Testing Observations at the Wood Stove Decathlon

By Norbert Senf

The Wood Stove Decathlon was a historic event. It was the first ever attempt to gather a collection of stoves in the field (literally, in this case) and test them for particulate matter (PM) emissions.

Norbert Senf, right, with Neils Wittus,
center, and John Ackerly

For something untried until now, the side-by-side field-testing can claim several firsts. 

It successfully compared stoves within a surprising range of categories including masonry heaters as well as retrofit kits. The project was a success not only as a media event but also in advancing the real world testing of wood burning stoves.

Cordwood is an extremely complicated fuel to get repeatable data with because it is so inherently variable. To add to the challenge, PM is particularly difficult to measure, even in a laboratory. While the test results from the Decathlon were not sufficient to provide PM numbers that allowed comparison with EPA numbers, they did allow a ranking of the stoves against each other. This is a substantial achievement in itself.

PM is the wood fuel pollutant of greatest interest since it causes the most public health concerns. Carbon monoxide (CO) is another pollutant.  It is created by incomplete combustion like PM, but it is much easier to measure. It is generally not considered a health hazard in low atmospheric concentrations outside of densely trafficked urban areas, and eventually oxidizes to CO2 on its own.

Due to new wood burning emissions regulations in Germany, two new portable instruments for measuring PM in the field were recently developed there. Fortunately, this happened just in time for the Decathlon to try them out. The instruments are limited to the 15-minute test cycle that is mandated in the German regulation, and therefore can only measure what happens during a portion of the burn. Measuring an entire test cycle will certainly be a goal for future Decathlons.

Common wisdom holds that low carbon monoxide (CO) emissions, which are easy to measure, will also ensure low PM, which is difficult to measure. The contest results did not bear this out. The stove with the lowest PM had the second highest CO. For the stove with the lowest CO, there were 4 stoves with lower PM. To be sure, the data set is limited. The 15-minute test window did not allow for average values to be measured over the burn of an entire fuel load.

Repeatability is one of the most important measures of data quality. Since each stove in the Decathlon received two (in theory) identical test runs, we can get a brief glimpse here, as well. Discarding obvious outliers, we see a coefficient of variation (CV) in repeat runs of 43% on PM, 40% on CO and 7% on efficiency. This compares favorably with EPA inter-laboratory repeatability studies, where the two stoves with the largest data sets both came in at 44% CV on PM. For masonry heaters, an MHA (Masonry Heater Association) laboratory study on repeatability with dimensional lumber fuel cribs yielded 10% CV on PM, 1.5% on CO, and 0.26% on efficiency.

The repeatability metric provides a useful baseline for judging data quality in future decathlons. There is an ongoing fueling protocol debate in the testing community between the repeatability achievable with fuel cribs, and the real world randomness of cordwood. EPA testing is currently done with cribs. To get a repeatable EPA cordwood number may require running a large number of (expensive) laboratory test runs and taking an average. To date, very little work has been done to provide data for either side of the debate.

All in all, the Wood Stove Decathlon was a great effort towards advancing our knowledge about how wood stove emissions compare in the real world. This was particularly valuable to see for different classes of appliances with no commonly defined EPA testing methods.

Valuable lessons and insights were had for designing a future challenge. Seeing the complex testing issues play out in real life was a unique educational opportunity for contestants, organizers, judges, regulators and the testing community itself.

Norbert Senf was one of the ten judges at the Wood Stove Decathlon. He joined early efforts to write codes and standards, and was a founding member of the Masonry Heater Association of North America (MHA). He currently chairs the MHA Technical Committee.

The Costs of Running the Wood Stove Design Challenge

From inception, to announcement, to selecting the teams, to holding the Wood Stove Decathlon, the Wood Stove Design Challenge unfolded over a 2-year period.  The total cost came to about $200,000 over those 2 years, and $157,000 of that was in 2013.

In 2013, the Wood Stove Design Challenge cost about $157,000 in direct cash expenses.  In addition, tangible, in-kind donations that we would have otherwise had to pay for accounted for more than $50,000.  The largest budget items were salaries ($39,000), the tent ($33,000), prize money ($30,000) and testing ($23,000).

Overall, our largest funders were NYSERDA ($47,000), the Osprey Foundation ($40,000), and the District of Columbia ($10,000).  In addition, we had extremely large in-kind support from ICC Chimney, which was probably in the $20,000 range, the Chimney Safety Institute of America, the mobile particulate sampling companies Wohler and Testo, Brookhaven National Lab, Popular Mechanics, Travis Industries and others.

One reason the Alliance was able to hold this competition for a total cost of $200,000 is that salaries were low, and we kept many expenses to a bare minimum.  If the Alliance were to do another similar Design Challenge, we would have to plan for a total of about $300,000 over a two year period, and use at least $200,000 of that for the year of the event.

