A Test Protocol for Automated Wood Stoves

Tom Butcher of Brookhaven Lab using
the protocol on the Wittus stove.
Photo: Kittner for Brookhaven Lab.

The fueling protocol used at the Wood Stove Design challenge is like no other.  Instead of filling a pre-heated firebox with a consistent amount of wood, setting it on a single air setting and letting it burn until the fuel is gone, as the EPA does for certification tests, we took a radically different approach.  

We wanted a fueling protocol that included features of how stove operators likely use their stoves, which includes starting from a cold start and reloading several times. But we went beyond that to mimic extreme operator behavior, by loading the stove full of wood and then turning the heat/air setting all the way down, which can put a stove into a temporary or long term dirty, smolder mode.  Our goal was to evaluate whether an automated stove could outsmart its operator - or the lab technicians running the protocol and run cleanly.  

Getting an overnight burn at a low air setting without putting the stove into a short or long smolder mode is something that many good stove operators can do, and good stove design helps them.  Our protocol sought to mimic some extreme modes operators may encounter with their stoves to see how automation can mitigate negative consequences of those extremes . 

The protocol was provided to the teams two months in advance, enough time to make sure that the

Lisa Rector, demonstrating the full
IDC protocol at the Wood Stove
Design Challenge for EPA staff.
Photo, Kittner for Brookhaven National Lab

protocol worked and competitors could request modification but not so much time that it would allow competitors to design directly to the protocol. The goal was  “creating a single test run that incorporates typical use scenarios and incorporates variability both in the operational modes and the fuel use patterns.”  The protocol was not intended to be a predictor of actual overall field performance (as other test method attempt to do), mainly because of the abbreviated nature of the protocol.  Rather, key operational factors were included to evaluate the automated response of a particular stove.

The outlines and purpose of the protocol was discussed by the Organizing Committee of the Challenge and the intensive process of writing it and testing it a lab was done by NESCAUM and Hearthlab Solutions, with assistance from Brookhaven National Lab and funding and support from NYSERDA.  

The protocol was a short, three-hour protocol that includes several reloads, as operators normally reload their stoves during the first three hours.  We are not aware of any other protocol that includes reloads.  We chose three hours because we had numerous stoves that had to be tested multiple times during a five-day period.  If testing crews could complete three tests of each stove, it would enable us to analyze the reproducibility and repeatability of our test results.  

AGH prepared the fuel loads for each
stove the week before the event.
Photo: AGH

Our working proposition was that stoves engineered with automated controls and appropriate and robust response techniques produce more repeatable results than manually operated stoves.  It is still too soon to tell whether these stoves had better repeatability than manually operated stoves.  Data will become available in early 2019 to help us answer these questions.  For background on the testing protocols used at the Wood Stove Design Challenge, click here. For initial results of the Challenge, click here.

We hope that elements of this protocol help EPA, other agencies and industry think through the process of what test methods should try to achieve and how.

Wood Stove Design Challenge – Automated Stove Competition – Stove X

Stove:                          Stove X

Dimensions:                XL x XH x XW

Volume:                       Xft³

Fuel species – beech and/or maple 

Fuel length: X

Start-up 

Fuel load density 4 lb/ft³

Amount of kindling: total amount determined by fuel load calculator  (kindling = 8-10 pieces of kindling weighs 1 lb., length must be at least 50% of test fuel length).

Amount of starter fuel: X lbs. +/- 5% - weight of each piece scaled to stove by fuel load calculator

1.    Stove is empty – no ashes

2.    Amount of paper for starter – 6 full sheets

3.    Amount of kindling is x lbs.

4.    Amount of starter fuel is x lbs.

5.    Fuel loading pattern is defined by the manufacturer’s instructions.  If no instructions are provided, a top-down burn protocol will be used.  For the competition, the manufacturer can build the fuel charge in the stove but cannot light off and will be hands off during the stove testing.  For startup phase – fuel can be loaded in multiple batches, but all fuel must be loaded within the first ten minutes of the phase.

6.    Air settings will be determined by the manufacturer. Up to 2 changes in air settings can be used during the start-up phase. 

7.    Fire will be started with a torch.  Torch can be used for up to 30 seconds

8.    Door can remain open for up to 5 minutes.  Manufacturer will set time and door position prior to competition.

9.    For the first 15 minutes (time starts at light-off), the door can be opened, and fuel adjustments made. A maximum of four fuel adjustments can be made. Door can remain open for no more than 30 seconds per fuel adjustment.  Door must be closed as soon as fuel adjustment is complete. 

10. Phase ends 30 minutes from light off or when there is loss of yellow flame, whichever comes first.  If start-up ends before 30 minutes, it should be noted in the testing comments, but no loss of points will occur.

