- Created: Friday, 08 March 2019 16:59
- Last Updated: Monday, 01 April 2019 15:12
- Written by Lorin
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Navajo Hybrid Dual-Fuel Stove & Survival Hybrid Wood Stove
A Story of Great Challenge & Reward
The story of Navajo & Survival Hybrid stoves had a fascinating start with the design and development of a clean burning, small, dual fuel stove for use on the Navajo Nation at the Four Corners of New Mexico, Arizona, Colorado & Utah.
Making the “impossible”, possible!
In 2016, the US EPA approached Woodstock Soapstone Co., to ask if we would be interested in designing a clean burning stove capable of burning both wood and coal. The design would be used on the Navajo Nation Reservation, as part of a consent decree with Arizona Public Service & Southern California Edison for violations to the clean air act. The settlement had designated funds for a stove change-out and weatherization program near the Four Corners region. This is a region where indoor and outdoor air quality is often quite poor, and a significant number of Navajo people suffer from respiratory and cardiovascular diseases as a direct result.
The obvious hurdles, and what other manufacturers deemed impossible, was engineering a low cost stove that could burn both wood and sub-bitumious coal cleanly. In fact, there were no EPA certified coal stoves in 2016, and a coal testing standard had
never been developed, these were a testament to the fact that it would be a challenging task.
Always up for a worthwhile challenge, we decided to accept!
In 2016, with the help from two very talented and dedicated engineering students at VTC, the Vermont Technical College, the development of what is now known as the Navajo Stove, a dual-fuel wood/coal stove with hybrid technology, began.
With Tom, the company president, leading the charge, Will & Leif, started in on the design and engineering work. The sub-bituminous coal from the Navajo reservation was shipped to our in-house EPA test lab in order to properly design and test a coal burning stove. The expertise of Larry Young, a local independent scientist, was sought to help with the coal burning aspect of this dual fuel stove heater.
It became apparent that the hybrid combustion system, used in several of our wood stoves, would be key to getting the low emission and efficiency results we wanted from the Navajo stove. The hybrid combustion system includes a catalytic combustor and a secondary air reburn. The challenge was to design the combustion system to maximize efficiency and reduce emissions for each fuel type. When burning wood only, the catalytic combustor and secondary air reburn would be in use, and as the end user transitioned to burning coal, or a mix of wood and coal, the secondary reburn system would become the primary reburn system, and the combustor would be safely housed in a “garage”, protecting it from the damaging effects coal exhaust has on catalytic combustors.
Designing a stove to meet the needs of the Navajo
To effectively design a stove that would fit the needs of the Navajo people, we partnered with the Navajo EPA and Johns Hopkins employees, already
working on the reservation, to provide us with infomation on the burn practices, type of fuel used, typical dwelling size and condition, as well as installation considerations.
For the Navajo people in the Four Corners region, the wood available is typically juniper and pine, and the coal coming from the area mines, on or near the reservation, is a soft, sub-bituminous coal.
Most families in this region, burn wood during the day, and coal at night to help extend the burn time. Families who burn coal do so for the low cost and extended burn times. However, there is a stigma associated with burning coal due to the strong sulfuric odor produced when burned in their old inefficient stoves, and many would prefer to burn wood only.
The standard home on the reservation is under 1000 sq.ft., with a large number of mobile homes, so an outside air adapter needed to be part of the design consideration.
The other major consideration was to design the stove that could be used with shorter than normal chimneys. The majority of homes on the reservation are single story structures, and recipients of the change-out program would receive a proper chimney, based on our specifications.
Again working with a scientist, we engineered the Navajo stove as a top vent stove, approved for a straight up installation only. In the internal design, we positioned the bypass door to open directly below the flue collar, to give the chimney pipe an immediate boost of heat to establish draft quickly. All of these design considerations allowed the chimney height to be a minimum of 11’-12’ and still draft properly.
Why stop there? We knew the engineering issues would need to be addressed, but what about the appearance? The Navajo people have such a rich artisan
culture, and symbolism plays such an important role in their beliefs. Why not use our metal cutting abilities to incorporate some Navajo designs and symbols to truely make the Navajo Stove their own? Cultural sensitivity was a concern, and we reached out to the Navajo EPA, and other organizations on the reservation, to get feedback on the designs and to make sure our interpretations would be well received.
Rolling out prototypes
As a small manufacturer, with steel fabrication capabilities, we could take a design from the computer, to a foam core model, to a steel prototype ready to test in the lab, with relative ease.
Once we were satisfied with the emissions and efficiency results we were seeing in our in-house test lab, we set out to build a small number of beta stoves for “real world” testing. A few of these beta models were tested locally, but we knew from experience that we needed to get the beta models into the hands of the people who would ultimately using them.
