Meet the teams: Backed by the EPA and DOE, top cookstove designers tackle the heatstove

This post is the sixth in a series introducing the 12 teams participating in the 2018 Wood Stove Design Challenge in November.

By John Ackerly, Ken Adler, and Shoshana Rybeck, Alliance for Green Heat

Cook stoves and international development 

Dean Still (left) with participants at an
Ethos conference near Seattle.

Dean Still leads the team at the Advanced Studies in Appropriate Technology Lab (ASAT) and has been involved with the international cook stove community for decades. He and his team have achieved many key breakthroughs in testing, stove design, instrumentation, and like most researchers and developers, they have had their share of dead ends, disappointments and flops.  

The New Yorker magazine featured Dean in a 2009 article about engineers who need to design stoves that cost no more than $10 so even the world’s poorest people can afford them. So, when we told Dean that cheap stoves by our standards were between $500 and $1,000, he laughed and said, “you would think that should be easy.”

ASAT won a $300,000 grant from the EPA to build a heat stove that makes electricity, thirty times more than the $10,000 that each team is getting from DOE through the Alliance for Green Heat. ASAT has another advantage that only a few teams have in the competition: they operate a testing lab so they can measure changes in emissions and efficiency with each iteration of the prototype.

ASAT's sister group, Aprovecho hosts
annual "stove camps" where innovators
work together to built and test designs

The challenge for ASAT is whether they translate their experience and skill making cookstoves into a successful heating stove that performs well in the lab and in the field. There is a tight timeline and ASAT is new to the way the EPA measures PM and efficiency for heat stoves—and the way that tests will be conducted at the Stove Challenge. Translating lab test protocols to real world emissions may be even tougher for cook stoves and oversight of cook stove labs is weak compared to EPA-approved heat stove labs. But the cook stove community is far more transparent, and test results and technologies are more freely shared in the common battle of a global enemy—daily exposure to wood smoke from traditional cooking practices.

ASAT’s strategy

Dean Still with Prince Charles, who
has been an advocate for the modern,
cleaner cookstoves

ASAT’s stove is unique from the start—it’s a rocket stove.  Rocket stoves are most common as a developing world cook stove where you feed small diameter fuel into an insulated chamber and let it burn the ends of the sticks. Rocket stoves designed for heating are usually called “rocket mass stoves” but the prototype coming to the competition in November 2018 will be a new, high tech, low mass hybrid of the Rocket stove.  

ASAT is using an expansive strategy and are integrating many innovative technologies, from fabric filters to laser smoke sensors that automatically adjust secondary air.  By keeping an open mind, the ASAT team is winnowing down technologies, but the danger is that they are doing this on a very short time-line and the prototype is still going through major changes with less than 6 months prior to the competition.

ASAT's lab in Cottage Grove, OR

ASAT is working to make a stove mostly for the Asian market that can benefit those who struggle to get heat and electricity independently with ultra-low emission rates. The stove will include an electrostatic filter for PM to capture escaping emissions. Dean says his stove will have “jets of pre-heated secondary air that create a zone of mixing like in the carburetor of a car where a combination of high temperatures, residence time and complete mixing result in close to complete combustion. The fan speed, the amount of smoke, CO, CO2, and temperature in stove will be shown on a LTD screen. A PM sensor in the chimney automatically adjusts the velocity of the secondary air jets.”

Thermoelectric technology 

With help from the EPA, ASAT is developing a stove that can be used to cook food, heat the home and create electricity mainly for rural households in Asia that have intermittent or no electricity. To do this, electronic designer and manufacturer Karl Walter and lab manager Sam Bentson have created a new type of TEG that fits into the evolving design. The team is currently working on the fifth iteration and are focusing on how to create reliable electricity in the most inexpensive way possible. 

Sam Bentson, ASAT Lab Manager

The team has been building their own TEG that is making electricity without the use of a water cooling system. Instead, their TEG uses a large radiator that is essentially an aluminum fin designed to move the most air at the lowest wattage possible. With the team solely using a radiator and not including a water cooled system, or even a fan, the model is far less expensive, which appeals to ASAT's dedication to making this as affordable as they can. The team hopes to develop a TEG for less than $100 that creates at least 15 watts of power, using a switch mode voltage regulator and usb connection. Karl Walter says, “Water cooling is great but there is also something to be valued in a simpler, robust approach.”

Creating an affordable cook stove with an attached TEG that does not have “moving parts” is no easy task. Thankfully, with the financial support of the DOE and EPA, ASAT has been able to fully delve into this project and work through the challenges they have faced. Karl says that for their team the largest challenges had to do with temperature differentials and power outputs. He says that finding a “realistic power output was difficult” as well as figuring out “what happens when you overheat the stove.” But, the team is on a two year contract for their EPA project and with a year remaining, they are optimistic about the future development of their product and plan to have a model prototype ready for market testing within the next 4 months.

ASAT follows the old adage to think globally and act locally. Their efforts to create stoves that benefit people around the world have had tremendous support from national and regional organizations and they hope to expose the powerful technology they’ve been working on to a larger audience at the challenge in November. 