2013 Decathlon Costs Salaries  (Jan. 1 - Nov. 30, 2013)
President (50%)	$23,000
Research Fellow	$3,200
Research Fellow	$1,875
Web/IT	$1,000
WSDC assistant  (50%)	$6,000
Taxes, benefits & payroll (50%)	$4,500
Sub-total	$39,575
Prizes
First prize	$25,000
Second prize	$5,000
Sub-total	$30,000
Contractors
Brookhaven National Lab	$23,000
Media consultant	$2,500
Sub-total	$25,500
Event costs
NPS cost recovery deposit	$1,800
NPS police	$2,244
Tent, generator, tables, chairs, etc.	$33,117
Portable restrooms	$535
Signs	$690
Add’l liability insurance	$809
Lunches/food	$950
Local Travel	$200
Judges hotel	$2,300
Transport	$1,500
U-Haul Rental & scaffolding	$680
Misc. event supplies	$3,500
Sub-total	$48,325
Other costs
Jan. Brookhaven Judges Meeting	$3,000
Supplies	$1,000
Copying/printing	$600
Rent, phones, etc. (50%)	$7,450
Misc.	$1,600
Sub-total	$13,650
Total 2013  Decathlon expenses	$157,050

EPA Inaction and an Industry Faction Are Holding us Back

On October 9, seven states and five environmental groups sued the EPA for failure to promulgate new emission standards for residential wood heaters.  If EPA had done its job years ago, as it was obligated to do under the Clean Air Act, the stove industry and consumers would be far better off today.

An example of the size of wood that
can be loaded in an outdoor boiler.

Instead, we have all been dragged down by an agency that has not taken residential wood heating seriously enough.  And some of the key outdoor wood boiler manufacturers have opposed reasonable state and local regulations on their products, leading to controversies with state air agencies and environmental groups that could be avoided.

The EPA did develop a voluntary program to help regulate outdoor wood boilers and states started adopting that in 2007.  Northeastern states, Indiana and Pennsylvania used that and Washington and Oregon effectively banned them outright. The states where outdoor boilers are most popular like Michigan, Minnesota and Wisconsin, bowed to industry pressure and did not adopt the EPA voluntary program to protect their residents from these polluting devices. The voluntary program thus failed to protect citizens in most states.

Privately, most people in the wood heating industry agree that outdoor wood boilers have given the entire wood burning community a black eye.  Those devices, particularly concentrated in the Great Lakes region, are contributing towards a negative view of wood heating at a time when the public and policymakers could have been developing better technology, better policies and better regulations.

But some outdoor boiler manufacturers, such as Central Boiler, while officially saying that they want to be regulated, have fought in state after state to keep selling old-fashioned polluting boilers.  And now they are fighting the EPA over what they feel are far too burdensome regulations.

Meanwhile, in Western Europe, where such technologies are rare or don’t exist at all, governments are vigorously supporting wood heat technologies through rebates and incentives. In Eastern Europe, authorties are struggling with coal heating, and often lack the political willpower and economic resources to address highly polluting classes of coal heaters.

One reason some Western European countries have been able to incentivize wood heating is that almost every country has a green label to identify the cleanest and most efficient stoves and boilers, which gives lawmakers the ability to give rebates and incentives to the best products.  In the US, there is no Energy Star program for wood heaters and industry put the brakes on a 2013 Washington state initiative to create a green label program.  Once we have a green label program, I think we will start to see the tide turn, with states beginning to shift consumer purchases towards the cleanest and most efficient wood and pellet stoves and pellet boilers.

In polluted urban areas, like Denver and Montreal and parts of the Pacific Northwest, we are likely to see more bans on the new installation of wood stoves and a shift toward pellet stoves.  This may not be ideal, but it is also a reasonable response.  Cordwood isn’t an appropriate energy solution for lots of people in densely inhabited urban areas, particularly those that experience weather inversions, when the technology is so dependent on operators using seasoned wood and giving the appliance enough air. 

In coming months, our community will be increasingly in the public spotlight as these lawsuits against the EPA get underway and we have a 90-day public comment period over the EPA’s long awaited regulations.  We are in an era where technology can make wood and pellet stoves far cleaner, while still being affordable.  Many of these stoves were on display the National Mall at the Wood Stove Decathlon in mid-November.  There, policy makers saw what stove engineers are working on and are capable of creating.  They saw first hand that wood heat technology is developing fast and can be a vital part of our renewable energy future, not just a relic of the past.

Outdoor wood boilers are the most polluting class of residential wood heaters on the market today, and as such they will be the most in the news.  But the EPA regulations are still vital in requiring both wood and pellet stoves to become cleaner and more efficient.  Once that happens, public opinion can begin to shift in a more favorable way towards deploying modern wood and pellet technology to reduce our reliance on fossil fuel, and shrinking the divide between US and European policy.

