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Automated Wood Stove Features Entering the Marketplace

Posted by Earth Stove on July 27, 2015 with No Commentsas , , , , ,

This year there are at least half a dozen stoves on the market that have some automated feature that didn’t exist on the market a few years ago. Many of these features help the stove burn somewhat cleaner, and are aiming at a demographic looking for easier operation. It’s still too early to tell how well the automated features work, compared to what they claim to do.

To truly understand the benefits of automation features, whether it be the traditional bi-metal coil or up-and-coming electronic sensors and on-board computers, you need to have side-by-side tests with the automation on and off. Easier said than done.  In Europe fully automated stoves – meaning stoves that you can “load and leave” – and the operator has no or limited control to adjust heat output, are already on the market.  None are on the market in the US as there is no test method to certify them.  The regulatory barrier to potentially far cleaner stoves from entering the US market is being addressed at the Collaborative Stove Design Challenge, where a automated stove testing protocol will be developed and submitted to the EPA.

Three major players in the US stove manufacturing community – Quadrafire, Travis and England Stove Works – now have automated systems to reduce start up and reloading emissions, which is one of the most important emissions issues that needs to be addressed. The Travis system uses electricity and is likely the most powerful of the three, and the other two don’t need electricity.  The England Stove Works stove has integrated their innovation in a very affordably price stove.

The real promise of automation is not to get a hot stove to hit an ultra-low particulate matter number in a lab, but to improve real-world performance by seamlessly optimizing performance throughout the burn cycle, to reducing start-up emissions and reducing emissions from unseasoned wood. EPA certification testing does not attempt to test these attributes of a stove, so stove companies have not had much incentive to invest a lot of time, effort and money to design for that.

In the United Kingdom solid burning heating devices are not classified by their size, i.e. stove vs. boiler, but by whether they are automatic or manual. To achieve a rating to be used in more polluted areas, manually operated stoves must submit lab tests showing 5 burns for each output level because “manually controlled appliances show much higher variation between tests.” Automatic appliances only have to be tested 3 times at each output level.

The chart below shows a wide variety of technology that exists in both stoves and boilers in Europe, but only exists in boilers in the U.S., and much of it is imported from Europe. (Click here for PDF that includes this chart and some discussion of these issues.)

In November 2014, Brookhaven Lab will be testing automated stoves and prototypes at a stove design workshop to see how effective they are. Their designers aspire to be part of a real trend of cleaner, more automated residential wood heating. But can they do it at an affordable price point? And, are consumers ready for them? Here, we will look at stoves with automated features that are already on the market.

A bi-metal coil acts as a heat-
sensitive thermostat which can partially
control the opening and closing of the damper.

1. The bi-metal coil. The oldest form of automation of steel wood stoves is the bi-metal coil which has been used on scores of stove models and is now mostly just used by a few catalytic stove makers, principally Blaze King and Vermont Castings. Some of the new automated features do something similar as the bi-metallic coil, but potentially do it much better. A bi-metal coil is simply a thermostat run by a metal coil that can close a damper down when its really hot, and open it up when its cooler. The stove’s air inlet can still be operated manually, but the bimetal coil will adjust the air inlet further. They tend to not work nearly as well on non-cat stoves, because the temperatures in a non-cat firebox can be more unpredictable, and if the coil shut down the air, or opened it too much, the stove would operate poorly – and critically – it adds far too much uncertainty in passing the EPA emissions certification test.

The rotating trigger mechanism in the
Smartstove Collection by Englander
reduces air flow once the stove is hot.

2. The next three stoves – the England Smartstove, the Quadrafire and the Travis – all use different automated approaches to starting the fire quicker and with fewer emissions. After the start-up period, the stove operates like any other. The Smartstove by England Stove Works was displayed at the Wood Stove Decathlon on the National Mall in 2013, but it was still being certified by the EPA so it was not part of the competition. The stove has an “automatic air setback mechanism” which is a primary air control with a rotating trigger which controls the opening and closing of air vents. When the operator starts a fire, they gives the stove maximum air and sets the trigger. When the stove gets hot enough, the trigger releases and primary air is reduced, while still providing ample secondary air.

Quadrafire’s Explorer 2 Start-Up air
control helps give the stove more
air in the first 25 minutes.

3. Another recent arrival on the market is Quadrafire’s Explorer II, which appears to provide similar automation. The website says “Automatic Combustion Control-provides the fire with air when it is most needed-leading to longer burns.” A marketing video says the operation is so easy that all you have to do is “load the wood, light the fire and walk away.” According to the installation manual, ACC is basically a timer which the operator must manually initiate with a control mechanism. Essentially, it opens the front air channel which allows air to enter for 25 minutes before closing. Once the front air channel is closed, manual controls are used to deliver preheated air to the top of the firebox to burn the rest of the unburned gases in the remaining three combustion zones.The Alliance confirmed with a company representative that no sensors are used or needed after the operator sets the timed control mechanism.

The slider on the Cape Cod
adjusts the rate of burns.

4. Travis industries Hybrid-Fire technology™ developed an automated “Greenstart” which shoots 1,400 degree air into the firebox for 15 minutes to start your fire, or when you reload. The Greenstart can significantly reduce start-up emissions, and emissions during reloading on a low temperature bed of coals, by jumpstarting the start-up process and heating the wood up faster than it would with newspaper. After the first 15 minutes, the stove has no automated features, but some of the Travis stoves that use catalysts are among the cleanest in the industry. The Travis Cape Cod stove won second prize in the Wood Stove Decathlon.

