New York and Canadian companies win technology challenge to automate the wood Stove

Jonathan Male, director of the DOE's Bioenergy
Technology Office, announces the winners.
Photo: Sam Kittner for Brookhaven National Lab.

(Washington, D.C.) – Two companies with years of experience in electronics and stove design won coveted first and second prizes in the 2018 Wood Stove Design Challenge, held in Washington DC from November 9 – 13. 

Manually operated wood stoves are extremely common throughout the northern US, Canada and Europe but no one has yet popularized a solution to prevent them from emitting excessive smoke in the hands of operators.

Wittus, a company based in Pound Ridge New York, teamed up with German engineers and won first prize for both the automated and thermoelectric categories with a living room unit that also heated water for space heating

The Wittus team who won first place in both
the automated and thermoelectric categories.
Photo: Kittner for BNL.

and generated an average of 161 watts and a maximum of 268 watts over the 2.5-hour test period. Total power output over the test period, net of parasitic losses, e.g., pumps and fans, was 276 watt-hours of electricity. The use of thermocouple sensors and fans facilitated clean and efficient combustion.

Stove testers from Brookhaven National Lab and
New York Department of Health.
Photo: Kittner for BNL.

Second prize went to Stove Builders International (SBI) a Quebec based company that designed a simple, affordable stove that allowed the operator to select high or low heat output and used a low-cost control board and thermocouple sensors to ensure that the stove burned cleanly.

Second prize in the thermoelectric category went to California based Vulcan Energy, who

SBI, a prominent Canadian stove manufacturer
spent years developing automated features.
Photo: Kittner for BNL.

developed a thermoelectric generator for the gravity fed Wiseway pellet stove that generated an average of 123 watts, and a maximum of 139 watts, during the 2.5-hour test period. Total power output over the test period, net of parasitic losses, was 235 watt-hours.

The People’s Choice award, based on votes from the general public, went to 509 Fabrications, for their unique gravity fed pressed log stove.

Key partners in the Challenge included Olympia
Chimney, and CSIA, and NFI installers from
Winstons Chimney and  Sugarloaf Chimney.
Photo Kittner for Brookhaven National Lab.

The goal of the Woodstove Design Challenge is to demonstrate how improved designs including sensors and computer controls can make wood stoves cleaner and more efficient. The technology boom of the past few decades has largely missed the wood stove industry, yet innovation still holds great promise. 

Researchers including Brookhaven National Lab, with support from the New York State

Fred Leavitt won 2d prize in thermoelectric
with Jonathan Male, DOE, Ramesh Koripella,
Sandia National Lab and John Ackerly, AGH.
Photo: Kittner for BNL

Energy Research and Development Authority (NYSERDA), have been developing new methods for the next generation of assessment protocols for wood heating appliances. Currently, most stoves in America are tested for EPA certification with standardized fuel pieces and spacing. Research has focused on in-home use operational practices, user fueling patterns, and new real-time measurement method techniques with random loading patterns and variability in piece size to better replicate real-life conditions.   

Automated stoves that are designed and tested with this new robust cordwood test method can help improve woodstove designs and in-use performance leading to higher efficiency and lower emissions.

Les Otten of Maine Energy Systems with Julie
Tucker of the USDA Forest Service.
Photo: Kittner for Brookhaven National Lab.

A team from Stony Brook University also competed in the event with a prototype that featured a unique wood drying and preheating chamber. The stove did not win a prize but offered students a rich opportunity to engage with national stove design and testing experts. A full list of the competing teams can be found here. 

Partners for the Design Challenge include NYSERDA, the Department of Energy’s Bioenergy Technology Office, the U.S. Forest Service, the Osprey Foundation and Olympia Chimney. The automated stoves were tested by Brookhaven National Lab. A complete list of partners and sponsors can be found here.

Meet the Teams: A New Zealand entrepreneur automates the wood stove - without using electricity

This post is the first in a series of technology and innovation blogs introducing the 12 teams participating in the 2018 Wood Stove Design Challenge in November.

By John Ackerly and Shoshana Rybeck, Alliance for Green Heat 

Alistair Gauld with the VcV stove. 

Variable Choke Venturi (VcV) technology has come a long way from New Zealand, where it was invented over a decade ago. It is a clever, simple device to improve combustion in wood stoves that is reliable and does not require electricity. Brian Gauld, an accountant in New Zealand, met the VcV inventor and bought the rights to it, convinced that it held the secret to cleaning up manually operated wood stoves.  

The VcV is a valve controlled by the draft generated by the stove when burning, but making it work effectively on a wood stove and then getting that stove certified was a much longer journey than Brian initially expected. There is a huge need for an automated, “idiot proof” stove in New Zealand, but the market is not big enough to justify the costs so Brian set his sights on the North American market. In 2008, he hired Ben Myren to help integrate the VcV valve into a stove. So began one of the most innovative and promising new stove technologies on the US market.

