Thursday, October 23, 2014

Automated Wood Stoves Entering the Marketplace

Updated: October 25, 2016: There are at least a half dozen stoves on the market that are fully automated or have some automated features that are gaining traction.  Many of these features help the stove burn cleaner and are aiming at a demographic looking for easier operation.

We define a fully automated wood stove as one where the consumer can "load and leave" and not have to worry about adjusting the air flow to get an optimum burn.  On all traditional wood stoves, the consumer must adjust one or two levers that control the air.  Often consumers don't do this well, resulting in poor combustion that fails to maximize efficiency or minimize smoke.  Thus, even a brand new wood stove that performed very well in the test lab can perform very poorly in the hands of an inexperienced or inattentive operator.

The Adventure series stoves were the
first American-made automated stove.
There are now two fully automated stoves on the market.  The first is the Adventure stove by Quadrafire, a large, mainstream manufacturer.  The other is the Catalyst by MF Fire, a very small start-up.  Both use electronic sensors to monitor combustion and adjust air flow as needed.  Both stoves need to be plugged in for optimal performance, but will still work if the power goes out.

MF Fire, a small Maryland
company is trying to disrupt
traditional stove technology.
The Adventure series stoves and the Catalyst are great options for consumers who want to minimize smoke from their stoves and enjoy the ease of automation.  With these two stoves you can leave for the day or go to sleep at night knowing that your stove won't be smoldering away, which is one of the leading causes of excessive pollution from both old and new wood stoves.

The real promise of automation is not to get a hot stove to hit an ultra-low particulate matter number in a test lab, but to improve real-world results by seamlessly optimizing performance throughout the burn cycle, reducing start-up emissions, and even reducing emissions from unseasoned wood.  EPA certification testing does not test for real-world performance, and incentive programs do not yet recognize the positive attributes of automated or semi-automated stoves, so stove companies have not had much incentive to invest a lot of time, effort, and money in developing them.

In Europe, fully automated stoves have been on the market for some time and are beginning to gain wider recognition from consumers and air agencies.  Two companies have advanced automatic stoves that unfortunately are not available on the US market: The Danish company Hwam, who developed the Autopilot IHS, and Austria's Rika, who developed the Rikatronic.  In the United Kingdom, solid burning heating devices are classified 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. (Click here for PDF that includes this chart and some discussion of these issues.)

In 2013 and 2014, the Alliance for Green Heat partnered with Brookhaven National Lab to assess and test automated stoves and prototypes at stove design competitions.  Their designers aspire to be part of a real trend towards cleaner, more automated residential wood heating.  But can they do it at an affordable price point?  And, are consumers ready for them?  Here, we look at stoves with partially automated features that are already on the market.

Partial automation solutions

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. One of the oldest forms 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.  A bi-metal coil is simply a thermostat run by a metal coil that can close a damper down when it's really hot, and open it up when it's 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 shuts down the air, or opens it too much, the stove would operate poorly, which adds far too much uncertainty in passing the EPA emissions certification test. A new, more sophisticated version of this technology is the VcV valve developed by a Australian company and Ben Myren.

The rotating trigger mechanism in the
Smartstove Collection by Englander
reduces air flow once the stove is hot.
2. Better start-up: Three companies have features that help start-up: the England Stove Works"Smartstove", the Quadrafire "Automatic Combustion Control" and the Travis "Green Start."  They 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.

Quadrafire's Explorer 2 Start-Up air
control helps give the stove more
air in the first 25 minutes.
Another recent arrival on the market is Quadrafire’s Explorer II, which provides a similar automated start-up.  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 slider on the Cape Cod
adjusts the rate of burns.
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.

3. Remote operation. A remote control device does not necessarily provide any automation to the air flow.  It can just allow you to do it manually from the couch.  However, some like the Nestor Martin’s Efel has a partial “automatic mode” that can keep the room at a desired temperature.  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.
Fully automated stove on the European market

1. The final two stoves are more fully automated stoves and are on the market in Europe, but not in the US.  Danish company HWAM 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. 
2. 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.

1 comment:

  1. 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 ...