Friday, December 7, 2018

New York and Canadian companies win technology challenge to automate the wood Stove

Jonathan Male, director of the DOE's Bioenergy
Technology Office, announces the winners.
Photo: Sam Kittner for Brookhaven National Lab.
(Washington, D.C.) – Two companies with years of experience in electronics and stove design won coveted first and second prizes in the 2018 Wood Stove Design Challenge, held in Washington DC from November 9 – 13. 

Manually operated wood stoves are extremely common throughout the northern US, Canada and Europe but no one has yet popularized a solution to prevent them from emitting excessive smoke in the hands of operators.

Wittus, a company based in Pound Ridge New York, teamed up with German engineers and won first prize for both the automated and thermoelectric categories with a living room unit that also heated water for space heating and generated an average of 161 watts and a maximum of 268 watts over the 2.5-hour test period. Total power output over the test period, net of parasitic losses, e.g., pumps and fans, was 276 watt-hours of electricity. The use of thermocouple sensors and fans facilitated clean and efficient combustion.

Stove testers from Brookhaven National Lab and
New York Department of Health.
Photo: Kittner for BNL.
Second prize went to Stove Builders International (SBI) a Quebec based company that designed a simple, affordable stove that allowed the operator to select high or low heat output and used a low-cost control board and thermocouple sensors to ensure that the stove burned cleanly.

Second prize in the thermoelectric category went to California based Vulcan Energy, who developed a thermoelectric generator for the gravity fed Wiseway pellet stove that generated an average of 123 watts, and a maximum of 139 watts, during the 2.5-hour test period. Total power output over the test period, net of parasitic losses, was 235 watt-hours.

The People’s Choice award, based on votes from the general public, went to 509 Fabrications, for their unique gravity fed pressed log stove.
Key partners in the Challenge included Olympia
Chimney, and CSIA, and NFI installers from
Winstons Chimney and  Sugarloaf Chimney.
Photo Kittner for Brookhaven National Lab.

The goal of the Woodstove Design Challenge is to demonstrate how improved designs including sensors and computer controls can make wood stoves cleaner and more efficient. The technology boom of the past few decades has largely missed the wood stove industry, yet innovation still holds great promise. 

Researchers including Brookhaven National Lab, with support from the New York State Energy Research and Development Authority (NYSERDA), have been developing new methods for the next generation of assessment protocols for wood heating appliances. Currently, most stoves in America are tested for EPA certification with standardized fuel pieces and spacing. Research has focused on in-home use operational practices, user fueling patterns, and new real-time measurement method techniques with random loading patterns and variability in piece size to better replicate real-life conditions.   

Automated stoves that are designed and tested with this new robust cordwood test method can help improve woodstove designs and in-use performance leading to higher efficiency and lower emissions.

Les Otten of Maine Energy Systems with Julie
Tucker of the USDA Forest Service.
Photo: Kittner for Brookhaven National Lab.
A team from Stony Brook University also competed in the event with a prototype that featured a unique wood drying and preheating chamber. The stove did not win a prize but offered students a rich opportunity to engage with national stove design and testing experts. A full list of the competing teams can be found here

Partners for the Design Challenge include NYSERDA, the Department of Energy’s Bioenergy Technology Office, the U.S. Forest Service, the Osprey Foundation and Olympia Chimney. The automated stoves were tested by Brookhaven National Lab. A complete list of partners and sponsors can be found here.

Thursday, December 6, 2018

The US needs an eco label for wood and pellet heaters


Europe’s extensive experience with stove eco-labels shows clear benefits

While Europe is far behind the US when it comes to national stove emission standards, European wood stove and wood smoke regulation is far ahead of the US in most ways.  Much of the credit is due to Europe’s history of using eco labels.  National regulations in the US, such as the 1988 and 2015 EPA regulations, only provide a floor below which stoves cannot go.  And efforts to keep that floor as low as possible to allow the sales of low-performing technology allows the entire industry to play by same low standards. 

Eco labels provide incentives to make stoves cleaner and more efficient.  In turn, those higher standards can influence the entire market. Eco-labels also provide a ready-made structure for change out and incentive programs to move the market toward cleaner and more efficient devices.  In the US, virtually all new stoves qualify for the federal tax credit and change out programs, abdicating one of the best opportunities to improve the stock of stoves in the country.   

Europe is battling the same problem as the US with wood stoves that perform far worse in the field than they did in the lab.  A recent German report concluded that “there aren’t enough incentives to develop more sophisticated technical solutions to reduce emissions in the real-world.”  One of the only solutions is to include sensors and microprocessors so that stoves can optimize combustion on their own. European stove producers have undertaken R&D with automated functions far more than US producers, leading to promising designs.  An eco-label could recognize these advances and help these stoves gain a foothold in the market.  

