twinfire stove.

We managed to find a BYOB restaurant which led to more red wine consumption. From left - Rod Tinnemore, Dave Misiuk, Amanda Aldridge, John Ackerly, Norbert Senf, Ellen Burkhard and LIsa Rector.

Final Day

The Catalus Ventus shows incredible hot catalyst temps compared to the both the stack and the firebox. This was during start up, when it was emitting maximum smoke, but between the catalyst, the fabric filter, virtually no smoke came out the stack.

Ivana Sirovica, a Research Fellow from Alliance for Green Heat, and Ben Myren, as Ben finished the final test of the week.

Tom Butcher using the Wohler particulate analyzer on the VcV stove. Because we used wood that was often above 25% moisture content, we had to deal with more moisture in our testing instruments.

Underneath the VcV stove is where the magic happens, and mechanical valves automatically close or open the primary or secondary air, depending on what the stove needs to maintain a clean and efficient burn. THis stove maintained a steady low burn rate with beautiful swirling flames in the upper part of the chamber.

Ben Myren shows how his thermocouples could read the temperature in 10 spots of the stove at all times. The top of the flue could be 250, when the air entering the catalyst was nearly 800, and 1300 in the firebox.

Brian Gauld, the owner of the VcV travelled from New Zealand, where there is also demand for automation that can improve stove performance far more than stoves are likely to perform when operated manually.

         Dr. Phil Hopke of Clarkson University and Mattian Woll of Testo.

Our cord wood was kiln dried and then shrink wrapped so it would maintain a constant moisture content. The wood was far wetter, on average, than wood used in EPA test certifications, which helped us assess how these automated stoves could perform with higher moisture content wood.

Preparation of kindling for the tests.

George Wei and Yussef were two of Brookhavens talented technicians. Both have worked on improving oil combustion systems, outdoor wood boilers and stoves.

The last stove is taken out, and demonstrates the challenge of testing the same day as removing stoves that are still hot!