The Promise of the Technology

Simply put, the valves increase or decrease the amount of combustion air entering the stove in response to static pressure changes at any given time, depending on how much combustion air the stove needs. Ben and Brian realized that by combining two VcV valves—one for primary air and one for secondary air—the VcVs could reduce particulate matter (PM) emissions even more, hoping that would be the key to reliably meeting the EPA’s 2020 standards. Brian and Ben were well on their way to building an automated stove without electricity, whereas other automated stove designers were trying to do the same thing with sensors, electronics and computer chips. The marketplace for wood stoves has a lot of folks who dislike the thought of a wood stove that needs electricity to operate. The simplicity of the Flamekeepers’ technology could go a long way to ensuring that the stove would not just operate well in the lab, but also in the hands of the average consumer. And that has been the great challenge of the wood stove since it was invented years ago.

Labeled diagram of on a VCV valve

From the moment the consumer lights the stove, they can shut the door, sit back, and enjoy the heat until it needs to be reloaded, according to Ben Myren. At the time of ignition, the second VcV is engaged, as explained in an illustrative informational video on the model. The Secondary VcV (S VcV), a disc attached to the secondary air inlet, rises and falls relative to static pressure, which increases and decreases with the amount of combustion taking place in the firebox. The S VcV functions all the time and supplies just enough secondary air during a burn to maximize combustion efficiency. Once the static pressure decreases at the end of the burn and more oxygen is needed to increase combustion, the P VcV disc goes down again. 

While most automated stoves and stove prototypes include a temperature sensor to help regulate air flow, thermometers require electronics and a control board which can be to be deceptively complicated and unhelpful to control combustion. Instead, static pressure can be a more reliable way to control what goes on inside the stove and what goes up the stove pipe. Ben says that temperature measurements can often be misleading when determining a stove’s combustion level and oxygen needs. 

When people hear about how the VcV works they think that it is very similar to a bi-metalic coil, which responds to heat, and closes down an air inlet as the stove gets hotter. Bi-metalic coils have been used for decades and a few manufacturers still use them even though they can be unpredictable during the lab certification process. Bi-metalic coils respond to heat, whereas the VcV responds to static pressure. While heat must move from the firebox to the coils, any change in combustion will automatically change the airflow, thus inciting an immediate VcV response. Therefore, Ben credits VcV technology with being far more efficient and simply better than a bi-metalic alternative. 

Advantages of Simplicity 

EPA test stove on scale with test filters 

being preheated in the background.

The simplicity of the VcV comes from the concept of letting the stove’s combustion determine its air flow needs at any given moment, which inherently reduces the operational errors. While the user may set the stove to a burn setting that is too low, the disc technology will not lift until the combustion, as determined by the static pressure, is at a high enough level to safely cut off the air flow. The stove will eventually go to that low setting, but not until the static pressure indicates the time is right. Therefore, consumers have the autonomy to choose the burn level they want, but the stove will only reach that level when it is able to do so cleanly. Ben also added a catalyst to the stove to ensure that it would operate well under 0.5 grams an hour and meet the 2020 EPA cordwood emission limits.

Brian and Ben also recognized and addressed one inherent problem in stove installations all over the US: varying heights of chimneys. The engine of a stove is its chimney, which creates a natural draft to pull both the primary and secondary air into the stove.  But homes can have chimneys anywhere from 10 to 30 feet high, which dramatically impacts combustion, and stove manufacturers have no way to address this as they build to the height of the chimney in the test lab—which is 14 to 16 feet. Brian and Ben realized that they could fit the VcV with heavier or lighter discs so that the stove could work well with any chimney height.  

At least one North America company has applied for licensing of the VcV technology and a stove with the VcV may also be licensed in New Zealand.  

Team Goals

Brian and Ben are no strangers to the Wood Stove Design Challenge. An early prototype of the stove competed in 2014. These prototypes showed great promise and led to the stove being the very first North American wood stove to be tested and certified with cordwood.

Ben Myren lighting a stove at the
2013 Wood Stove Design Challenge

Brian’s son Alister Gauld is also a part owner of the company and will be in Washington in November when the stove will be put through its paces by professional stove technicians to see whether it performs as designed. While Ben and his lab tech Eric Schaefer were just hired by Brian on a daily basis and have no financial stake in the company, they are proud of helping to develop the first non-electric automated stove in North America that can help clean up our air-sheds far better than stoves that can be left to smolder by their owners. The beauty of the VcV is that the owner doesn’t even have to know how it works inside or that it is a groundbreaking stove. From the outside it will look exactly like a traditional stove that will keep the house warm in a power outage.

Contact the team

Brian Gauld

brian@thevcv.com

Ben Myren 
myren.ben@gmail.com

Alistair Gauld
Alistair@harts.co.nz

Eric Schaefer

ericsschaefer82@gmail.com

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.