Results of the 2018 Wood Stove Design Challenge

 By John Ackerly

The first day of testing, showing Ben Myren Prof.
Phil Hopke and Rebecca Trojanowski.
Photo: Kittner/BNL.

Conducting rigorous and transparent field testing of thirteen stoves in five days is a feat that is unheard of in the wood stove community.  The goals were also unique: fairly test stoves against one another with cordwood; help each team to improve their units and help educate a wider public about novel stove technologies that challenge how we think about the traditional, manually operated EPA certified wood stove.

The 2018 Wood Stove Design Challenge took place from Nov. 9 - 13, featuring 10 stoves in competition and 3 showcase stoves. The stoves were selected and judged by members of the

Large screen monitors provided real time data during
a test run of the Integrated Duty Cycle fueling
protocol under development. Photo: Kittner/BNL

Organizing Committee.  The Alliance for Green Heat (AGH) was the principal architect, organizer and host of the event.  Each of the 10 competition stoves received a $10,000 grant made possible by the DOE's Bioenergy Technology Office.

The Wittus team from New York
and Germany. Photo: Kittner/BNL

In the automation stove category, there were three market ready stoves that successfully went through a rigorous fueling protocol and proved that they could burn relatively cleanly and efficiently even when an operator tried to turn down the heat setting too far and at the wrong times.  An SBI stove and the VcV stove that had been in development for many years showed the value of multi-year R&D and testing, resulting in stoves that may only cost $500 more than a similar,

Staffers from EPA, DOE, USDA and Congressional
offices were able to learn about stove testing and
 engage with teams and judges. Photo: AGH

  

non-automated version.  To us, this is a major breakthrough and stoves like these should show a path to far cleaner cord wood heating in America.  

The SBI team. Photo: Kittner/BNL

The other automated stove was a German-American unit that heated water, made electricity and provided a living room fire experience with a downdraft flame into a lower chamber. While this was not an affordable stove to most Americans, it could have a reasonable pay-back over a number of years, depending on the users cord wood price.  This stove impressed both the Brookhaven National Lab and the Masonry Heater Association testing teams with ultra-low carbon monoxide numbers in the single digits under some conditions, and ultra-high efficiency.  

Ben Myren, one of the top wood stove testing experts
in the US, talking with Larry Brockman of the EPA's
BurnWise program.  Photo: Kittner/BNL

Automated stoves are regarded as one of the best, and only ways to help ensure that manually operated EPA certified stoves perform well not just in the testing lab, but in the homes of consumers.  For automated stoves to start gaining a foothold in the market federal, state and local government recognition and support will be required.

An automated pellet boiler by Maine Energy Systems capped with a Stirling Engine was the most

A Tesla owned by Osprey Foundation head, Bill Clarke,
 being charged by Maine Energy System pellet 
boilers with a Stirling engine. Photo: Kittner/BNL

futuristic of the entries, especially since it was charging a Tesla car in front of the tent. This compact unit could heat a business or multi-family dwelling and provide up to 5 kW of electricity.  

The five testing teams used different equipment
to gather a variety of data. Photo: Kittner/BNL

In the thermoelectric category, the judges concluded that “the most innovative thing is that almost all teams used commercially available thermoelectric modules and showed that it is feasible to generate useful electrical energy without sacrificing the energy efficiency or impeding the heat quality of

This is a Swiss-made electrostatic precipitator for
residential wood stoves that reduced PM by 50 -
90% in our testing.

the wood stove.  Most designs returned the waste heat after electricity generation into useful radiant heat into the room to increase efficiency.  These designs prove that the woodstoves is a good potential commercial opportunity for thermoelectrics to generate useful electrical energy and also increase their commercial appeal for consumers.”

It was clear that stoves or boilers with Thermoelectric Generators (TEG) could produce 100 to 250 watts of power. While this is a relatively modest amount of electricity, larger automated stoves or boilers operating 15 to 20 hours per day may help supplement limited solar power output during winter months. 