1^stReload

Fuel load density 5 lb/ft3

The SBI managed to handle
the protocol quite well.
Photo: "Kittner for BNL"

Allowable Fuel piece weight: determined by fueling calculator

Target pieces for load: 4

Fuel load weight: determined by fueling calculator +/- 5% 

1.    Immediately after the end of start-up Phase, open stove door. 

2.    Chop existing wood with a fuel piece and to the extent possible smooth coalbed.

3.    Load 1^stReload charge following the specifications for this phase provided above. 

4.    Fuel loading pattern defined by the manufacturer’s instructions. Options are:

a.    East/west

b.    North/south

c.    Criss-cross

5.    Close door immediately after loading fuel. Maximum time to reload 60 seconds.

6.    Air settings/thermostat immediately turned to low demand

7.    During 1^streload phase one (1) fuel adjustment is allowed.  Additional fuel adjustments can be requested but the total score deduct 2 points for each additional fuel adjustment. Door can remain open for no more than 30 seconds for a fuel adjustment.  Door must be closed as soon as fuel adjustment complete.  

a.    Teams can make recommendations about when and how to make fuel adjustments.  

b.    Additional fuel adjustments interventions can be made at the request of the stove team.  Each additional fuel adjustment results in a loss of 1 points from scoring. 

8.    Air Adjustments - During the 1^stReload phase no air adjustments can be made unless judge(s) determine an intervention is required. Each intervention results in a loss of 2 points from scoring for every x minutes the air settings differ from the protocol. Interventions that result in point loss, will be completed upon request by the stove team.

9.    1^stReload Phase ends after 45 minutes (75 minutes from light-off).

2^ndReload

Fuel load – 2 pieces

Allowable fuel piece weight: determined by fuel calculator

1.    Immediately after the end of 1^stReload Phase, open stove door.

2.    Break up/chop/reposition remaining fuel to the extent possible.

3.    Load 2^ndReload charge following the specifications for this phase provided above. 

4.    Fuel loading pattern defined by the manufacturer’s instructions. Options are:

a.    East/west

b.    North/south

c.    Criss cross

5.    Close door immediately after loading fuel.  Maximum time to reload 60 seconds.

6.    Air settings/thermostat immediately turned to high demand

7.    During 2^ndReload phase no fuel adjustments are allowed. 

a.    Fuel adjustments can be requested but the total score deduct 1 point for each additional fuel adjustment. Door can remain open for no more than 30 seconds for a fuel adjustment.  Door must be closed as soon as fuel adjustment complete.

8.    Air Adjustments - During the 2^ndReload phase no air adjustments can be made unless judges determine an intervention is required. Each intervention results in a loss of 2 points from scoring for every x minutes the air settings differ from the protocol.

9.    2^ndReload Phase ends after 30 minutes (105 minutes from light-off).

3^rdReload

Allowable Fuel piece weight: determined by fuel load calculator

The testing crew for the automated test
protocol.
Photo Sam Kittner for Brookhaven National Lab.

Target pieces for load: 4

Fuel load weight: determined by fuel load calculator

1.    Immediately after the end of 2^ndReload Phase, open stove door.

2.    Break up/chop/reposition remaining fuel to the extent possible.

3.    Load 3^rdReload charge following the specifications for this phase provided above. 

a.    Load large piece first, then small piece, large piece, small piece, etc until no more wood fits in the stove.

4.    Fuel loading pattern defined by the manufacturer’s instructions. Options are:

a.    East/west

b.    North/south

5.    Close door immediately after loading fuel. Maximum time to reload 90 seconds.

6.    Air settings/thermostat immediately turned to low demand

7.    During 3^rdReload phase one (1) fuel adjustment is allowed within the first 10 minutes of the phase.  

a.    Additional fuel adjustments interventions can be made at the request of the stove team.  Each additional fuel adjustment results in a loss of 1 points from scoring. Door can remain open for no more than 30 seconds for a fuel adjustment.  Door must be closed as soon as fuel adjustment complete.

8.    Air Adjustments - During the 2^ndReload phase no air adjustments can be made unless judges determine an intervention is required. Each intervention results in a loss of 2 points from scoring for every x minutes the air settings differ from the protocol.

9.    3^rdReload Phase ends after 75 minutes (180 minutes from light-off).

Disruption Phase:

Optional Phase TBD by organizing committee

1.    No wood is loaded.

2.    Unit is placed in disruption mode, this could be: eliminating power, disengaging catalyst, etc.

3.    Disruption phase lasts 15 minutes.  

4.    Visible emissions may be the only measurement.

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