5. The Nestor Martin’s Efel has an “automatic mode” that can keep the room at a desired temperature. Or in timer mode, it can adjust the room temperature at a pre-set time. The stoves uses a simple ambient air thermostat in a remote control device that you can operate from the couch or anywhere nearby. If you don’t use it in automatic mode, the remote control allows the user to adjust the intensity of the fire just as you would with a manual air control. One of the key things that distinguishes this Efel from truly automated stoves is that there are no sensors in the stove that can prevent the stove from smoldering or override an adjustment by the operator that would make the fire smolder.

HWAM’s Autopilot technology uses
sensors, along with a bi-metal spring to
regulate combustion temperatures.

6. The final two stoves are more fully automated stoves and are on the market in Europe, but not in the US. Danish company HWAM, whose automation will be third-party tested and assessed at Brookhaven Lab in November, has integrated a new patented system-Autopilot. Along with the Austrian Rikatronic, described below, the Hwam is one of the most advanced and fully automated stoves in Europe. HWAM 3630 IHS features a control system that electronically measures combustion conditions through the use of a lambda oxygen sensor and a thermocouple. An onboard computer then allocates combustion air through three separate valves to help the consumer achieve the same results at home that are obtained in test labs under ideal conditions. According to the Danish Technological institute, HWAM stoves with this system are 17% more efficient and produce 40% more heat.

Rikatronic has a microprocessor-controlled
motor and a flame temperature sensor
which drives the RLS air distribution system.
The light tells you the optimal time to reload.
By pressing the button, the stove knows
 it has fresh wood to handle. 

7. There are numerous versions of the Rikatronic wood heater system. The Fox II stove features manual and automatic control settings. In manual mode the air distribution can be controlled in each combustion phase-even in the event of a power outage. Automation in Rikatronic technology works with a microprocessor-controlled motor and flame temperature sensor which operates the RLS air distribution system. Airflow in each of the 5 combustion zones is effectively adjusted for efficient burn. A red light indicates the optimal time to reload the stove. You can set the room temperature you want and once the required room temperature is reached, you can activate the eco mode by pressing the Rikatronic³ button. This causes the air supply to be optimally controlled to maintain the fire for as long as possible, without smoldering, and to leave behind as little ash as possible. Power consumption is 2 – 4 watts.

The first five stoves described here represent American innovations that can partially reduce excessive wood smoke, while the last 2 stove from Europe represents a more holistic approach that can help reduce emission not just in the start up, but throughout the burn cycle.  They are all still relatively new technologies and we are likely to see more companies improve upon them in coming years.


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

Posted by Earth Stove on July 24, 2015 with No Commentsas , , , , , , ,
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: 

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Rookie Wood Stove Makers Get Highest Score in Design Workshop

Posted by Earth Stove on July 22, 2015 with No Commentsas , , , , , , ,

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.


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Old-timey wood stoves need to get new-timey if we really want to make use of them

Posted by Earth Stove on July 19, 2015 with No Commentsas , , , , , , ,

Monday, December 8, 2014Nashua Telegraphby David Brooks Tom Butcher from Brookhaven Lab,second from right, tests an automated stove from New Zealand. Ben Myren,left, did R&D work on it. I don’t think very hard when I light up the old wood-burning stove in my basement. Turns out, that might be a problem. “Combustion technology is incredibly complex. […]

EPA Declines to Release Efficiency Data on Wood Pellet Stoves

Posted by Earth Stove on July 18, 2015 with No Commentsas , , , , , ,

On Thursday, the EPA said it would not release efficiency data on pellet stoves, one of the most popular renewable energy technologies in American homes.  About one million homes use pellet stoves in the United States, yet none of the major stove manufacturers disclose the tested efficiency of their products.  The EPA recently set stricter […]

Wood and Pellet Stove Tax Credit Extended through Dec. 31, 2014

Posted by Earth Stove on July 16, 2015 with No Commentsas , , , , , , ,

Stove manufacturers routinely claim75% efficiency to be eligible for thetax credit, even when stoves are farbelow 75%.  The average wood andpellet stove may be around 70%. Updated on December 16, 2014 – A short term extension of the $ 300 federal tax credit to purchase a new wood or pellet stove was signed into law by […]

20 Stunning Wood Fired Hot Tubs from Around the World

Posted by Earth Stove on July 14, 2015 with No Commentsas , , , , , ,

Wood fired baths are an ancient tradition, dating back at least to Roman times when baths called hypocausts were built by running hot flue gases under a stone tub.  Those Roman tubs were also off the grid, as are these.  Some are quirky, some romantic, some practical and some just downright hedonistic.  Which is your […]

How to claim the $300 stove tax credit

Posted by Earth Stove on July 13, 2015 with No Commentsas , , ,

President Obama signed into a law a package of tax credits including the one for wood and pellet stoves.  The stove credit is for $ 300 for stoves purchased between Jan. 1, 2014 and Dec. 31 2014, making it almost entirely a retroactive “incentive.” To take the credit, taxpayers need to use IRS Form 5695. […]

As Utah debates seasonal stove ban, Salt Lake County adopts stricter rules

Posted by Earth Stove on July 10, 2015 with No Commentsas , , , , , , , , ,

The proposed state seasonalban affects 75% of the Utahpopulation.  As Utahns debate a seemingly doomed proposal to ban seasonal stove use,  Utah’s most populous county enacted its own rules banning stove use on both mandatory and voluntary air actions days as of Jan. 1, 2016. In other counties, voluntary air action days continue to be […]

Flurry of Lobbying on Furnaces and Test Methods on Eve of New Stove Rules

Posted by Earth Stove on July 7, 2015 with No Commentsas , , , , , ,

The Office of Management and Budgetis in the Old Executive Office Buildingnext the White House. Sources confirmed that the EPA is set to announce the new wood heater rules on Tuesday, February 3rd, the court ordered date.  After years of debate and anticipation about cost impacts and emission standards for stoves and outdoor boilers, the […]