Contact the team at:

Dean Still
managerstovetec@gmail.com

Sam Bentson
managerstovetec@gmail.com

Karl Walter
karl@waltech.com

Experts Gather in Seattle to Design Cleaner Wood Stoves

By John Ackerly

President, Alliance for Green Heat

In January I attended an amazing conference where about 60 people came together to share ideas on building cleaner, more efficient stoves.  But the conference wasn’t just about stove design; it was also about how to incentivize them, how to monitor their use, and how to deploy the clean ones more widely. 

 

Conference organizers

Speakers gave several presentations showing diagrams of optimal use of primary and secondary air.  Most of the discussion was about the two streams of secondary air and exactly where and when to get them into combustion chamber.  On one model, tests showed that it was critical to get the secondary air lower in the combustion chamber when the stove was operating on low so a separate channel carried it another inch down the stove wall.  And, it was found that if this air was not preheated, the stove operated just as well – often better – than if it was preheated.  One reason is that the air created more turbulence if it sank, rather than rising quickly along with the combustion gases.

Another major topic discussed was how to get people to give up their old polluting stoves and invest in new, efficient ones.  Some research showed that even when families understood how much wood they would save with a new stove, they were still very resistant to giving up their old one.  And, if they did buy a new one, the old one was not always discarded, but used in another place. 

One of the most fascinating subjects concerned the use of wireless sensors that could remotely monitor the temperature of the stove so researchers could learn more about the operating habits of the owner.  PM sensors could also show how the operating habits of owners impacted indoor air quality and measure the improvement compared to the old, more polluting stove.

Outside the classroom, we lit the stoves to see how fast they would be free of visible smoke.  The following day we tested the stoves with a dilution tunnel, not for any certification, but just to learn how testing was done, and to see how design changes impacted efficiency, CO, and PM emissions.  Engineers freely shared their innovations with others, and with the government officials from the EPA and European agencies, who also attended.

What distinguished this wood stove gathering from others I was familiar with is that the engineers and experts were all sharing their work and designs without first patenting their ideas.  It wasn’t about selling anything, but about a community working together, including to help existing and potential manufacturers build cleaner stoves. 

Unfortunately for some of us, the conference was about international cook stoves, not domestic heat stoves.  It made me painfully aware of how vibrant that community is in terms of sharing ideas and designs, and attracting so many different universities and small entrepreneurs.  It was organized by a non-profit called ETHOS: “Engineers in Technical and Humanitarian Opportunities of Service”.  The organization’s mandate is to facilitate research and development of appropriate technology by forming collaborative partnerships between universities, research laboratories, engineers, non-governmental organizations and the private sector.

As I sat in the sessions, which were fascinating, I kept wondering why such a collaborative and urgent campaign had developed around international cook stoves and not domestic heating stoves.  Part of the reason must be that the leadership and culture in humanitarian groups, which are publicly funded, compared to the private sector where companies are vying for market share.  Several of the groups and companies had DOE funding for R & D.

One of main leaders of that group is Dean Still, Executive Director of the Oregon based Aprovecho Research Center, a world leader in open source stove technology development.  Dean is a charismatic figure with seemingly boundless energy, the kind of person whom people rally around.  He oversees a biomass stove research laboratory that conducts emission equipment manufacturing, and is the author or co-author of six books and dozens of technical reports and articles on clean stoves.

 

Dean Still with Prince Charles

There has been some collaboration between Aprovecho and the domestic heat stove community over the years.  Dr. Larry Winiarski, a long-time Aprovecho figure, invented the rocket stove (http://en.wikipedia.org/wiki/Rocket_stove) and Aprovecho has worked on numerous rocket mass heating stove projects in China, Tibet, Nepal, the Andes, etc.  Omni Test labs, an EPA accredited wood stove test lab, helped Aprovecho set up their dilution tunnel and emission testing system for cook stoves. 

After the conference, which was in Seattle, I drove down to Portland to visit Omni and Dirigo Test labs and discuss how the new EPA wood stove regulations would impact test labs.  Then I kept driving south to Cottage Grove, Oregon where Aprovecho is based.  I spent a few days with Dean Still and his dedicated team of engineers and test lab technicians (14 staff in all).  Every summer they run a “stove camp,” which I had read about in the feature story, “Hearth Surgery,” in the New Yorker Magazine.

Stove camp is a hands-on workshop where participants try to tweak stove designs and test them to see if they can improve efficiency and emissions.  Dean and I got to talking about doing a Heat Stove Camp this summer, where up to 50 participants would bring innovative wood stoves to tweak and test.  Normally at stove camp, applicants are selected based on their background and pay a minimal fee.  Each morning, everyone reviews the test results, which are data logged from the previous day’s tests, and discusses what design elements work best.  In the afternoon, participants can alter designs in the fully equipped metal shop, and then test them again. 

Dean and others think that their extended community can come up with designs that meet the 1.3 gram per hour mark without using a catalyst.  They have extensive experience using combustion fans in stoves, which some think is one of the keys to ultra low emissions.  One model that Aprovecho uses is to collectively design and test a stove, and then have a non-profit patent it so it can be open sourced, allowing anyone to build from it.  If this could be done for a stove that hits the 1.3 grams that the EPA is proposing all stoves meet in coming years, it would be a natural extension of the Wood Stove Decathlon, and help lift all boats.