Our First Trip: Beta models & Woodstock Soapstone head west to the Navajo Nation Reservation
After identifying a half dozen willing beta testers in need of stove upgrades, we shipped the beta stoves, chimney systems and hearth pads, to Albuqurque,
NM. Shortly thereafter, Lorin, Glenn, and Jack , from Woodstock Soapstone Co., flew out to pick up the shipment and continue on to the Navajo Reservation to complete the beta installations. As documented in our blog posts, our crew went out with very little prior information on each change-out installation, but we knew from discussions with the USA EPA, Navajo EPA, and the Johns Hopkins employees conducting home air quality tests on the reservation, that most, if not all, of the change-outs would require a proper chimney and floor protection.
Every installation had it’s own set of challenges that had to be worked out on the spot to ensure a safe installation. This was not always a small feat, given the sheer location of the installations, often long distances from any hardware or building supply stores. Ultimately, every installation was sucessfully completed, providing our beta testers with a new stove, operational training, a Class A chimney that would draft properly for improved indoor air quality and proper combustion, installed with proper clearances to eliminate future fire hazards, as well as proper floor protection.
Testing is Completed & Production Begins
Improvements based on beta experiences were then implemented into what would become the production stove. Testing was completed and the Navajo Hybrid & Survival Hybrid, the wood only version, received EPA approval and UL certification by late 2017. The wood test achieved emissions of 1.13 gm/hr and an efficiency rating of 79.43% and the average coal emissions was 4.95 gm/hr, with efficiency of 59.7%. We did sacrifice quite a bit of efficiency to clean up the coal emissions, but felt it was necessary to address the negative effects of increased coal emissions.
In early January of 2018 the first 6 production models of the Navajo Hybrid Wood/Coal Stove and the first 30 models of the Survival Hybrid Wood Stove made their way through the production floor.
The 6 Navajo stoves were promptly shipped out to the reservation, and this time Lorin, Glenn, Will, and Roy Hatch (independent videographer) headed out to the reservation to get the production models in use. Our second trip served several purposes: 1) Replace the beta stoves with production stoves; 2) Complete a new installation along with the company responsible for assessing change-out applicants. 3) Obtain enough footage for training videos.
Below is a series of images from a new installation completed in January 2018 in a Navajo hogan (see right). The impact that the new installation had on the family was profound. When the Woodstock crew first arrived to access the home/stove for the change-out, Josephine, one of the family members who suffers from respiratory and cardiovascular issues, was barely audible due to the poor air quality conditions in the home, the roof around the pipe was open to the outside causing a draft, an old stove in very poor condition with a makeshift door, and the owner kept an open container of ash and live coals by the stove.
After installing the new stove and sealing the ceiling, the positive effects on the air quality and heat in the home were recognized immediately. The Woodstock crew checked back with the family over the next two days. Josephine’s voice was clearing up and she reported that everyone slept well, there was no fighting over blankets, and she didn’t need to get up in the middle of the night to tend the fire. On our last day on the reservation a final check was made and Josephine was like a whole new woman with a clear voice, well rested and full of energy.
Since the January 2018 trip, 20 Navajo stoves were shipped out in late February/early March of 2018 as an official launch of the change-out program, then another 50 shipped in December, 2018. To help start the change-out program on the right footing, Lorin and Glenn made a return trip to the reservation to provide technical support to the Navajo installers and to help provide operational support to the new owners.
Woodstock Soapstone took a risk, one that had little to no monetary gain (all of the the R&D, travel, and labor both in and out of the shop, was paid for by Woodstock Soapstone), but so far the rewards have been worth the effort. Ultimately the EPA plans to complete 500-700 stove change-outs and weatherization upgrades. We certainly hope all our efforts will pay big dividends in the lives of the Navajo people receiving the upgraded systems.
The Survival Hybrid Wood Stove- Beyond the Navajo Stove
After dedicating a great amount of time, resources, and money to develop a dual-fuel hybrid stove wth limited use, it only made sense to make a hybrid
wood stove using the same basic design as the Navajo Stove, without the coal burning aspect.
As the coal/wood Navajo designed stove was developed for use only on the Navajo Nation, we don’t offer it specifically to the public at large. Since we often get calls from potential customers expressing interest in a smaller, efficient, clean-burning stove, it made sense to us to build a version of the Navajo Hybrid stove designed for wood only, that would be available to everyone.
This wood only version became our Survival Hybrid stove, and a welcome addition to our growing family of clean-burning and high efficiency wood stoves.
The Survival Hybrid, rated to heat 1000sq ft, has a very low 1.13 gm/hr emissions, 79.4% efficiency and three great designs (The Orchard, Lodge, and Navajo) to choose from, a built in ash pan, and two burners to work as a cooktop. You can get all of this for a very affordable price point.
Customers who choose the Navajo designed artwork for their Survival Wood Stove, will have the cost of the Navajo artwork donated, through Woodstock Soapstone Co., to Red Feather. Red Feather is a non-profit organization working with native tribes (currently the Hopi and Navajo) to develop sustainable solutions for their housing needs, including home weatherization, energy efficient appliances, roof and window repair and informative workshops. We feel that donating the cost of the Navajo style art work is one more way we, and our customers, can make a difference in the quality of life for the native people in and around the Navajo Reservation.
For more information and specifications on the Survival Hybrid Wood Stove, click here.