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.
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.
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.
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.
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.|
|Taylor Myers and Ryan
Fisher with the Mulciber,
the highest ranking stove.
|The Wittus team with the Twinfire.|
|The VcV, wired to monitor
temperature in key spots
|The ClearStak team with the
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 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.
A Comparison of Eligibility Requirements for Stoves Incentive Programs
October 31, 2014
* This efficiency level was not measured or enforced in any meaningful way.
** This program only allows upgrades from lower to higher efficiency using the EPA default numbers.
*** MD and ME allow for professional inspection in lieu of professional installation.
**** No efficiency minimum; higher efficiency stoves get higher rebate amounts.
Monday, December 8, 2014
by 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. Numerous chemical engineers, combustion engineers, mechanical engineers around the world are constantly trying to understand the intricacies associated with combustion. It is absolutely not what you and I would think – just light a match … especially when you want to get clean combustion and use wood efficiently,” said Rob Rizzo, manager of the Renewable Thermal Program for the Massachusetts Department of Energy Resources.
Rizzo was among the organizers of the 2014 Stove Design Workshop held in November at Brookhaven National Laboratory in New York, the latest in a number of attempts to add some high-tech wizardry to that staple of New England life, the wood stove. (For details, see forgreenheat.blogspot.com/2014/11/rookie-wood-stove-makers-get-highest.html)
Why tinker with something as well-established as wood stoves?
Because, like me, most people don’t think too hard when using them, which makes them inefficient and polluting.
We use green wood or wet wood, and we fiddle with the damper in the wrong way, causing partial combustion and thus more pollution.
The Stove Design Workshop, like a national Stove Design Challenge in 2013 that featured two New Hampshire entries, wants to find technology that can better cope with our stupidity.
The five finalists in the design workshop used a variety of techniques to work around people, including oxygen sensors that control fuel-to-air ratio, a common emission-control technique in cars, and a New Zealand stove that has a “barometrically operated variable choke venturi tube” to control the amount of combustion air entering a stove, particularly at lower burn rates.
“The whole concept with the design challenge is to come up with solid-wood stove that eliminates the human interface. Basically hit a start button and walk away; that is the concept we’re aiming at,” he said.
This already happens with pellet stoves, of course, which is why pellets has led a wood-burning renaissance for building heat.
The drawback is that they burn pellets made of compressed sawdust rather than the wood I can snag for free off my property, especially after the Thanksgiving snowstorm knocked down so many big limbs.
The lure of free fuel means that a lot of people still burn non-pelletized wood for some or all of their heat, although it’s not clear how many.
I have never been able to find good data about people who use cordwood (a.k.a. “roundwood”) as their principal heat source, partly because it’s hard to pin down. I, for example, use it only as a minor supplement of the pellet stove in the living room and our oil-fired furnace.
Rizzo said he didn’t know any data either, but he said that wood stoves remain important, especially in western Massachusetts.
Just as important as convenience is cleanliness. Wood stoves can produce a lot of pollution, particularly fine-particle soot, that is a health hazard. This is particularly a problem around Keene, which has a lot of wood-burning stoves and a geography that traps air in certain weather conditions.
New Hampshire has used rebates to get people to turn in their old stoves for cleaner versions, although with limited success.
But those cleaner stoves aren’t all that great; they’re little more than old stoves with catalytic converters in the stovepipe. Hence the push to build a better mousetrap, so to speak.
“It’s exciting to see new ideas coming forward. We have some educated guesses but we need to do better,” Rizzo said.
“We need to collect more data, about efficiency, emissions, consumption volumes, and also source of wood, sustainability of wood source, quality of wood source. Because rural America is always going to be burning round wood.”
|Stove manufacturers routinely claim
75% efficiency to be eligible for the
tax credit, even when stoves are far
below 75%. The average wood and
pellet 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 President Obama on Dec. 19, after having passed the House and the Senate.
The law extends a host of tax provision through Dec. 31 2014, making it almost entirely a retroactive tax credit. A two-year deal that would have extended selected tax credits through Dec. 21, 2015 fell through.
The tax credit, which started out at $ 1,500 applied to all stoves that were at least 75% efficient. The stove industry used a loophole to help ensure that all EPA certified wood stoves and all pellet stoves could claim to be 75% efficient. As a result, many consumers are unwittingly buying stoves that may be less than 60% efficient, or even less than 50% efficient. Pellet stoves in particular can be very low efficiency, saddling consumers with unnecessarily high pellet fuel bills.
Of the hundreds of stove models on the market, manufacturers have only disclosed actual, third party verified efficiencies for about 20 models and they are listed here. Blaze King is the only stove manufacturer who discloses actual efficiencies for all their models. To date, all the major pellet stove manufacturers have refused to disclose any actual efficiencies. Seraph Industries, a very small pellet stove maker, has disclosed their efficiencies and they are quite high.