Without an effective eco-label, R&D support, and meaningful incentives, stove technology could easily languish again, as it did after the minimum 1990 NSPS and 1995 Washington State regulations were met.  While pellet stoves were far cleaner, their efficiencies were often very poor, because there was no motivation to produce cleaner or higher efficiency units.  

The increase of stove sales and usage since 2000 has resulted in greater air pollution in both Europe and the US, leading to outright bans in some areas and a much harder road for stoves to be accepted as a top tier renewable energy technology.  Without a way for consumers and policy makers to easily distinguish between the best available technology and mediocre technology that just meets the minimum national emission standards, the fate of even the best stove technology is uncertain.

A recent workshop hosted by International Cryosphere Climate Initiative in Amsterdam for European stove producers highlighted the threats that existing stove technology and testing regimes face, as European nations take more aggressive stances against wood stoves without turning to pellet technology as a solution.  

In Europe, there is a new push for a pan-European eco label that would recognize the cleanest and most advanced units.  Progressive members of the European industry association, CEFACD, are pushing for this label to counter public perceptions that stoves are simply too dirty for the modern world.  Currently, the required EU labelling scheme only looks at efficiency, similar to the Energy Star program in the US.  But efficiency is not as important as cleanliness in the field.  The Alliance for Green Heat has tried to reform the federal tax credit to consider both PM and efficiency, but we are only making progress on the efficiency front.  After years of campaigning, the efficiency listings on the EPA stove list may finally be used, ending a decade of widespread industry misinformation.

Eco labels are not a silver bullet, and weak ones can even be a form of greenwashing.  Several European labels have struggled to only recognize the top of the market instead of the broad majority of units, a problem that the US Energy Star label has also faced.  To keep eco labels effective and relevant, their eligibility criteria needs to be updated as technology improves.

Eco labels can also help advance pellet stove technology which has proved to be relatively clean in the field.  Few nations have capitalized on advanced pellet stove and boiler technology to tackle the fossil fuel domination of the heating sector.  In the meantime, the electrification of heating is advancing quickly though heat pumps.  

Efficient cold climate heat pumps are an excellent technology and can be paired with pellet units.  In other cases, pellet technology is still preferable.  Austria has made great strides in pellet boilers, and regional R&D and incentives are helping the nation accept the technology.  But the only country in the world to embrace advanced pellet stove technology is, surprisingly, Italy.  In the US, New England states provide incentives for expensive pellet boilers, but have largely ignored pellet stoves, which still have huge potential. 

Industry wants sales but the periodic surge of wood stoves sales can backfire.  In the UK, the government foolishly gave incentives for basic, manually operated wood stoves, which helped fuel a rapid rise in wood smoke that is now causing a legitimate backlash.  In Denmark, a surge of sales occurred when the Baltics became part of the European Union, allowing cheap imported cord wood to make wood heating more affordable than renewable district heating.  In the US, the surge happened from 2000 – 2008, leading to an increased use of burn bans and a push for a stricter NSPS.  And local events like the Montreal ice storm of 1998, ended up motivating the city of Montreal to take one of the most radical steps of banning the use of existing stoves, including many certified stoves that emit more than 2.7 grams an hour.   Now many European cities are looking at Montreal style solutions.  All of these examples could have been avoided, or at least mitigated, if federal, state, and local agencies created a better foundation for pellet heating.  

The slow sales of pellet stoves and boilers would benefit from a recognizable eco label that identified the top performers.  However, when wood and pellet equipment producers are represented by the same industry association, the producers of wood stoves and boilers that just meet the minimum standards can be a powerful force in opposing eco-labels.  And this leads us back to where we are today, without sufficient recognition and incentives for the very best wood and pellet technology. 

A lack of leadership and interest from the EPA, DOE, and wood stove industry has prevented Energy Star from developing a program for wood and pellet stoves.  And, Energy Star is founded on the goal of reducing fossil fuel usage, so reducing the use of wood and pellets doesn’t easily fit.  If a new eco label emerges in Europe, it could be adopted and used in the US and Canada if it had the backing of enough stakeholders. Or, European brands could simply start using a European label and try to gain recognition among North American consumers.

Wood and pellet stoves sales in the US are declining, and this decline is likely to continue with winters gradually warming, fossil fuel prices staying relatively low, and greater awareness of the health impacts of wood smoke.  If the status quo isn’t working, maybe it’s time to try something different.  Think eco label.

Tuesday, December 4, 2018

Indoor and ambient air quality testing at 2018 Stove Design Challenge

By Dan Ciolkosz, Assistant Research Professor in Pennsylvania State University's Department of Agricultural and Biological Engineering and John Ackerly, President of the AGH. Dan and John were judges and members of the Organizing Committee of the Wood Stove Design Challenge.

In addition to measuring particulate matter (PM) in the chimney stacks of stoves at the 2018 Wood Stove Design Challenge, the Alliance for Green Heat also measured levels of PM inside and around the tent.  The tent had 13 wood heaters in it, of which 10 burned cord wood, 2 burned pellets and one burned a densified log.  At any one time, eight to ten of the units were usually operating, providing an opportunity to look at the impact on indoor air and the air around the tent.