Fred Legget of Vulcan Energy 
with a TEG adapted to a Wiseway.
Photo: Kittner/BNL

The George Washington University, Unforgettable Fire and ASAT teams all successfully used off the shelf technology, while TEG expert Fred Leavitt of Vulcan Energy used commercially available TEGs by Hi-Z, and adapted the gravity fed Wiseway pellet stove to get a more steady 130 watt output. 

The Wittus cord wood stove was by far the most market ready and was able to make 250 watts, and it peaked at over 300 when using low moisture pressed wood logs.  Ken Adler, AGH’s Program Director of Thermoelectrics, coordinated the thermoelectric side of the competition and the thermoelectric testing.

University teams have been a key part of the Design
Challenge with SUNY Stony Brook competing this year.

Scoring was done using a numeric rubric based mostly on data produced by the testing equipment but judges did have discretion to award some points based on their subjective assessment in several areas.  Judges assessed automated stoves by these criteria and thermoelectric stoves by these.

And the awards goes to …

The Wittus team won both first prizes.
Photo: Kittner/BNL

·     * First Prize for automated stoves: Wittus.  Great performance on particulate matter, CO, efficiency and safety.

·     Second prize for automated stoves: SBI. A fully automated non-catalytic stove using only 2 sensors that may only cost $500 more than if it were non-automated.

·     * First prize for thermoelectric stoves: Wittus - again;  The highest electric output of up to 250 watts, and an integrated design that can maintain stable electric output.

·     * Second prize for thermoelectric: Vulcan Energy, using the Wiseway pellet stove that produced more than 100 watts and good PM reduction.

Stove testers Tom Butcher, Jake Lindbeg, Rebecca 
Trojanowski Photo: Kittner/BNL

·     Innovation prize: SBI, for simplicity.  The use of only one thermocouple and a sensor on the door, enabled the designers to regulate the stove despite attempts by the testers to turn the heat demand down and make it perform poorly. 

·     * The People’s Choice Award: 509 Fabrications.  Despite being a new, small company without an extensive social media network, the 509 Fabrications pressed log stove was a consumer favorite, garnering more votes than any other stove. 

The MHA testing crew: Ron Pihl, Jim 
Schales, Norbert Senf, Mark Seymour 
and Boris Kukojl. Photo: MHA

Unique and rigorous testing

The 2018 Wood Stove Design Challenge pushed the limits of rigorous wood stove testing both in terms of the amount and variety of technology used, and the fueling protocol, which is far more rigorous than any standard fueling protocol.   More details about this will be forthcoming.  Data produced by this event will show the extent to which automated stoves can navigate fueling protocols where testers try to make stoves go into smolder mode, to see if the automation is robust enough to avoid that.  Data is also more valuable for understanding real world venting conditions, as EPA approved test labs terminate in a warm indoor space, not the colder outdoors.  

Real time emission displays allowed testers teams
and judges to learn more about performance patterns.
This shows exceptional  CO and stack temps on the
Wittus. Photo: Senf

Between Brookhaven National Lab and the Masonry Heater Association, we had up to 5 separate testing teams, allowing many stoves to be tested at once.  We

Jonathan Male, head of DOE's Bioenergy
Technologies Office introducing the awards
Photo: Kittner/BNL

also wanted to have ensure that the Brookhaven and MHA teams could  periodically test the same stove at the same time.  Norbert Senf of the MHA had worked for months to automate the Condar, and the new Condar controls worked very  well, with minimal glitches. They did three runs simultaneously with Brookhaven National Laboratory who used a diluter and Testo 380. Comparisons of the two approaches will be published at some point.

Air quality testing during the Design Challenge

During the Challenge, we monitored indoor and outdoor air quality to get some sense of the impact

Tinted stove pipe donated by Olympia Chimney, 
showing mostly invisible smoke during the event
Photo: Kittner/BNL

from 9 – 13 wood and pellet stoves operating under one roof.  We used a Thermo Scientific pDR-1500 Aerosol Monitor, an Speck indoor PM monitor and a Purple Air PA-II - SD monitor.  Results were mixed, with most indoor readings between 20 - 35 micrograms per cubic meter, but with far higher spikes. The EPA short term PM standard is 35 micrograms per cubic meter.  Outdoor numbers were usually around

Les Otten, right, with Maine Energy Systems
Okofen Pelletmatic E-max CHP unit. Photo: MYSys

10 micrograms per cubic meter. Often the Speck showed  moderate to elevated inside the tent, but on several occasions, prototype stoves released excessive smoke into the tent – and outside of it.  We will issue a more detailed report on this. 

