DOE should focus resources on R&D to advance automated stove technologies

 The Department of Energy Bioenergy Technologies Office (BETO) released a Request for Information (RFI) seeking feedback on defining the goals and objectives for a planned effort to collect in-situ wood heater performance data in the field. The deadline to submit comments was September 30, 2024. John Ackerly, AGH President, submitted the following comment: 

There are a number of small portable
emission testing devices for wood stoves
that can be used in situ, or larger lab
equipment can be moved to a home.

"We believe BETO should minimize its role in funding in-situ testing efforts because in-situ testing is usually very complex and expensive, given BETO’s funding for residential wood heater technology development. There are many distinct objectives and reasons to do in-site testing, and stakeholders could eloquently make the case for any number of them. But given the size of BETO’s budget, we do not feel there is a compelling enough type of in-situ testing that is likely to be undertaken.

BETO’s mandate is to “support the development of cleaner burning, higher efficiency residential wood heaters” and it seems this has been interpreted more broadly over time, which is understandable to some point, given the dearth of high quality applications to develop next generation stove technology.

We would urge BETO to only fund in-site testing to the extent it directly focuses on modern, more automated stove technology. For example, it may be worthwhile doing some in-situ testing with an automated stove side by side with a traditional manually operated one, to provide data about how beneficial automation can be, if at all.

The list of questions in the Four Categories suggest that this RFI is wide-ranging without parameters related to development of cleaner burning, high efficiency residential heaters. In the United States, stoves must be tested for PM 2.5 to be certified for sale. Efficiency, as measured by B415, is not regulated, but tested and an existing IRS tax credit gives an incentive to hit 75% efficiency, HHV. Any new generation of more modern, cleaner and efficient wood stoves will need to focus on these metrics first.

To understand the potential of modern, automated stoves, it may be just as relevant to study pellet stoves, to understand how and why they have such a predictable emissions profile, compared to cordwood stoves. It is also relatively easy to test how clean and efficient pellet stoves are in-situ after 1 to 10 years in operation.

To achieve testing goals of how pellet stoves perform after 1 – 10 years of use, I would recommend simply using a Testo 380 and principally test for PM2.5, enabling more sampling of more devices.

There are a multitude of academic inquiries into residential wood smoke but BETO should first determine what avenues there are to more directly advance an R&D agenda, which could include emissions data showing how automation can reduce emissions. Cordwood furnaces have already made the transition from being manually operated to controlled by sensors, and the evidence is clear that sensors will keep a boiler or furnace far cleaner.

Some stakeholders who are heavily invested in manually operated stoves may want BETO to undertake in-situ testing studies, which can be endless. But one test of this RFI will be whether those stakeholders who are doing R&D on modern, more automated stoves need in situ testing data, and if so, what kind. Similarly, it may be instructive to see what kind of in-situ testing is recommended by stakeholders who regulate wood stoves, or are involved in health related studies.

BETO could consider doing an RFI on how to develop the next generation of wood stoves in the United States. R&D is perhaps the most important avenue but DOE funding in the solar, wind and geothermal sectors address scores of barriers to bringing a renewable technology to scale. Those barriers can also be addressed in the eco-system surrounding the wood heater community. Obviously, the wood heater sector will never have that level of resources, requiring a careful assessment of where scarce resources can best be used.

An RFI that engages this community on how to advance automated stove technology may help better understand why major manufacturers are hesitant or whether there are other initiatives that could be undertaken. In-situ testing may be one of them, but an RFI solely on in-site testing sends a confusing message to the wood heating community unless BETO better explains how it is part of a strategy to develop modern, more automated stove technology.

Final Report on Wood Stove Decathlon from Brookhaven Lab

Reproduced below are the absract and introduction of a 17-page paper that gives an excellent overview of the technical aspects of testing stoves on the National Mall for the Wood Stove Decathlon, held in November 2013.  To read the entire report, click here.

Innovative fine particulate measurement systems for the Wood Stove Design Challenge 

R. Trojanowski1, T. Butcher1, C. Brown1, G. Wei1, Y. Ahn2 , and J. Wong2 

1. Energy Conversion Group, Brookhaven National Laboratory, Upton, New York, USA 

2. Chemical and Molecular Engineering Department, Stony Brook University, Stony Brook, New York, USA 

ABSTRACT 

The rising price of fossil resources has contributed to the increase in the amount of wood-fired residential heating appliances. Wood stoves are often overlooked by the public as a clean and renewable source due to concerns about particulate (PM) emissions. In order to gain acceptance in the market the Alliance for Green Heat and

Popular Mechanics magazine initiated a Wood Stove Design Challenge (WSDC). The selected teams designed stoves that incorporated the best practices in design and operation to maximize efficiency and minimize PM and carbon monoxide (CO) emissions since most often high emissions are seen as a result of incomplete combustion. Further, a testing protocol for the challenge was developed specifically to measure the emissions in a non-laboratory setting. Standard testing procedures may not be representative of in-use fuel and operational practices and, due to the competition venue and schedule contstraints, could not be used for the WSDC. New portable PM sampling technology released in the European market recently was adopted for the competition and evaluated to current U.S. PM measurement methods to build a correlation. 

INTRODUCTION

Tom Butcher uses the Wohler portable
particulate sampler to test a stove.