The 13 wood and pellet units were in an uninsulated tent the size of a basketball court that had considerable air leakage and cannot be compared with a permanent structure.  The tent was on an open field area on the National Mall.

PM Measurements were recorded at discrete times, in and around the National Wood Stove Design Challenge tent, on November 9 and 10. Measurements were taken using a Thermo Scientific pDR 1500 aerosol monitor, set to a 5-second integration interval (thanks to George Allen of NESCAUM for use of his meter). These readings correspond to total particulates in the air, though it is likely that the majority of the particulates are in the "fine particulate" range of less than 2.5 microns. Readings were taken at a height of 1m above the ground. Exterior readings were taken at a location 15 meters from the building, north, south, east and west of the building. When elevated levels were detected outside, additional readings were taken to track the length of the contaminant plume. 

We also used an indoor Speck PM monitor, and a Purple Air PA-II-SD monitor.  Often the Speck showed  good, moderate or elevated inside the tent.  Due to technical difficulties we were not able to get the Purple Air monitor online during the event, or download the data yet, but we should have that data soon.

Indoor and Outdoor Measurements, Nov. 9
Figure 1: Measured PM inside and near tent 
On November 9th, the day was drizzly with light or no wind. PM levels inside the tent were notably elevated, ranging from 28 to 142 micrograms per cubic meter. Outside the tent, PM levels were most commonly 9-13 micrograms per cubic meter, except for elevated levels measured west (downwind) at 11:40am, which were 95 micrograms per cubic meter. Additional measurements taken at that time on the west side of the tent indicate that elevated PM levels existed as much as 100m west of the structure.  The EPA short term PM standard is 35 ug/m3 for a 24 hour average. 

Figure 2: Plume on West side of tent

Indoor and Outdoor Measurements, 10 Nov.
On November 10th, the day was clear and blustery. PM levels inside the tent were not as elevated as the previous day, ranging from 21-23 micrograms per cubic meter. outside the tent, PM levels were most commonly 8-10 micrograms per cubic meter, except for elevated levels measured east (downwind) near midday, which were 118 micrograms per cubic meter. Additional measurements on the east side of the tent showed elevated levels more than 100m west of the structure.

Figure 3: Measured PM inside and near tent
Figure 4: Plume on east side 

Logged Indoor Readings, 10 November

The sensor was left in logging mode for several hours during the day on November 10th, allowing us to track trends and variability of PM levels within the tent. Measurements were logged every 10 seconds, from ~10am until ~3pm.

Figure 5. Measured PM inside tent Nov. 10.
The mean PM level in the tent during this time was 33.5 micrograms per cubic meter, with a 5th and 95th percentile of 14.5 and 63 micrograms per cubic meter. The overall trend was fairly steady, with the exception of fluctuations at the time of the manual outdoor readings (~10:45, 12:45, 14:45), as well as elevated values during the period from about 10:05 to 10:35. This elevated period may be due to either a period of lower wind (i.e. less fresh air infiltration in the tent) or unusual stove activity within the tent.

As we already noted, it's tough to draw any broad conclusions from these measurements, for two notable reasons:
- The tent is an unusual structure, in terms of its infiltration characteristics and airflow patterns. 
- There were many stoves in operation, some of which were in a beta test mode that may not be representative of typical use. 


That being said, these measurements are a good reminder that some stoves can create elevated particulate levels in the air inside as well as outside a building, and wood stove designers and users should take this into consideration when selecting and using wood burning appliances.  We expect that a few of these stoves, including but not limited to the pellet units, created virtually undetectable PM inside and outside of the tent.  Conversely, several prototype stoves spewed excessive smoke when being reloaded, and could have contributed a great majority of the indoor smoke.  For most of the event, there was no visible smoke coming from the chimneys, though during start up and at other times, several stoves were producing excessive smoke.  One expert estimated that smoke becomes invisible around 2 grams an hour.

As a final note, recent developments in sensor technology have made measurement and recording of particulate levels much less expensive, which should allow us all to do a better job designing and using wood heat systems in a clean and "neighbor friendly" way.  

Saturday, December 1, 2018

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.

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

2ndReload
Fuel load – 2 pieces
Allowable fuel piece weight: determined by fuel calculator
1.    Immediately after the end of 1stReload Phase, open stove door.
2.    Break up/chop/reposition remaining fuel to the extent possible.
3.    Load 2ndReload 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 2ndReload 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 2ndReload 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.    2ndReload Phase ends after 30 minutes (105 minutes from light-off).

3rdReload
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 2ndReload Phase, open stove door.
2.    Break up/chop/reposition remaining fuel to the extent possible.
3.    Load 3rdReload 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 3rdReload 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 2ndReload 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.    3rdReload 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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