A note of gratitude

Julie Tucker of the USDA Forest Service, with
DOE's Jonathan Male and  AGH's John Ackerly
Photo: Kittner/BNL

 The Wood Stove Design Challenge is a collaborative process involving three major donors - the Department of Energy's Bioenergy Technology Office, New York State Energy Research and Development Authority and Osprey Foundation and scores of in-kind and volunteer partners.  Olympia Chimney and Masonry Heater Association were key in-kind partners, along contributions by West Penn Power

Dusty Henderson with the 509
Fabrications pressed wood log stove
that won the People's Choice Award. 

Sustainable Energy Fund, HPBA, Schott-Robax, Lignetics, Chimney Safety Institute of America, Society for American Foresters, National Fireplace Institute, Catalytic Hearth Coalition, Biolite local sweeps and installers and others were key in enabling the event to occur.  

Unless otherwise noted, photos taken by Sam Kittner and made possible by funding from Brookhaven National Lab and can be used freely by all, with attribution to "Sam Kittner for Brookhaven National Lab."  Photos attributed to AGH can also be used freely and attributed to "Alliance for Green Heat."

The GW University Team. Photo: Kittner/BNL

The innovative rocket stove entry from
ASAT being tested by Ben Myren
Photo: Norbert Senf

Our tent was right between the Capitol and the Washington Monument.
Photo: Kittner/BNL 

Photo: Kittner/BNL

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.

NYSERDA Provides Grant to Develop Automated Wood Stove

In an effort to bring more automation to the wood stove, New York State Energy Research and Development Authority (NYSERDA) is providing a $49,000 grant to support the Alliance for Green Heat to test and work towards improving automated wood stove designs.

The project will bring some of the world’s leading automated stoves and prototypes to Brookhaven National Lab in November to test their performance and assess which designs hold the most promise in smoke reduction, reliability and consumer demand.  Seven companies with different approaches to automation are competing in the event.

John Rhodes, CEO of NYSERDA
announcing Renewable Heat NY
funding in August 2014

 NYSERDA support is part of Governor Cuomo’s Renewable Heat NY initiative, which encourages the expansion of sustainable markets in New York State for high-performance wood-fired heating technology and encourages the use of renewable biomass fuel, such as cord wood and wood pellets. NYSERDA has become the largest supporter of research on residential wood and pellet heating technology in the U.S. 

This project, called the Collaborative Stove Design Workshop, is a follow-on to the successful Wood Stove Decathlon on the National Mall in November 2013 that was also supported by NYSERDA.  Unlike the Decathlon, which was a more formal technology competition, this Workshop will bring a variety of experts together to study and help improve the automated designs, some of which may be open sourced so anyone can build from them.

“A wood stove is only as good as its operator and its fuel,” said John Ackerly, President of the Alliance for Green Heat (AGH).  Automation can eliminate the widespread problem of operators who don’t give their stoves enough air at the right times, leading to excessive smoke in rural communities, suburban neighborhoods and towns.  It can also mitigate the problem of using unseasoned wood. “Pellet stove technology represents the biggest breakthrough in residential wood heating in the past quarter century but we believe more breakthroughs are possible,” Ackerly said.

The Organizing Committee that oversees the project consists of John Ackerly, Alliance for Green Heat; Ellen Burkhard, NYSERDA; Tom Butcher, Brookhaven National Lab; Craig Issod, founder of Hearth.com; Mark Knaebe, US Forest Service; Ben Myren, Myren Consulting; Norbert Senf, Masonry Heater Association; Dean Still, Aprovecho Research Center; Rod Tinnemore, Washington Department of Ecology; and Rebecca Trojanowski, Brookhaven National Lab. Additional funding comes from the Osprey Foundation and the US Forest Service.

Applications to attend and take part in the workshop are being accepted until September 1.