A Brief Analysis of Stoves at the Wood Stove Decathlon

The danger of naming a winner at a competition like this is that the many achievements of the non-winners receive little focus. Here we list the top 6 stoves in each category: Overall Performance, Innovation, Affordability, Particulate Matter Emissions, Efficiency, Market Appeal and Carbon Monoxide Emissions. We try to note the trends between stove classes and the stand out performances of stoves that did not win prizes.

The scoring was done by nine judges. Three of the areas -- PM emissions, efficiency and CO emissions -- were scored only by the testing equipment, meaning the judges had no discretion to change the grade of the stoves for those three areas. Each stove was tested at least two times. For more on scoring see: http://forgreenheat.blogspot.com/2013/11/how-stoves-are-scored.html

OVERALL

1) Woodstock Soapstone
2) Travis
2) Wittus
4) Intercontinental
4) Ecolabel Tile Stove
4) Hwam

Woodstock Soapstone

The Grand prize went to a finely tuned, naturally drafting catalytic wood stove without any electronic controls. In fact, the winning Woodstock Soapstone hybrid is very similar to the design of one of the second place stoves, the Cape Cod by Travis.  Wittus is also a naturally drafting steel stove that has a unique downdraft burn into a lower chamber. Technically, this is a non-cat stove, but its design has little in common with the traditional non-cat stoves on the market today.

The fourth and fifth top overall stoves were masonry stoves, and while they did not take home any prizes (due to their high pricetags and perceived lack of innovation, as the underlying designs and principles are so old), it is clear that they performed extremely well overall.  Two of the top 6 stoves overall had electronic sensors and computers.

INNOVATION

HWAM

1) HWAM
2) Wittus
3) IntensiFire
4) Woodstock Soapstone
5) Mulciber
6) Travis

The two top innovation scores went to a Danish stove and a German stove.  First place went to the Hwam Autopilot stove with its onboard computer and oxygen sensor. If testing lasted many hours, not just 15 minutes, these features would have likely helped the stove receive higher overall points. The stove also alerts the homeowner to the optimum time to reload and how much wood to reload. There is no control on the stove for users to adjust; they can simply load it and leave, knowing that the stove will do the rest.

The IntensiFire claimed the number 3 spot because it is a relatively simple, elegant solution for old, uncertified stoves. And Mulciber, the University of Maryland stove, took 5th place with a pressurized, fan driven combustion chamber and co-axial stack.

AFFORDABILITY


1) Woodstock Soapstone
2) Walker Stoves
2) IntensiFire
4) SmartStove
5) Travis
6) Intercontinental

Tom Morrissey’s hybrid Ideal Steel from Woodstock Soapstone is clearly a great value given its size, BTU output and performance. The company has committed to retail it for $2,000 and hopefully that doesn’t mean it’s a loss leader for the company. The Walker stove, a hybrid rocket stove that can be made with more thermal mass, also impressed the judges and has lots of potential to get on the market for less than $2,000.

This is the one area that the SmartStove appears in the top 6 rankings for its control system that can automate virtually any non-catalytic stove, significantly reducing its overall emissions for about $200 on top of the stove price.

PARTICULATE MATTER EMISSIONS

Mulciber

1) Mulciber
2) Intercontinental
3) Woodstock Soapstone
4) Wittus
5) Ecolabel Tile Stove
6) Travis

In the emissions category, seen by many experts as the key goal of high performing stoves, the underdog team from the University of Maryland took a surprising first place with a least one run where the PM 2.5 particulates were so low they were barely measurable. The students used a home-made catalyst and a unique self-cleaning particulate trap to achieve these results.

Again, the masonry stoves did very well along with the other catalytic stoves. The Travis Cape Cod has the lowest PM measurement of any certified wood stove at .45 grams an hour, one tenth of the more stringent Washington State limit, when tested with dimensional lumber.

EFFICIENCY

1) Wittus
2) Tulikivi
3) Ecolabel Tile Stove
4) Mulciber
5) Intercontinental
6) IntensiFire

Wittus

All the masonry stoves performed extremely well in the efficiency category, even though the top spot went to the downdrafting German Wittus stove that has a relatively small firebox. Since efficiency is measured using a stack heat loss method, the masonry stoves could lose most of their heat to the masonry mass before exiting the chimney. The University of Maryland’s Mulciber stove often had stack temperatures around 200 degrees, half that of some of the other stoves.