 As the price of heating oil has increased, more residents in the northeastern region of the United States have returned to heating with wood. Most existing wood stoves date from before the Environmental Protection Agency (EPA) implemented emission certification requirements for these devices. These less efficient wood stoves often cause high amounts of smoke, yielding particulates known to trigger coughs, throat and mucosal irritation, acute respiratory infections, occurrence of asthma and other diseases over prolonged exposure. A review from Bølling et al. reported residential wood combustion has also been reported to contribute significantly to raised levels of air pollution locally, both with respect to increased levels of fine particles (particulate matter with an equivalent aerodynamic diameter < 2.5 μm; PM2.5), the organic particle fraction, particle bound polycyclic aromatic hydrocarbons (PAH) and volatile organic compounds. Even those wood stoves that do meet EPA’s Phase II requirements may have unacceptably high emissions once in use. This is due to several factors including the design of the appliance, weather patterns and location, combustion activity, wood species and quality, and operator habits. While the EPA is developing new regulations, the test method used for certification is not representative of in-use fueling and operational practices. 

Designs that improve combustion and emission performance, thermal efficiency, and operational  

The Decathlon tent on the National
Mall, in between the Capitol and
the Washington monument

variability are needed in the U.S. heating market. Modern wood stoves have shown reduced reported emission factors compared to conventional wood stoves, 34-330 mg/MJ from 50-2100 mg/MJ, respectively. However, if the modern stoves are not operated correctly the combustion performance can be compromised yielding higher emissions.

This event showcased advanced technologies that could help address the problem of increased particulate emissions and enable the continued use of wood as a renewable fuel. The teams selected came from various backgrounds, ranging from established wood stove companies to independent inventors and engineering student teams. Some of the stoves selected for the WSDC were controlled by microprocessors and connected to smartphones while others were ultra-efficient stoves based on 17th century Scandinavian designs. Several state-of-the-art hybrid stoves that are already on the market were also included4. Six of the 12 finalists were from Europe. 

Teams were judged on their innovation, emission and efficiency performance, affordability and consumer ease. In November 2013 on the National Mall in Washington D.C., ten judges (made up of leading experts from Popular Mechanics, the New York State Energy and Research Development Authority (NYSERDA), the U.S. Forest Service, Washington State Department of Ecology, DOE’s Brookhaven National Laboratory (BNL), The Biomass Thermal Energy Council (BTEC), the Osprey Foundation, the Masonry Heater Association and UC Berkeley) tested and assessed the 12 stove finalists and announced an overall winner as well as winners in specific categories. 

A key challenge in this competition was measuring the particulate emissions accurately in a field environment. This project sought to develop an energy efficiency and emissions testing protocol for the WSDC which reduces the variability due to fuel and operations. The current standard test method (EPA Method 28) involves testing stoves using a dilution tunnel. Since the WSDC was held at the mall in Washington D.C., this test method would not suit and so there was the challenge of measuring the emissions in a repeatable real-time way, in a non-laboratory environment. Recently, new portable particulate measurement systems have been introduced in Europe for field inspection of biomass heating systems. Two specific products were selected for use in this project the Testo 380 and Wöhler SM 500. Both analyzers are a low cost option and offer the advantage of ease and portability. 

To determine the accuracy, precision, instrument range, and applicability for use in the WSDC for thermal efficiency and emissions of these portable direct measure analyzers, an evaluation was conducted while simultaneously following the standard methods for determining the emissions.  From laboratory testing, BNL developed a testing protocol implementing the analyzers for the competition.

To read the entire PDF report, click here.

For more information about the 2013 Decathlon, click here.

For information about the 2014 Collaborative Stove Design Workshop, click here.

Innovative Fine Particulate Measurement Systems for the Wood Stove Design Challenge

This blog originally had a poster and text about the details of the PM analyzers that we will use at the Decathlon.  However, because some of the findings were preliminary and not finalized, we have taken down the poster and text, except for the abstract, below.  We will repost the poster and content when it is more finalized. - Editors

Abstract

As the price of heating oil has increased in the US, more residents are returning to wood heat. Most existing wood stoves date from before the EPA implemented emissions certification requirements for these devices. Even those wood stoves that meet EPA’s Phase II requirements often have unacceptably high emissions once in use. This is due to several factors including fuel quality, operator habits and design. While the EPA is developing new regulations, the test method used for certification is not representative of in-use performance and the performance criteria in the test fall short of high efficiency or low emissions.

Designs that improve combustion and emission performance, thermal efficiency, and operational variability are needed in the U.S. heating market. The Alliance for Green Heat and Popular Mechanics Magazine has initiated the Wood Stove Design Challenge (WSDC) to address these needs by developing a competition for manufacturers, innovators, and university teams working towards these objectives.

This project seeks to develop a WSDC energy efficiency and emissions testing protocol which reduces the variability in fuel and operator. The current test method (EPA Method 28 WHH) involves testing stoves using a dilution tunnel. Seeing that the WSDC is held at the mall in Washington DC, this test method does not suit. Recently, new particulate measurement systems have been introduced in Europe, both the Wöhler SM 500 and testo 380. Both analyzers are a low cost option and offer the advantage of ease and portability. To determine the accuracy, precision, instrument range, and applicability for use in the WSDC for thermal efficiency and emissions, these portable direct measure analyzers, an evaluation will be conducted while simultaneously using the standard methods for determining the emissions.

There is, also, interest in the potential use of instruments of this type for field evaluation of the performance of both stoves and boilers.

The technology of these systems include near real-time, sub-microgram sensitivity, and is the only filter-based mass monitoring technology which has these properties and does not depend on questionable, surrogate measurements for mass