What is surprising here is that neither the Woodstock Soapstone nor the Travis placed in the top 6, even though they have 3rd party efficiency testing that rates them around 82% in the EPA wood stove list. This could mean that these other stoves could hit efficiencies even higher, around 84 or 85% using the EPA’s B415.1 test, or it may simply mean that the efficiency testing and methodology at the Decathlon favored masonry stoves or was not good enough to measure very minor differences between very efficient stoves.

Travis

MARKET APPEAL

1) Travis
2) Wittus
3) Woodstock Soapstone
4) Ecolabel Tile Stove
5) Hwam
6) Tulikivi

The more polished stoves that were already in production won out here, with the catalytic and masonry stoves vying again for top spots. The judges appeared to vote based on what they thought was likely to appeal to the average consumer based on aesthetics, without regard to price.

CARBON MONOXIDE EMISSIONS

1) Travis
2) Woodstock Soapstone
3) Tulikivi
4) Tile Stove
5) Intercontinental
6) IntensiFire

Again, this category was a battle between the catalytic stoves and the masonry stoves, with the catalytic stoves taking the top spots. The University of Maryland team also used a catalyst but insufficient air on at least one run hurt their CO levels. It is noteworthy that the IntensiFire made it into the top 6, given that it used a very simple, affordable change to an old, uncertified stove.

Woodstock Soapstone, Travis and Wittus Win the Wood Stove Decathlon

FOR IMMEDIATE RELEASE: November 20, 2013

Woodstock Soapstone, Travis and Wittus    Win the Wood Stove Decathlon

Catalytic, Masonry and Electronically Controlled Stoves Show High Results in Testing

Washington D.C. – In an international competition to significantly reduce pollution from wood stoves on the National Mall, one finalist, Woodstock Soapstone of New Hampshire, won first prize of $25,000. Two other teams, Travis of Washington State and Wittus of New York, were awarded $5,000 each. The teams were recognized for all around performance in efficiency and emissions, affordability, consumer appeal and innovation. Members of Congress Dan Benishek (R-MI), Chris Van Hollen (D-MD), Jared Huffman (D-CA), Paul Tonko (D-NY) took part in the awards ceremony.

The Woodstock Soapstone Team

In accepting the first prize of $25,000, Woodstock Soapstone owner Tom Morrissey announced that he was giving part of the prize money to two other teams - Walker Stove and Intensi-Fire - who had come to the Decathlon on a shoestring and needed funds for their work. Travis donated their $5,000 to the Alliance for Green Heat to help pay for the expenses of the Decathlon.

“These award-winning technologies are part of the solution for millions of Americans to reduce their reliance on fossil heating fuels,” said John Ackerly Founder and President of the Alliance for Green Heat, which organized the Wood Stove Decathlon. "We'd like to thank all the teams for participating and contributing to an ongoing educational effort to help the US government appreciate the potential of cleaner and more efficient wood heating," Ackerly added.

Competitors represented a wide range of wood stove technologies. Two of the top three winners were catalytic hybrid stoves. While the three masonry stoves did not take home prizes, they had some of the highest scores in efficiency and cleanliness.  

The Wittus Twin Fire, that was tied for second prize overall, scored highest in the efficiency category. Travis’s Cape Cod Hybrid, which also tied for second overall, scored highest in consumer appeal and for low carbon monoxide. The Hwam 3630 IHS scored highest in innovation, with its oxygen sensor and control device that alerted the consumer when and how much wood to reload. The Woodstock Soapstone, which won the Grand Prize, also won in the affordability category. And the University of Maryland’s stove, the Mulciber, won in the lowest particulate matter category. 

The overall ranking of stoves was:

WOODSTOCK SOAPSTONE		1
TRAVIS		2
WITTUS		2
INTER-CONTINENTAL		3
TILE STOVE		3
HWAM		3
TULIKIVI		4
INTENSI-FIRE		5
MULCIBER		5
WALKER STOVES		6
SMART STOVE		7
KIMBERLY		8

The competition differed from EPA tests of wood stoves in several key respects to more closely resemble how consumers use stoves. First, the stoves in the competition were tested using cordwood instead of 2x4s and 4x4s. Second, technicians loaded stoves with 12 pounds of wood per cubic foot of firebox space for the first round of testing, whereas EPA only uses 7 pounds of wood per cubic foot.

Two of the stoves made small amounts of electricity and four had electronic control systems. More detailed analysis will be forthcoming. The primary funders of the Wood Stove Decathlon are NYSERDA, the Osprey Foundation, the District of Columbia Urban Forestry Administration, the US Forest Service, the West Penn Power Sustainable Energy Fund and the Arbolito Foundation. 

# # #

The Alliance for Green Heat is an independent non-profit that promotes high-efficiency wood heating as a low-carbon, sustainable and affordable heating solution. The Alliance seeks to make wood heat a cleaner and more efficient renewable energy option, particularly for those who cannot afford fossil fuel heat.